To begin with, I do not claim to have a complete understanding of The Special
Theory of Relativity. I do believe I understand the basics involved, though, if
only on a philosophical level. I do know SR's mathematics follow from its two
basic postulates, if they are true, SR is true. They are:
(1) The speed of light 'c' is a universal constant, the same in any inertial frame. An inertial frame is one in which unaccelerated objects move in straight
lines at constant velocity.
(2) The laws of physics are the same in any inertial frame, regardless of position or velocity.

The speed of light. I don't believe there is any question that light travels at
299,792,458 meters per second in a vaccum. Scientists have bounced lasars
off reflectors on the moon, for instance, to arrive at this exact number. But
that is only giving the speed of light in one reference frame, as would bouncing light off any object, whether it has relative velocity in regards to
the timing station or not. I know of no experiment in which the velocity of light
has been MEASURED emitted from a source moving at a high relative velocity
to the scientist making the measurement. But SR says it would be the same.
I want to focus on the second postulate, but I want to do it slightly
different than the textbooks do it. I want to focus on the TRAVELER'S frame.
I have posted something like this before, but got no answer. It is a simple
thought experiment, which is common in SR exercises of course.

Jill is the traveler. She is to make a round trip from Earth to a spacestation
that is stationed 6 light months from Earth, to deliver a part, for example.
Unknown to her at the time of her departure, she became pregnant the night
before she begins her trip. She leaves on Jan. 1, 2010. Her ship can very
quickly attain a speed of .95c, and also decrease speed quickly. She becomes
aware of her pregnancy two months into her trip, according to her on-board
clock. She looks at a clock on Earth and only about 19 days has passed on it.
She drops off the part and begins here return trip to Earth. After 9 months have elapsed on her on-board clock, she has her baby. She looks at the clock
on Earth again, and only about 84 days have passed on it. When nearing the
end of her trip, she sees over one year has passed on her on-board clock and
her baby is 3 months old. She looks at the clock on Earth again and about
114 days have passed on it. How much older will she be when she steps off
the ship on Earth and what happens to the baby? I realize that according to
SR, time is moving more slowly for her during the trip according to Earth's clocks and she does not have time to have the baby. So, was her on-board
clock running FAST, not slow, in regards to Earth's frame of reference? Was
her view of the Earth's clock the true time and her on-board clock a fantasy?
If her view of the Earth's clock was the true one, that would indicate she was
traveling at a velocity greater than the speed of light. There would be no
time dilation, and by default, no length contraction. Can someone clear up
my confusion, USING JILL'S FRAME OF REFERENCE?

You neglected length contraction as seen by Jill. While she is traveling at .95c the distance shes measures between Earth and Buoy will only be 1.86 light-months. It will take her only only a little under 4 months according to her clock to make the round trip at .95c. It coincides with the little under 4 months that Earth sees as passing on her clock due to time dilation.

Of course during the time she is traveling at .95c she will see only about 18.6 days pass on Earth during each leg (inbound and outbound) of her trip for a total of 37.2 days.

But, this doesn't account for what she sees as happening to Earth's clock during the acceleration phases of her trip. Because of the way that Relativity behaves for observers in accelerated frames, during the time she is decelerating to a stop at the buoy and when she starts to accelerate back towards Earth, she will actually see Earth's clock jump forward a total of 327.8 days. This means that the total time that she sees as passing on Earth during her trip will be 1 year, The same time as measured by the Earth clock. During which time she will have aged a little under 4 months. Her baby isn't born on the trip according to either her or an Earth observer.

Special Relativity
The issue is that Jill proceeds through no less than three inertial frames of reference - Earth's frame (on Earth), outward bound frame, Earth's frame (at the space station), inward bound frame, Earth's frame (on Earth).
Inertial frames are the only frame we can consider in Special Relativity.

When you work through Jill's changes from one frame to the another, you find that her perspective of current time on Earth changes dramatically during the transitions.

The end result is that Jill's accumulated time during the trip is less than Earth's accumulated time during the trip.


General Relativity
If you really want to consider Jill to be stationary the whole time, you can not do so with Special Relativity (Inertial frames are the only frame we can consider in Special Relativity.), but you can do so using General Relativity. In that case, Jill's frame is sometimes inertial, and sometimes not... when she is accelerating, her frame is not inertial.

During periods of acceleration, the only way for Jill to reconcile these facts:
(1) she is stationary,
(2) she has to exert a force (fire the ship's rockets) to remain stationary, and
(3) everything that isn't exerting a force is accelerating
Is to conclude that a uniform gravity field spontaneously sprang up across the whole Universe (Remember this is an artificial situation. It seems much more realistic to me to simply conclude that Jill is not in the same reference frame for the whole journey; however, this does illustrate the key tenet of GR, that gravity and inertial acceleration are essentially the same thing).

This means that during the acceleration periods, Jill's perspective of the current time in different places across the Universe changes dramatically, due to gravitational time dilation.

The end result is that Jill's accumulated time during the trip is less than Earth's accumulated time during the trip.


For more complete explanations, have a look here:
UseNet Relativity FAQ - The Twin Paradox (http://www.weburbia.demon.co.uk/physics/twin_paradox.html)

Thanks, Janus58. Now, during this acceleration phase when she sees the Earth's clock
jump forward 327.8 days, are you saying NO time passes for Jill or her clock in her
reference frame? That time only passes for her during the less than 4 months of
inertial travel? Would no time pass for a traveler that accelerated for half of a trip
and decellerated (same as acceleration) the other half, regardless of the rate of acceleration or length of the trip measured by an Earth-based observer? If not, how
much time passes on Jill's clock during the 327.8 days?

2Inquisitive: After making very accurate measurements of the speed of light in about 1883, Michaelson and Morley designed and performed the now famous Michaelson/Morley experiment in about 1888. The experiment has been performed many times since then with more sensitive equipment, and perhaps with a differently designed apparatus. The M/M experiment measured the speed of light relative to a moving frame of reference, namely the earth.

The M/M apparatus sent beams of light down long evacuated equal length tubes at right angles to each other. The apparatus could be rotated. It was the intent of the experiment to determine the absolute motion of the Earth through was then called the ether. The concept of the experiment was as follows It was (is) known that the surface of the Earth moves about 1000MPH at the Equator and slower at latitudes closer to the Poles. It was (is) known that the Earth moves about 67,000MPH in its orbit around the sun. In modern times (perhaps not then), it is known that the Earth has even greater speeds relative to distant fixed stars due to galactic rotation and the movement of the local galactic cluster toward a Great Attractor some where far from us.


The apparatus was precise enough to record noticeable speed differences due to the Earth’s motion.


When the apparatus was rotated it was expected that different velocities would be measured, due to the alignment relative to the Earth’s motion. In particular, it was expected that different velocities would be measured in the two parallel pipes due to their different orientation relative to the moving frame of reference (the Earth).


No matter how the apparatus was rotated, the speed measured in the two evacuated pipes was the same.


To more accurately describe the experiment, it should be noted that the original M/M experiment only attempted to detect a difference in speed in the two pipes at right angles to each other. In later experiments, the actual speed of light has been measured in different directions relative to the Earth.There are three possible explanations of the M/M experiment. The Earth is stationary, an explanation that would have elated the religious leaders at the time of Galileo. This explanation has never been accepted by modern physicists.


The Earth drags the ether in its vicinity, causing it to move at the same velocity as the Earth. Various modern scientists have espoused this explanation. I suspect there is some good reason for rejecting it without further analysis, but do not know of any such reason. Modern physicists reject the notion of the ether, required by the 19th century belief that light was a wave phenomenon.


The measured velocity of light is constant in all inertial reference frames, and is not affected by the motion of the observer.The latter explanation was used by Einstein as the basis for his Special Theory of Relativity. The Theory predicted the results of various other experiments, including time/distance contractions. These predictions have been tested and verified by experiments other than the M/M experiment, resulting in general acceptance of Special Relativity and the demise of belief in ether-based theories.

It should be noted that some creditable physicists claimed that there were errors in or alternative explanations for the M/M experiment. Mossbaur (?spelling?) Effect measurements of time have been used to verify time dilation effects due to relativistic motion and gravitation effects, providing extremely strong evidence favoring Special & General Relativity.

All the answer above are EXcellent! I just want to correct one teensy misgiving in Pete's answer where he said "...during the acceleration periods, Jill's perspective of the current time in different places across the Universe changes dramatically, due to gravitational time dilation". I just want to clarify that the phrase "time dilation" refers to the apparent SLOWING of others' clocks; but when dealing with acceleration, or gravity, there'll be relative slowing of clocks in one direction and relative hastening of clocks in the opposite direction.

Thanks, Dinosaur, I have read the M/M experiment many times in the past. They failed
to detect the either they were seeking to confirm, true. A question. How fast does
lightning travel through our atmosphere? How fast does EM radiation travel through
our atmosphere? Is it possible that our atmosphere acts like a conductor for EM waves
as well? No matter how fast, or slow, light is traveling when it enters our atmosphere,
it travels at the same speed within it, just as it travels at a different speed in other
mediums, such as water. The timed measurement of light's velocity when it is reflected
off a 'mirror' on the moon? The light was emitted from Earth and measured on Earth,
giving the correct velocity, but there was no relative velocity to suggest any speed
other than the speed it was emitted. One way to verify that the speed of light is
constant in all reference frames would be to conduct an experiment in the vaccum
of space where light was emitted from a transmitter traveling at a high relative velocity
from the receiver, also in space, measuring the speed of light. But how do you measure
the one-way velocity of light? All that would be shown is that the light would redshift.
That is why I chose to focus on postulate number two. My question concerning Jill's
on-board clock, and her rate of aging, during the acceleration phase was not answered. Of course, everyone knows that according to GR, her clock will run fast
during that phase, the more the acceleration, the faster the clock runs when compared
to a stationary clock in Earth's frame of reference. SR states she will age slower in the
inertial frame of her trip, GR states she will age faster during the accelerating phase.
Wonder why the Hefele & Keating experiment failed to show SR's time dilation? If Jill
had left a twin on Earth, would there be much difference in their ages after all time
dilations were taken into account? Is Newton wrong after all? That is what I fail to see.

... Would no time pass for a traveler that accelerated for half of a trip and decelerated the other half ..? .. how much ..?
Time will seem to pass normally for all observers in their native frame, regardless of their circumstances... it is only other's clocks that get distorted, relatively. I won't mess with the actual math, but time IS ticking away for Jill during her deceleration approaching the space station -- it's just that Earth's clock is ticking relatively faster.

