Motor Daddy's absolute space and time

[Motor Daddy]

Who are you to dictate that my imaginary lattice can't move? It's all the more capable of moving because it's imaginary.

It's not a question of whether pink elephants can fly, it's a question of DISTANCE in space. You're not getting it, James. At 12:00 is there a specific distance between you and the center of the moon? Is it possible for that distance to move?

No we're not. We're talking about my definition of distance that uses my imaginary lattice.

We're talking about the coordinate system of space. We're talking about 3 dimensional distance in the infinite volume of space. We are not talking about objects of mass that can travel in that space.

You can invent your own different definition if you like. I'm just trying to teach you some physics. If you'd prefer to retreat to your fantasy world at this point, I understand.

It is not my definition, it is a fact. At any given time there is a distance between you and every point in space, whether you know it or not.

If an observer moves through the blocks, then the observer sees the blocks moving. That's just one way they can move.

There's nothing to see, James, it is simply an imaginary coordinate system that is defined by light travel and clocks. Can you see the coordinate (25,50,265)? Where is it, James? It could be anywhere!

 

[Motor Daddy]

Grumpy, you are missing the point.

Yes, the light always travels at c from the point in space it was emitted. The source (red dot) does not stay at that point in space, so as far as the red dot is concerned, every point on the outer most circle is a different distance away from the red dot at any given point in time. When the outer most light sphere reaches the grid box on all sides simultaneously, the red dot is not at the center of the grid box, it is closer to the right side. That means that according to the red dot, light traveled a different distance away from him in every different direction, which means he has to say that the speed of light is different in all different directions. The only reason he has to say that is because he considers himself "at rest."

How do you justify the fact that points on the outer most light sphere are a different distance away from the red dot at the end of the animation?

 

[Grumpy]

Motor Daddy

We're talking about the coordinate system of space. We're talking about 3 dimensional distance in the infinite volume of space. We are not talking about objects of mass that can travel in that space.

We are talking about Relativity, which you seem not to understand, but to want to actively disrupt with absolute non-sense and argument. If you can't post appropriately to that topic, don't post at all.

origin

Relativistic doppler effects 1
Relativistic doppler effects 2

Excellent sources of thourough explanations of Relativity's effects, well above the simplistic picture I have been trying to conveigh, especially the first one(Bookmarked). Thanks, and I welcome any contribution from someone who evidently understands this on a level above my own(and math gives me headaches).

Emil

They were postulates in the original papers, they are confirmed facts today.

”

Please give a link.

Warpped spacetime and frame dragging

http://science.nasa.gov/science-news/science-at-nasa/2011/04may_epic/

Gravity wave radiation

http://www.caha.es/18-billions-of-suns-support-einstein.html

Time dilation

A first confirmation of relativistic time dilation was found in the extended half-life of fast-moving muons (B.Rossi and D.B.Hall 1941). These come into being at a height of 10 to 20 km over the earth's surface, when high-energy particles of cosmic radiation strike atoms in the terrestrial atmosphere. Muons differ from electrons in that they have a much larger mass and are unstable. Slow muons have an average life span or 'half-life' of 1.52 µs. The extremely fast muons, which are produced by the cosmic radiation, move nearly at the speed of light and should therefore according to Newton travel about 1.52·10-6 · 3·108 m, approximately 456 m, during their life time. The flow of muons should therefore be halved, if one decreases the altitude by 456 m. However it actually decreases much more slowly. Since the muons are created at an altitude of about 15 km, they must travel 33 times the distance 456 m to reach sea level. Out of 233 muons only one should reach our detector. However this does not fit the observed density of the muon stream: in Germany approximately 200 muons per square meter per second are counted at sea level.

http://www.relativity.li/en/epstein2/read/b0_en/b4_en/

Grumpy

 

[Motor Daddy]

Motor Daddy



We are talking about Relativity, which you seem not to understand, but to want to actively disrupt with absolute non-sense and argument. If you can't post appropriately to that topic, don't post at all.

origin

You are making claims that you can't support. Answer my question. How do you justify that points on the outer most light sphere are a different distance away from the red dot in the pic?

 

[Grumpy]

Motor Daddy

How do you justify the fact that every point on the outer most light sphere is a different distance away from the red dot at the end of the animation?

Because that is not what an observer aboard the moving spacecraft would see. He would see this...

