there is the old story of two twins born, and one is immediately put on a rocket and flies around earth for 20 years, and when he comes back his twin is 20 and he is only 5 or whatever. My question has always been, does he look like he's 5 or does he look like he's 20? Does the clock running differently due to the speed change the aging process?

different inertial reference frames mean different relative times for real, so he looks like he's five because he IS five, just as the other is really twenty. (though those numbers are maybe a smidge exagerated, depending on how close to the speed of light you're going)

So are planets that orbit the sun faster than the Earth younger than the Earth, even if they were formed close to the same time?

I believe that would be correct, yes. It's hard to say that it would be a significant difference though if they are not very close to the speed of light, which I don't think they are, so the effects are likely nominal. Perhaps a few thousand years difference per billion passed or less... I'm not sure about the numbers there, I'm just guessing.

I think that it's correct that technically, every particle in the universe is in a slightly different time frame.

I believe that would be correct, yes. It's hard to say that it would be a significant difference though if they are not very close to the speed of light, which I don't think they are, so the effects are likely nominal. Perhaps a few thousand years difference per billion passed or less... I'm not sure about the numbers there, I'm just guessing.

I think that it's correct that technically, every particle in the universe is in a slightly different time frame.

I think I take a slight exception to your answer. Granted they all have a different orbit velocity but that is not relative to other orbits. i.e. just what is this velocity relative to? LIne of sight relative velocity produces relavistic affects. Orthogonal motion does not between the observer and observed.

The fact is every particle as you say has a multitude of ages depending on what the relative velocity of the observer is. Orbits generally I don't think qualify for time dilation.

MacM,

I think I take a slight exception to your answer. Granted they all have a different orbit velocity but that is not relative to other orbits. i.e. just what is this velocity relative to? LIne of sight relative velocity produces relavistic affects. Orthogonal motion does not between the observer and observed.


Hahaha, so there is no time dilation (or Lorentz's contraction) for ship orbiting earth? May be you should give us your other guess about particles in particle accelerator. Is there any time dilation for those particles?

MacM, the orbit velocity wouldn't matter here because they are in a different position relative to the gravitational field of the sun. As the spacetime is bent more, closer to the sun, then the time on orbits closer to the sun would appear to flow slower as measured by the people in outer orbits who are in the less intense part of the sun's gravitational field.

According to Special Relativity, objects in orbit can undergo relativistic effects. They
do not have to be line of sight to us, only in a different frame of reference because
of their velocity. Particles circling around a ring in a particle accelerator are said by
SR to undergo time dilation. Special Relativity is based on frames of reference, not just
on distance separation between two objects only. SR says objects at close to the
speed of light are in a different frame of reference than the stationary observer and
measure time and distance differently than the stationary observer. That is where the
paradoxes come from, comparing measurements from one frame of reference to the
same measurements taken from a different frame of reference. As I have said, I have
seen nothing that convinces me that SR is true, but I do have a kind of basic understanding of its mechanics, but not an in-depth understanding. According to SR,
planets orbiting at different velocities will be in different frames of reference, but the
relativistic effects will be very minor because of the 'slow' velocities, as Wes said.

by Paul T,

"Hahaha, so there is no time dilation (or Lorentz's contraction) for ship orbiting earth? May be you should give us your other guess about particles in particle accelerator. Is there any time dilation for those particles?"
================================================== =========

Are you positive there is time dilation shown for those particles in a particle accelerator? You do realize that muons created in a particle accelerator have lifetimes
ranging from less than one microsecond to over 6 microseconds? The 2.2 mean lifetime
is an 'average'. How fast are the ones that last 2.2 microseconds travelling? Their
lifetimes seem to be based on their energy, not their velocity. And those wide-ranging
lifetimes can all come from one group or 'bundle' of pions when they decay producing
one 'bundle' of muons.

LIne of sight relative velocity produces relavistic affects. Orthogonal motion does not between the observer and observed.

