This is mainly for MacM and friends who seem to have a unique perspective on what is real and what isn't. Let's use Einsteins train and embankment with observers on both (Bob on the train, Alice on the embankment) Atmospheric effects ignored as usual.

Bob has a rock and drops it out the train window.

Embankment perspective:

Rock traces out a parabolic path as it falls.

Train perspective:

Rock traces out a straight path as it falls.

Which path is physically real and why?

Oh Mac, where are you?

Can I give it a shot, super?
To begin with, your question is inadequate in details. Here are two scenarios.

(1) Bob drops the rock from the train to the embankment. The rock aquires a spin due
to relative motion upon hitting the ground. Therefore the rock DID NOT follow a
straight path to the ground. Alice's frame is preferred.

(2) Bob drops the rock from the train to the floor of the train. The rock DOES NOT
aquire a spin when it hits the floor of the train, therefore Bob's frame is the
preferred frame in this version. A straight path down.

Any other questions regarding real physics?

What odd replies.

Forget the rock,

U cant say the same about light according to the Genetic Brain Defect (GBD = Einstein).

Forget the rock,

U cant say the same about light according to the Genetic Brain Defect (GBD = Einstein). :D

Not too short

To begin with, your question is inadequate in details

Why do people constantly insist on adding things to my experiments to make themselves feel better?

2inquisitive Can I give it a shot, super?
To begin with, your question is inadequate in details. Here are two scenarios.

(1) Bob drops the rock from the train to the embankment. The rock aquires a spin due to relative motion upon hitting the ground. Therefore the rock DID NOT follow a straight path to the ground. Alice's frame is preferred.

(2) Bob drops the rock from the train to the floor of the train. The rock DOES NOT aquire a spin when it hits the floor of the train, therefore Bob's frame is the preferred frame in this version. A straight path down.

Any other questions regarding real physics?

That's not the problem I stated. Christ on a stick.

It's so gaddamned simple. The rock sticks in mud when it hits, ok? There's only one scenario. Bob drops a rock from the train. Done.

I'm asking you a simple question. Is the train moving wrt the earth, or is the earth moving wrt the train? Who's perspective is "physically real".

This is mainly for MacM and friends who seem to have a unique perspective on what is real and what isn't. Let's use Einsteins train and embankment with observers on both (Bob on the train, Alice on the embankment) Atmospheric effects ignored as usual.

Bob has a rock and drops it.

Embankment perspective:

Rock traces out a parabolic path as it falls.

Train perspective:

Rock traces out a straight path as it falls.

Which one is physically real and why?

Both are physically real (if they happened they must be real). This is assuming that neither Bob nor Alice are under the influence of drugs, alcohol, etc, so what they measure is real in their frame of reference. In the frame of the train the rock follows a straight path. In the embankment, the rock follows a parabolic path. These are facts, not subjective impressions

Thank you Lucas.

by superluminal:

(Bob on the train, Alice on the embankment)

Bob has a rock and drops it.
================================================== ==============
me:

You didn't say WHERE Bob dropped the rock, just that he was on the train and dropped a rock. Maybe it fell on his toe?
================================================== ==============

by Lucas:

These are facts, not subjective impressions
================================================== =============

So, you are stating a rock attaining a spin from hitting the embankment from a moving train (or moving embankment) is a 'subjective impression' and the perceived path the rock follows is a 'fact'? How quaint.

Sorry. Out the train window.

2inq,

You're not getting it. I'm only interested in who's analysis of the PATH the rock takes is the "real" one. Linear, or parabolic?

i'm still not catching why the rock must acquire a spin, can you explain?
How many rocks have you launched during your life? Do all of them acquire a spin?

Lucas, he's not getting it. The question is very simple. The path of the rock. If the rock hits the groung it will "roll" due to the relative motion between train and embankment. That's the "spin" he's talking about. Has nothing to do with what I'm asking.

by superluminal:

Which one is physically real and why?
================================================== =============

Sorry, superluminal, but you asked a specific question as how to identify the 'physically real' frame, not about perceived paths of the rock. I read your question closely, as always. I AM into details, you know.

Ok. Which path is physically real? Linear or parabolic?

The paths the rock will take are subjective, depending on what frame of reference the observer is in. Example, if the observer is located at the sun (heliocentric frame), then the path of the rock will be much more complex still. But in ALL 'real' frames, the rock
will acquire a spin (rotation). That is not subjective, that is physically 'real'. At least,
that I how I view physics, that is why I don't always agree with the simplified SR gedankens.

Well, thanks for your input 2inq. I believe you've skirted around the point of this very nicely.

Next?

This is mainly for MacM and friends who seem to have a unique perspective on what is real and what isn't. Let's use Einsteins train and embankment with observers on both (Bob on the train, Alice on the embankment) Atmospheric effects ignored as usual.

Bob has a rock and drops it out the train window.