...to him he would be stationary and all the rest of the Universe would be moving. The first movie is what an observer sees of a source of light moving in relation to him, the second is what he sees if the source of light is stationary in relation to him. It is a simplified illustration of the Doppler effects of light(it doesn't include time dilation, mass effects or length contraction in spacetime).

Grumpy

 

[Motor Daddy]

Motor Daddy



Because that is not what an observer aboard the moving spacecraft would see. He would see this......to him he would be stationary and all the rest of the Universe would be moving. The first movie is what an observer sees of a source of light moving in relation to him, the second is what he sees if the source of light is stationary in relation to him. It is a simplified illustration of the Doppler effects of light(it doesn't include time dilation, mass effects or length contraction in spacetime).

Grumpy

That is NOT what an observer on a spacecraft would see, and that is NOT what I asked you. How do you justify points on the outer sphere being different distance away from the red dot in the photo below? You do agree the red lines are different lengths, correct?

 

[Grumpy]

Motor Daddy

That is NOT what an observer on a spacecraft would see, and that is NOT what I asked you. How do you justify points on the outer sphere being different distance away from the red dot in the photo below?

Yes, that is exactly what the observer in the spacecraft would see. The outer sphere was emitted at the point in the very center of that sphere, the next outer sphere was emitted at the point in the exact center of the second sphere, and so on. The spacecraft is moving, by the time the first sphere reaches the outer limit of the frame the spacecraft has moved on. But every point on that outer sphere is equidistant from the point it was emitted from in space and time(IE the center of the screen). The red dot is moving at a good percentage of lightspeed, in the time since the first pulse was emitted it has moved closer to where that light wave is travelling. But every sphere expands from it's point of emmision at the same speed in all directions.

Grumpy

 

[Motor Daddy]

Motor Daddy



Yes, that is exactly what the observer in the spacecraft would see. The outer sphere was emitted at the point in the very center of that sphere, the next outer sphere was emitted at the point in the exact center of the second sphere, and so on. The spacecraft is moving, by the time the first sphere reaches the outer limit of the frame the spacecraft has moved on. But every point on that outer sphere is equidistant from the point it was emitted from in space and time(IE the center of the screen). The red dot is moving at a good percentage of lightspeed, in the time since the first pulse was emitted it has moved closer to where that light wave is travelling. But every sphere expands from it's point of emmision at the same speed in all directions.


Grumpy

How do you justify the red lines being different lengths??? Answer my question!

 

[arfa brane]

A comment on the current Motor Daddy confusion: the red lines are "rays" each intersecting the same number of wavefronts. The reason they have different lengths to an external observer (namely, you) is because the Doppler effect increases frequency ahead of, and decreases frequency behind, a moving object. From the source frame, all the rays are the same length: N.B. (as long as there is no "stationary medium" to compare the source velocity to).

So given that last point, the existence or absence of a medium is why the diagrams are general, except as noted, the third diagram is of a source moving at or greater than the speed of wave propagation, which is excluded in SR. it isn't excluded from materials simply because they also represent a frame of reference which is stationary to moving waves.

[/QUOTE]

If the diagram represents a source moving through space and emitting light, the velocity of the wavefronts is constant, but the observed frequency is relative to the frame of reference. Note that if the source is a spaceship with observers aboard, they see the external universe looking redshifted behind them and blueshifted ahead. Their lightcone is distorted and the time axis is rotated toward their direction of motion.

 

[Motor Daddy]

A comment on the current Motor Daddy confusion: the red lines are "rays" each intersecting the same number of wavefronts. The reason they have different lengths to an external observer (namely, you) is because the Doppler effect increases frequency ahead of, and decreases frequency behind, a moving object. From the source frame, all the rays are the same length.

If the diagram represents a source moving through space and emitting light, the velocity of the wavefronts is constant, but the observed frequency is relative to the frame of reference. Note that if the source is a spaceship with observers aboard, they see the external universe looking redshifted behind them and blueshifted ahead. Their lightcone is distorted and the time axis is rotated toward their direction of motion.

Are you now speaking for Grumpy? Are you his official voice, and that anything you say it's as good as him saying? I need to be clear on that before I waste my time on answering you, and he then responds with a different answer telling me to ignore you.

I assure you, you are wrong. I can tell you the velocity of the red dot, the length of the line to the coordinate (0,10), and the time of travel of the picture from when the red dot was at coordinate (0,0). I can also prove that in the frame of the red dot, the speed of light is measured to be different in different directions, and I can tell you those speeds.