Wrong again.

different time flow in different orbits around the sun is a result of general relativity, not special

Fallen Angel, are you familiar with simultaniety? There does not have to be large
velocity differentials for flow of time to be affected. That IS Special Relativity.
General Relativity postulates clocks run slower in higher gravity frames of reference
and is also responsible for some time dilation, but the difference in time measurements
on Earth and Pluto would be very minor because of the sun's gravity, for example. The clock also runs faster the further it is from the planet's surface, according to GR.

i don't disagree with you 2inquisitive, i wasn't taking SR into account when I posted. i think we agree that both are revelant and both are small effects :D (at least around Sol)

different time flow in different orbits around the sun is a result of general relativity, not special

It is the result of both. The combination of relative velocity difference and difference in gravitational potential.

MacM,



Hahaha, so there is no time dilation (or Lorentz's contraction) for ship orbiting earth? May be you should give us your other guess about particles in particle accelerator. Is there any time dilation for those particles?

I'll skip responding to your post since it is nothing more than an effort to distort the meaning of my post.

MacM, the orbit velocity wouldn't matter here because they are in a different position relative to the gravitational field of the sun. As the spacetime is bent more, closer to the sun, then the time on orbits closer to the sun would appear to flow slower as measured by the people in outer orbits who are in the less intense part of the sun's gravitational field.


We can agree on this but gravittional time dilation was not the issue. It was orbital velocity and age due to time dilation in that respect. My comment was velocity relative to what. If I am moving orthogonal to you we have no relative velocity between us.

According to Special Relativity, objects in orbit can undergo relativistic effects. They
do not have to be line of sight to us, only in a different frame of reference because
of their velocity. Particles circling around a ring in a particle accelerator are said by
SR to undergo time dilation. Special Relativity is based on frames of reference, not just
on distance separation between two objects only. SR says objects at close to the
speed of light are in a different frame of reference than the stationary observer and
measure time and distance differently than the stationary observer. That is where the
paradoxes come from, comparing measurements from one frame of reference to the
same measurements taken from a different frame of reference. As I have said, I have
seen nothing that convinces me that SR is true, but I do have a kind of basic understanding of its mechanics, but not an in-depth understanding. According to SR,
planets orbiting at different velocities will be in different frames of reference, but the
relativistic effects will be very minor because of the 'slow' velocities, as Wes said.

My post surely wans't that clear. I do not disagree with what you have said. The point I was trying to make was "Velocity Relative to what?"

That is the age question is not absolute but varies with every observer.

by Paul T,

"Hahaha, so there is no time dilation (or Lorentz's contraction) for ship orbiting earth? May be you should give us your other guess about particles in particle accelerator. Is there any time dilation for those particles?"
================================================== =========

Are you positive there is time dilation shown for those particles in a particle accelerator? You do realize that muons created in a particle accelerator have lifetimes
ranging from less than one microsecond to over 6 microseconds? The 2.2 mean lifetime
is an 'average'. How fast are the ones that last 2.2 microseconds travelling? Their
lifetimes seem to be based on their energy, not their velocity. And those wide-ranging
lifetimes can all come from one group or 'bundle' of pions when they decay producing
one 'bundle' of muons.

I would like to see this as support for the meaning of my post but I cn't. Just what is the differance in your opinion in "Energy" and "Velocity"?

Wrong again.

Oh really.

Suppose you show us mathematically that the distance between the earth and the moon vries as a function of its orbit velocity. Don't try and trick the question.

That is we all understand the the velocity must be different at different distances.

The question assume that mass will be varied to keep the moon in its natural free fall orbit (the orbit doesn't change nor need to be changed), only tits orbital velocity changes.

Show us your math on how the radius of the orbit changes from either the moon's perspective or the earth's.

I anxiously await your mathematical demonstration.

different time flow in different orbits around the sun is a result of general relativity, not special

On this I can agree.

MacM,


The question assume that mass will be varied to keep the moon in its natural free fall orbit (the orbit doesn't change nor need to be changed), only tits orbital velocity changes.

Show us your math on how the radius of the orbit changes from either the moon's perspective or the earth's.


This is the response from an ignorant.

Oh really.



Show us your math on how the radius of the orbit changes from either the moon's perspective or the earth's.