Embankment perspective:

Rock traces out a parabolic path as it falls.

Train perspective:

Rock traces out a straight path as it falls.

Which path is physically real and why?

Just because the perspective of the train sees that there is only one source of energy at work, doesn't mean that the others do not exist. I would answer that the stationary embankment has the physically real perspective, if it has less kinetic energy than the train.

I believe we should take the perspective of an object with the smallest observed kinetic energy in order to find all forces at work, and figure out what is the actual physical reality.

Our own physical reality is based on a certain baseline of kinetic energy. Objects "at rest" on the Earth have that baseline, whereas anything else exceeds the kinetic energy of the object "at rest".

Now, the train, seeing the embankment go by, can ascertain that it is in motion, so its reality should also account for the second axis of velocity and the kinetic energy behind the motion. Obviously, perspective does not equal truth.

But, if the train does not see the embankment, and the rock continues to move with the train after reaching an equilibrium on the vertical axis, I don't see how the train can say that the rock moves in any other way than a straight line.

Where are you going with this?

Thanks jayleew.

I believe he is leading to the point that there is NO absolute frame of reference...correct?

Sort of. More specifically what I am leading to is that there is NO absolute "physical reality". This is at the heart of MacM's and others confusion regarding spacetime and SR/GR.

I think MacM is afraid to respond to this since it clearly points out the flaw in his thinking.

Hi 2inq,
(1) Bob drops the rock from the train to the embankment. The rock aquires a spin due to relative motion upon hitting the ground. Therefore the rock DID NOT follow a straight path to the ground. Alice's frame is preferred.

(2) Bob drops the rock from the train to the floor of the train. The rock DOES NOT aquire a spin when it hits the floor of the train, therefore Bob's frame is the preferred frame in this version. A straight path down.

Any other questions regarding real physics?
Bob is in a factory, and drops a rock onto a conveyor belt. The rock acquires a spin due to delative motion upon hitting the belt. Therefore the rock DID NOT follow a straight path to the belt, right?

Did the rock follow a staight path from Bob's hand?

Damn fine question.

This is mainly for MacM and friends who seem to have a unique perspective on what is real and what isn't. Let's use Einsteins train and embankment with observers on both (Bob on the train, Alice on the embankment) Atmospheric effects ignored as usual.

Bob has a rock and drops it out the train window.

Embankment perspective:

Rock traces out a parabolic path as it falls.

Train perspective:

Rock traces out a straight path as it falls.

Which path is physically real and why?

Both of the different perspectives are valid, but I contend that they both represent one physical reality. The vertical component of the rock's motion is that it is accelerating toward earth at 9.8 m/s^2 and the horizontal component of the rock is that it is co-moving with the train at same velocity. Other known motions could also be included, such as the rotation of earth, and the revolution of earth around the sun. If a muon is approaching the earth at near light speed, it's perspective of the situation is just as above, but with the entire system in motion toward the muon at near light speed. In order to avoid complicated transforms, the clock and meter-stick which are most local to the rock could be used, even from the muon frame of reference.

The reason I interject this "one physical reality" concept into an otherwise straightforward thread is that it often seems to me that SR theory could be interpreted as requiring more than one physical reality. I assume it is just our (my?) inability to understand what AE was really trying to say, and not a flaw in the theory itself. Most of us remember earlier posts where it was claimed that a satellite sees clocks on earth ticking slow while simultaneously earthlings see the satellite clock ticking slow. We later agreed (I think) that this multiple-reality problem was in error and that the time dilation was not reciprocal due to the acceleration of the satellite which could be interpreted as "always falling" toward earth.

So, Superluminal, with utmost respect, please allow me to restate your question about multiple realities in SR terms, as simply as I can:

Two clocks are seperated by a great distance, synchronized, and then set into motion toward each other with equal velocities. As observers, our frame of reference is stationary to the midpoint -- the place where the clocks will eventually collide. From our reference frame, the clocks collide when each clock has an exactly equal reading. However, from the reference frame of either of the clocks, they collide when their own clock is ahead of the other clock by some amount. Which of these is the "one physical reality," or, how can these differing accounts be reconsiled as I did with respect to the falling stone?

Nice post Neddy. I would just point out this:


Neddy Bate:

Both of the different perspectives are valid, but I contend that they both represent one physical reality. The vertical component of the rock's motion is that it is accelerating toward earth at 9.8 m/s^2 and the horizontal component of the rock is that it is co-moving with the train at same velocity.

Other known motions could also be included...


From the embankment, the observed or "known motions" of the rock indeed have a vertical and horizontal component that traces out a parabola. From the train the only "known" motion is vertical. Reality for Bob (on the train) and his rock includes no horizontal component.

Every assessment you make of the reality of a frame must be from that frame only. Motions of the earth, solar system, etc. are only motions if viewed from the appropriate frame. I am contending that SR is clear that "reality" as we commonly think of it is completely relative.