.. My question concerning Jill's on-board clock, and her rate of aging, during the acceleration phase was not answered. Of course, everyone knows that according to GR, her clock will run fast during that phase, the more the acceleration, the faster the clock runs when compared to a stationary clock in Earth's frame of reference..
Everyone knows it?? I don't know it! My understanding is that from the perspective of a non-accelerating observatory, ie. Earth, only SR time slowing can be attributed to Jill's accelerating craft, based on her speed. But from Jill's perspective, while she accelerates, she sees Earth's clocks (1) slowed by SR time dilation as well as (2) slowed or hastened based on the gravitational potential gradient inferred from the G-forces of acceleration.

One must choose one's words ever-so delicately when discussing Relativity. it is not sufficient to just say one clock is slow compared to another... one has to identify which clock belongs to the observer, and then remark as to how the other guy's clock rate is reckoned by that observer.

Thanks, Janus58. Now, during this acceleration phase when she sees the Earth's clock
jump forward 327.8 days, are you saying NO time passes for Jill or her clock in her
reference frame?
No, The only way NO time would pass for her is if she were able to instantaneously accelerate from .95c to 0 and back to .95c. When I said that the time "jumps", I was taking you at your word that her ship would accelerate "very quicky" up to .95c.(That the time duration that Jill measures during accleration was so short that we could ignore it and still get a fairly accurate answer.)

That time only passes for her during the less than 4 months of
inertial travel? Would no time pass for a traveler that accelerated for half of a trip
and decellerated (same as acceleration) the other half, regardless of the rate of acceleration or length of the trip measured by an Earth-based observer? If not, how
much time passes on Jill's clock during the 327.8 days?

The amount of time that passes for Jill while accelerating depends on the rate of acceleration. If she accelerates slowly, she will take longer to reach .95c according to both her clock and the Earth clock. She will also travel a longer percentage of the distance between the Earth and the buoy while accelerating. This in turn, shortens the percentage of the trip that she spends traveling at .95c (As well as increasing the total length of time that she experiences during the trip.)

That 327.8 day figure only works when you assume that Jill accelerates up to .95c "very quickly". If she accelerates more slowly then she will see a different amount of time pass on Earth. The thing is that Jill will always measure the same total amount of time as passing on Earth as the Earth measures, no matter what mixture of accelerating/coasting she uses during the trip (even though she will measure a shorter total amount of time as passing for herself.)

All the answer above are EXcellent! I just want to correct one teensy misgiving in Pete's answer where he said "...during the acceleration periods, Jill's perspective of the current time in different places across the Universe changes dramatically, due to gravitational time dilation". I just want to clarify that the phrase "time dilation" refers to the apparent SLOWING of others' clocks; but when dealing with acceleration, or gravity, there'll be relative slowing of clocks in one direction and relative hastening of clocks in the opposite direction.

I guess that makes us even :)

Thanks, fellows. I do understand where I was making my mistake now. But I still think
I see something left out of most of these type discussions concerning the twin paradox. It would only affect the accuracy of the Lorentz factor slightly, though.
While in the inertial phase of the trip, SR states that Jill's clock is running slow in
accordance with the Lorentz factor. But I usually (never?) see General Relativity's
prediction that her clock is running fast while in the inertial phase (no acceleration, no
gravity, so her clock runs faster than Earth's clock in Earth's gravity well). Would this
not offset at least part of the time dilation due to relative velocity?

General relativity includes special relativity.

So, Jill could calculate her velocity relative to Earth while in a inertial frame, correct?
In her inertial frame, she would see 72 hours tick off on her on-board clock while the
Earth completed one rotation. But when she starts accelerating, the Earth would spin
like a top! Same thing when she slows down (decellerates), Earth's apparent rotational
speed will change from seemingly too slow in her inertial frame to much too fast in her
non-inertial frame. Correct?

... when she starts accelerating, the Earth would spin like a top! Same thing when she slows down (decelerates), Earth's apparent rotational speed will change from seemingly too slow in her inertial frame to much too fast in her non-inertial frame. Correct?
No... during Jill's initial acceleration phase away from Earth, she would perceive Earth's clock (or likewise its rotational speed) slowed -- a slowing that is in addition to any slowing attributable to relative motion. That's because, as I've stated, when gauged from an accelerating frame, distant clock rates are slowed in one direction but hastened in the opposite direction. Later, when she decelerates to dock with the remote space station, then the gradient slopes in the opposite direction and Earth's rotation (and likewise its clocks) would be seen to hasten -- a hastening that is compounded upon the slowing that derives from relative speed.

[Of course, the aforementioned slowing/hastening distortions -- the ones derived from acceleration that is -- are proportional to how far away the other frame's clock is located. So the slowing attributed to Earth's clock, as Jill accelerates away, is a much smaller distortion than the hastening attributed to Earth's clock as she decelerates approaching the distant space station.]

Before we get any further, let's be crystal clear about one thing: Jill might as well be going from one space outpost to another, because this discussion has nothing whatsoever to do with Earth's "gravitational well" and its effects on clocks. When we talk about, for example, a "gravitational potential gradient" (my phrasing a few posts back), we are referring to the well-known equivalence of gravity and acceleration. You don't even have to invoke GR to deal with acceleration in flat (unencumbered) space, as the formulae are (I'm mighty certain) derived as a straightforward integration of the basic Lorentz transform.

So here's a summary. When you are in an accelerating spacecraft, you naturally feel a pull, a tug, in one and only one direction. When you feel (and measure) that tug, you know that distant clock rates must be reckoned as being slower (than your own) in the direction of that tug yet faster off in the opposite direction -- just as it is with material gravitational wells, ie. slower clock rates are found toward the direction of tug, and faster rates the opposite way. Such distortions are in addition to the relativistic time dilation (slowing) based simply on relative speed. I think that sums it up.

by dristam:
"Before we get any further, let's be crystal clear about one thing: Jill might as well be going from one space outpost to another, because this discussion has nothing whatsoever to do with Earth's "gravitational well" and its effects on clocks. "
================================================== ===========

I am a bit lost here. My reference above: "But I usually (never?) see General Relativity's
prediction that her clock is running fast while in the inertial phase (no acceleration, no
gravity, so her clock runs faster than Earth's clock in Earth's gravity well). Would this
not offset at least part of the time dilation due to relative velocity?" My understanding is that clocks run slower closer to the surface of the Earth due to Earth's 'gravity well',
the same as any clock, the more intense the gravity, the slower the clock runs, a
prediction of General Relativity. During Jill's inertial phase (no gravity, no acceleration)
shouldn't Jill's clock run faster than Earth's clock which IS experiencing gravity? I am
speaking only of GR's gravitational effects. I realize SR's predicted slowing of Jill's clock
due to relative velocity will have the greatest impact, but shouldn't GR's gravitational
effects offset the numbers slightly (Lorentz transforms)? Lorentz wasn't aware of GR's
effects when he developed the Lorentz transformations, was he?

... but shouldn't GR's gravitational effects offset the numbers slightly (Lorentz transforms)? Lorentz wasn't aware of GR's effects when he developed the Lorentz transformations, was he?
Touchay! I suppose you're right, but the qualifier "slightly" is an immense understatement. The distortions added by Earth's gravity to the entire scenario which you outlined in post #1 is ULTRA-infinitessimal, and would be considered orders of magnitude into the realm of the negligible.

And no, I'm fairly certain that Lorentz didn't know it... BUT, from his own formulae can be derived the distortions attributable during acceleration (in flat space), which is the experiencing of a G-force and which is an analogous phenomenon. I'd just love to be corrected if I err.

Yes, I suppose you're correct. The gravitational effects would only become a factor
it the 'other' clock were located near the event horizon of a black hole or other high
gravity source. Thanks.

To begin with, I do not claim to have a complete understanding of The Special
Theory of Relativity. I do believe I understand the basics involved, though, if
only on a philosophical level. I do know SR's mathematics follow from its two
basic postulates, if they are true, SR is true. They are:
(1) The speed of light 'c' is a universal constant, the same in any inertial frame. An inertial frame is one in which unaccelerated objects move in straight
lines at constant velocity.

Excuse me 2inquisitive for bursting in so late in the discussion, but a quote I have used published in the Handbook of Astronautical Engineering Vol 1 chapter 11, describes your statement (which isn't necessarily incorrect) that

"It is impossible to detect or measure unaccelerated translatory motion of a system through free space."

I take this to mean that using radar for instance the relative velocity of inertial reference frames can be measured easily, but not the absolute velocityi.e which is moving in what directionand at what actual velocity, so if two frames are approaching each other at some 6000 units for instance neither can use experimental methods to determone the "actual" motion" say that measured with respect to the embankment or home planet, I call Ve.

It seems to me that your question, while pertinent to SR theory, may not be pertinent to the laws of physics.

For instance, say the two frames Vn and Vm both detect a "closing" condition which may mean that they are actually approaching each other or that one is moving faster than the other and is catching up.

Say the Vn frame launches a remote piloted vehicle "dubbed the Aquila) a velocity probe, Pn, with all the radar capability of the Vn frame, plus acceleration ability. Pn starts accelerating in the rearward direction of Vn and maintains a carfeul relative velocity record of Pn and Vn and also measures Pn - Vm with the on coming frame, only during periods of uniform velocity, which seems to be actually approcahing because Pn by successive accelerations and coasting at a uniform velocity in between acelerations finally reaches a velocity such that Pn - Vm = 0 and that Pn - Vn is 4000 as measured by Pn during the exercise. This is the new value Vm would measure by itself had Vm accelerated and coasted etc. Pn, Vn and Vm all know, or knew, the relative velocity of 6000 units, but now we see that Vm is actually approaching at 4000 unuits, hence, Vn - Vm = Vn - (-4000) and therefore Vn + 4000 = 6000 and Vn = 2000.

Of course both Vn and Vm could have an underlying motion of whatever, similar to the motion that all Vn have with respect to the embankment, Ve, before the frames accelerate but it is unlikely. Notice that all Vn, Vm etc,only, always accelerate to create a relative > 0 in the first instance and that Ve never accelerates, therefore all Vn are akways > Ve having inherited the underliying orbital motion attributed to the Ve frame of reference, which for all intents and purposes is moving in a straight line at uniform, constant velocty, at least as far as any measurements significant to the Ve and Vn relative velocity is concerned. The Vn and Vm are, from the get go, absolte velocities.

In any event the absolute velocity difference was measured and detected which catagorically contradicts the 1st postulate of SR. Notice that no measurements were taken during any accelerations and that the measurments were taken in free space.