The radius doesn't, but the circumference does.

For now, we'll ignore the GR effect of the difference in gravitational potential between Earth and Moon, and just deal with the Relative velocity.

Imagine two measuring tapes, one extending from the Moon to Earth, and the other following the circumference of the moon's orbit and stationary wrt the Earth. Since the measure form Earth to moon is at all times 90 degrees to the Moon's orbital motion there is no length contraction along this axis and both Earth and the Moon agree to the radius of the orbit. (you could imagine a third measuring tape fixed to the Earth. When the two radial tapes move by each other, the marks on both will match perfectly)

Now as the moon orbits the Earth alongside the other measuring tape someone holds out a meter stick and compares it to the marks on the tape. He will note that due to length contraction, The marks on the measuring tape designating 1 meter will be closer together than 1 meter according to his stick. If he counts the number of marks he passes in one orbit, and taking into account that these marks are less than one meter, he will come up with a smaller circumference than the Earth bound observer would (for who the marks on the Measuring tape are 1 meter apart.

by MacM:

"The point I was trying to make was "Velocity Relative to what?"

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

Relative to the other frames of reference, Mac. According to SR, different velocities
in respect to the velocities of the observer's frame of reference require different
frames of reference. The observer's frame is the the 'rest' frame and anything moving
in regards to his frame is in a different frame of reference, even for non-relativistic
velocities. At non-relativistic speeds, the time dilation and length contraction would
be so small as to be almost unmeasurable. That was the reason Heffle and Keating's
clocks on a plane were inconclusive, they were not accurate enough. If the clocks
were perfectly accurate, either time dilation supporting SR would have been shown
or no time dilation refuting SR would have been shown. Later examinations of their
actual time recordings revealed H&K 'fudged' the results from inaccurate clocks to
support SR. As I have said, I have my doubts about SR, but the theory is consistent.
You won't 'disprove' SR by finding a mistake in theory itself, it only shows an inadequate understanding of the theory. However, the supposed 'proofs' of SR
are open to debate. At best, support is only inferred, the theory has not been
'proven'.

If I am moving orthogonal to you we have no relative velocity between us.

You appear to be equating relative velocity with the rate of change in distance between two objects.

While the concept of "rate of change in distance between objects" appears valid, it is subtly different to the concept to which physicists attach the label "relative velocity".

Relative velocity, in standard usage, is the rate of change in position of one object relative to another. "That's the same thing!" you might say. Not quite - position is defined not only by distance, but also by direction. An object 10m North of me is obviously in a different position to an object 10m East of me.

MacM,
This is the response from an ignorant.

We note that you really don't have a relavistic answer.

MacM:

Suppose you show us mathematically that the distance between the earth and the moon vries as a function of its orbit velocity. Don't try and trick the question.

I don't see how that is at all relevant to what I posted. I never claimed that.

For more information, read Janus58's last post.

Oh really.

Suppose you show us mathematically that the distance between the earth and the moon vries as a function of its orbit velocity. Don't try and trick the question.

That is we all understand the the velocity must be different at different distances.

The question assume that mass will be varied to keep the moon in its natural free fall orbit (the orbit doesn't change nor need to be changed), only tits orbital velocity changes.

Show us your math on how the radius of the orbit changes from either the moon's perspective or the earth's.

I anxiously await your mathematical demonstration.


MaC, James R didn't say what you claim he said. All he said was that when you said LIne of sight relative velocity produces relavistic affects. Orthogonal motion does not between the observer and observed. . And indeed you are wrong.
You want to see the math:
if in frame S1, a particle is at positions (x,y,z,t) and has velocity (v_x,v_y,v_z), in reference frame S2 that moves with respect to S1 at velocity V in the x direction, the position of the particle will be (x',y',z',t') and its velocity (v'_x,v'_y,v'_z) that are related by:

x' = γ(x-Vt);

y' = y;

z' = z;

t' = γ(t - Vx/c²);

where γ = 1/&sqr;(1-V²/c²)

and the transformation of velocity will be given (since v_x = dx/dt and v'_x = dx'/dt' and similar relations for the y and z directions):

v'_x = (v_x - V)/(1-v_xV/c²);

v'_y = v_y/γ(1-v_xV/c²);


v'_z = v_z/γ(1-v_xV/c²);

So you can see that even if there is no motion of the particle in the x direction (take v_x = 0), there are still relativistic effects in the orthogonal directions ( y and z).