Both are real, however the question of linea and curved is dependent on the backdrop that supports the comparison.
How can you tell whether a line is curved or straight? Would be another question.
it may appear to be a curved line but this is only because it is relative to your own velocity.

Is the line curved or is it straight. It may appear to be either but what is it really?

Or..[most importantly].. How can you force a rock to follow a curved vector regardless of your speed at release. What forces are being applied to force the rock to follow anything other than a straight line?

If those forces are in place what forces are they?

If we assume no atmospheric frictions etc

QQ:

Both are real, however the question of linea and curved is dependent on the backdrop that supports the comparison.

In other words, reality is frame dependent. Reality is is relative. Yes.

In other words, reality is frame dependent. Reality is is relative. Yes.
If reality is totally dependent of light information and how we interpret that information it is relative however as I questioned:
Newtons first law, states that an object will travel in a straight line unless acted on by some other forces.
I wish to ask Alice what forces are invloved that cause the rock to travel in a curved path?
If Alice can adequately answer that question then I would consider her perspective as a physical interpretation. Bob on the other hand sees the rock travel in a straight line which conforms with Newtons 1st law.
How can he reconcile that Newtons 1st law is an illusion of light information?

awww!!! come on did I ask a good question or what...... :p

QQ,

Both frames obey Newtons laws. I'm not sure what you're asking...

QQ,

Both frames obey Newtons laws. I'm not sure what you're asking...

Well to this ignorant of physics person if Alice sees a rock travelling in a curved path when it should according to Newton travel in a straight line she should question how a curved path is physically possible and what forces are acting on that object to give it it's curve.....is this not a fair question?

How does the curved path conform with Newtons 1st law?
If it doesn't does this make Alice doubt what she is seeing or not?

The questionis about what is real yes?
So the contention is that a curved path is real....all I am doing is questioning the reality of seeing a curved path, when I think Newton would require a straight path. Thus what Alice is seeing is an illusion of light and not a physical reality. However Both Bob and Alice can only see light so both realities are real but only in the realm of light information and not necessarilly in the realm of physical reality.

if there was no one to see the rock fall would it's path be curved or straight?

QQ:

...if Alice sees a rock travelling in a curved path when it should according to Newton travel in a straight line she should question how a curved path is physically possible and what forces are acting on that object to give it it's curve.....is this not a fair question?

Yes. The only force acting on the rock is gravity. The rock has a horizontal speed which Alice knows (she can measure the speed of the train). When the rock is dropped, it accelerates toward the ground at 9.8ms/^2. This is all in perfect accord with Newton.

Newton said that an object will travel in a straight line only if not acted on by a force. In this case, it's gravity.

Good?

if there was no one to see the rock fall would it's path be curved or straight?

Ha! What rock??? :D

Yes. The only force acting on the rock is gravity. The rock has a horizontal speed which Alice knows (she can measure the speed of the train). When the rock is dropped, it accelerates toward the ground at 9.8ms/^2. This is all in perfect accord with Newton.

Newton said that an object will travel in a straight line only if not acted on by a force. In this case, gravity.

Good?
So would Alice conclude that the curve she is seeing is a perception due relative velocity or a real curve due to physical laws?

This is the very fundamental you are seeking an answer to...yes? Is it a perception or a physical reality?
No matter whose perception we rely upon, either frame, Newton states the rock will travel in a straight line.

And that is all there is to it, either throw out Newtons laws or keep them....

Obviously the rock can only travel in a straight line......so in answer to your thread question if we disregard light info delays etc only the straight line is possible. Unless you can explain in the physics of Newton how a rock can follow a curved path.

Ha! What rock??? :D

the mythical rock , the god of rocks the one that can not be seen because light hides it from view..... :D

The one that is phiosophically aligned with Zenisms

QQ:


So woudl Alicce conclude that teh curve she is seeing is a perception due relative velocity or a real curve due to physical laws?
A real physics curve.

This is the very fundamental you are seeking an answer to...yes? Is it a perception or a physical reality?
A reality. To alice.

No matter whoses perception we rely upon, eiether frame Newton states the rock will travel in a straight line.

No! In Bob's frame the rock posseses no horizontal velocity and will expect it o fall in a perfectly straight line per newton. In Alices frame the rock has a horizontal velocity and will expect it to fall in a parabola per newton also.

And that is all there is to it, either throw out Newtons laws or keep them....
Nope. You did not understand what Newtonian mechanics says about bodies with and without forces acting on them. Now you do. Right?

Obviously the rock can only travel in a straight line......
Nope, now that you understand a bit more newtonian mechanics, right?

so in answr to your thread question if we disregard light info delays etc only the straight line is posible.
Now you know light perceptions have nothing to do with this problem, right?

