Speed of light for different observers

[Agerhell]

The twin paradox is not a purely theoretical example of how SR works. It's the other way around. SR is an example of a theory that explains the facts of the twin paradox.

Are you objecting to the experiments proving the twin paradox because they were done with mechanical clocks rather than with living biological beings?

What correlation are you concerned with and what does -1 mean?

Well, you know the twin paradox is not exactly proven... As it is normally described the traveling twin ages slower because he is accelerating...

In experiments time goes faster in weaker gravitational fields, higher up from the Earth its faster than on sea level and at the radial distance from the Sun of Jupiter it goes faster than on the earth...

Also clocks have shown to slow with velocity relative to gravitational fields... On Earth the velocity in relation to the centre of the Earth is most important. If you send a space probe out on an interplanetary journey the velocity in relation to the sun is what is most important...

Regarding sending clocks outside the solar system, no such experiments have been performed even though one of the Voyagers passed the 100 astronomic units from the sun mark some year ago...

 

[PAllen]

Well, you know the twin paradox is not exactly proven... As it is normally described the traveling twin ages slower because he is accelerating...

In experiments time goes faster in weaker gravitational fields, higher up from the Earth its faster than on sea level and at the radial distance from the Sun of Jupiter it goes faster than on the earth...

Also clocks have shown to slow with velocity relative to gravitational fields... On Earth the velocity in relation to the centre of the Earth is most important. If you send a space probe out on an interplanetary journey the velocity in relation to the sun is what is most important...

Regarding sending clocks outside the solar system, no such experiments have been performed even though one of the Voyagers passed the 100 astronomic units from the sun mark some year ago...

I think of muons surviving a long time in an accelerator ring a perfect demonstration of the twin paradox. Gravity is constant over this scale, you have a round trip (literally).

Also, I consider any comparison of two different paths through spacetime as examples of the twin paradox in GR context. Some of the airplane experiments have entailed round trips. To make an accurate prediction, both gravity changes and speed had to be factored in, with the results agreeing with prediction to within experimental error.

If you want to insist on a 100% pure SR verification, with no GR component, you have the silly requirement that the universe must be empty. The total geometric structure of the universe is inconsistent with the flat Minkowski metric. What one can say is the SR effects within the context of GR are well verified, including the 'combined' twin paradox. And that the pure SR case does not exist in our universe.

 

[sisoev]

The twin paradox is not a purely theoretical example of how SR works. It's the other way around. SR is an example of a theory that explains the facts of the twin paradox.

There are two types of paradoxes; derived from inconsistent logic or explaining inconsistent logic.
The paradoxes are fact, but they do not hold factual truth.

I am sure Einstein got the idea for the twin bothers from Jules Verne's book "Around the World in Eighty Days"
But there is no paradox in that book

 

[Dale]

Time dilation is not a scientific factor, it is not something you can actually see, measure, touch etc. ...
And because of the nature of time dilation, every other experiment done can be explained with it

This is not the case. Do you understand what it means for a theory to be falsifiable? A theory is considered falsifiable if there is a possibility of finding experimental evidence against it.
http://en.wikipedia.org/wiki/Falsifiability

You are suggesting that SR is non-falsifiable because a) time dilation is not measurable and b) everything else can be explained in terms of time dilation. So you are suggesting that any observation can be made compatible with SR simply by adjusting a non-observable parameter to fit the experimental outcome.

This is simply not the case. SR is falsifiable. Time dilation is measurable. SR makes specific predictions on the result of very high precision experiments. SR has no free parameters at all to adjust to fit an experimental outcome.

Your claim is completely baseless.

We can say that there is very strong correlation between decay of particles and increase in speed, and although i don't know the exact correlation i am 100% certain, it is not -1.

The correlation is 1/\sqrt{1-v^2/c^2}, exactly as predicted by SR.

 

[Dale]

You guys are seeing the graphics as third observers.
NO, forget about observing it from aside.
The graphics are to show the path of the light in every single frame.
"Single" frame means that it is treated the same way as the other; either both in motion or both in rest when examined for light path.

OK, so which is which? Is the first graphic the one where they are both in motion or is it the one where they are both at rest?

Btw, this is a very weird and non-standard way of drawing graphics, particularly since you have the source drawn as a single object. In one graphic the top of the source will be moving and the bottom stationary and in the other graphic the top of the source will be stationary and the bottom will be moving. Also, since each graphic is mixing frames clearly the distances will be mixed in each graphic also. No paradox there, just a weird drawing.

 

[Dale]

Well, you know the twin paradox is not exactly proven.

Yes, it is. See:
http://www.edu-observatory.org/physics-faq/Relativity/SR/experiments.html#Twin_paradox

 

[A.T.]

but that doesn't mean i started to believe that even if there is actual biological changes occurring in the bodies of the traveling objects they would be because time is "slowing down". The only way time dilation is proven is through decay of elementary particles

So you think that moving elementary particles decay slower, but moving living creatures don't age slower? That would create paradoxes like this one:

A clock uses the decay of elementary particles to measure 1 hour, then releases a dog from a cage. Some observer moves at high speed relative to the dog and the clock. For him the elementary particles in the alarm clock are moving very fast so they decay much slower (experimental fact). In his frame it takes decades for the cage to be opened. But according to you he would still observe the dog aging at a normal rate, so in his frame the dog would die in the cage.

 

[Denius1704]

Einstein didn't come up with time dilation, it was already an explanation used in the Lorentz Ether Theory.

I'm sorry about the ignorance shown in who came up with time dilation first, but the point i was making was different.

How can you say that time dilation is not a scientific factor? Would you also say that time is not a scientific factor because you cannot actually see, measure, touch, etc, it?

Time is purely a philosophical factor and can be debated for countless hours. Taking a philosophical term and implementing it into a scientific theory just doesn't make sense to me.

I also don't understand your last sentence in the preceeding quote. Can you elaborate on what you mean?

The twin paradox is not a purely theoretical example of how SR works. It's the other way around. SR is an example of a theory that explains the facts of the twin paradox.

Are you objecting to the experiments proving the twin paradox because they were done with mechanical clocks rather than with living biological beings?

What correlation are you concerned with and what does -1 mean?

You said it yourself, the twin paradox is a paradox only to the people that don't understand the physics of SR and through a bit of explanation i saw the logic of it as seen through SR. But in its essence (when you understand the mechanics of it) it is also a proof of time dilation as well, but only a theoretical explanation.

I am not objecting to the experiments proving the twin paradox, i am objecting to the term they use to explain it (time dilation)

I am not concerned with the correlation, i am concerned BECAUSE it's a correlation and nothing more. The -1 would suggest that there is a direct causal connection between the two factors, namely 1. Increase in speed and 2. lowering of the decay times of particles, but a -1 correlation is factually impossible so that would mean that there is a 3rd factor involved between those two factors and that 3rd factor in my opinion is something else than time dilation (because of it's purely theoretical and philosophical definition).

 

[Denius1704]

This is simply not the case. SR is falsifiable. Time dilation is measurable. SR makes specific predictions on the result of very high precision experiments. SR has no free parameters at all to adjust to fit an experimental outcome.

Your claim is completely baseless.

The correlation is 1/\sqrt{1-v^2/c^2}, exactly as predicted by SR.

The key phrase in your statement was "Time dilation is measurable". You don't seem to understand that what i am trying to say is, that it is quite possible that the factor you are observing is NOT actually time dilation, but something else completely.

And the formula you provided for the correlation between the two factors i mentioned, whatever the numbers are, in the end they would not make the outcome equal to 1 or -1, so that would mean that a direct causal connection between the two factors is indeed non existent.