 

[arfa brane]

Are you now speaking for Grumpy? Are you his official voice, and that anything you say it's as good as him saying? I need to be clear on that before I waste my time on answering you, and he then responds with a different answer telling me to ignore you.

Please don't bother wasting your time. I mean that, really. I don't think anyone on planet earth is capable of dealing with even one of your "answers", or of convincing you you've made a mistaken assumption.

 

[James R]

Motor Daddy:

It's not a question of whether pink elephants can fly, it's a question of DISTANCE in space. You're not getting it, James. At 12:00 is there a specific distance between you and the center of the moon? Is it possible for that distance to move?

Yes, it is quite possible for distances to move.

Consider two cars driving along a highway in adjacent lanes at the same speed. The distance between the cars is measured by the length of a line drawn between the two cars. And that distance moves along with the cars, from the point of view of somebody standing at the side of the road.

We're talking about the coordinate system of space.

There are many coordinate systems of space, not just one.

It is not my definition, it is a fact. At any given time there is a distance between you and every point in space, whether you know it or not.

No. There are many distances between me and any other given object, which depend on who is doing the measuring.

Recall that this thread is titled "Relativity, really".

There's nothing to see, James, it is simply an imaginary coordinate system that is defined by light travel and clocks. Can you see the coordinate (25,50,265)? Where is it, James? It could be anywhere!

And so....?

On another matter:

Grumpy, you are missing the point.

Yes, the light always travels at c from the point in space it was emitted. The source (red dot) does not stay at that point in space, so as far as the red dot is concerned, every point on the outer most circle is a different distance away from the red dot at any given point in time. When the outer most light sphere reaches the grid box on all sides simultaneously, the red dot is not at the center of the grid box, it is closer to the right side. That means that according to the red dot, light traveled a different distance away from him in every different direction, which means he has to say that the speed of light is different in all different directions.

You're working in the wrong frame of reference. The picture in which the dot moves is not the view of a person riding along with the dot - it is the view of a person watching the dot moving along. That ought to be obvious.

Also, bear in mind that the diagram where you measured the distances to the outer circle is actually a series of snapshots of the wave over a period of time. The outer wave was emitted when the dot was in the centre of the picture, not at the instance when the dot is at the right of the picture.

How do you justify the fact that points on the outer most light sphere are a different distance away from the red dot at the end of the animation?

The red dot moved to the right after the light was emitted at the centre of the picture.

How would you justify it?

 

[Motor Daddy]

Motor Daddy:
Yes, it is quite possible for distances to move.

No it is not possible for distance to move. Objects move, James. Distance doesn't move. Distance is not an object capable of moving. Distance is 1 dimensional space between two points in space.

Consider two cars driving along a highway in adjacent lanes at the same speed. The distance between the cars is measured by the length of a line drawn between the two cars. And that distance moves along with the cars, from the point of view of somebody standing at the side of the road.

I am not talking about a ruler placed between the cars and moving with the cars, I am talking about the distance between the cars. The distance is not moving with the cars, the distance is remaining unchanged. Distance doesn't move, have you lost your marbles? Do you really believe the distance between you and the center of the moon moves?

No. There are many distances between me and any other given object, which depend on who is doing the measuring.

There is one distance between you and the center of the moon at 12:00. We are not talking about a duration of time, or light travel, we are talking about 1 dimensional space.

You're working in the wrong frame of reference. The picture in which the dot moves is not the view of a person riding along with the dot - it is the view of a person watching the dot moving along. That ought to be obvious.

The picture of the dot moving is a series of facts of the location of the dot at any given point in time. It is also a series of facts as to where the light sphere is located. It is not up for debate. It is written in stone that the light sphere has a specific radius of 299,792,458 meters exactly 1 second after being emitted. That is not up for debate, for any observer. We are talking about a light sphere in space and a source in that same space. Just like it is not up for debate the specific distance between you and the moon at any given point in time, it is also not up for debate the radius of the light sphere at time t=1, and where the source is located at t=1 in that same coordinate system.

Also, bear in mind that the diagram where you measured the distances to the outer circle is actually a series of snapshots of the wave over a period of time. The outer wave was emitted when the dot was in the centre of the picture, not at the instance when the dot is at the right of the picture.

Yes, the outer wave had a radius of 0 at t=0. At t=1 the radius of the outer wave is 299,792,458 meters.

If the red dot claims to be at rest, how does he justify the red lines being different lengths from his "at rest" position? In other words, according to the red dot, the light is traveling away from him at different speeds in different directions, because the outer light sphere is different distances from him along those red lines. Bear in mind, the light did not travel along those red lines from his position. He has no choice but to conclude light travels at different speeds along those red lines.