Unless you can explain in physics how a rock can follow a curved path.
Newton.

but the curve is a plotted curve a visual curve, the rock is still only travelling a straight path.....regardless of how you plot it.

Ok...lets rephrase the question a little?

Explain the forces acting on the rock for the rock to actually follow a curved path?
If you were aboard the rock would you determine your path is curved or straight?

Just to clarify and allow a little focus:

Explain the forces that make the path of the rock curved?

QQ,

but the curve is a plotted curve a visual curve, the rock is still only travelling a straight path.....regardless of how you plot it.

No way Jose. It's moving in a parabolic trajectory wrt the earth.

Explain the forces acting on the rock for the rock to actually follow a curved path?

As the rock falls, it maintains its horizontal velocity (wrt the earth) which is constant (no air drag). It falls under the acceleration of gravity - it's velocity increasing as the square of time. Mathematically the form is similar to y = -xt² (a parabola)

Interesting note: The trajectory of a tossed rock is really a tiny segment of an elliptical orbit. It's only a parabola by assuming the earth surface is locally flat.

so can any one explain the forces acting on the rock to make it's path curved......

SL it is the reality of the rocks path that is in question. I understand that on a graph we plot a curve etc, I understand that from an obervation POV both realities a real but this does not answer the question about forces acting on the rock to cause the curvature of it's path.
We are discussing the difference between perception and reality. I see three realities here. One is Bob's, another is Alices and another is the rock itself.
Now as far as I can tell if we can't describe the forces that conform to Newtoins Laws and accept that the rock has a curved path then we are in contradiction of Newtons first law.

The rock according to Newton must be experiencing forces that allow it a curved path. I ask what are those forces.??

Gravity!? What didn't I explain?

From the rock's POV Bob flies up in a straight line while Alice curves away in a parabolic trajectory! Cool!

so a constantly applied vertical force of gravity is somehow curving the path of the rock?

OK let's change the scenario a little.

btw this is interesting I think.

If the rock is programmed to travel in a straight line from teh train to the ground and we have two witnesses to this event Bob and Alice as per earlier scenario.

We know with absolute assurance that the rock will travel a straight path to the ground.

What do Bob and Alice Observe?

QQ,

so a constantly applied vertical force of gravity is somehow curving the path of the rock?
Of course. This is basic highschool physics (no offense - just trying to put it into perspective).

If the rock is programmed to travel in a straight line from teh train to the ground and we have two witnesses to this event Bob and Alice as per earlier scenario.

We know with absolute assurance that the rock will travel a straight path to
the ground.

What do Bob and Alice Observe?


Bob - straight
Alice - curved, but no longer in a parabola since you have supplemented the rocks motion with some sort of "programmed" thrust.

QQ,


Of course. This is basic highschool physics (no offense - just trying to put it into perspective).



Bob - straight
Alice - curved, but no longer in a parabola since you have supplemented the rocks motion with some sort of "programmed" thrust.

No offense taken, I think you know my knowledge shortcomings by now.

So Alice sees the rocks motion as curved even though we know the rocks motion is straight.

So is Alices observation just a perception or is it reality?

this is the question...yes?

Alice knows that the rock is programmed to be straight pathed.
Yet she sees it as curved what does she conclude about her observation?

I think she finds that perception of the rocks path is relative to relative velocities and that the reality of the rocks path is not.....

So Alice sees the rocks motion as curved even though we know the rocks motion is straight.

This is the point of the whole thread. Only Bob knows this. Alice knows the other version of just-as-valid reality.

There is no "ultimate" physical reality. JamesR said something like, the reality is spacetime and everyone with different relative motions see a different crosssection of it, or something like that. I like that phrase.

Programmed to be straight wrt Bob only. Forget the programming. Gravity does this for you anyway. To bob it falls straight, to alice it curves. Both completely and utterly valid.

This is the point of the whole thread. Only Bob knows this. Alice knows the other version of just-as-valid reality.

There is no "ultimate" physical reality. JamesR said something like, the reality is spacetime and everyone with different relative motions see a different crosssection of it, or something like that. I like that phrase.
the word SEE is the operative word.

SL. if some one throws a ball at your face from a distance and that ball has constant uniform velocity. It appears to accelerate as it gets closer to you.
Does this mean that in reality the ball is accelerating or in unform and constant velocity?
Is the accelleration witnessed by you a reality or an illusion of relativity?

So? No one claims that one frame ever does anything other than make observations (see) of other frames. How could they?

SL. if some one throws a ball at your face from a distance and that ball has constant uniform velocity. It appears to accelerate as it gets closer to you.

No it dosen't. It appears to get larger as a function of the angle subtended in my field of vision, the rate of which is related by the sine of the angle.

Any test I could do would show constant velocity.

Does this mean that in reality the ball is accelerating or in unform and constant velocity?

Is the accelleration witnessed by you a reality or an illusion of relativity?