Again, I apolgize for jumping in like this and do hope I have offered something for serious consideration.

geistkiesel

by geistkiesel:
"
Excuse me 2inquisitive for bursting in so late in the discussion, but a quote I have used published in the Handbook of Astronautical Engineering Vol 1 chapter 11, describes your statement (which isn't necessarily incorrect) that

"It is impossible to detect or measure unaccelerated translatory motion of a system through free space."
================================================== ============
by me:
???? I never made such a statement or anything close to it. Did you read any of the
posts?
================================================== ============
by geistkiesel:
"It seems to me that your question, while pertinent to SR theory, may not be pertinent to the laws of physics."

================================================== ==========

me again:
Which question are you referring to? I had many and the excerpt of mine you quoted had no question. geistkiesel, you are welcome to 'jump in' anytime you want, but I
say to you... DO NOT attribute statements to me that I never said just to advance
your own agenda. That said, of course you are welcome to contribute.

To begin with, I do not claim to have a complete understanding of The Special
Theory of Relativity. I do believe I understand the basics involved, though, if
only on a philosophical level. I do know SR's mathematics follow from its two
basic postulates, if they are true, SR is true. They are:
(1) The speed of light 'c' is a universal constant, the same in any inertial frame. An inertial frame is one in which unaccelerated objects move in straight
lines at constant velocity.
(2) The laws of physics are the same in any inertial frame, regardless of position or velocity.

2inquisitive I thought I had copied the (1) statement above and it was to this that I was referring.

As to the question I referred to was:


Can someone clear up
my confusion, USING JILL'S FRAME OF REFERENCE?

2inquisitive complained about geistkiesel's misquoting and about 2inquisitive's un identified "question".

me again:
Which question are you referring to? I had many and the excerpt of mine you quoted had no question. geistkiesel, you are welcome to 'jump in' anytime you want, but I
say to you... DO NOT attribute statements to me that I never said just to advance
your own agenda. That said, of course you are welcome to contribute.

As I was referring to the last line, ambiguously perhaps,(ok it was anmbiguous) the totality of your post was intended to be put into issue. My reply described a simple method where the absolute velocityy of two inertial frames can easily be determined by observers on the frames.
I reply as follows:

Quoting geistkiesel in reply to 2inquisitive:

"Excuse me 2inquisitive for bursting in so late in the discussion, but a quote I have used published in the Handbook of Astronautical Engineering Vol 1 chapter 11, describes your statement (which isn't necessarily incorrect) that

"It is impossible to detect or measure unaccelerated translatory motion of a system through free space."

I take this to mean that using radar for instance the relative velocity of inertial reference frames can be measured easily, but not the absolute velocityi.e which is moving in what directionand at what actual velocity, so if two frames are approaching each other at some 6000 units for instance neither can use experimental methods to determine the "actual" motion" say that measured with respect to the embankment or home planet, I call Ve."

As I hope you can see I was attempting to link my statement regarding the impossibility of measuring motion, other than relative motion. I said the handbook quote "describes your statement" I made no assertion that you made the 'impossiile' statement, I said, and I repeat the handbook statement describes your statement, which is how I see it.

Regarding 'the question': I was referring to was the last line of your post, though it couls equally apply to all the questions you made, expressly or implicitly.

If the speed of light is measured as the known constant C, then there is no such thing as relative velocity for frame and photon, other than Vc - Vn =C, always which means that there is no motion of Vn to measure because it is always zero, by theoretical distate, AKA axiom. It is impossible to detect motion of a frame as you described, or so says the SR postulate.

Likewise, there is no relative velocity for the observers on the frame, or no such real and accurate statement that the "Vc photon is going by us faster than we are travelling of degree, Vc - Vn.", which to me does not alter the constant nature of the speed of light in the slightest - it describes how faster Vc is than Vn.

The rest of my post, which I fear you may have summarily discarded for reasons of my stumbling inaccuracy, as you saw it. I intended to show, which I claim I did show, that indeed the abso;ute motion can be detected, in a direct and unambiguous way, albeit theoretically denied. So , this is my agenda, I admit it now, and for every oher post on the subject matter in the past.

Further, that by discarding the measurement of any relative velocity of frame amd photon being other than equal to zero, forever, means that the creators of SR projected that, no way, could any experimetnal arrangement constructed that would contradict the postulate, and demanded hat Vn be set to zero when making the measurement. This seems hypocritical, as well as being unnecessary as any experimental data can be viewed on its own terms. Instead, we are told to save our research money, "we already know the answer" and of course the logical implications of the theory.

Your statement as quoted, without any reference to "relative velocity", is 100% accurate, but is misused and abused. For the same reason that the charge on an electron cannot be mathematically manipulated and is a universal constant, as the charge can be effectively smothered in the vicinity of a dozen positive charges, This does not mean that the failure to detect the elctron's charge meanst that the charge went to zero, or was diminished, it means the charge was not detected, period.

If the speed of light is constant and I assume it is, then that velocity should always be the measured velocity, differentiating between "relative motion". and the absolute motion, of course.

Finally, ask yourself a queston following this:

Observers on Ve, the earth platform, measures the speed of light as C with respect to Ve, or 1.) Vc - Ve = C.
The the same observer measures the velocity of Vn, with respct to Ve, or 2.) Vn - Vc = Vn.

Subtracting 1.) from 2.) we see, C > Vc - Vn > 0 , which only demonstrates the relative velocity of frame and photon, both measured with respect to a common frame, to wit, Ve.

If the observer on Vn sees the photon going past he kniows from the get go that the photon is moving with velocty C with respect to Ve, the same reference frame that effectively defined the Vn motion which is always, and unambiguously, Vn > Ve. Ve is never observed to vary its motion in the slightest.

It is physically impossible, when Vn - Ve > 0, relative motion is observed, from whatever fame of reference, for Vn to be other than > Ve as it is Vn that accelerated, only. Ve is moving with ubniform motion in a straight line, as you inferred, but did not express it directly.

The observation of the photon going past Vn is a measurement. The frame velocty Vn, with respect to Ve, was also measured and known to a high degree of accuracy.

Like I asked above: Any questions?

geistkiesel

by geistkiesel:
"It is impossible to detect or measure unaccelerated translatory motion of a system through free space."
================================================== =============

That is YOUR statement, not mine. Your statement would only be true if you were enclosed in a container in free space with no windows or instruments. I said IF SR's
TIME DILATION IS A FACT, your motion and relative velocity to Earth could be
calculated by watching Earth's rotation and your on-board clock, providing that
relative velocity were relativistic (a significant percent of c). If your relative velocity
to Earth was not relativistic OR if SR's time dilation is a fantasy, the Earth would
make one rotation in 24 hours by your on-board clock. Absolute motion you say?
There can be only relative motion, the motion between two or more objects, each
having its own reference frame. SR uses the supposed constancy of the speed of
light as an absolute reference frame. No matter how high your relative velocity is in
relation Earth or any other object, you are stationary in relation to light, your relative
velocity in regards to light is 299,792,458 meters per second in a vacuum. Or, if we
can't tell which has movement, we could say we are moving at 299,792,458 m/s and
light is stationary.

by geistkiesel:
"It is impossible to detect or measure unaccelerated translatory motion of a system through free space."
================================================== =============

That is YOUR statement, not mine. Your statement would only be true if you were enclosed in a container in free space with no windows or instruments.
Actually is not my quote it was a staement describing the fundamental postulate of SR (Vol 1 Handbook of Astronautical Engineering [with forward by Werner von Braun] , which I said then and repeat here is equivalent to what you stated was your understanding of one of the two basic postulates of SR. I did not say you believed my version, or even your own, I just said the versions were equivalent.

I said IF SR's
TIME DILATION IS A FACT, your motion and relative velocity to Earth could be
calculated by watching Earth's rotation and your on-board clock, providing that
relative velocity were relativistic (a significant percent of c). If your relative velocity
to Earth was not relativistic OR if SR's time dilation is a fantasy, the Earth would
make one rotation in 24 hours by your on-board clock. Absolute motion you say?
There can be only relative motion, the motion between two or more objects, each
having its own reference frame.

A frame in space merely turns on his absolute velocity speedometer, which is noting moire than a series of phiotons emitted wrt to the suspected motion, i.e. in three directions. as the photons are i nvariant in the drift moption of their transverse components (one can mostly alazys see a beam of light whole standing to one side through some side lobe radiation process).

Yes, absolute motion, with respect to absolute zero velocity = zero. When you shine a light into free space, we'll remove the clutter, what is each photon doing? Assuming the valoiditity of the independence of the motion of light with respect to the source of the light, a photon once emitted draws an invariant and perfect line through space that is moving at velocity = zero. A continuous pulse of photons movng perpendicular to the motion of a vehicle define a velocity = 0 frame, a coordinate axis. Therefore a photon released in the front of a ship will appear to move to the rear of the ship assuming forward motion, but it is the ship that is moving absolutely with respect, perpendicular, to the photon line. An enclosed speedometer can be constructed by making a three double layered planar array sof these photons all directed to an emmitter/absorber on the opposing face of the array. At zero velocity the emitted photons will strike the photon absorber located directly opposite, if the there is motion perpendicular to the direction of the photons the photon will be absorbed by an emmitter/absiorber to one side of the source of the emitted photon that is moving in line that is staionary in space.

SR uses the supposed constancy of the speed of
light as an absolute reference frame. No matter how high your relative velocity is in
relation Earth or any other object, you are stationary in relation to light, your relative
velocity in regards to light is 299,792,458 meters per second in a vacuum. Or, if we
can't tell which has movement, we could say we are moving at 299,792,458 m/s and
light is stationary.

I half agree with you [but as an aside, the statement you just made sounds like some serious ly uttered ninsense.]. I understand the matter to be that when performing the mathmatics of all of this that at some piont the obsever sets his frame to zero, being justified by the equivalance of inertial frames doctrine. The half I believe of your understanding is that they The SR theorists) must still make some mathematical manipulation to have the numbers crunch out properly in order thagt their theory comes out correctly.. Also. the assumption that light will always be mesured as C is true enough, but that the relative velocity of frame and photon is always = 0 is ludicrous. Say you measure the speed of light with resapect to the embankment, Ve, planet earth and you measure C. Then you measure the relative velocity of an inertial frame Vn > 0, also with respect to Ve, which you publish the results to the space ship navigator just before launch. You merely show how fast light travels wrt Ve, and hiow fast the Vn frame was travelling the realtive velocity of frame and photon wrt to a common frame is C - Vn < C but this does not mean a velocity of light was meaasured < C only that the speed of light with respect to a common frame is simply Vc - Vn.