The red dot moved to the right after the light was emitted at the centre of the picture.

Not according to the red dot. According to the red dot he was always "at rest." Which is it, according to the red dot, is he moving or is he at rest?

How would you justify it?

By saying the red dot has an absolute velocity, which it does, and can be measured according to the distance between the red dot and the center of the outer light sphere. The light never traveled the path of the red lines away from the red dot, which it would have had to do if the red dot was "at rest."

 

[James R]

Motor Daddy:

No it is not possible for distance to move. Objects move, James. Distance doesn't move.

Define "distance". I did it above. Obviously, your definition is different. So, let's have it.

I am not talking about a ruler placed between the cars and moving with the cars, I am talking about the distance between the cars.

What else is the distance between the cars other than what you measure with a ruler?

There is one distance between you and the center of the moon at 12:00. We are not talking about a duration of time, or light travel, we are talking about 1 dimensional space.

But if an observer is flying from the moon towards me, he will measure a different distance betweem myself and the centre of the moon than I measure. So, there isn't just one distance.

The picture of the dot moving is a series of facts of the location of the dot at any given point in time. It is also a series of facts as to where the light sphere is located. It is not up for debate. It is written in stone that the light sphere has a specific radius of 299,792,458 meters exactly 1 second after being emitted. That is not up for debate, for any observer. We are talking about a light sphere in space and a source in that same space.

This is a special feature of light, and I agree with you on this matter. The same argument does not apply to anything that moves slower than the speed of light.

Yes, the outer wave had a radius of 0 at t=0. At t=1 the radius of the outer wave is 299,792,458 meters.

Yes.

If the red dot claims to be at rest, how does he justify the red lines being different lengths from his "at rest" position?

That picture is the view of a reference frame that sees the red dot moving. The red dot's rest frame doesn't draw the same picture. In the dot's rest frame, the waves move out at the same speed in all directions, and therefore the same wavefronts are at equal distances from the dot at all times.

In other words, according to the red dot, the light is traveling away from him at different speeds in different directions, because the outer light sphere is different distances from him along those red lines.

No. In the dot's reference frame, the outer light sphere's boundaries are at the same distance from the dot at any instant in time.

Bear in mind, the light did not travel along those red lines from his position. He has no choice but to conclude light travels at different speeds along those red lines.

You're ignoring the constancy of the speed of light in ALL reference frames.

Recall that in your fantasy universe, the speed of light is different in different directions for "moving" reference frames. That's the imaginary world in which an "absolute" frame exists. In the real universe, however, the speed of light is the same in all directions in ALL inertial reference frames.

Not according to the red dot. According to the red dot he was always "at rest." Which is it, according to the red dot, is he moving or is he at rest?

He is moving in the frame of the observer watching him go past and at rest in his own rest frame. There is no absolute frame. That's a fantasy of yours, remember? In reality, there are no preferred frames.

By saying the red dot has an absolute velocity, which it does, and can be measured according to the distance between the red dot and the center of the outer light sphere. The light never traveled the path of the red lines away from the red dot, which it would have had to do if the red dot was "at rest."

There's no such thing as absolute velocity. That's another part of your fantasy world. Remember?

 

[arfa brane]

If the red dot claims to be at rest, how does he justify the red lines being different lengths from his "at rest" position?

The source of confusion here appears to be your inability to understand that looking at the red lines from a point which is not the location of the source is the reason they are different lengths. Furthermore, if there is a stationary medium, say the surface of a lake a boat is moving across, an observer in motion with the source will be able to see the waves, so they will see the same thing an observer who is stationary relative to the surface can see.

But space is not a medium, so it follows that "seeing" wavefronts of light does not mean looking at how they propagate. You can't see light moving. It also follows that an observer moving with the source can't measure their velocity relative to space, if that's what you assume the diagram represents--a two dimensional surface made of nothing.

There is no problem in physics with running things backwards in time, so doing that, you see that because all the red lines intersect the same number of wavefronts, then if their velocity is the same in all directions an observer moving with the source will measure each red line as being the same length (for the "incoming" spherically concave waves).

 

[Motor Daddy]

Motor Daddy:

Define "distance". I did it above. Obviously, your definition is different. So, let's have it.

Distance is the 1 dimensional space between any two points of the imaginary 3 dimensional coordinate system of the infinite volume of space.

What else is the distance between the cars other than what you measure with a ruler?