Nullified.

I still would like to know how two constantly applied forces on a rock: horizontal momentum and gravity, can make the rocks path curved....sure we may percieve it as a curve, plot it and construct all sorts perception based scenarios but I woudl have thought that if two forces are applied unformally would generate a straight line path.....to get a curve I would have thought probably naively that one of those forces would have to change in strength in a uniform way to permit a curve.

QQ,

but I woudl have thought that if two forces are applied unformally would generate a straight line path.....to get a curve I would have thought probably naively that one of those forces would have to change in strength in a uniform way to permit a curve.

First, the horizontal momentum of the rock is not a force. It's a just a uniform state of motion. Gravit, of course is a force (or acts like one). The only force acting on the rock is gravity.

Second, forces always produce acceleration if the body is free to move. a = F/m. Distance varies with the square of time. d = 0.5*a*t².

So the curve of the rock seen by alice is a result of a constant speed in x and a square relationship in y.

Two BALANCED forces (directed along the same axis but opposing each other) acting on an object result in zero motion. Any combination of forces which is UNBALANCED will cause a free body to accelerate, in a straight line. If, however, the body already has a uniform velocity component relative to another observer, it will appear to follow a curved trajectory just as in earths gravity field.

QQ,


Of course. This is basic highschool physics (no offense - just trying to put it into perspective).



Bob - straight
Alice - curved, but no longer in a parabola since you have supplemented the rocks motion with some sort of "programmed" thrust.

Central to the discussion of special relativity is the idea of an inertial frame (or reference). This is basically a coordinate system, which might be attached to an observed object or to the observer, which undergoes no acceleration. Consequently, the relative velocity between two inertial frames is necessarily constant, providing what we refer to as uniform motion.

superluminal, you are discussing Newtonian Mechanics now. What happened to Special Theory, gravity is inconsequential, or ignored, remember?

QQ,



First, the horizontal momentum of the rock is not a force. It's a just a uniform state of motion. Gravit, of course is a force (or acts like one). The only force acting on the rock is gravity.

Second, forces always produce acceleration if the body is free to move. a = F/m. Distance varies with the square of time. d = 0.5*a*t².

So the curve of the rock seen by alice is a result of a constant speed in x and a square relationship in y.

Two BALANCED forces (directed along the same axis but opposing each other) acting on an object result in zero motion. Any combination of forces which is UNBALANCED will cause a free body to accelerate, in a straight line. If, however, the body already has a uniform velocity component relative to another observer, it will appear to follow a curved trajectory just as in earths gravity field.

Is the rock accelerating as it falls in this scenario? If so does Bob see the accelleration from his perspective? If Bob sees the rock accelerating would it not also show a curved path to Bob but inverse in curvature to Alice? Due to the fact that the horizontal momentum is not changing?

Central to the discussion of special relativity is the idea of an inertial frame (or reference). This is basically a coordinate system, which might be attached to an observed object or to the observer, which undergoes no acceleration. Consequently, the relative velocity between two inertial frames is necessarily constant, providing what we refer to as uniform motion.

superluminal, you are discussing Newtonian Mechanics now. What happened to Special Theory, gravity is inconsequential, or ignored, remember?

well said 2inq......although I must accept that I am still incorrect.....

Say we take our scenario out into space and make all aspects inertial. All frames are non-accellerating including our projectile.

Say we have two ships A and B
Ship A is like the train and ship B is like the embankment, There are no significant gravitational effects.

Ship A fires a projectile perpendicular to it's vector at a uniform rate of velocity. Say the projectile has a uniform velocity of 100kmh.

Will that projectile travel a straight path or a curved one?
Note: I am talking about the projectile and not what A or B sees but the actual path of the projectile.

Basic physics that needs to be cleared up ...for me at least any way.....[not to mention other readers]

Logically I would expect that the projectile travells a straight line path but would be observed differently by ship A and ship B.
If the projectile travells a curved path and not a straight line path I would like to know or discover how this curvature is achieved.

Central to the discussion of special relativity is the idea of an inertial frame (or reference). This is basically a coordinate system, which might be attached to an observed object or to the observer, which undergoes no acceleration. Consequently, the relative velocity between two inertial frames is necessarily constant, providing what we refer to as uniform motion.

superluminal, you are discussing Newtonian Mechanics now. What happened to Special Theory, gravity is inconsequential, or ignored, remember?

well said 2inq......although I must accept that I am still incorrect.....

Not well said. And 2inq, thanks for the lesson in elementary bullshit. I wasn't quit up to speed on that inertial frame coordinate system thingy. BTW, can you read???

Do you see anywhere in this thread references to SR? This is about the simple concept of relative reality. This is not an SR thread.

It's a fucking train and an embankment of dirt. The players are Bob, Alice, and a rock and I can't get simple consensus on how a dropped rock falls. Did I mention the rock has cracks and little pits in it? That might be important to the discussion.

