# Thread: The Relativity of Simultaneity

1. Motor Daddy, can you tell me when this happens :

In your scenario of y and z times being 0.832 seconds?

2. Originally Posted by Neddy Bate
Do you agree I was correct?
v(x)=0.79927794245177367361794866830634 c
t(x)=2.4910067488714731588930217979394 seconds

Like I asked you, how does relativity resolve the issue that it takes ~2.49 seconds to travel the length of .5 light seconds in the cube frame?

3. Originally Posted by Neddy Bate
Motor Daddy, can you tell me when this happens :

In your scenario of y and z times being 0.832 seconds?

0.27788925112852684110697820206067 seconds

4. Originally Posted by Motor Daddy
v(x)=0.79927794245177367361794866830634 c
t(x)=2.4910067488714731588930217979394 seconds
Thank you.

v(x)=0.799
t(x)=2.491

Is pretty darn close to my answers, v(x)=0.8 and t(x)=2.5.

v(x)=0.79927794245177367361794866830634 c
t(x)=2.4910067488714731588930217979394 seconds

Like I asked you, how does relativity resolve the issue that it takes ~2.49 seconds to travel the length of .5 light seconds in the cube frame?

Relativity says that your diagram is correct for the reference frame through which the cube is moving. You drew your diagram with the cube moving relative to the reference point from which the light expands. But relativity says things look differently in the cube frame. In the cube frame, relativity says the reference point from which the light expands would always be at the center of the cube.

5. Originally Posted by Motor Daddy
0.27788925112852684110697820206067 seconds
Agreed.

6. Originally Posted by Neddy Bate
Thank you.

v(x)=0.799
t(x)=2.491

Is pretty darn close to my answers, v(x)=0.8 and t(x)=2.5.
Close but no cigar.

Originally Posted by Neddy Bate
Relativity says that your diagram is correct for the reference frame through which the cube is moving. You drew your diagram with the cube moving relative to the reference point from which the light expands. But relativity says things look differently in the cube frame. In the cube frame, relativity says the reference point from which the light expands would always be at the center of the cube.
Well then relativity would be wrong, because the light sphere doesn't expand relative to the source, it expands relative to the point in space the light was emitted, regardless of what the source does.

My diagram was built on the measured times to the receivers in the cube, nothing else. From those measured times at the receivers I am able to calculate the absolute velocity of the box.

You say relativity can do that too?

Tell me the distances and times in the cube frame from the source to the receivers of the .832 second example. There is no changing times and distances in the cube. The only way you know the times is to measure them, and the clocks read .832 seconds. You can not change those times and say they are actually something different!

7. Gosh, I was hoping we were past this difference between MD's Light Box coordinate system and SR's coordinate system and its Lorentz transformations.

Two different animals. Each with its own logic. You can believe one or the other but not both. If you believe in one I suspect that you cannot be convinced of the other.

The cult is small, lol

8. In SR the light box is in motion relative to the point of emission, and the point of emission is in motion relative to the light box.

In MD the light box is in motion relative to a fixed point of emission, and the point of emission is fixed in absolute space relative to the light box. Its not a subtle difference, lol.

If you believe that once a light wave is emitted in space it traverses space at the same invariant speed, i.e. c, then MD relativity makes sense.

That is the question the sorts out cult members.

9. And I go on unheeded that there is an observed effect attributed to time dilation that has been confirmed in different ways. Time dilation in MD is as yet unexplained except that we know it is not due to the mathematics of Lorentz transformations that define SR time dilation and length contraction between frames.

It is due to something else or MD is wrong. Which is it. Cult members should put on their thinking caps, lol.

10. Wow! 55 pages and still going! I find Einstein's SR fascinating, but I was thinking about the following situation...
Let us return to the opening post with the train and embankment and two flashes of light. Instead of having lightning strikes, let us replace it with two lampposts on the train, one on each end. So, we have exactly the same scenario except the flashes of light are coming from lampposts instead of lightning. We also have somebody on the train with a bag in his hand standing next to the lamppost in the rear of the train, the one that flashes after the one in front.
After the light flashes in front, and before the light in the rear flashes, he covers it up with the bag, thereby blocking the light. Now, how do we explain this from the point of view of the embankment observer? There is no passage of time between the two flashes of light. So we seem to have a paradox.

11. Zeno, you should just be glad that MD stuck with this thread long enough to get his point across. The MD's Box and MD's Light Box graphics lay out an unambiguous example of the invariant speed of light from a fixed point of emission.

They also graphically represent how an observer can determine his motion relative to that fixed point based on the difference in time that the light reaches his receptors. It implies that the speed of light is not the same in all reference frames if it is propagated in another reference frame even though light will always travel at c relative to its point of origin.

12. Originally Posted by Zeno
After the light flashes in front, and before the light in the rear flashes, he covers it up with the bag, thereby blocking the light. Now, how do we explain this from the point of view of the embankment observer? There is no passage of time between the two flashes of light. So we seem to have a paradox.
If the bag goes over the lamp before it flashes, then nobody sees it flash. In the embankment frame, the flashes would still be simultaneous, but there would be a bag hiding one of the flashes, that's all. No paradox.

13. Originally Posted by quantum_wave
Gosh, I was hoping we were past this difference between MD's Light Box coordinate system and SR's coordinate system and its Lorentz transformations.

Two different animals. Each with its own logic. You can believe one or the other but not both.

MD's light box calculations are perfectly compatible with SR. It's just that under SR, all of MD's assumed measurements would have come from the reference frame relative to which the emission point of the light remains fixed. In the diagrams, that reference frame is the "paper" on which the diagrams are drawn. All MD is doing is saying, "If these measurements came from the cube frame, then the cube would know his absolute speed." Yes, that's true, but those kinds of measurements have never been measured in the "cube frame".

14. Originally Posted by Motor Daddy
Close but no cigar.
You're mean. I refuse to go out past 6 decimal places.

v(x) = 0.799278c
t(x) = 2.491007 seconds

Well then relativity would be wrong, because the light sphere doesn't expand relative to the source, it expands relative to the point in space the light was emitted, regardless of what the source does.
You have no experimental evidence for this. In fact, if you were correct about this, then GPS would not work. Guess what? GPS works.

My diagram was built on the measured times to the receivers in the cube, nothing else.
Your diagram was built upon assumed light travel times inside the cube. In reality, your travel time calculations only hold true in the "rest frame" through which your cube is moving.

From those measured times at the receivers I am able to calculate the absolute velocity of the box.
From your assumed times, you were able to calculate the velocity of the box relative to the "rest frame" through which you cube is moving.

You say relativity can do that too?

Tell me the distances and times in the cube frame from the source to the receivers of the .832 second example.
Relativity would tell you that the distances in the cube frame are all 0.5 lightseconds, and the travel times would all be 0.5 seconds. There would be no need for the concept of "absolute velocity". Just as in the GPS system, there is no need for the concept of "absolute velocity" of the earth.

There is no changing times and distances in the cube.
You asked for the times and distances in the cube frame, and I told you they are 0.5 seconds and 0.5 lightseconds, respectively. Now want to make a law that says relativity must use the MD time of 0.832 seconds? That doesn't leave a lot of room for relativity to correct your errors.

The only way you know the times is to measure them,
Measurements are taken experimentally. You just made up some numbers, and called them "measurements".

If you think the y receiver can be at two different coordinates at the same time then tell me both.
Ok. We're assuming light is emitted at t=t'=0 in the embankment and train frames. The y receiver is initially located at (x,y,z)=(x',y',z')=(0,0.5,0), where the distances are in light seconds.

You say that the light reaches the y receiver after 0.65 seconds. I assume that is in the embankment frame using embankment clocks.

In 0.65 seconds, light travels a distance of 0.65 light seconds.

For light to hit the y receiver, the y receiver must have travelled a distance:

$d = \sqrt{(0.5)^2 + x^2} = 0.65$

Here, x is the x coordinate of the y receiver when the light hits it.

Solving for x we find x = 0.42 light seconds.

So, the coordinates of the y receiver when the light hits it in the embankment frame are (x,y,z)=(0.42,0.5,0).

In the box/train frame, things are much easier, since the y receiver never moves. The coordinates of the y receiver when the light hits it are (x',y',z')=(0,0.5,0).

Summary of y receiver coordinates when light hits it:

Embankment frame: (x,y,z)=(0.42,0.5,0)
Train frame: (x',y',z')=(0,0.5,0)

Since it takes 0.65 seconds for the box to move 0.42 light seconds in the x direction, the speed of the box in the embankment frame is

speed = 0.42/0.65 = 0.65c.

That is, the train is moving at 65% of the speed of light.

Can relativity tell me the absolute velocity of the box?
No. Absolute velocity doesn't exist.

Does relativity acknowledge that it takes .65 seconds for light to travel from the source to the y and z receivers?
See calculation above, which is in accordance with relativity. Based on your calculations, do you agree that the speed of the box is 0.65c? If so, then we agree. If not, then one of us is wrong.

Well then relativity would be wrong, because the light sphere doesn't expand relative to the source, it expands relative to the point in space the light was emitted, regardless of what the source does.
See my helpful diagram in post #1027, which shows exactly this. Note that the train-frame diagrams would be wrong in the Motor Daddy universe, where light would not expand in a sphere, as I explained in post #1027.

My diagram was built on the measured times to the receivers in the cube, nothing else. From those measured times at the receivers I am able to calculate the absolute velocity of the box.
No. you only calculate the velocity of the box relative to the embankment.

16. Originally Posted by Zeno
After the light flashes in front, and before the light in the rear flashes, he covers it up with the bag, thereby blocking the light. Now, how do we explain this from the point of view of the embankment observer? There is no passage of time between the two flashes of light. So we seem to have a paradox.
Originally Posted by Neddy Bate
If the bag goes over the lamp before it flashes, then nobody sees it flash. In the embankment frame, the flashes would still be simultaneous, but there would be a bag hiding one of the flashes, that's all. No paradox.
So, in the train frame of reference the event of placing the bag over the lamppost occurs after the first light flash. In the frame of reference of the embankment, the event of placing the bag over the lamppost occurs before the first light flash. So, if the person on the train places the bag over the lamppost a certain amount of time after the first light flash from the frame of reference of the train, how can we determine how long before the first light flash did the person do it from the embankment frame?

17. Originally Posted by James R
Ok. We're assuming light is emitted at t=t'=0 in the embankment and train frames. The y receiver is initially located at (x,y,z)=(x',y',z')=(0,0.5,0), where the distances are in light seconds.
There is no embankment. You are in a cube in space, with no reference to any other object outside of the cube.

Originally Posted by James R
You say that the light reaches the y receiver after 0.65 seconds. I assume that is in the embankment frame using embankment clocks.
There is no embankment, so you assume wrong. You are in a cube in space. It took .65 seconds for light to travel from the source at the center of the cube to the y and z receivers.

Originally Posted by James R
In 0.65 seconds, light travels a distance of 0.65 light seconds.
Correct.

Originally Posted by James R
For light to hit the y receiver, the y receiver must have travelled a distance:

$d = \sqrt{(0.5)^2 + x^2} = 0.65$

Here, x is the x coordinate of the y receiver when the light hits it.

Solving for x we find x = 0.42 light seconds.

So, the coordinates of the y receiver when the light hits it in the embankment frame are (x,y,z)=(0.42,0.5,0).
There is no embankment. It is not .42 light seconds, it is .41533. Is that what you meant?

Originally Posted by James R
In the box/train frame, things are much easier, since the y receiver never moves. The coordinates of the y receiver when the light hits it are (x',y',z')=(0,0.5,0).
Again, you are in the cube. The y receiver's clock read .65 seconds. How do you figure it read .5 seconds? Are you trying to say that regardless of the motion of the box in space, that the time will always read .5 seconds at the y receiver?? That is simply impossible, James, as I've clearly shown in the diagram.

Originally Posted by James R
Summary of y receiver coordinates when light hits it:

Embankment frame: (x,y,z)=(0.42,0.5,0)
Train frame: (x',y',z')=(0,0.5,0)

Both wrong. There is not an embankment frame. There is light emitted from a source fixed at the center of the cube. You are in the cube. It took .65 seconds for light to reach the y receiver.

Originally Posted by James R
Since it takes 0.65 seconds for the box to move 0.42 light seconds in the x direction, the speed of the box in the embankment frame is

speed = 0.42/0.65 = 0.65c.

That is, the train is moving at 65% of the speed of light.
It is not .42 light seconds, it is .41533 light seconds.

Originally Posted by James R
No. Absolute velocity doesn't exist.
You're wrong, as I've clearly shown in the pic.

Originally Posted by James R
See calculation above, which is in accordance with relativity. Based on your calculations, do you agree that the speed of the box is 0.65c? If so, then we agree. If not, then one of us is wrong.
The absolute velocity of the box is .638971 c, so no, I don't agree.

What object do you think relativity says is in motion at the velocity of .638971 c, which the box is supposedly relative to? Do you think the red dot in the pic is traveling away from the box? Do you think the red dot is an object that is capable of motion? Do you understand what the red dot is?

Originally Posted by James R
No. you only calculate the velocity of the box relative to the embankment.
There is no embankment. There is no object to be traveling away from the box for relativity to claim is in motion. In your fantasy world, a train in motion can consider itself to be at rest and the tracks to be in motion, and nobody can say which is actually in motion, correct? Well, I am saying the cube in my pic is in motion, and guess what, there is no other object to make your false claims about. The red dot is not an object and is not capable of motion. There is nothing there, it is the point in space that the light was emitted at t=0. Light travels away from that point, regardless of what the source does. If the source moves away from that point, there is nothing there, it is simply a point in space, incapable of motion.

You are dead wrong, and so is relativity, James.

Relativity claims the times will always be .5 second on the clocks.

Do you really believe that if you tested the times, and found the times were .5 seconds on all receivers, that if you went to sleep in the box, and I came along and attached a rocket engine to the outside of your box and fired it, and accelerated the box to an unknown velocity, that when you woke up and tested the times again they would still be .5 seconds? If you think so, then your cheese has definitely slid off your cracker!

18. James is correct from the perspective of SR.
MD is correct from the MD's Light Box perspective.

I predict both are firm in their positions so I would like to ask MD to think about upgrading the box. More receptors; maybe say by adding a receptor at each corner making a total 14 receptors. And have you done any calculations of motion in more than one axis? These new receptors should help.

And multiple flashes equally spaced ... and maybe bursts long enough to show different frequencies ... the possibilities are endless, lol. Like when an spaceship goes spinning out of control when hit by an enemy laser weapon.

19. Originally Posted by quantum_wave
James is correct from the perspective of SR.
SR is incorrect so James is incorrect. It is impossible for the times to be .5 c in the cube frame in my pic. It is impossible to measure the speed of light to be c in the cube frame.

Originally Posted by quantum_wave
And have you done any calculations of motion in more than one axis? These new receptors should help.

x time: .761972 seconds
y time: .761972 seconds
z time: .92 seconds

Component velocities:

v(x) = .2300c
v(y) = .2300c
v(z) = .4022c

Coordinates of source at center of cube at .761972 seconds: (0.17525356,0.17525356,0.3064651384)

x .761972(.2300c) 0.17525356
y .761972(.2300c) 0.17525356
z .761972(.4022c) 0.3064651384

Coordinates of source at center of cube at .92 seconds: (.2116,.2116,.370)

x .92(.2300c) .2116
y .92(.2300c) .2116
z .92(.4022c) .370

Coordinates of source at center of cube at 1.0 seconds: (.23,.23,.4022)

x 1.0(.2300c) .23
y 1.0(.2300c) .23
z 1.0(.4022c) .4022

Distance center of cube traveled from start coordinates (0,0,0) to (.23,.23,.4022) in 1 second is 155,072,655.74 meters, so the absolute velocity of the center of the cube is 155,072,655.74 m/s.

20. Originally Posted by Motor Daddy
SR is incorrect so James is incorrect. It is impossible for the times to be .5 c in the cube frame in my pic. It is impossible to measure the speed of light to be c in the cube frame.

x time: .761972 seconds
y time: .761972 seconds
z time: .92 seconds

Component velocities:

v(x) = .2300c
v(y) = .2300c
v(z) = .4022c

Coordinates of source at center of cube at .761972 seconds: (0.17525356,0.17525356,0.3064651384)

x .761972(.2300c) 0.17525356
y .761972(.2300c) 0.17525356
z .761972(.4022c) 0.3064651384

Coordinates of source at center of cube at .92 seconds: (.2116,.2116,.370)

x .92(.2300c) .2116
y .92(.2300c) .2116
z .92(.4022c) .370

Coordinates of source at center of cube at 1.0 seconds: (.23,.23,.4022)

x 1.0(.2300c) .23
y 1.0(.2300c) .23
z 1.0(.4022c) .4022

Distance center of cube traveled from start coordinates (0,0,0) to (.23,.23,.4022) in 1 second is 155,072,655.74 meters, so the absolute velocity of the center of the cube is 155,072,655.74 m/s.

Motion on two axes? Not a very good graphic on my part but do you see the motion is linear re. the center of the box, but rotational re. the corners?

Let me describe the motion because I’m not very good at drawing in MSPaint.

Motion is linear along the x axis with rotation on one axis perpendicular to the x axis.

A light flash from the light source in the cube is emitted and the cube moves away from that point in space. The light sphere expands from that point in space.

The receptors begin to receive the light with the box in one frame and that frame has rotation on the y axis. We number the receptors, number 1 is the first to receive the light.

Based on the order and light seconds recorded (we number each consecutive receptor base on the order that they received the light), we learn something about the speed of the box and the rotation of the box.

Assuming continued regular motion along x and regular continued motion of y around the x axis, we could emit sequential bursts timed to record motion throughout rotation around the x axis and we could plot out the motion of the light box relative to the point of emission, strictly from data generated and received from within the box, I bet.

Or why not a light sphere instead of a light box. With receptors at all intersections on the wire grid and all 1/2 light second from the light source in the center?

Think of the motion of the light sphere that could be detected by sequential light flashes, and an on-board computer of course, lol.