1 dimensional space defined by a coordinate system.

But if an observer is flying from the moon towards me, he will measure a different distance betweem myself and the centre of the moon than I measure. So, there isn't just one distance.

It is impossible for any motion to occur from 12:00-12:00.

That picture is the view of a reference frame that sees the red dot moving. The red dot's rest frame doesn't draw the same picture.

That picture is a record of locations of the light sphere and the source at any given point in time. It is not debatable. That picture is a record of the past. It is a recording of the facts of the coordinate system of space.

In the dot's rest frame, the waves move out at the same speed in all directions, and therefore the same wavefronts are at equal distances from the dot at all times.

That is a false statement. We have been over this many times, James. It is impossible for the outer light sphere to reach receivers that are fixed to the source an equal distance away in the x,y, and z directions, in the same amount of time, unless the source has an absolute zero velocity, in which case all observers will agree that the sphere is an equal distance away in all directions of the source.

No. In the dot's reference frame, the outer light sphere's boundaries are at the same distance from the dot at any instant in time.

NO THEY ARE NOT! It's impossible to use the same coordinate system and have two different results for two different observers. The animation is a record of the past. It is set in stone! There is not two different versions of history there is one!

You're ignoring the constancy of the speed of light in ALL reference frames.

It's not so much that I ignore it but that you can't prove it. The red lines don't lie!

Recall that in your fantasy universe, the speed of light is different in different directions for "moving" reference frames. That's the imaginary world in which an "absolute" frame exists. In the real universe, however, the speed of light is the same in all directions in ALL inertial reference frames.

That is not imaginary, that is a fact. Using the same coordinate system in space for all objects means an absolute frame for all. There is ONE universal coordinate system defining the infinite volume of space, in which light travel time defines the meter in that coordinate system.

He is moving in the frame of the observer watching him go past and at rest in his own rest frame. There is no absolute frame. That's a fantasy of yours, remember? In reality, there are no preferred frames.

In reality there is one coordinate system, not more. All objects and light are relative to that coordinate system.

There's no such thing as absolute velocity. That's another part of your fantasy world. Remember?

Wrong. If the red dot is not at the center of the outer light sphere it had an absolute velocity, as shown in the pic.

 

[arfa brane]

Distance is the 1 dimensional space between any two points of the imaginary 3 dimensional coordinate system of the infinite volume of space.

In Motor Daddy's universe, the two points defining a 1-dimensional distance aren't allowed to be in motion.

It is impossible for the outer light sphere to reach receivers that are fixed to the source

Especially if the light sphere is expanding in time, in which case it will be impossible for the light to reach receivers on the source at any future time.

It's impossible to use the same coordinate system and have two different results for two different observers

And again we encounter MD's inability to understand that there can be more than one coordinate system (actually there are an infinite number in spacetime).

Using the same coordinate system in space for all objects means an absolute frame for all.

Ditto. I don't know about any theories that use the same coordinate system for all objects. Even ordinary people probably understand that their individual subjective frame of reference isn't the same as anyone else's. So it isn't something we apply even at a social level. It's nonsense, obviously.

In reality there is one coordinate system, not more. All objects and light are relative to that coordinate system.

Try ringing all your friends and telling them they're in the same frame of reference as you. You might get a few laughs if any of them have a modicum of intelligence.

Wrong. If the red dot is not at the center of the outer light sphere it had an absolute velocity, as shown in the pic.

Motor Daddy knows how to calculate the velocity of an object relative to absolutely nothing, aka space. He isn't telling anyone how at the moment because it's a bit hard to explain.

 

[Aqueous Id]

Motor Daddy:

Cutting to the chase - do you refute SR/GR, if so, why, and how you explain the evidence for it?

 

[James R]

Motor Daddy:

Remember where I showed you what was wrong with your "absolute space" fantasy and walked you through the basics of reference frames? Have you forgotten all that?

Distance is the 1 dimensional space between any two points of the imaginary 3 dimensional coordinate system of the infinite volume of space.

But there are many coordinate systems, not just one.

It is impossible for any motion to occur from 12:00-12:00.

Correct. The extent of length contraction depends only on instantaneous velocity.

That picture is a record of locations of the light sphere and the source at any given point in time. It is not debatable. That picture is a record of the past. It is a recording of the facts of the coordinate system of space.

But that's only in one reference frame. Different reference frames use different coordinate systems. Relativity tells us that no single coordinate system is preferred over any other.