The concept of simple Galileian relativity seems to be so hard to understand, how could we ever talk about SR? I guess we might as well all go be farmers or cosmetic reps for all the progress made around here.

Ok here I'll end this thread.

The answer is there is only one reality. All clocks tick the same. Nothing length contracts. Reciprocity means that two clocks both tick slower than the other - really! - thus destroying SRT. The rock falls in a straight line and Alice is on drugs. The ether is real and old Albert was a complete dipshit. The earth is clearly a preferred frame. We do really need to explore other ways of explaining the phenomena that SR seems to explain so well 'cause it just don't feel right. It don't make no common sense! Dang it. The embankment has an absolute velocity of 34.78km/s wrt the luminiferous ether. Of course since relativity has absolutely no proof, it's just as good to suppose that gravity is due to vacuum pressure. I'm sure that's it. Vacuum pressure pushing us all down. I like the sound of that. I think its better than GR. Sounds better anyway.

Done. Lock this thread. Everything makes sense now.

by superluminal:

"Do you see anywhere in this thread references to SR? This is about the simple concept of relative reality. This is not an SR thread."

"More specifically what I am leading to is that there is NO absolute "physical reality". This is at the heart of MacM's and others confusion regarding spacetime and SR/GR."

"Every assessment you make of the reality of a frame must be from that frame only. Motions of the earth, solar system, etc. are only motions if viewed from the appropriate frame. I am contending that SR is clear that "reality" as we commonly think of it is completely relative."
================================================== ========

Here are just a couple references to SR by YOU.

I understand 'relative reality'. I have a cocktail table in my room. But I can't
tell what its shape is. The damn thing keeps changing shape every time I change my viewing location. It is oval if I am standing close to it and looking down upon it. If I sit on the floor, the damn thing is a slender rectangle with
protrusions sticking out (legs) that I didn't 'see' before. So, there is no 'reality'
to its shape, its shape is completely relative to my location. Uh, just in case you say that is all one frame of reference, I can also move my legs quickly (run) and cause the table to circle me, changing shape as it does.

SL I am sorry to be a part of your frustrations. However My questions are sincere and certainly not directed at attacking SRT.
You have asked a specific question about relative realities and whilst I agree that light or visual realities may be different and relative the actual reality which we can't necessarilly observe may not be so relative.

When asking my first question about newtons first law I assumed that all frames including the rocks were not accellerating and for this I apologise for. My mistake.

QQ:

Say we take our scenario out into space and make all aspects inertial. All frames are non-accellerating including our projectile.

Say we have two ships A and B
Ship A is like the train and ship B is like the embankment, There are no significant gravitational effects.
Yep.

Ship A fires a projectile perpendicular to it's vector at a uniform rate of velocity. Say the projectile has a uniform velocity of 100kmh.
Yep.

Will that projectile travel a straight path or a curved one?
Note: I am talking about the projectile and not what A or B sees but the actual path of the projectile.

The actual path wrt what? This is THE fundamental flaw in thinking that makes even simple relativity so difficult to grasp. This comes from living on the surface of the earth and assuming that it is an immutable reference against which all other objects must move and that there must be a way to figure "absolute" motion.

2inq will go on about the ICRF as being some kind of absolute reference. Can you see why it's not 2inq? It's just another "earth" syndrome. It has nothing to do with the relative motions between bodies.

There is no "actual" path. There is no fixed backdrop against which to state the "actual" motion of anything.

Logically I would expect that the projectile travells a straight line path but would be observed differently by ship A and ship B.
If the projectile travells a curved path and not a straight line path I would like to know or discover how this curvature is achieved.

Then you are not thinking logically. In your example, since there are no forces involved and therefore no acceleration, the projectile will appear to move in a straight line wrt A and B. A and B will appear to move in a straight line wrt the projectile. And APPEAR is the correct word. All relativistic effects are only what one observer MEASURES of another. Objects in different states of motion observe complete symmetry wrt each other. Yet each is as "real" to one observer as the other.

In my spacetime on the train the rock follows a straight path. In yours on the embankment, it follows a simple acceleration-induced (gravity) curve.

by superluminal:

"2inq will go on about the ICRF as being some kind of absolute reference. Can you see why it's not 2inq? It's just another "earth" syndrome. It has nothing to do with the relative motions between bodies."
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Bullshit, superluminal. I have NEVER said the ICRF was an absoulte reference frame. I
have always qualified my statements as to the ICRF as being 'kind of like' an absolute
frame, but not a true absolute reference frame. In the solar system version of the International Celestial Reference System, the ICRF is a heliocentric frame of reference
in which the sun does not move, it is at fixed coordinates. All 'rest frames' are based on fixed coordinates for the frame. Are they absolute reference frames? No, I have always stated that more information, and more accurate information, can be obtained by using the ICRF for events within the solar system. It is easy to determine WHICH object is moving with greater velocity WITHIN this frame of reference, and its specific
location within the solar system. Relative to a faraway galaxy, for instance, the velocities would be different relative to that galaxy, but the velocities within the solar system would remain the same if the solar system clock were used, not the 'other'
galaxie's clock. You do realize the ICRF IS mainstream science don't you, it is an international standard.
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by superluminal:

"There is no "actual" path. There is no fixed backdrop against which to state the "actual" motion of anything."
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There is no 'actual' shape to my cocktail table. It has no reality is what you are stating, superluminal. That is because you CANNOT describe its actual shape from any one reference frame. The more 'points of view' (reference frames) one uses, the closer
to reality the description can become. Reference frames are a mathematical contrivence used to model reality, they are NOT reality in of themselves. The reference frame model is inadequate to accurately describe reality, it does not mean a reality does not exist. The goal of science SHOULD be to keep devising improved models, not declare what we have now is near perfect.

It is easy to determine WHICH object is moving with greater velocity WITHIN this frame of reference...
...
Relative to a faraway galaxy, for instance, the velocities would be different relative to that galaxy


So, it's just another third frame of reference. A reference of convenience for solar system operations. I agree completely. Any set of relative velocities would appear differently to a different set of reference coordinates. Absolutely correct and a good statement of simple relativity.

Your coffee table example is insignificant. You are trying to analogize (new word ?) between a coherent object which can be completely shape analyzed in a single frame from any perspective and therefore has complete "reality" within that frame. Analyze your coffee tabel from your rest frame with it moving at 0.5c wrt you, then you will indeed come up with a big disagreement of reality between you and the guy travelling with it.

Frames a mathematical contrivance that helps describe what we actually OBSERVE in nature ("reality").

Just a thougt and counter to what we observe:

In another thread there is reference to a zigzagging light path between two or more mirrors. Light can be seen to be bouncing of these mirrors showing us a zigzagging path.
If we assume for a moment that there is nothing reflecting the light between these mirrors how can we say conclusively that we are observing a zig zagging path.

Light can never be seen in transit so we assume it's path is zig zagging.

Do we observe the path of a photon? Nope. we only assume it.

So it is very easy to state a falacy of observation and then determine a physical fact with that observation.
All these diagrams that show a path of light are only suppositions and imaginary. As light can never be observed other than in reflection or source.

and only at the reflector/source and never away from the reflector/source.

So proving a photon exists as a isolatable entity is akin to proving the Christian God exists.....based only on faith and what can be determined only by default and not directly.

So observation can be assumed as well as fact.

QQ,

As I said, quantum physicists, as I understand it, don't strictly speak of the photon as a "thing" that can be visualized. It is the correlation of an event here (electron drops a level or two or three...) and an electron there (jumps up a level or two or three...).

Clearly there is a coupling that involves energy. It's called a photon.

If you observe a red laser beam shining on a wall in a vacuum, what do you see? A red dot on the wall. That's it. If you put some smoke in between, what do you see? A nice beam of light because some of the "photons" are scattered by the smoke toward your eye. I take this as a pretty good sign that something is travelling from the laser to the wall. That, coupled with the fact that single instances of this "photon" thingy can knock electrons right out of a metal (photoelectric effect courtesy AE), leads me to believe pretty firmly that an isolatable thing called a photon exists.

QQ,

As I said, quantum physicists, as I understand it, don't strictly speak of the photon as a "thing" that can be visualized. It is the correlation of an event here (electron drops a level or two or three...) and an electron there (jumps up a level or two or three...).

Clearly there is a coupling that involves energy. It's called a photon.

If you observe a red laser beam shining on a wall in a vacuum, what do you see? A red dot on the wall. That's it. If you put some smoke in between, what do you see? A nice beam of light because some of the "photons" are scattered by the smoke toward your eye. I take this as a pretty good sign that something is travelling from the laser to the wall. That, coupled with the fact that single instances of this "photon" thingy can knock electrons right out of a metal (photoelectric effect courtesy AE), leads me to believe pretty firmly that an isolatable thing called a photon exists.
Thanks Sl, I am now doing a little research into QM and QED.....something I should have done ages ago.

If a red laser shows a path through smoke or fog to me all this possibly shows is the path of focussed resonance reflecting off "fog " particles as it is effects those fog particles in a straight line. The "Fog" paticles become relfectors.
To me at present it is not sufficient evidence that the light is travelling. Although intuitively it looks that way. Intuitively, because lights velocity is so entrenched in our thinking.
If I was a budding scientist who knew nothing of lights velocity and observed a red beam of light in a fog would I automatically assume that light is in transit? I still can see no movement just a steady glowing line through a fog of particles......

I would if I was totally unbiased assume nothing or at least two possible out of many possible positions.
One that light may be traveling or that the fog particles are just reflecting the effect of light at an intensity relative to the distance from the source.