P.S. And yes every theory is falsifiable, that's why it is a theory, and Froyd's theory is still just a theory but no one is making any attempt (or a successful one when there is an attempt), because it manages to put everything so nicely together. What people tend to overlook is that a few steps were skipped when explaining it, and it didn't go from A to B to C and so on, but it just made a few skips from A to C to E and so on. The steps were skipped, because they were unknown and still are, hence the impossibility of disproving it.

 

[Denius1704]

So you think that moving elementary particles decay slower, but moving living creatures don't age slower?

No, but what i do think is that you didn't really understand what i was trying to say. Look above to my other replies.

 

[A.T.]

it is quite possible that the factor you are observing is NOT actually time dilation, but something else completely.

Yeah, it could be invisible fairies that make everything that moves run/decay slower with their magic slowmo-dust, just to fool us to believe in time dilation.

And yes every theory is falsifiable,

Wrong. The theory above is not falsifiable. You will never be able to prove there are no invisible fairies that have magic slowmo-dust.

 

[Dale]

The key phrase in your statement was "Time dilation is measurable". You don't seem to understand that what i am trying to say is, that it is quite possible that the factor you are observing is NOT actually time dilation, but something else completely.

Complete nonsense. Time dilation simply means that a moving clock runs slow. So if you measure a moving clock running slow then you have measured time dilation by definition.

It is like saying that because the pre-Copernicus people used a geocentric model of the solar system that it was quite possible that the year they were measuring was not actually a year but something else completely. A year is the name of the observation, not the name of the theoretical explanation for it. Similarly time dilation is the name of the observation, not the name of the theoretical explanation for it. In relativity time dilation is explained by the two postulates, but time dilation is an experimental fact that any viable theory of physics must predict.

And the formula you provided for the correlation between the two factors i mentioned, whatever the numbers are, in the end they would not make the outcome equal to 1 or -1, so that would mean that a direct causal connection between the two factors is indeed non existent.

More nonsense. Clocks don't run backward so the factor will never be negative, and if they slow then the time dilation factor will not be 1.

P.S. And yes every theory is falsifiable

No, not every theory is falsifiable. For example, intelligent design is not falsifiable.

What people tend to overlook is that a few steps were skipped when explaining it, and it didn't go from A to B to C and so on, but it just made a few skips from A to C to E and so on. The steps were skipped, because they were unknown and still are, hence the impossibility of disproving it.

This forum is not the place for anti-relativity crackpots. Again, SR is imminently falsifiable, your claims here are patently false.

 

[ghwellsjr]

Time is purely a philosophical factor and can be debated for countless hours. Taking a philosophical term and implementing it into a scientific theory just doesn't make sense to me.

I don't know how we're ever going to make any progress with time dilation if you have this view of time.

You said it yourself, the twin paradox is a paradox only to the people that don't understand the physics of SR and through a bit of explanation i saw the logic of it as seen through SR.

Post #53 on this thread was the beginning of my explanation that helped you understand the logic of the Twin Paradox:

https://www.physicsforums.com/showthread.php?t=526763?&page=4

However, it was not an explanation as seen through Special Relativity. It was merely a description of what each twin actually sees of the other one's clock during the trip, which has nothing to do with any particular theory. It's a statement of the facts which any theory must abide by.

If I were to use SR to explain the theory behind the Twin Paradox, I would have established a Frame of Reference in which the home twin is forever at rest and provided coordinates in that frame for events at the start of the trip, the turn-around point, and the end of the trip. These coordinates would have demonstrated the time dilation for the traveling twin but not for the home twin and the difference in aging upon return. But this explanation would not have illustrated what each twin would actually see during the trip.

I would then use a different Frame of Reference and the Lorentz Transform to show that the same conclusion would be reached even though the Earth twin is now experiencing time dilation all the time and the traveling twin only experiences time dilation during half his trip.

And finally I would use a pair of Reference Frames in which the traveling twin is always at rest and the home twin is the one that is experiencing time dilation but still, the traveling twin is the one that ends up having aged less than the home twin at the end of the trip.

This is the whole point of SR: you can pick any Frame of Reference to define, demonstrate and analyze a scenario and you always get the same final answer.

I'd like to be able to help you learn SR but I fear that you have some grave philosophical objection to it that will prevent you from even taking a first step. Others have also tried and apparently haven't gotten anywhere.

But in its essence (when you understand the mechanics of it) it is also a proof of time dilation as well, but only a theoretical explanation.

I am not objecting to the experiments proving the twin paradox, i am objecting to the term they use to explain it (time dilation)

I am not concerned with the correlation, i am concerned BECAUSE it's a correlation and nothing more. The -1 would suggest that there is a direct causal connection between the two factors, namely 1. Increase in speed and 2. lowering of the decay times of particles, but a -1 correlation is factually impossible so that would mean that there is a 3rd factor involved between those two factors and that 3rd factor in my opinion is something else than time dilation (because of it's purely theoretical and philosophical definition).

Where did you get this aversion to time dilation? Has somebody been teaching you that it is bogus?

 

[Denius1704]

Complete nonsense. Time dilation simply means that a moving clock runs slow. So if you measure a moving clock running slow then you have measured time dilation by definition.

Complete nonsense. Time dilation simply means that time runs differently, and YOU are equating time running differently to clocks running slowly. Again skipping from A to C directly.

More nonsense. Clocks don't run backward so the factor will never be negative, and if they slow then the time dilation factor will not be 1.

More nonsense. In a correlation between two factors the coefficient can run from 0 to 1 or from 0 to -1 depending on whether the one factor increases together with the other factor or the one increases and the other one decreases. I have no idea why you are talking about clocks running backwards.

No, not every theory is falsifiable. For example, intelligent design is not falsifiable.

A theory stays a theory while it is falsifiable, after that it becomes a fact. And intelligent design is not a theory, it is a belief, at best a philosophical proposition.

This forum is not the place for anti-relativity crackpots. Again, SR is imminently falsifiable, your claims here are patently false.

Crackpot... not really, just curious and nonconformist. Just like sisoev also tried to tell you, there is a difference between being "anti" and "non". I guess i was asking too much for open mindedness. As scientists you need to be open to new ideas or old ideas expressed in a different way, otherwise progression turns to stagnation.

And A.T., no actually i don't think it's "invisible fairies", now THAT would be crack-potty. If i knew i wouldn't waste my time discussing my theories in forums, i would be a Nobel prize winner.

We can go back and forth throwing "smart" remarks about our knowledge or lack of thereof, but i am not interested in that. I saw that the way that the current threads are going we won't reach any conclusion, i expressed my views and i am done.

Cheers.

 

[Denius1704]

Where did you get this aversion to time dilation? Has somebody been teaching you that it is bogus?

Nobody has been teaching me anything about it. Actually you ghwellsjr taught me the most about it in the past couple of weeks. I do like the attitude you have towards people with other understandings and you do try to keep you cool most of the time :)

The aversion (although i don't think it's actually an aversion per se) comes from a purely philosophical point of view and the thought that because scientists are happy with the current explanation they are stopping from examining the possibility of extra factors that might be able to push the technological advancement of our era even further. It's the close mindedness that bothers me, because every time i talk with a physicist about this subject they tend to get on the defensive just like a christian might. That sort of attitude bothers me, nothing more.

SR has helped with a LOT of things and the way we see the Universe, but i don't know if it's enough to see the whole picture. I don't know how else to explain it.

 

[ghwellsjr]

Nobody has been teaching me anything about it. Actually you ghwellsjr taught me the most about it in the past couple of weeks. I do like the attitude you have towards people with other understandings and you do try to keep you cool most of the time :)

The aversion (although i don't think it's actually an aversion per se) comes from a purely philosophical point of view and the thought that because scientists are happy with the current explanation they are stopping from examining the possibility of extra factors that might be able to push the technological advancement of our era even further. It's the close mindedness that bothers me, because every time i talk with a physicist about this subject they tend to get on the defensive just like a christian might. That sort of attitude bothers me, nothing more.

SR has helped with a LOT of things and the way we see the Universe, but i don't know if it's enough to see the whole picture. I don't know how else to explain it.

I think the issue with the physicists that you have talked with is your reluctance to learn SR so that you can understand it. It's really very simple--not like GR which is really very complex. Once you understand SR, you can then understand why people who haven't bothered to learn SR cause so much frustration with those who do understand it and you can become one of those who will experience the frustration of those who refuse to learn SR as you try to help them over the hump.

And there are plenty of scientists who would love to find a flaw in Einstein's theories so they could take the throne of being the smartest person in the world. One of the September issues of Scientific American a few years back featured some of these scientists and their ideas. And they are good for the scientific enterprise because they help establish the reliability of a good theory.

 

[A.T.]

The aversion (although i don't think it's actually an aversion per se) comes from a purely philosophical point of view ...

Wrong forum. Go there:
https://www.physicsforums.com/forumdisplay.php?f=112

 

[Agerhell]

I think of muons surviving a long time in an accelerator ring a perfect demonstration of the twin paradox. Gravity is constant over this scale, you have a round trip (literally).

Also, I consider any comparison of two different paths through spacetime as examples of the twin paradox in GR context. Some of the airplane experiments have entailed round trips. To make an accurate prediction, both gravity changes and speed had to be factored in, with the results agreeing with prediction to within experimental error.

If you want to insist on a 100% pure SR verification, with no GR component, you have the silly requirement that the universe must be empty. The total geometric structure of the universe is inconsistent with the flat Minkowski metric. What one can say is the SR effects within the context of GR are well verified, including the 'combined' twin paradox. And that the pure SR case does not exist in our universe.

I am actually saying that for both effects of importance for the twin paradox, time dilation due to gravitational potential and time dilation due to high velocities, you must take the locally dominant gravitational field into account. You cannot really explain the time dilation due to high velocities in a way that is consistent with measurement within the framework of special relativity where you totally ignore gravitation.

Yes, it is. See:
http://www.edu-observatory.org/physics-faq/Relativity/SR/experiments.html#Twin_paradox

Citing from the above provided link:
"The so-called “twin paradox” occurs when two clocks are synchronized, separated, and rejoined. If one clock remains in an inertial frame, then the other must be accelerated sometime during its journey, and it displays less elapsed proper time than the inertial clock."

Is is the explanation that the difference in time elapsed is because one of the twins have undergone acceleration and not the other that I think is very troublesome... All experimental evidence (if you can, show me otherwise) points in the direction that what matter for an atomic clock is what speed it has in relation to the locally dominant gravitational field and how deep it is in the gravitational potential of that field, and has nothing to do with who has undergone acceleration. Example:

Two twins take off in spacecraft s both going at 100 km/s radially outwards from the sun. One twin keeps going outwards at the same speed, he stays in the inertial reference frame. The other twins accelerate by 100 km/s towards the sun so that he is at rest relative to the sun, he is the accelerated twin.

1. Whose clock do think will run faster, the accelerated twin that is at rest with respect to the sun or the twin that stays in the inertial frame moving at 100 km/s outwards from the sun?

2. When the twin that stays in his inertial frame reaches the radial distance from the sun of Pluto he decides to accelerate with a 100 km/s towards the sun, so that both twins now are at rest with respect to the sun. If the two twins send their time by light signals to each other, which twin do think will have experienced more elapsed time according to his atomic clock?

3a. The twin at Pluto moves infinitely slow back to the first twin. They compare their clocks. Who will show more elapsed time?

3b. The twin closest to the sun moves infinitely slow to the twin at the radial distance of Pluto. They compare their clocks. Who will show more elapsed time.

(I am a bit unsure what I would answer to 3a and 3b)

For the sake of argument let us ignore the fact that they have been spending time at different gravitational potential and only consider the time dilation due to velocity.

I could make a lot of other examples but if you stay with the assumption that on Earth it is basically speed in relation to the centre of the Earth that matters and in the solar system, far from any planet, it is basically the speed in relation to the sun that matters you tend to get the right result.

 

[sisoev]

OK, so which is which? Is the first graphic the one where they are both in motion or is it the one where they are both at rest?

Btw, this is a very weird and non-standard way of drawing graphics, particularly since you have the source drawn as a single object. In one graphic the top of the source will be moving and the bottom stationary and in the other graphic the top of the source will be stationary and the bottom will be moving. Also, since each graphic is mixing frames clearly the distances will be mixed in each graphic also. No paradox there, just a weird drawing.

As I said in the OP, initially this experiment was set in opposite direction.
there is a small confusion in the post you comment.
What I meant was that your persistence to exclude the distance from the path should be checked by setting the experiment in the other direction.
Then you'll get different result.
Your way of thinking will give then longer than the truck distance for the light in A frame.
Your argument gives shorter or longer distance, but never the distance of the truck.
How do you explain that?

Here it is.
And yes, the source is a single object, attached to the truck.
It sicks out for B to see the emitted light.

[PLAIN]http://onegative.org/speed-of-light21.gif

 

[ghwellsjr]

I am actually saying that for both effects of importance for the twin paradox, time dilation due to gravitational potential and time dilation due to high velocities, you must take the locally dominant gravitational field into account. You cannot really explain the time dilation due to high velocities in a way that is consistent with measurement within the framework of special relativity where you totally ignore gravitation.



Citing from the above provided link:
"The so-called “twin paradox” occurs when two clocks are synchronized, separated, and rejoined. If one clock remains in an inertial frame, then the other must be accelerated sometime during its journey, and it displays less elapsed proper time than the inertial clock."

Is is the explanation that the difference in time elapsed is because one of the twins have undergone acceleration and not the other that I think is very troublesome... All experimental evidence (if you can, show me otherwise) points in the direction that what matter for an atomic clock is what speed it has in relation to the locally dominant gravitational field and how deep it is in the gravitational potential of that field, and has nothing to do with who has undergone acceleration. Example:

Two twins take off in spacecraft s both going at 100 km/s radially outwards from the sun. One twin keeps going outwards at the same speed, he stays in the inertial reference frame. The other twins accelerate by 100 km/s towards the sun so that he is at rest relative to the sun, he is the accelerated twin.

1. Whose clock do think will run faster, the accelerated twin that is at rest with respect to the sun or the twin that stays in the inertial frame moving at 100 km/s outwards from the sun?

2. When the twin that stays in his inertial frame reaches the radial distance from the sun of Pluto he decides to accelerate with a 100 km/s towards the sun, so that both twins now are at rest with respect to the sun. If the two twins send their time by light signals to each other, which twin do think will have experienced more elapsed time according to his atomic clock?

3a. The twin at Pluto moves infinitely slow back to the first twin. They compare their clocks. Who will show more elapsed time?

3b. The twin closest to the sun moves infinitely slow to the twin at the radial distance of Pluto. They compare their clocks. Who will show more elapsed time.

(I am a bit unsure what I would answer to 3a and 3b)

For the sake of argument let us ignore the fact that they have been spending time at different gravitational potential and only consider the time dilation due to velocity.

I could make a lot of other examples but if you stay with the assumption that on Earth it is basically speed in relation to the centre of the Earth that matters and in the solar system, far from any planet, it is basically the speed in relation to the sun that matters you tend to get the right result.

You should know by now, when discussing the Twin Paradox, that until the twins are colocated, you cannot say whose clock has elapsed less time.