In the dot's rest frame, the waves move out at the same speed in all directions, and therefore the same wavefronts are at equal distances from the dot at all times.

That is a false statement.

But you said the speed of light is the same in all directions, so it must be true.

Ah, but wait! We had this conversation previously. Do you remember? We concluded that in your fantasy world the speed of light is not the same in all directions in all reference frames, whereas in the real world (Einstein's world), the speed of light is the same in all inertial frames).

We have been over this many times, James. It is impossible for the outer light sphere to reach receivers that are fixed to the source an equal distance away in the x,y, and z directions, in the same amount of time, unless the source has an absolute zero velocity, in which case all observers will agree that the sphere is an equal distance away in all directions of the source.

You keep using the term "absolute", as in "absolute zero velocity". There's no such thing. That's a fantasy of yours, as we established previously.

No. In the dot's reference frame, the outer light sphere's boundaries are at the same distance from the dot at any instant in time.

NO THEY ARE NOT! It's impossible to use the same coordinate system and have two different results for two different observers. The animation is a record of the past. It is set in stone! There is not two different versions of history there is one!

Two different observers use two different coordinate systems. The animation shows only one of them. As for history, relativity preserves things like causation, so there's no problem there. Any event that happens occurs in all coordinate systems, and if A causes B in one coordinate system that remains true in all the others too.

Recall that this thread is about relativity, not about the Motor Daddy Fantasy Universe. Please try to stay on topic.

You're ignoring the constancy of the speed of light in ALL reference frames.

It's not so much that I ignore it but that you can't prove it. The red lines don't lie!

The red lines are correct. There's no need for them to lie.

As for proof, we previously established that all real-world evidence is against you and for Einstein. Did you forget?

Recall that in your fantasy universe, the speed of light is different in different directions for "moving" reference frames. That's the imaginary world in which an "absolute" frame exists. In the real universe, however, the speed of light is the same in all directions in ALL inertial reference frames.

That is not imaginary, that is a fact. Using the same coordinate system in space for all objects means an absolute frame for all. There is ONE universal coordinate system defining the infinite volume of space, in which light travel time defines the meter in that coordinate system.

Asserting an error many times never makes it any truer, you know.

In reality there is one coordinate system, not more. All objects and light are relative to that coordinate system.

Even in the same reference frame, there are multiple coordinate systems. Consider cartesian vs. polar coordinates, for instance.

There's no such thing as absolute velocity. That's another part of your fantasy world. Remember?

Wrong.

You're dropping that part of your fantasy? Great!

If the red dot is not at the center of the outer light sphere it had an absolute velocity, as shown in the pic.

No. It just had a velocity in the frame that the picture shows. That's all.

Since you can't remember anything relevant about reference frames, you're stumbling around in the dark again. I have no intention of attempting to walk you through the basics again. It appears you have the memory of a goldfish.

 

[James R]

Here's a link to the earlier thread, Motor Daddy, since you don't remember any of it:

Relativity of simultaneity

And here are the relevant diagrams again:

As you will recall, the diagrams show the emission of light from a source at the centre of a square box (the "train"). Going down each diagram, we see three snapshots of the light wave, each at later times.

When the box is stationary, we agree of the centre set of diagrams: the light spreads out at the same speed in all directions.

Now, let the box move to the right.

In Einstein's universe, an observer in the box sees no difference from when the box was stationary, in accordance with the Principle of Relativity. An observer watching the box move to the right sees the events labelled "embankment frame". Here, the box is length-contracted in the direction of motion, so that it appears rectangular rather than square. Note that the light spreads out at equal speeds in all directions from the source point (indicated by the dot) in this frame. The physical source (flashlight or whatever - not shown), is of course fixed in the centre of the box and is seen by the embankment as moving to the right with the box. The light is observed in this frame to hit the "back" of the box before it hits the front.

In the Motor Daddy Fantasy World, an observer in the box ("Motor Daddy - train frame") sees no length contraction, and the physical source point (not shown) does not move, as in Einstein's picture. However, in the Motor Daddy universe the light travels faster to the left than to the right, so it hits the "back" wall of the box before the front wall, as shown. The point of emission (the dot) remains fixed in the Motor Daddy Fantasy Absolute Space, and so tracks backwards relative to the box.

How do we tell whether Einstein's picture or Motor Daddy's picture is correct? Only by experiment. And all experiments support Einstein and none support Motor Daddy.

So, it's out with the Motor Daddy fantasy. The results are in: Einstein wins.