No one has to measure the speed of light anymore. Just look out the window and subtract the space ship velocity with respect to Ve.

Lastly I understand that no phyiscal experiment can be devised to measure motion in field free space, relative motion yes, but that is th 3elomit or swo they say. I undertand that one needn't b;lind the navigator first, he can look out as many windows as they want, but they still cannot tell who is moving "really".

by Dinosaur:

"2Inquisitive: After making very accurate measurements of the speed of light in about 1883, Michaelson and Morley designed and performed the now famous Michaelson/Morley experiment in about 1888. The experiment has been performed many times since then with more sensitive equipment, and perhaps with a differently designed apparatus. The M/M experiment measured the speed of light relative to a moving frame of reference, namely the earth."
================================================== ===========

Dinosaur, are you familiar with the M/M experiment? If so, how can you conclude "the
experiment measured the speed of light relative to a moving frame of reference, namely
the Earth?" M/M set up a coherent light source a few meters from their interferometer,
and checked for differences in interference patterns from parallel to Earth's movement through space and perpendicular to Earth's travel.They were looking for an aether wind blowing
from the direction of Earth's travel through space. Of course, no such wind exists. But there was NO RELATIVE VELOCITY to
measure between their light emitting source and their measuring instrument, so how
could the experiment possibly prove the invarance of the speed of light in all inertial
reference frames? It only shows that the Earth is not moving through a 'stationary'
aether, nothing to do with moving frames of reference. The light source and the testing instrument were stationary with respect to each other.

2Inquisitive: You are correct in stating that the later M/M experiments did not actually measure the speed of light as did the earlier ones. Actually, I am more familiar with the M/M experiment than my post would suggest. I was aware that it showed that light traveling along two orthogonal routes traveled the same distance in the same amount of time, without actually measuring the speed.

It is my understanding that interference effects were used to measure a speed difference over two paths because this allowed more precise results than those attainable via subtraction of pairs of speed measurements. It is also my understanding that the M/M experiments implied that the speed of light would be measured to be the same no matter how the measuring apparatus was oriented relative to the direction of the Earth’s motion.

It is also my understanding that the M/M experiment indicated that the motion of the Earth had no effect on measurements of the speed of light. I believe that this experiment caused Einstein to assume the speed of light as a constant independent of the motion of the observer, although he made a more general assumption than the constancy of the speed of light: His axiom is that the laws of physics are the same for observers in all inertial reference frames. This axiom leads to the conclusion that the speed of light is constant in all reference frames. Note that Maxwell’s equations lead to the same conclusion.

BTW: I think that there have been modern experiments showing that the speed of the light source does not affect the measured speed of light. One such experiment measures the speed of the light emitted by particles moving at relativistic speeds.

I do not know how to answer all that is implied by your post, but will make comments in bold relating to your post. . . . there was NO RELATIVE VELOCITY to measure between their light emitting source and their measuring instrument, so how could the experiment possibly prove the invarance of the speed of light in all inertial reference frames? I do not know enough about SR to explain how it could show such invariance. It is my belief that Einstein and others interpreted the M/M experiment as evidence of such invariance, although (as mentioned above) SR derives the invariance from the assumption that the laws of physics are the same for all observers in all inertial reference frames.

It only shows that the Earth is not moving through a 'stationary' aether, nothing to do with moving frames of reference. It is my understanding that stationary with respect to the aether implied absolutely stationary, according to the classical physics of the late 19th century, unless one assumed that the Earth dragged the Aether along with it. There were good reasons to not assume such a dragging effect, which would be noticeable due to effects on light from distant stars. The absolutely stationary interpretation does not seem to be acceptable to anybody.

The light source and the testing instrument were stationary with respect to each other. This is true, but the light being measured was moving with respect to the Earth as it traveled from the source to the measuring instruments. That is, it was moving relative to an inertial frame, namely the Earth.I always wondered about Einstein’s axiom claiming the equivalence of the laws of physics over all inertial reference frames. Was he thinking of some specific phenomena other than light propagation? Did he feel that the constancy of the speed of light implied the axiom for then unknown phenomena? I have always believed that the M/M experiment was the basis for his axiom.

2Inquisitive: You posted the following. . . . One way to verify that the speed of light is constant in all reference frames would be to conduct an experiment in the vaccum of space where light was emitted from a transmitter traveling at a high relative velocity from the receiver, . . . An experiment similar to your suggestion has been done. There are particles which move at relativistic speeds and emit photons. The speed of such photons has been measured. As predicted by believers in SR, the speed measured was about 186,000 miles (about 300,000 km) per second.

The above was not done in outer space, but seems to confirm SR.

2Inquisitive: You posted the following.An experiment similar to your suggestion has been done. There are particles which move at relativistic speeds and emit photons. The speed of such photons has been measured. As predicted by believers in SR, the speed measured was about 186,000 miles (about 300,000 km) per second.

The above was not done in outer space, but seems to confirm SR.

Thanks, Dinosaur. I am not trying to be argumentative with you personally,
so I hope you do not take it that way. I know you are just repeating current
physics dogma that is currently passed around. I see it all the time, regarding
experiments that 'prove' relativity. M/M is one that is often cited to 'prove'
the speed of light invariant in all reference frames. It did not even measure the speed of light, they were looking at interference patterns. A cut & paste:
"A Michelson interferometer
The actual Michelson-Morley experiment used more mirrors than is shown, the light being reflected back and forth several times before recombination. It was performed in the basement of a stone building close to sea level"
http://www.wordiq.com/definition/Michelson-Morley_experiment

I just like to closely read the experiments I often see cited to see what they actually show. The ones I have read 'proving' Special Relativity are ambiguous
to me. Do you happen to remember what the experiment was that measured
the speed of photons emitted from a relativistic particle, or who performed it?
Do you know what kind of instrument was used to measure a photon's speed?
I do know in particle accelerators, they don't measure the speed of massive
particles, let alone photons. They measure the kinetic energy. Some physicists, usually not the ones doing the experiments at the accelerators,
then use the kinetic energy figures to calculate the speed of the particles
using relativistic equations.

Another point about the speed of light I have realized in the past. Light propagates
through any medium at a particular speed. For instance, shine a beam of light through
an aquarium filled with water. The light enters the aquarium travelling at about 272,538,598 meters per second, the speed of light in air. It travels through the water
at about 225,000,000 m/s, the speed of light in water. When the beam exits the
other side of the aquarium, it speeds up to 272,538,598 m/s again. Earth's atmosphere
is a medium, whatever speed light is traveling when it enters our atmosphere from
space, it will always travel at the same speed within our atmosphere. Place a huge
aquarium in orbit to slow light down, and we will still record the same speed of light
on the Earth's surface. Now, is that speed within our atmosphere invarant to all reference frames? No matter how fast you are moving in relative velocity to the
source, will the speed of light always be invariant? Cherenkov radiation, emitted by
particles moving at faster than light speeds through our atmosphere or water, would
seem to call that into question. If the speed of light is invariant in a medium, how could
anything, a particle or whatever, exceed the speed of light in that medium? Wouldn't
the particle have to always 'see' the relative velocity of light as 272,538,598 m/s and
never be able to lessen that relative speed, let alone surpass it?

To: 2inquisitive

You seem sincere. I will try to help you get happy with SR, constancy of light speed etc.

With regard to M/M experiment: Perhaps an analogy will help: Consider you are measuring the speed of a boat, with fixed speed motor of course. Assume you have a "start pole" stuck in the dirt below the water and sticking up into the air. Also you have a "turn around Pole" exactly one mile from the start pole, and a stop watch. As the boat passes the start pole, headed straight for the turn arround pole, the stop watch begins to run. It stops when you return to the start pole. The time shown on clock is T1. T2 is measured the same way, but this time the line between the start pole to the turn arround pole is perpendicular to the course used for the T1 measurement. If T1=T2, you are in a pond, if not, you are in a river. M/M found light is in a pond.

Speaking of water and light, I'll address your second concern: Light is massless, particles have mass. Thus light can instantlly change speed, but not particles. Hence when a relativistic charged particle enters water it is going faster than light can go (why this is so later) and because of its charge, it exerts electric forces on the protons and electrons of the water. This force accelerates them (mainly the electrons) and they radiate (light usually - typically a soft blue). The light is always being generated adjacent to the particle and expanding away from it as fast as it can. The light front is thus a cone trailing behind the particle, exacly like the shock wave in air produced by a ojbect moving thru air too fast for a pressure wave (sound) to travel in air.

Now a few, slightly inaccurate, words as to why light moves more slowly in water etc.:
Light is an electromagnetic wave (except on Monday, Wen. and Friday when it is a massless particle, but that another story.). Thus it also exerts a force on the charges of the water and once again this causes them to radiate; howver this time the oscillate at the frequency of the light stimulating them (but not in phase with it - and that is the mportant point). Effectively you have two sign waves of the same frequency - the original one plus the localy radiated one. If you do the math to add two sign waves of same frequency, but different phases, you will find that the sum is a also a sign wave, of the same frequency but with phase not equal to either of the two waves. That is as light goes thru the water is becomes a new wave. Here it gets more complex than I want to go into. (we must distinguish between the group and phase velocities) but I think you can now understand that the rate that this constantly generated new wave make it thru the water could be slower than if it were not constantly exciting the electrons of the water. Note that if the electrons do not bang into anything while they are radiating, the original wave does not lose energy.

Hope this helped. Sorry, but old professors do get a little long winded. You seem to be at the stage of your progress in science where you would benefit from my disguised physics book. Visit: Dark Visitor.com if you like the way I teach. It is a scary story (Ice age returns in 2008 and all the physics in it is correct, but not conventionally taught.) What ever you do, keep that questioning, inquisitive viewpoint.

Excuse me .. if two frames are approaching each other at some 6000 units for instance neither can use experimental methods to determine the "actual" motion say that measured with respect to the embankment or home planet, I call Ve.
Any entity can accurately measure its velocity relative to Ve at any time. That's not the same as "actual" or "absolute through space" velocity.
.. Pn .. finally reaches a velocity such that Pn - Vm = 0 and that Pn - Vn is 4000 as measured by Pn during the exercise.
If Vn and Vm measure 6000 with respect to one another and Pn-Vm=0, then Pn is comoving with Vm and will likewise measure 6000 with respect to Vn... NOT 4000! Where did that come from??
Of course both Vn and Vm could have an underlying motion of whatever .. but it is unlikely. That's a real gem.
.. which catagorically contradicts the 1st postulate of SR.
No it doesn't.