As light can not be seen with out a reflector I would also assume that the refelctor and light are somehow fundamentally intertwined in physics and not necessarilly separate their realities as in photon vs reflector but simply conclude that they are one and the same thing. Maybe a new word "Phoflection" might be in order....ha

Also I might point out that to take a position of inconclusivity allows me to achieve what I would consider an eventually better understanding of light.
To automatically conform to most persons thinking would I feel close the door on my own understanding....thus I look at the assumptions made and attempt to verify those assumption.
Is lights veloicity an assumption or has it been thoroughly determined as valid?
Is there another explanation for the same pheno that opens the door to other discoveries?
These are the sorts of questions I ask myself.

So I look at our understanding of light and wonder is there another way of describing the same thing.

The next step of course is to prove the difference.

I do realise this is off topic but if my thoughts on light being a resonance effect over zero distance the understanding of light is greatly simplified. NO such thing as wave particle dualities or questions about whether mass or masssless etc....
BUt as I said earlier I am searching for evidence that can be observed that will provide substance to my thoughts.

Because the reflector and light are so intwined this evidence is extremely hard to find.... as neither exsts with out the other.....
Interestingly enough it is SRT's reasoning and mathematics that actually proves my position by it's [if we assume for a moment] possible error in observation. As all those difficulties with dilations and contraction wash away even though they still may exist as physical pheno if light is determined to be a resonance effect over zero distance.

QQ,
In addition to the objections SL has raised, I see one major monkey wrench in the way of your ideas. Maxwell's equations. They unmistakably describe a propagational (wave) phenomenon.

Thanks for that...I shall research them. BTW you comment is greatly appreciated.

QQ,
In addition to the objections SL has raised, I see one major monkey wrench in the way of your ideas. Maxwell's equations. They unmistakably describe a propagational (wave) phenomenon.

Does Maxwells Equations assume distance >0 as being relevant to that wave propagation? Silly question as they must assume distance >0.....hmmmmm....
I am working on the premise that distance is an illusion of three dimensional objects within zero dimensional space.....
[because philosophically the universe can not function unless space is zero dimensional or at least two dimensional. - inertia requires zero dimensionality]
Machs principle springs to mind. I believe AE took inspiration from Mach in his theorising.

any way........

Do you see anywhere in this thread references to SR? This is about the simple concept of relative reality. This is not an SR thread.

It's a fucking train and an embankment of dirt. The players are Bob, Alice, and a rock and I can't get simple consensus on how a dropped rock falls. Did I mention the rock has cracks and little pits in it? That might be important to the discussion.

Done. Lock this thread. Everything makes sense now.

This is the funniest thing i've read on sciforums lately... :D

Thanks for making my day superluminal...

Does Maxwells Equations assume distance >0 as being relevant to that wave propagation? Silly question as they must assume distance >0.....hmmmmm....

Bearing in mind it's been a while since I studied them, yes. The distribution and time dependance of the E field throughout space generates the B field, and concurrently the converse occurs. B field creates the E field. The simultaneous solution of these two relations is a propagation through space.

I am working on the premise that distance is an illusion of three dimensional objects within zero dimensional space.....
[because philosophically the universe can not function unless space is zero dimensional or at least two dimensional. - inertia requires zero dimensionality]
Machs principle springs to mind. I believe AE took inspiration from Mach in his theorising.

any way........

I thought Mach's principle depended on gravity having a finite speed of propagation. I could be wrong.

Say we take our scenario out into space and make all aspects inertial. All frames are non-accellerating including our projectile.

Say we have two ships A and B
Ship A is like the train and ship B is like the embankment, There are no significant gravitational effects.

Ship A fires a projectile perpendicular to it's vector at a uniform rate of velocity. Say the projectile has a uniform velocity of 100kmh.

Will that projectile travel a straight path or a curved one?
Note: I am talking about the projectile and not what A or B sees but the actual path of the projectile.

Basic physics that needs to be cleared up ...for me at least any way.....[not to mention other readers]

Logically I would expect that the projectile travells a straight line path but would be observed differently by ship A and ship B.
If the projectile travels a curved path and not a straight line path I would like to know or discover how this curvature is achieved.
QQ,
The trajectory would necessarily be a straight line, otherwise there would be a constant force on the projectile. The motion of the projectile has two components, the motion of the frame and the orthogonal motion. Looking at the matter from the point of view that the motion is all wrt some zero velocity point(s) measured directly or using "distant immovable stars", or whatever method one uses to develop an immovable frame of reference.

I have objections from using the train as a reference frame from which the train is "at rest" and dropping a ball down ward and while a straight line on the train is "seen" from the embankment another trajectory. SR negates motion when it exists and imposes all the theoretical impositions on motion we are all familiar with.

Geistkiesel :cool: