# Thread: A space time experiment . . .

1. This experiment is a though and arithmetic experiment.

We do make sum assumptions.

One assumption we make to do this experiment we assume time is absolute.

Now we have an observe A, traveler B and a destination C, one light year away.

Now the traveler B leaves observe A at 1/2 the speed of light. It will take 2 years fot the traveler to reach the destination.

The destination is year -1. at the time the traveler left. So from the observers point of view it will be 3 years before the observer sees the traveler arrived 1 light year away.

The observer sees the traveler's clock running slow at 2/3 speed.

The traveler is going to arive in two years. And will see his observer at year 1 when the traveler arrives at year 2.

So the traveler sees the observer's clock slower at 1/2 speed.

Shouldn't they see each other's clock rates slower at the same amount? One would think so.

The only way that can be possible to see both clocks appear to run at the same rate is if the traveler's time is to also be running slower according to relativity. And so this shows that time is not absolute and not the same every were.

2.

3. Originally Posted by 37818
This experiment is a though and arithmetic experiment.

We do make sum assumptions.

One assumption we make to do this experiment we assume time is absolute.
Well, that is going to cause you some problems...

Now we have an observe A, traveler B and a destination C, one light year away.

Now the traveler B leaves observe A at 1/2 the speed of light. It will take 2 years fot the traveler to reach the destination.
You need to be careful whose frame of reference you are using. It will take 2 years according to the observer.

The destination is year -1. at the time the traveler left.
Why isn't the time the same at the destination. You mentioned "absolute time"; wouldn't this imply it is the same time everywhere?

So from the observers point of view it will be 3 years before the observer sees the traveler arrived 1 light year away.
OK. It takes 2 years for the traveller to get there and 1 year for the light to return. That makes sense.

The observer sees the traveler's clock running slow at 2/3 speed.
No. The observer sees the traveller's clock running at 87% of his.

But if you are asserting absolute time, then surely he will see the other clock running at the same speed as his?

The traveler is going to arive in two years.
He will arrive in 2 years according to the observer. He will arrive in 1.7 years (I think) according to him.

And will see his observer at year 1 when the traveler arrives at year 2.
I'm pretty sure that is wrong, but I don't have time to work it out right now.

So the traveler sees the observer's clock slower at 1/2 speed.
No. The traveller sees the observer's clock running at 87% of his.

Shouldn't they see each other's clock rates slower at the same amount? One would think so.
They do. (Ignoring any acceleration at the start/end of the journey.)

The only way that can be possible to see both clocks appear to run at the same rate is if the traveler's time is to also be running slower according to relativity. And so this shows that time is not absolute and not the same every were.
Ah, I see. (I should have read the whole thing first!) But without relativity, they would see each others clocks running at the same speed. So, I'm not sure your argument works.

4. Originally Posted by Strange
Originally Posted by 37818
This experiment is a though and arithmetic experiment.

We do make sum assumptions.

One assumption we make to do this experiment we assume time is absolute.
Well, that is going to cause you some problems...

Now we have an observe A, traveler B and a destination C, one light year away.

Now the traveler B leaves observe A at 1/2 the speed of light. It will take 2 years fot the traveler to reach the destination.
You need to be careful whose frame of reference you are using. It will take 2 years according to the observer.

The destination is year -1. at the time the traveler left.
Why isn't the time the same at the destination. You mentioned "absolute time"; wouldn't this imply it is the same time everywhere?

So from the observers point of view it will be 3 years before the observer sees the traveler arrived 1 light year away.
OK. It takes 2 years for the traveller to get there and 1 year for the light to return. That makes sense.

The observer sees the traveler's clock running slow at 2/3 speed.
No. The observer sees the traveller's clock running at 87% of his.

But if you are asserting absolute time, then surely he will see the other clock running at the same speed as his?

The traveler is going to arive in two years.
He will arrive in 2 years according to the observer. He will arrive in 1.7 years (I think) according to him.

And will see his observer at year 1 when the traveler arrives at year 2.
I'm pretty sure that is wrong, but I don't have time to work it out right now.

So the traveler sees the observer's clock slower at 1/2 speed.
No. The traveller sees the observer's clock running at 87% of his.

Shouldn't they see each other's clock rates slower at the same amount? One would think so.
They do. (Ignoring any acceleration at the start/end of the journey.)

The only way that can be possible to see both clocks appear to run at the same rate is if the traveler's time is to also be running slower according to relativity. And so this shows that time is not absolute and not the same every were.
Ah, I see. (I should have read the whole thing first!) But without relativity, they would see each others clocks running at the same speed. So, I'm not sure your argument works.
By "seeing" he is taking into account Doppler effect(non-relativistic), this is how he arrives at the 2/3 value.

5. Originally Posted by Janus
By "seeing" he is taking into account Doppler effect(non-relativistic), this is how he arrives at the 2/3 value.
Ah yes. I see that now. Doesn't the argument still depend on both the "stationary" observer and the traveller seeing the same speed of light? And if you start from there, the you end up with special relativity automatically. But it is an interesting argument.

6. Originally Posted by 37818
This experiment is a though and arithmetic experiment.

We do make sum assumptions.

One assumption we make to do this experiment we assume time is absolute.

Now we have an observe A, traveler B and a destination C, one light year away.

Now the traveler B leaves observe A at 1/2 the speed of light. It will take 2 years fot the traveler to reach the destination.

The destination is year -1. at the time the traveler left. So from the observers point of view it will be 3 years before the observer sees the traveler arrived 1 light year away.

The observer sees the traveler's clock running slow at 2/3 speed.

The traveler is going to arive in two years. And will see his observer at year 1 when the traveler arrives at year 2.

So the traveler sees the observer's clock slower at 1/2 speed.

Shouldn't they see each other's clock rates slower at the same amount? One would think so.

The only way that can be possible to see both clocks appear to run at the same rate is if the traveler's time is to also be running slower according to relativity. And so this shows that time is not absolute and not the same every were.
Here's the thing, if you assume absolute time, then you are using the non-relativistic Doppler shift formula. And in this case, you are also assuming an absolute frame to which you are measuring the speed of light and the traveler. This leads to the Classical Doppler Shift:

c is the speed of light
Vr is the velocity of the receiver (positive when approaching the source)
Vs is the velocity of the source (positive when receding from the receiver)

So when the receiver is the Earth and source the traveler you get 2/3, Like you did. This tells me that you are assuming that the light travels at c relative to the Earth and that the Earth is at rest in this scenario. This also means that the Traveler is "moving" relative to the frame in which the light moves at c.

So, when the receiver is the traveler and the source the Earth, you get 1/2.

In other words, under these assumptions, you do not expect the Earth and traveler to see the same Doppler Shift. You are essentially describing a classical aether universe, and there is nothing incompatible with absolute time in this.

To get the doppler shift to be the same for both you would have to assume one of the following:

That the light travels at c only relative to the source. But in this would mean that the light coming from the traveler to the Earth would not be traveling a c relative to the Earth and the Earth would not see a doppler shift of 2/3 coming from the Ship, but 1/2 just like the Traveler sees coming from the Earth. This also is not incompatible with absolute time.

Or we assume the postulates of Relativity, which results in the Relativistic Doppler shift. But the Relativistic Doppler shift would give a value of 1/3, and is derived from the assumption of non-absolute time to start with.

To sum up, none of the assumptions made in the above scenarios proves non-absolute time in of themselves. It is only after comparing the predicted result from each to what we measure in real life itself that tell us which is true.

7. All the above comments and criticisms are of course correct. But, I think, miss the point of this exeriment. The non-relativistic dopper shift will not pass a physical experiment, for one thing. And the point of this experment was to show relativity must be true.

Using different distence and different speed give resultes that are just a bad, assuming absolute time.

The intent was to show relativity must be true. Maybe some of you might think of how this experiment might be better presented to show that a relativistic solution can only be the right one. And that the idea of absolute time must be false. Which it is.

8. Originally Posted by 37818
All the above comments and criticisms are of course correct. But, I think, miss the point of this exeriment. The non-relativistic dopper shift will not pass a physical experiment, for one thing. And the point of this experment was to show relativity must be true.

Using different distence and different speed give resultes that are just a bad, assuming absolute time.

The intent was to show relativity must be true. Maybe some of you might think of how this experiment might be better presented to show that a relativistic solution can only be the right one. And that the idea of absolute time must be false. Which it is.
This has been experimentally shown by the Ives-Stillwell experiment :

Ives

It is also central in explaining the spectrum of the microquasar SS433 :

SS 433 - Wikipedia, the free encyclopedia

9. Originally Posted by Markus Hanke
Originally Posted by 37818
All the above comments and criticisms are of course correct. But, I think, miss the point of this exeriment. The non-relativistic dopper shift will not pass a physical experiment, for one thing. And the point of this experment was to show relativity must be true.

Using different distence and different speed give resultes that are just a bad, assuming absolute time.

The intent was to show relativity must be true. Maybe some of you might think of how this experiment might be better presented to show that a relativistic solution can only be the right one. And that the idea of absolute time must be false. Which it is.
This has been experimentally shown by the Ives-Stillwell experiment :

Ives

It is also central in explaining the spectrum of the microquasar SS433 :

SS 433 - Wikipedia, the free encyclopedia
Yes. And so in principle it is really nothing new.

The idea of this experiment here was so that most anyone can do do it. With nothing more, maybe, than with a piece of paper, a pencil, and maybe even a calculator with a square root function to show and work the correction.

The intent was so to make the necessity of time dilation as a physical part of our universe can be understandable. So using this, as an experiment, how might its presentation be improved.

 Bookmarks
##### Bookmarks
 Posting Permissions
 You may not post new threads You may not post replies You may not post attachments You may not edit your posts   BB code is On Smilies are On [IMG] code is On [VIDEO] code is On HTML code is Off Trackbacks are Off Pingbacks are Off Refbacks are On Terms of Use Agreement