.. the phrase "time dilation" refers to the apparent SLOWING of others' clocks; but when dealing with acceleration, or gravity, there'll be relative slowing of clocks in one direction and relative hastening of clocks in the opposite direction.
I was right in substance but wrong in terminology. It was dandy of Pete after all because on other authoritative sites, such as Usenet Physics FAQ, the term "gravitational time dilation" is employed to denote the phenomenon. I balk at that though, for the reasons stated; it should be termed to connote a two-way gamut. 'Maybe "gravitational time flow pitch (or slant)"... or "grav'l temporal pitch" -- uh, or something.

Thanks, Billy T, I do appreciate your response. You said M/M found light is in a pond.
I agree with you 100%. My further interpretation is that the pond is Earth's atmosphere. I see no evidence of an 'aether' on Earth's surface, unless one chooses
to call Earth's atmosphere an aether. But, the question is, is light invariant in all frames
of reference in this 'pond.' M/M was done in a basement using a stationary coherent
light source a few meters away from their interferometer. I have always maintained that light travels from it's source (emitted) at a constant velocity for whatever medium
it is in. Light's speed will change (refraction) when it enters a different medium, and
back again when it exits the second medium and reenters the first medium. Earth's velocity through space would have no effect on this. The source and the receiver were
both moving at the same velocity, no relative velocity was present to either confirm
or disprove invariance. You do see where I am comming from, don't you? Not being a
trained physicists, I may think a little differently than them, hehe. I am not insinuating
'I am right and they are wrong', just that I may follow a different line of reasoning. These are the type of things that I would like to clear up. I will certainly admit I am
wrong when I am shown a REASON I am wrong, which I am sure would be often.
I have more comments, if anyone is interested (I have been told my 'philosophical'
questions were useless if I couldn't do the math). I just view sciforums as a discussion
forum and thought some questions may help others' understanding, as well as my own.
I have to be out of town for a few hours, but will be back. I hear the moans.

2Inquisitive: I consider myself more knowledgeable than many who post here, but not close to being an expert. I do not consider myself as knowledgeable in SR/GR as James R and various others who also post here. I was able to cope with the mathematics when I took an introductory course in SR many years ago, but the implications seemed counter to my intuition. At the time I took the course I was convinced that the SR conclusions were valid, but do not consider that observation to be a convincing argument for others.

Since then, I usually have not been sufficiently motivated to concentrate long enough to properly analyze arguments relating to SR. As an undergraduate, passing the course was an important motivation. On the rare occasions when I was willing to concentrate on a discussion, I have either sided with SR or been confused and unable to reach a conclusion.

Now, my opinions are primarily based on respect for the scientific establishment. SR has been accepted by them for about 100 years. If some simple thought experiment involving twin journeys or multiple clock scenarios could uncover a serious problem with SR, I would expect that some mainstream genius would have discovered or endorsed the argument and published it in a major journal.

Mainstream physicists are neither charlatans nor fools. For well over 200 years the better theories have rarely (have they ever?) found serious errors in the theories being replaced. The older theory has generally been found to be inapplicable to experiments/conditions not known at the time of the older theory or else beyond the capabilities of the technology available to the older theory. Newtonian gravitation equations are still used by NASA.

Check article at the following URL. It discusses Cerenkov radiation caused when a particle or quantum entity travels faster in a medium than light can travel in that medium. http://www2.slac.stanford.edu/vvc/theory/trackhadrons.html
It is the speed of light in a vacuum which cannot be exceeded.

Check the article at the following URL.
http://galileoandeinstein.physics.virginia.edu/lectures/michelson.html

The following can be found there if you read far enough into the article.It is now possible to produce particles, called neutral pions, which decay each one in a little explosion, emitting a flash of light. It is also possible to have these pions moving forward at 185,000 miles per second when they self destruct, and to catch the light emitted in the forward direction, and clock its speed. It is found that, despite the expected boost from being emitted by a very fast source, the light from the little explosions is going forward at the usual speed of 186,300 miles per second. In the last century, the emitter theory was rejected because it was thought the appearance of certain astronomical phenomena, such as double stars, where two stars rotate around each other, would be affected. Those arguments have since been criticized, but the pion test is unambiguous. The definitive experiment was carried out by Alvager et al., Physics Letters 12, 260 (1964).Those two sites should provide clues to other perinent sites.

As for the M/M experiment, my intuition does not make it obvious to me that it proves the constancy of the speed of light in all inertial reference frames, but smarter people than I seem to believe it is equivalent to such an experiment. Note that an experiment which actually measured the speed of light over the two routes would result in the same conclusions, whatever those conclusions might be. I am convinced that the M/M experiment as performed showed that classical speed calculations were not applicable to the motion of light.

Whatever one might think is implied/proven by the M/M experiment, all sorts of evidence seems to support various SR concepts derived from Einstein’s interpretation of that experiment. In modern times experiments have verified that the counterintuitive results obtained via use of Lorentz Transformation calculations are valid. Objects moving at relativistic speeds act as though time and distance variables are different for them than for the stationary observer. All the arguments involving the twin paradox and other clock experiments are basically an argument relating to the validity of the Lorentz Transformation calculations.

Either the Lorentz Transformation calculations are valid or they are not. The experimental evidence supports the Lorentz Transformation calculations. Verbal descriptions of various clock experiments accompanied by different calculations disagree with those calculations, but can be made consistent with intuitive notions. I accept the mathematics and the opinions of experts rather than my intuition.

..You said M/M found light is in a pond... My further interpretation is that the pond is Earth's atmosphere. .. I have more comments, if anyone is interested.
:eek: Yes, I'd like to hear more comments, please.

A Relativity example, out in deep space: Two ships are moving away from one another and a light signal is transmitted. The sender sees the light eventually "catch up" to the other receding craft. But the receiver sees the light travel the FIXED distance equal to how far apart the two crafts were at the moment the signal was launched. In summary, EACH AND EVERY observer sees light behave as if his own vantage is a stock still World unto itself.

Thanks, Dinosaur, the paper by Alvager et al is exactly the kind of experiments I am
interested in reading. I have not read that one before, but the only problem is, I still
haven't read it as I can references to the paper and not the paper itself unless I buy
it. I will keep looking hopeing to find an on-line copy somewhere for FREE, hehe. I
thought the excerpt and the article by Fowler was a little sloppy, though, in reference
to the Alvager experiment. Did Alvager measure the speed of the light from the little
'explosions' to be exactly 186,300 miles per second or was that Fowler's statement?
The reason I ask is that light does not travel at 186,300 miles per second in Earth's
atmosphere and the experiment was carried out in a particle accelerator, not in a
vacuum. But that is really no big deal. Remember I said that I thought light traveled at
a constant velocity in whatever medium it was in? Slowing down when entering water
and then speeding back up upon reentering the air? That light entering Earth's atmosphere would travel at the same rate regardless of whether it was traveling
FASTER or SLOWER than that speed when it entered the medium? I don't advocate
adding velocities in a medium. I DO question whether an observer moving toward that
same light at a high rate of speed would measure it to be invariant in velocity. When I
say adding velocities in a medium, I mean light itself doesn't travel faster just because
it was emitted from a moving source. Light doesn't travel faster than light. Seems to me that was what Alvager proved, which I agree with. His receiver was not moving TOWARD the 'explosion'. My question is, would an observer moving toward
or away from the light itself, not the source I guess you could say, measure a different
velocity for light. I know STR states one would not, and that the particle that emitted the light would see the light move away from it's frame of reference at near 'c'.

edit: I just deleted a subsquent post because I really had my math messed up. Sorry.

Thanks, Dinosaur. I am not trying to be argumentative with you personally,
so I hope you do not take it that way. I know you are just repeating current
physics dogma that is currently passed around. I see it all the time, regarding
experiments that 'prove' relativity. M/M is one that is often cited to 'prove'
the speed of light invariant in all reference frames. It did not even measure the speed of light, they were looking at interference patterns. A cut & paste:
"A Michelson interferometer
The actual Michelson-Morley experiment used more mirrors than is shown, the light being reflected back and forth several times before recombination. It was performed in the basement of a stone building close to sea level"
http://www.wordiq.com/definition/Michelson-Morley_experiment

I just like to closely read the experiments I often see cited to see what they actually show. The ones I have read 'proving' Special Relativity are ambiguous
to me. Do you happen to remember what the experiment was that measured
the speed of photons emitted from a relativistic particle, or who performed it?
Do you know what kind of instrument was used to measure a photon's speed?
I do know in particle accelerators, they don't measure the speed of massive
particles, let alone photons. They measure the kinetic energy. Some physicists, usually not the ones doing the experiments at the accelerators,
then use the kinetic energy figures to calculate the speed of the particles
using relativistic equations.

Actually, if you look very close at the diagram of the MM set up there is glaring flaw, that violates the indenpendence of he motion of light with respect to the motion of the origin of the light.It appears that when setting up the experiment the light moving transverse to the direction of motion was directed to the "triangle trajectory", where most writers refer to this distance being due to the motion of the mirror "dragging the photon along " with the moving frame.

However, if light motion is truly independent of the motion of the source, then the mirror, i.e. the source, cannot drag the photon along. Instead the photon is reflected back along the same trajectory the light took in arriving at the mirror. It appears that in the zeal to get an interference pattern a huge bias was interjected in the experimental arrangement by aiming the photon along the triangular path.which significantly reduced the expected findings.

Therefore, when reflecting back the arrival of this beam at the point to the half silvered mirrors, should look like thios:

\ \ | | <---This is the pattern the interferometer should see:
\ \| | the distance moved during reflections. m \ | |
\ |\ |
-> __ \| |_________<--___________-->| mirror <-- motion =>
|\ \
| \ \
| \ \
|
|
|
_|_ **

This** is the trajectiory if the photon was reflected perpendicular to the downward moving beam and was taking advantage of the independence of the motion of light with respect to the motion of the source of the light,
The Dayton Miller experiments repeated the MM experiments many thousands of times over and verified the MM results, which were not null, or zero. MM and Miller both found a reative motion of 8 km/ sec which was significantly less than the expected observation of some 29.8 km/sec due to the earth orbit around the sun velocity, but the results werfe not null (see (Dayton Miller vol 5 The Reviews of Modern Physics 1933 202-243), I was unable to find the paper referenced but this should do the trick as well; it is a discussion of the results but it is fairly complete.
http://www.orgonelab.org/miller.htm

However this velocity is << than the velocity of the sun through space that was measured at 208 km/sec which pretty much swamped the orbital and rotational velocities. As a look at the trajectory motion, look at the radius of the earth sun orbit = 1,49 X10 ^8 km. The sun moving at 208 km/sec travels 86146*365.26sec*(208 km /sec) = 6.54 x 10^9 km. The angle between the sun/earth orbit and the yearly distance traveled by the sun is tan^-1(1.49 x (10^8))/(6.54 x 10^9) = 1.3 degrees, which shows that the earth's motion is confined to a narrow helical band approximately 2 x1.3 = 2.6 degrees that is 3 x 10 ^8 km in diameter by 6.54 x 10^9 km long.

geistkiesel
11-18-2004
http://www.wordiq.com/definition/Mi...rley_experiment

Geistkiesel
11-18-2004

OK, let me try this again. I will try to keep my example simple so I don't get lost in
my simple mind. To begin with, I am sure the physicists among you are aware of the
way the meter is defined. It is 1/299,792,458ths of the distance light will travel in a second. The relationship of a
meter, a second and the speed of light is defined and cannot change unless the speed
of light changes also. This is important for my example.
I am going to use Newtonian physics for my example of Jill's trip to a spacestation for
a reason, to show the relationships of time, distance and the speed of light IN JILL'S
FRAME OF REFERENCE. The spacestation is one light year away, as measured from Earth before her trip. She quickly accelerates to half the speed of light. Using Newtonian physics, it will take her appox. two years to reach the station by her clock
and by her meter. The same time would be recorded on Earth. But Special Relativity
assumes her clock will run slower and distances will contract. My question. Do BOTH
occur at the same time or EITHER her clock slows OR her meter is contracted? For
the speed of light to be measured at 299,792,458 m/s by her in her reference frame,
both have to occur at the same time. Change only one, and you change the speed of
light in her frame. The problem is as I see it, if her clock slows AND her meter contracts, her clock will still record the same elapse time to reach her destination as
a clock on Earth, two years. No time dilation shown between the two clocks. You
say the distance to the spacestation is contracted in her frame of reference, but her
meter and her clock remain consistant with the speed of light? How does she measure
this decreased distance without changing the laws of physics or the speed of light?
SR theoriests maintain time dilation is a fact, as supported by the muon-in-atmosphere
experiments and experiments in particle accelerators. If time dilation is a fact, then
the speed of light is not constant in all inertial frames of reference, at least the way
I see it. I still believe the Lorentz transformations only give a distorted view of reality
caused by the delay of information recieved by an observer in a rest frame 'looking'
at information from a moving frame at a relative velocity. Can someone set me straight
here? I know I must have made some mistakes.

The problem is as I see it, if her clock slows AND her meter contracts, her clock will still record the same elapse time to reach her destination as
a clock on Earth, two years.

Are you sure about that?

OK, let me try this again. .. The problem is as I see it, if her clock slows AND her meter contracts, her clock will still record the same elapse time to reach her destination as a clock on Earth, two years. No time dilation shown between the two clocks. You say the distance to the spacestation is contracted in her frame of reference, but her meter and her clock remain consistant with the speed of light? How does she measure this decreased distance without changing the laws of physics or the speed of light?..I know I must have made some mistakes.
A person's OWN clocks and rulers N*E*V*E*R distort! Learn that and you're home.

The distance Earth-to-station contracts because that is the alien, the moving frame, from Jill's perspective. She measures the relative velocity the same as Earthlings do. So she's travelling a shorter distance at the same velocity, so 'the journey' takes less time, according to her clock. I put "the journey" in scare quotes because from Jill's perspective she is stock still; it's the Earth-to-station frame that moves... at least that is the relativistic purist way to see it.

You cannot understand the Lorentz Transform phenomenon by thinking only about length contraction and time dilation. Another distortion is time dissynchronicity, which turns out to be a crucial third factor (but not in every imaginable scenario, so it often gets passed over).

A person's OWN clocks and rulers N*E*V*E*R distort! Learn that and you're home.

The distance Earth-to-station contracts because that is the alien, the moving frame, from Jill's perspective. She measures the relative velocity the same as Earthlings do. So she's travelling a shorter distance at the same velocity, so 'the journey' takes less time, according to her clock. I put "the journey" in scare quotes because from Jill's perspective she is stock still; it's the Earth-to-station frame that moves... at least that is the relativistic purist way to see it.

You cannot understand the Lorentz Transform phenomenon by thinking only about length contraction and time dilation. Another distortion is time dissynchronicity, which turns out to be a crucial third factor (but not in every imaginable scenario, so it often gets passed over).

She is traveling a shorter distance at the same velocity, AS MEASURED IN HER
FRAME OF REFERENCE. Her clock is running slow, along with the shorter meter, or the velocity she figures will be different. One meter is defined as
1/299,792,458ths of a second, the second would have to be shorter as well
as the meter shorter to keep the same velocity of light the same.

Are you sure about that?

Her clock will record one second for every 299,792,458 meters she travels.
Do you think a clock on Earth would record a different time? This is assuming
the speed of light at 299,792,458 m/s in either frame. The time itself could
be said to be shorter, but the display of accumilated time would be the same
as Earth's clock and there would be no difference in her rate of ageing according to her clock.

by dristam:
"The distance Earth-to-station contracts because that is the alien, the moving frame, from Jill's perspective. She measures the relative velocity the same as Earthlings do. So she's travelling a shorter distance at the same velocity, so 'the journey' takes less time, according to her clock. I put "the journey" in scare quotes because from Jill's perspective she is stock still; it's the Earth-to-station frame that moves... at least that is the relativistic purist way to see it."
================================================== ==============

OK, we have stablished that the speed of light defines the meter. An invariant speed
of light means the length of her meter cannot change in Jill's reference frame, wrt her
second. She always travels one meter in 1/299,792,458ths of a second. So the distance between the Earth and the spacestation is said to contract in her FOR. That
is how she travels to the spacestation in fewer of her seconds, there are fewer meters
to travel, not shorter meters. And that has to be a reality in her FOR, NOT a distortion
or perception, correct? Distances physically contract to consist of fewer meters along
her line of travel, correct? So, in Jill's FOR, the Earth and the spacestation have to
contract along her direction of travel. The Earth is half as thick as it is wide, a flattened sphere, correct? And this is real, not just her perception, correct? It must be
in order for her to travel the distance in fewer of her seconds, and fewer of her meters
as defined the the speed of light. The Earth's moon would also be contracted, and if
the orbit were viewed edge-on, the orbit would be the same in width, but contracted
in depth, very elliptical, correct? The moon would also orbiting much slower and much
closer to the Earth at the times it lined up with Jill's trajectory. Using the laws of physics, please tell me what keeps the slower and closer orbiting moon from falling to
the Earth. What keeps the whole universe from falling into chaos along Jill's trajectory
of travel. Remember, SR theorists state this frame of reference is as real as the one
from Earth. Otherwise she could not travel the distance in fewer of her meters and seconds. Would the moon orbiting at half the distance at times not cause huge tides?
When Jill returned to Earth, would she find a devastated planet, or would she realize
all the effects caused by contracted distances were a distortion, an illusion caused by
simple time delays in recieving information during her voyage? If the contracted distances were an illusion, then so was the ability to transverse them in fewer of her
seconds, as defined by the speed of light. Comments?

Her clock will record one second for every 299,792,458 meters she travels.
In Jill's frame, she's not travelling. Earth and the station are travelling, at c/2.
So, Jill's clock will record one second for every 149,896,229 meters that the Earth travels, but this is all beside the point.

Do you think a clock on Earth would record a different time? This is assuming the speed of light at 299,792,458 m/s in either frame. The time itself could be said to be shorter, but the display of accumilated time would be the same as Earth's clock and there would be no difference in her rate of ageing according to her clock.

You're drifting from the point I was responding to, which was:
The problem is as I see it, if her clock slows AND her meter contracts, her clock will still record the same elapse time to reach her destination as a clock on Earth, two years.

First, Jill's clock runs slower in Earth's frame.
This means that the time between two events on Jill's ship will be longer in Earth's frame than measured by Jill's clock.
If the two events are:
a) leave Earth, and b) arrive at space-station, then it is clear that time dilation suggests that the elapsed time recorded by Jill is shorter than the two years recorded on Earth.

But is that consistent with length contraction? Let's see...

In Jill's frame, the space-station travelling at c/2 reached her in less than two years.
Therefore in Jill's frame, the space-station must be closer than one light year.

This is consistent with length contraction. Distances measured from a moving frame are shorter.


I *think* that you're confused on the length contraction bit - are you thinking that since Jill's meter contracts, she should actually seem to travel *further*?? It is true that a meter stick in Jill's frame will be measured as less than a meter in Earth's frame... but that's not relevant, since the end-points of the distance we're concerned with are in Earth's frame. So, the relevant meter-stick relationship is how Earth meter-sticks appear in Jill's frame; not vice-versa.

She always travels one meter in 1/299,792,458ths of a second
Since when is Jill travelling at light-speed?

Don't mix your reference frames, Pete. Jill's meter cannot shorten in her reference frame, or the constancy of the speed of light would be violated. Remember, 299,792,458 meters traveled in one second. Doesn't matter if her meter is shorter than the Earth's meter, her second would have to shorten by the same relationship to keep the SOL the same. Same as saying you could travel one mile in 60 seconds or
1/2 mile in 30 seconds, they have to change the same to keep SOL constant for her.
Jill would have to measure FEWER METERS for her clock to record fewer total seconds
than Earth's clock would record. Jill's velocity is measured by her in her FOR, invariant
to 'c', not by Earth's clock.

Since when is Jill travelling at light-speed?

Opps. Sorry, I meant to say Jill always measures light's velocity at 299,792,458 m/s, and her meter cannot shorten without her measurement
of the speed of light changing. In her FOR, it does not matter what Earth's
meter or second is.

by Pete:
"
First, Jill's clock runs slower in Earth's frame.
This means that the time between two events on Jill's ship will be longer in Earth's frame than measured by Jill's clock.
If the two events are:
a) leave Earth, and b) arrive at space-station, then it is clear that time dilation suggests that the elapsed time recorded by Jill is shorter than the two years recorded on Earth.

But is that consistent with length contraction? Let's see...

In Jill's frame, the space-station travelling at c/2 reached her in less than two years.
Therefore in Jill's frame, the space-station must be closer than one light year.

This is consistent with length contraction. Distances measured from a moving frame are shorter."
================================================== ===========

You are correct, Pete, but you left out the relative values. If her clock is running half as fast as Earth's, 1/2 second of her time would be equal to 1 second of Earth's time.
Then her meter would be 1/2 as long as Earth's meter. Light would travel at the same velocity in either frame, 299,792,458m/s. She would travel at the same velocity in either frame, 149,896,299 m/s. The only way to get her to her destination in fewer
ticks of her clock in relation to Earth's clock is to reduce the NUMBER of meters she has to travel in her frame, in real physical distance, not just saying 'her meters are
contracted.' Read my above post about the effects of reducing real physical distance
along her direction of travel.

So here's a summary. When you are in an accelerating spacecraft, you naturally feel a pull, a tug, in one and only one direction. When you feel (and measure) that tug, you know that distant clock rates must be reckoned as being slower (than your own) in the direction of that tug yet faster off in the opposite direction -- just as it is with material gravitational wells, ie. slower clock rates are found toward the direction of tug, and faster rates the opposite way. Such distortions are in addition to the relativistic time dilation (slowing) based simply on relative speed. I think that sums it up.
If acceleration affects are directional and velocity affects not directional then it seems you have described absolute motion detetection for accelerating and decelerating passengers and measuring devices.

For clocks being inanimate objects, how does a clock know if it is supposed to dilate, or speed up? What mechanism is there for the frame clocks to maintain a memory of prior acclerated, or decelerated motion, and the same for passengers that can "sense" the direction of the accelerations/deccelerations?

I assume the instantaneous velocity of the accelerating/decelerating frame is counted as velocity? as opposed to acceleration?


An acclerated passenger feeling a tug one way and assumes what you said, then say she goes to sleep and wakes up disoriented and cannot remember which way the tug was, how is she to know if she is being tugged further along or is being deccelerated in the "opposite" direction? The same for the her clock. Say someone picks up the clock tosses it around in the air and sets the clock back in its original place. Will the clock know the difference in decceleration and acceleration?

Lets assume the clock feels the acceleration on the back plate of the clock. Now someone rotates the clock pi radians, resting the clock's backplate against a surface identical with the unrotated position. Now when the clock deccelerates the force is felt exactly the same by the clock, i.e. pressure on the back plate directed the same direction through the clock. What will the clock speed do in the moving frame and all the others also.

I do not know how to answer all that is implied by your post, but will make comments in bold relating to your post.I always wondered about Einstein’s axiom claiming the equivalence of the laws of physics over all inertial reference frames. Was he thinking of some specific phenomena other than light propagation? Did he feel that the constancy of the speed of light implied the axiom for then unknown phenomena? I have always believed that the M/M experiment was the basis for his axiom.

Because if he did not make the assumption then there would be no special relativity, an occupation that kept Einstein going for a half a cnetury.

GeistKiesel: I was wondering about the specific axiom he used. The M/M experiment as interpreted by him seems to support the notion that the speed of light is constant as measured by observers in any inertial reference frame. I do not think M/M supports the stronger axiom he used as the basis for GR.

The M/M experiment essentially indicates that an observer in a closed room cannot determine the state of motion of the room via experiments with light.

The Einstein axiom is equivalent to stating that an observer in a closed room cannot determine the state of motion of the room via any experiments. This axiom can be used to prove the weaker axiom about experiments with light.

Perhaps the two axioms are equivalent, but they do not seem to be.

You are correct, Pete, but you left out the relative values. If her clock is running half as fast as Earth's, 1/2 second of her time would be equal to 1 second of Earth's time.
It is clear from this statement that you are working in Earth's frame of reference.

Then her meter would be 1/2 as long as Earth's meter.
True. Objects in Jill's frame will be physically shorter in Earth's frame.
But we're working in Earth's frame, looking at a distance native to Earth's frame (since both Earth and the spaceship are in Earth's frame).
In Earth's frame the distance between Earth and the spaceship is one light-year.

In Earth's frame, Jill travels one light-year in two years, and in that time Jill's clock indicates less than two years.

Light would travel at the same velocity in either frame, 299,792,458m/s. She would travel at the same velocity in either frame, 149,896,299 m/s. The only way to get her to her destination in fewer
ticks of her clock in relation to Earth's clock is to reduce the NUMBER of meters she has to travel in her frame, in real physical distance.
True. The salient point is that In Jill's frame, lengths of objects in Earth's frame are shorter.
In Jill's frame, the distance between Earth and the spaceship is shorter than one light year. This is due to the Earth meter contracting in Jill's frame.

So, in Jill's frame, the spaceship travels less than one light year in less than two years to reach her. The Earth travels the same distance in the same time moving away from her.


Note:
Jill's meter contracting in Earth's frame is irrelevant in this problem, because the only distance in consideration is a distance native to Earth's frame - a distance between objects stationary in Earths' frame.

In Earth's frame, that distance is uncontracted - one light year.
In Jill's frame, that distance is contracted - less than one light year.

And what velocity does she measure in her frame, Persol. You are not being specific,
if her distance (meter or light year) contracts in her frame, does her second not have to contract the same amount? Remember how distance is measured, by the constancy
of the speed of light. Contract her distance, contract seconds, in her frame,
by the same amount and her travel time remains the same.

.. For clocks being inanimate objects, how does a clock know if it is supposed to dilate, or speed up? ..

But you are making the very same fundamental error that 2inquisitive is continually making. Under Relativity, one's own clocks and measures never get distorted. Hear me well! One's OWN clocks and measures NEVER EVER SUFFER A SINGLE DISTORTION. The clock and ruler distortions are what an observer must ascribe to alien frames, to distant entities in alien gravitational fields (or to those at a different height/potential in the same field), and to entities in relative motion -- NEVER to the observer's native clocks and rulers. I'd like to take this opportunity to vigorously drill that into everyone's mind. Let it sink in, deep in.

But you are making the very same fundamental error that 2inquisitive is continually making. Under Relativity, one's own clocks and measures never get distorted. Hear me well! One's OWN clocks and measures NEVER EVER SUFFER A SINGLE DISTORTION. The clock and ruler distortions are what an observer must ascribe to alien frames, to distant entities in alien gravitational fields (or to those at a different height/potential in the same field), and to entities in relative motion -- NEVER to the observer's native clocks and rulers. I'd like to take this opportunity to vigorously drill that into everyone's mind. Let it sink in, deep in.

Bullshit, dristam, I am not making that error! Jill measures the speed of light as
constant, it travels in her frame the same as Earth's frame, one meter in
1/299,792,458ths of a second, her meter and her second. Period! Get that
in your head. If you shorten her meter, in relation to Earth's meter, then you
have to shorten her second, in relation to Earth's frame, by the same ratio
or you change the speed of light IN HER FRAME. You cannot use an Earth-
based viewpoint to change her physics, as the Lorentz transforms do.

2inquisitive, are you conceptually comparing Jill's second and Jill's meter to some "absolute" meter and second?

Bullshit, dristam, I am not making that error!
I'm delighted to hear it. So now only poltergiestksl makes that misconception. :m:

2inquisitive, are you conceptually comparing Jill's second and Jill's meter to some "absolute" meter and second?

No Pete. I am saying the speed of light defines how many meters one can
travel in one second in their frame of reference. If Jill travels 149,896,299
meters per second in Earth's frame of reference, she MUST travel 149,896,299
of HER meters per one of HER seconds, or she will measure the speed of light
differently. Her clock will accumilate the same amount of time to travel between the Earth and the space station as the Earth's clock, even though
her meters are contracted and her seconds are slower as viewed by an
observer on Earth.

What the Lorentz transforms do is to mix frames of reference in a sly way. LT is using
Earth's meter (distance) frame and Jill's slower clock frame to allow her to travel the
distance in fewer ticks of her clock. But by mixing frames, the Lorentz transforms are
changing physics in Jill's frame, not allowing her to measure a meter as 1/299,792,458ths of her second, as defined by the speed of light.

Pete, you can say there is an 'absolute' meter and second for every observer in
their own reference frame, regardless of their relative velocity in regards to any
other reference frame. It is defined by the constancy of the speed of light. I will
repeat it again, light travels 299,792,458 meters in one second for any observer
in their own reference frame. Their meter and their second is defined as an unchanging
relationship in their own frame.

Of course...

I don't understand why you think that the Lorentz Tranforms imply differently.

Of course...

I don't understand why you think that the Lorentz Tranforms imply differently.

What the Lorentz transforms do is to mix frames of reference in a sly way. LT is using
Earth's meter (distance) frame and Jill's slower clock frame to allow her to travel the
distance in fewer ticks of her clock. But by mixing frames, the Lorentz transforms are
changing physics in Jill's frame, not allowing her to measure a meter as 1/299,792,458ths of her second, as defined by the speed of light.

I disagree, 2inquisitive.

Can you use the Lorentz transforms to formally demonstrate that Jill measures a different light-speed?

Are you aware that the Lorentz Transform is derived directly from the premise that light-speed is the same in all frames?

Are you suggesting that this derivation is flawed?

Have you ever worked through the derivation?

No, I cannot show the derivation is flawed from WITHIN the derivation. Can you
formally demonstrate that Jill can measure HER meter as anything other than
1/299,792,458ths of HER second? Then can you demonstrate why we should use
EARTH'S meters and HER supposedly slow-running clock to calculate HER travel
time? If Jill is traveling at a velocity 1/2 the speed of light by HER clock and HER
meter, how can she travel a distance of one light year in less than two years of
her time? Does the distance between the Earth and the spacestation physically
contract by HER measurements?

Can you formally demonstrate that Jill can measure HER meter as anything other than 1/299,792,458ths of HER second?
Of course not. In Jill's (or any other) frame, a meter is equal to the distance light travels in 1/299792458 seconds.

Then can you demonstrate why we should use EARTH'S meters and HER supposedly slow-running clock to calculate HER travel time?
You're not thinking terribly clearly.
In Jill's frame, she isn't travelling - Earth and the Space station are travelling.
The question isn't "what's Jill's travel time", it's "what's the Space-station's travel time in Jill's frame?".

If Jill is traveling at a velocity 1/2 the speed of light by HER clock and HER
meter
She's not.
In Jill's frame, she is motionless.

how can she travel a distance of one light year in less than two years of
her time?
She doesn't. In Jill's frame, she doesn't travel any distance at all.

Does the distance between the Earth and the spacestation physically
contract by HER measurements?
Yes.

Sorry, Pete. I will try to restate the gedankin in terms more suitable for the Special
Theory of Relativity. I want to see if the final answer changes.

We agree how the meter is defined and is measured in any observer's own frame of
reference, the distance light travels in 1/299,792,458seconds.
(1) Can you demonstrate why we should use Earth/spacestation's meters and Jill's
supposedly slow-running clock to calculate the Earth/spacestation travel time in Jill's
frame of reference?

(2) If the Earth/spacestation is traveling at a velocity 1/2 the speed of light by Jill's
clock and meter, how can the Earth/spacestation travel one lightyear in less than
two of Jill's years?

(3) Does the distance between the Earth and spacestation measure fewer of Jill's
meters while they (Earth/spacestation) are in relative motion with regards to Jill's frame of reference? I mean less than appox. nine quadrillion meters?

(1) Can you demonstrate why we should use Earth/spacestation's meters and Jill's supposedly slow-running clock to calculate the Earth/spacestation travel time in Jill's frame of reference?
The concept Earth/spacestation's meters is poorly defined in your posts.

The Earth-spacestation distance is the item of interest. It is shorter in Jill's frame than in Earth's frame.

Do you agree that Jill measures the distance between Earth and the Space-station as less than one light-year?

(2) If the Earth/spacestation is traveling at a velocity 1/2 the speed of light by Jill's clock and meter, how can the Earth/spacestation travel one lightyear in less than two of Jill's years?
They don't - they travel less than one lightyear.

(3) Does the distance between the Earth and spacestation measure fewer of Jill's meters while they (Earth/spacestation) are in relative motion with regards to Jill's frame of reference? I mean less than appox. nine quadrillion meters?

In Jill's moving frame, the distance between Earth and the Space-station is less than one light-year.

by Pete:
"Do you agree that Jill measures the distance between Earth and the Space-station as less than one light-year?"
"In Jill's moving frame, the distance between Earth and the Space-station is less than one light-year."
================================================== ==============

No, I do not agree that Jill measures the distance between the Earth and the spacestation as less than one light-year. If one light-year is nine quadrillion meters,
how many meters does she measure the distance as? Remember the definition of a
meter. Also, Jill's frame is not moving, the Earth/spacestation frame is moving
in the current scenairo.

No, I do not agree that Jill measures the distance between the Earth and the spacestation as less than one light-year.

Do you accept length contraction?
Do you agree that a meter stick in Earth's frame aligned with the Earth-spacestation direction is shorter than a meter according to Jill?

I'm trying to pin down a point of common understanding that we can build on.

No, sorry Pete, I do not accept length contraction. That has always been the reason
I could not accept Special Relativity. When I first started learning a little about SR,
that was when I balked, the one thing I could not accept by MY logic. But I could
not figure out how to show it false. I have now, at least in my own mind, but you
and other Physicists may not agree. I am going to try to explain, it was hard to come
up with a way to demonstrate it.
From the previous examples, I hope you see a contradiction. It is easy to say 'her
distances contract' but how to show it in real numbers without changing physics in
her frame. I know how the Lorentz transforms do it, so it does not appear to be a
problem from WITHIN the mathematics for the physicist. Simultaneity. Remember all
the diagrams explaining simultaneity? Understand now why SR likes to use the traveler
in a stationary frame and the other frame (Earth/spacestation) as the one moving?
What simultaneity does is 'shift' the traveler (Jill) in the moving (Earth/spacestation)
frame. That is how she has less distance to travel. But is it true in reality? I do not
believe it is, I believe it is an illusion. Of course, I cannot claim that I am right and
the Lorentz contractions are wrong, but it is what I believe. I do not believe you, or
any other physicist, can put real numbers to this 'shift/contraction' without changing
the laws of physics. Of course, I may be wrong!!

You're welcome to read my web site, 2inquisitive, which attempts to clarify all of that.

Thanks, dristam, but it is clear to me already. You cannot have Jill using Earth/spacestation meters to make her measurements. Once the Earth/spacestation
frame has completed its journey past Jill, and she is near the spacestation, what
distance and how much time passed on her clock? If you want to use gamma, assume
her velocity as .866c so we have a .5 contraction, easy to work with. (plus I know
that one without having to look it up!) SR says(I think) that the Earth/spacestation
frame will complete its one lightyear journey in one year accumilated time on Jill's
clock. Jill's meters, and lightyear, are defined by the constancy of the speed of light.
So, what happened, did she travel at the speed of light? Or does she measure fewer
meters between herself and the Earth at this point, real meters, not an illusion? Using
these real meters, what is the distance between the Earth and the moon, assuming the moon is between her and the Earth in its orbit? A mean distance would be 192,200
km. If the moon happened to be at Perigee in its orbit of Earth, the distance would be
181,650km. The Earth itself would half as thick as it is wide. What keeps the moon in
orbit? No, this is not real, it is an illusion. But if the distance is an illusion, Jill cannot
record a reduced time for the event to happen, her meter and her second is defined
by the speed of light. Or, do you state the speed of light changes in Jill's frame?

by Pete:

"Do you accept length contraction?
Do you agree that a meter stick in Earth's frame aligned with the Earth-spacestation direction is shorter than a meter according to Jill?"
================================================== ============

Pete, I've just looked over your post again and the thought struck me about the
difference in the way we may be visualizing this contraction. How do you see it?
I hadn't thought of it this way, but are you thinking of the contraction in the
Earth/spaceship frame as the contraction of empty space *between* the Earth
and spaceship? I see the line of contraction as going to infinity in both directions
along the direction of travel, contracting every physical object along that line in
one dimension only. Thus the flattened Earth and contracted distance between the
Earth and moon, etc. Even though the Earth/spacestation frame meter may be shorter
than Jill's, Jill still measures the distance and time of travel with HER meter and clock
in Her frame of reference, her reality. If the Earth/spaceship frame has physically
shortened, she will measure that as fewer meters and less time elapsing on her clock.
Do you visualize that distance as only empty space and everything extending in a straight line beyond that space as normal and uncontracted?

Thanks, dristam, but it is clear to me already.
Think of Jill as stock still in her own little domain.. well actually not little, because it extends out to everywhere. And in this domain of her's, light always advances in a straight line at speed c... light's path advances through that uncomplicated conventional 3D space with respect to which Jill is stock still. Jill's clocks and her 3D space never vary from perfect Newtonian sanity. The crucial thing to remember is that all light signals seem to originate at some fixed point in Jill's simple 3D realm, and later end at another fixed point; neither the source's nor the destination's motion can ever change that.

Of course, any material things that are in relative motion to Jill, they seem all red-shifted and pale, all slowed down, enervated; and they're all contracted -- including the spacings between them if they advance as one 'fleet' so to speak. And those moving realms also have unsynchronized time.

As for light moving a straight line, exceptions: gravity can cause it to bend, or if Jill accelerates it will also appear to bend.
:) edit: it'll bend but won't alter its speed, even if the gravity pull is exactly aligned with the light path.. in which case the only effect would be an alteration of the signal's frequency.

Thanks, dristam. Your description pretty well matches what I had envisioned
and read before. I was aware her spaceship would appear undistorted to her,
as well as any outside object or spaceship traveling at the same relative velocity as Jill (or should I say 'resting' in the same reference frame as Jill,hehe). It is the outside universe that is in relative motion to Jill that
concerns me. You say it 'seems' contracted and Doppler-shifted. The
Doppler shift I have no problems with, other than I thought the objects
that were moving 'toward' Jill would be blue-shifted and the objects moving
'away' (behind) Jill would be red shifted.Does the 'contraction' also change
all to red shift? 'Seems.' That is a word I have trouble with. The moon 'seems'
closer and larger when it is setting over the ocean than when it is overhead.
But I couldn't travel to it in less time or measure a 'contracted' distance.
You do know what I have problems with? The contraction, to my understanding, would have to be PHYSICAL in nature, not just appear that
way, for Jill to time and measure it as a contraction. An illusion would not
allow her to record less time on her clock as it moved by, would it?

Doppler shift is an additional dynamic, not attributable to relativistic distortion. Don't confuse the two, as one may be compounded upon the other in a real life situation; but a Doppler distortion is not Relativity per se. When I said they are red-shifted, I was talking about the consequence of relativistic time dilation.

As for "seeming" versus "real", there's no big difference. What is subjectively real to Jill may not be real to someone else. For example, distant things "seem" smaller, right?? So if you watch a house burn from an observatory a couple of miles away, it's a small fire and you don't even feel the heat; but if you watch it burn from five feet away, you'll get scorched. All that matters is causation: that which is subjectively real to you can be the cause of things.

An excellent analogy, dristam. But the way I see it now. I can hold a meter stick at
arms length at the 'safe distance' and the burning house will 'seem' much shorter than
a meter. I can 'seemingly' take one step to the side and cross the length of the house.
But when I measured the house before it began to burn, it was many of my meter
sticks. Can I 'really' walk the length of a house in one step and a fraction of a second?

..But when I measured the house before it began to burn, it was many of my meter
sticks.
Aye but you had a different subjective reality at that time, based on your vantagepoint. [You mean "before I got a safe distance away" of course, not "before it began to burn".]

An excellent analogy, dristam. But ... Can I 'really' walk the length of a house in one step and a fraction of a second?
All that matters is causality. Relativistically speeding entities "come across" all distorted to you, the stock still observer... how they come across is how they will affect you.

That is my point. Distortion is not reality. My meter is still 1/299,792,458second. If a one lightyear slice of the universe travels past me in one year, I am going the speed
of light, period.

That is my point. Distortion is not reality. My meter is still 1/299,792,458second. If a one lightyear slice of the universe travels past me in one year, I am going the speed of light, period.
Dead wrong. If that slice travels past you then it's an indication of their speed, not your own. And we both know that physical entities cannot attain c!

Dead wrong! You are mixing frames. Jill is the one that has to record the one year
time on HER clock. Remember? She returns to Earth younger than her Twin.

One other little scenario. Remember in the twin paradox when the traveling twin has
reached .866c relative to Earth, from the frame of reference of the Earth observer?
The Earth observer says her ship has contracted by one half in length, while remaining
the same in width, according to the Earth observer. The Earth observer says her clock
is running half as fast as the Earth's. Have you thought about what we are saying in
observation? In the travelers direction of travel, her meter and her clock have the
correct ratio to keep her speed of light constant, both are reduced by half. But what
happens to the speed of light when measured width-wise? Does her clock then speed
up so the speed of light remains constant? This is from the Earth based frame of reference now, I know SR states she sees no such change. Does it not seem we are
imposing a breach of physics on her from our frame of reference?

.. Have you thought about what we are saying in observation? .. her meter and her clock have the correct ratio to keep her speed of light constant, both are reduced by half. But what happens to the speed of light when measured width-wise? ..
No it doesn't work that simply, because you also have to take int