As I told you more than once. If you want to find flaws in SR: Go and first learn Relativity.

1100f,

I accept your presentation but want to note your closing comments "As I told you more than once. If you want to find flaws in SR: Go and first learn Relativity.", are ill advised.

For example when I gave James R., the situation of two rockets in space he concluded each saw the same distance for whatever the relative velocity (my view also) but when I then suggested that one of the rockets was actually still sitting on the launch pad on earth, he quickly came to a different conclusion, even though it wasn't the same one that was being argued where the rocket sees lorentz contraction and the earth saw none.

The simple fact is that if simultaneity is at issue in the earth-rocket case, it would also have been at issue in the two rocket case and his answers therefore must be in opposition. He can't have given the correct answer in both cases. Assuming that both answers are not correct. If either answer is correct then I have given correct answers depending which view one wants to pursue.

The simple truth is, while I was clearly wrong on this issue, most times I am just as right as those that claim to be experts. It is only by shifting views, etc., that arguements are made against my statements and/or understandings.

You don't have to agree with this assessment, I think most can see what I have just said is true given the example above.

MacM:

I don't see how that is at all relevant to what I posted. I never claimed that.

For more information, read Janus58's last post.

My error. I stand corrected. Thanks.

If a spaceship leaves the Earth and accelerates to 99% the speed of light, then according to someone on the planet of origin, the planet is stationary and the spaceship is moving at .99c, regardless of whether his motion is orthogonal or not. Direction is irrelevant, as long as the frame is inertial (unaccelerated). According to someone on the ship, he is stationary and the planet is moving at .99c. Neither is more correct than the other. Each is stationary from his own viewpoint. Each will observe the other as having proccesses which occur very slowly. Specifically, each will observe the other as having clocks which run at 14.1% of normal speed. Neither is more correct. However, to take the simple case in which the spaceship turns around to come back, it then undergoes accelerated motion and, hence, is no longer an intertial reference frame. This is what differentiates the two systems and why less time passes for the inhabitant(s) of the ship than the planet, and not the other way around.

MacM:

For example when I gave James R., the situation of two rockets in space he concluded each saw the same distance for whatever the relative velocity (my view also) but when I then suggested that one of the rockets was actually still sitting on the launch pad on earth, he quickly came to a different conclusion, even though it wasn't the same one that was being argued where the rocket sees lorentz contraction and the earth saw none.

That is incorrect. I stated quite clearly that it makes no difference if one rocket is on the launch pad. See the "FTL spin off" thread for a complete explanation.

The simple fact is that if simultaneity is at issue in the earth-rocket case, it would also have been at issue in the two rocket case and his answers therefore must be in opposition. He can't have given the correct answer in both cases.

Wrong. I have completely solved this problem. See the "FTL spin off" thread.

The simple truth is, while I was clearly wrong on this issue, most times I am just as right as those that claim to be experts. It is only by shifting views, etc., that arguements are made against my statements and/or understandings.

Your problem in that case, as I've said, was to mix reference frames and thereby muddy the waters. Once we sort out the frames, everything becomes clear. See the "FTL spin off" thread.

MacM:

That is incorrect. I stated quite clearly that it makes no difference if one rocket is on the launch pad. See the "FTL spin off" thread for a complete explanation.

Wrong. I have completely solved this problem. See the "FTL spin off" thread.

Your problem in that case, as I've said, was to mix reference frames and thereby muddy the waters. Once we sort out the frames, everything becomes clear. See the "FTL spin off" thread.

LOL: You state that "Both see the same distance". Then change your mind and ultimately admit that you are circumventing my stated case by only taking the view of one clock. And I'm mixing frames? LOL.

One clock view is one view. It takes two to tango or produce relative velocity. But you have finally admitted that when describing the function including simultaneity.