There is no time dilation (split from The twin Paradox revisited)

[Boltzmannbrain]

6 hours ago, martillo said:

And you succeeded. My calculations were wrong. I admit it now.

Any acceleration. Gravity, vehicles' accelerations, whatever.

I think time dilation and length contraction exist as observed on different frames in Relativity Theory but also the relativity of simultaneity. I'm thinking the things could run such a way that different aging is something that could actually not take place ever. I mean, as Genady said some at some post, the timestamps in the clocks of each traveler is always the same so aging actually would not actually take place. That's what happens in the problem we analyzed with constant velocities and no acceleration so valid between inertial frames only. Now I'm speculating on the possibility that something similar could happen with accelerated frames. Just speculating with the idea now. As Markus Hanke said there's some experiments showing time dilation in accelerated frames but may be, just may be, aging could be something different that could actually not take place in this case too may be due to the relativity of simultaneity. I mean time is affected by accelerations but simultaneity too and so may be the timestamps (clocks' readings) could always be the same...

You are right.  There is no actual time dilation or length contraction for anything.  They are only perceptions/observations.  This might cause a stir here, but it's true.

[martillo]

35 minutes ago, Boltzmannbrain said:

You are right.  There is no actual time dilation or length contraction for anything.  They are only perceptions/observations.  This might cause a stir here, but it's true.

That's it. Thanks! (+1)

By the way... If you find this stirring wait for the next thread of mine...

[Lorentz Jr]

1 hour ago, Boltzmannbrain said:

There is no actual time dilation or length contraction for anything.  They are only perceptions/observations.  This might cause a stir here, but it's true.

Really? Do you have some proof or evidence for that? According to the Lorentz transformations, less time passes for the astronaut in the twin paradox than for the twin who stayed on Earth. In @martillo's language, the earthbound twin's beard is longer than the astronaut's beard. What part of that do you not believe, and why don't you believe it?

Edited February 21, 2023 by Lorentz Jr

[swansont]

1 hour ago, Boltzmannbrain said:

You are right.  There is no actual time dilation or length contraction for anything.  They are only perceptions/observations.  This might cause a stir here, but it's true.

How do clocks (such as used in the Hafele-Keating experiment)  “perceive” time?

[Boltzmannbrain]

2 hours ago, Lorentz Jr said:

Really? Do you have some proof or evidence for that? According to the Lorentz transformations, less time passes for the astronaut in the twin paradox than for the twin who stayed on Earth. In @martillo's language, the earthbound twin's beard is longer than the astronaut's beard. What part of that do you not believe, and why don't you believe it?

I will try to explain as best I can.

First we will start with time dilation; it is much easier than explaining the perception of length contraction.  For any object, time runs the same, 1 second per second.  That I don't think is too controversial or misunderstood.  So time dilation is only perceived; it doesn't actually happen to anything.  Yes the twin will have a bigger beard when when they meet.  But remember, the twin with the longer beard is actually still perceiving his/her own time in the past (with a short beard) at 1 second per second.  So the younger twin is only meeting his/her sibling in the future.  No time dilation actually occurs for the object that is perceived to have dilated time.

Second, length contraction, this is much harder to explain, so here is a spacetime diagram.  Imagine Bob is in a ship flying by Alice really fast at the point p.  Imagine that the origin is brought to point p (I did not put it all at the origin because it crammed everything together too much).  Alice sees the ship contracted from point p to g, say 3 meters.  Bob is in the ship, and it has its normal length from his point of view, say 10 meters. 

Assume all points p, s and g synchronize their clocks.  At the point that they sync their clocks, you might notice that Alice sees point g of the ship, while Bob sees point s of the ship.  s and g are the same 2 points on the ship, but they are seen at different angles in spacetime.  There is no length contraction; it is also a matter of perception.

 

 

  

 

 

 

Edited February 21, 2023 by Boltzmannbrain

[Lorentz Jr]

1 hour ago, Boltzmannbrain said:

For any object, time runs the same, 1 second per second.  That I don't think is too controversial or misunderstood.  So time dilation is only perceived; it doesn't actually happen to anything.

That doesn't mean it didn't happen. It only proves that it wasn't perceived in the dilated reference frame.

1 hour ago, Boltzmannbrain said:

  Yes the twin will have a bigger beard when when they meet.

Then it's real. By definition, anything that everybody agrees on is real.

1 hour ago, Boltzmannbrain said:

No time dilation actually occurs for the object that is perceived to have dilated time.

Actually, that is  the definition of time dilation. If the person noticed something happening, it would be considered some kind of more specific change, not a change in the flow of time itself. By definition, time dilation is when less time elapses in one reference frame than in some other frame.

1 hour ago, Boltzmannbrain said:

Second, length contraction, this is much harder to explain

The thread is about time dilation, not length contraction.

[Boltzmannbrain]

10 minutes ago, Lorentz Jr said:

That doesn't mean it didn't happen. It only proves that it wasn't perceived in the dilated reference frame.

It happens, but it doesn't happen to anything.  It is only perceived by an outside observer.  

Quote

Then it's real. By definition, anything that everybody agrees on is real.

I agree.  But the twins are now in different points in time even though they see each other as aged differently.

Quote

Actually, that is  the definition of time dilation. If the person noticed something happening, it would be considered some kind of more specific change, not a change in the flow of time itself. By definition, time dilation is when less time elapses in one reference frame than in some other frame.

I agree.  I wasn't trying to say that time dilation is wrong.  From what I read in martillo's post, I believe that he or she is taking the semantics too strictly, thus causing doubt in time dilation altogether.  So I tried to explain time dilation in this way.

[Lorentz Jr]

43 minutes ago, Boltzmannbrain said:

It happens, but it doesn't happen to anything.  It is only perceived by an outside observer.  

Meaningless word games. If time dilation "happens", it has to happen to the astronaut, because his state of motion changed.

43 minutes ago, Boltzmannbrain said:

I agree.  But the twins are now in different points in time even though they see each other as aged differently.

Your definition of time is meaningless. The twins are standing right in front of each other, each tugging on the other's beard.

[martillo]

It must be remembered the point of discussion is that in the current solution for the twins' paradox the travelling one will meet the stationary one with less beard and it can be only speculated now a possible different solution with both meeting with same beard and so same age. This cannot be demonstrated so easily. It would involve apply General Relativity on the time of the acceleration of the travelling twin in the turning back considering the relativity of simultaneity in the same way we applied for our case of twins travelling just in inertial frames without acceleration. The point is that if current solution has applied this properly or not. This is area of General Relativity only where I have no expertise at all to enter and so I cannot help here. I agree with Boltzmannbrain point of view but I cannot help.

Edited February 21, 2023 by martillo

[Genady]

20 minutes ago, martillo said:

It must be remembered the point of discussion is that in the current solution for the twins' paradox the travelling one will meet the stationary one with less beard and it can be only speculated now a possible different solution with both meeting with same beard and so same age. This cannot be demonstrated so easily. It would involve apply General Relativity on the time of the acceleration of the travelling twin in the turning back considering the relativity of simultaneity in the same way we applied for our case of twins travelling just in inertial frames without acceleration. The point is that if current solution has applied this properly or not. This is area of General Relativity only where I have no expertise at all to enter and so I cannot help here. I agree with Boltzmannbrain point of view but I cannot help.

All this has been already said and debunked. Nevertheless, the OP repeats themselves without any progress.

The OP is going in circles ignoring input from various members and not supporting their claims with any evidence. 

This thread is now a troll. The OP does not discuss in good faith.

 

* the OP above refers to @martillo

Edited February 21, 2023 by Genady

[martillo]

20 minutes ago, Genady said:

The OP does not discuss in good faith.

I just said I'm not able to discuss here because goes beyond my expertise and cannot help. I'm just  saying I cannot discuss here anymore.

[Markus Hanke]

14 minutes ago, martillo said:

It would involve apply General Relativity on the time of the acceleration of the travelling twin

No, it wouldn’t. This is purely a SR problem, and all it involves is comparing the lengths of the two world lines, which is a straightforward (though not always easy to evaluate) line integral:

\[\tau =\int _{C} ds=\int _{C}\sqrt{\eta _{\mu \nu } dx^{\mu } dx^{\nu }}\]

wherein C is the path in question.

Now, even without having to consider any specific numbers, we can work out the differential ageing between the two. Suppose we have two events in spacetime, A and B, which we connect via two different paths (the two twins) - we assume for simplicity that the two events have the same spatial coordinates, and differ only in time; this would correspond to (eg) one twin remaining stationary and inertial somewhere, and the other one travelling away and returning again, so that they both start off together at rest, and finish together at rest. This is the simplest possible twin scenario.

Let’s use a coordinate system that has its origin at event A, and a metric with sign convention (+,-,-,-). The inertial twin then simply traces out a world line of length

\[\tau_{1} =\int _{A}^{B} ds=\int _{A}^{B}\sqrt{\eta _{00} dx^{0} dx^{0}} =\int _{A}^{B} d\tau\]

The other twin, the one that is travelling away and returning, on the other hand traces out a world line of length

\[\tau_{2} =\int _{A}^{B} ds=\int _{A}^{B}\sqrt{\eta _{\mu \nu } dx^{\mu } dx^{\nu }} =\int _{A}^{B}\sqrt{( d\tau )^{2} -( dx)^{2}}\]

wherein dx depends on the spatial path of that travelling twin. Since we know from the extremal value problem in variational calculus that the inertial traveller always maximises the path length between given events (using this sign convention in the metric), and since the two paths in this scenario are not identical, we can immediately conclude that it must be the case that 

\[\tau _{1}  >\tau _{2}\]

This also implies that the path of the travelling twin can never be a geodesic, so it cannot be everywhere inertial.

[studiot]

4 hours ago, Boltzmannbrain said:

It happens, but it doesn't happen to anything.  It is only perceived by an outside observer.  

The problem with this is that it is in opposition to one expression of a fundamental point of relativity.

Notably that the is no preferred point of view.

Discussing only from the POV of the own frame of a subject, is a preferred point of view.

Edited February 21, 2023 by studiot

[joigus]

9 hours ago, Boltzmannbrain said:

You are right.  There is no actual time dilation or length contraction for anything.  They are only perceptions/observations.  This might cause a stir here, but it's true.

Wrong! When you try to make an object get in a garage and it's longer than the door, you must rotate it to make it fit. That's forshortening. One would think forshortening is just a matter of perception. But if you don't rotate the object, you will end up damaging the door, or the object, or both. So it's real enough for me, and for anybody, and not just a matter of 'perception.'

Now suppose you have a muon in the atmosphere, moving slowly towards the ground.* It doesn't reach the detector at ground level, simply because it doesn't live long enough. Move at close to the speed of light and it will reach the ground. Now, I don't know what you call real, but that's real enough for me.

Time dilation is is the equivalent of forshortening due to rotation, but in this case it happens in space and time. Lorentz transformations are (hyperbolic) rotations within a certain (t,x) plane.

Only when the observed object stops, or decays, this extra time due to time dilation can be 'cashed in,' so to speak. Clocks 'know' about it.

Similarly, when we try to re-orient the object we got in the garage, we can tell it doesn't fit**. How did it get in then? The foreshortening we used to get it in was very real.

The elongation of the muon's lifetime that allowed it to reach the ground was real too.

Unless you're willing to take it one further step and start discussing what's real and what's not. I won't follow you down that road.

Decades ago there was a famous problem about two tethered spaceships and whether space contraction was real. It went around the CERN cafeteria, and many --professional physicists, mind you-- thought the conclusion of the analysis was that it was just an illusion. John Bell managed to prove it must be real.

* Not a typical situation, because cosmic rays typically reach the atmosphere close to the speed of light.

** Spatial equivalent of the twin brother in the twin paradox turning back to Earth, not being inertial anymore, and checking clocks. 

[Boltzmannbrain]

7 hours ago, Lorentz Jr said:

Meaningless word games. If time dilation "happens", it has to happen to the astronaut, because his state of motion changed.

 

No, it definitely does not happen to the astronaut or anything.  Time flows at the same rate for everyone/everything. 

 

Quote

Your definition of time is meaningless. The twins are standing right in front of each other, each tugging on the other's beard.

Yes, that also happens.  But when they are tugging on each others beard, the other twin is still travelling to the meeting point.

 

Again, I am not saying time dilation is wrong or doesn't exist.  It's just a way of looking at exactly what it is.  When people hear common phrases like, "one twin ages 10 years while the other twin only ages one week" that can be taken the wrong way.  It could mean that the twin in the ship only experienced one week.  I am trying to explain to martillo this ambiguity, especially because I believe that is how he or she has been thinking about time dilation.  

Edited February 21, 2023 by Boltzmannbrain

[Genady]

1 minute ago, Boltzmannbrain said:

It could mean that the twin in the ship only experienced one week. 

But it is precisely what it means.

[Boltzmannbrain]

4 hours ago, studiot said:

The problem with this is that it is in opposition to one expression of a fundamental point of relativity.

Notably that the is no preferred point of view.

Discussing only from the POV of the own frame of a subject, is a preferred point of view.

Time dilation only happens to a POV.  It does not happen for the object being viewed.  This is widely understood; it is not controversial at all, at least for mainstream physics.

[Lorentz Jr]

18 minutes ago, Boltzmannbrain said:

No, it definitely does not happen to the astronaut or anything.  Time flows at the same rate for everyone/everything. 

Your use of the word "happen" is meaningless. What happens to the astronaut is that his beard grows less than his twin's beard, regardless of how he perceives the flow of time, i.e. how time flows "for him".

18 minutes ago, Boltzmannbrain said:

Yes, that also happens.  But when they are tugging on each others beard, the other twin is still travelling to the meeting point.

There are only two twins in the twins paradox.

Edited February 21, 2023 by Lorentz Jr

[Boltzmannbrain]

4 hours ago, joigus said:

Wrong! When you try to make an object get in a garage and it's longer than the door, you must rotate it to make it fit. That's forshortening. One would think forshortening is just a matter of perception. But if you don't rotate the object, you will end up damaging the door, or the object, or both. So it's real enough for me, and for anybody, and not just a matter of 'perception.'

Now suppose you have a muon in the atmosphere, moving slowly towards the ground.* It doesn't reach the detector at ground level, simply because it doesn't live long enough. Move at close to the speed of light and it will reach the ground. Now, I don't know what you call real, but that's real enough for me.

Time dilation is is the equivalent of forshortening due to rotation, but in this case it happens in space and time. Lorentz transformations are (hyperbolic) rotations within a certain (t,x) plane.

Only when the observed object stops, or decays, this extra time due to time dilation can be 'cashed in,' so to speak. Clocks 'know' about it.

Similarly, when we try to re-orient the object we got in the garage, we can tell it doesn't fit**. How did it get in then? The foreshortening we used to get it in was very real.

The elongation of the muon's lifetime that allowed it to reach the ground was real too.

This is also widely misunderstood.  The muon experiences the same amount of time as the observer.  The muon *does not* experience different time than the observer, even though I see that term written everywhere.  

If you look at it in a spacetime diagram, the muon cheats; it takes a different angle through spacetime.  It takes a "shortcut" even though we were always taught that the fastest way to get from point A to point B is a straight line.  It turns out the fastest way to get from point A to point B is to go really fast.

22 minutes ago, Genady said:

But it is precisely what it means.

No, that is wrong.  This is a perfect example of why I brought this up with martillo.

[Genady]

2 minutes ago, Boltzmannbrain said:

No, that is wrong. 

What is wrong about it?

[Boltzmannbrain]

9 minutes ago, Lorentz Jr said:

There are only two twins in the twins paradox.

No, there are an infinite number of twins in every moment in time, or every "slice in the block". 

[Lorentz Jr]

5 minutes ago, Boltzmannbrain said:

No, there are an infinite number of twins in every moment in time, or every "slice in the block". 

Your use of the word "twins" is meaningless. 😄

Apparently there's an infinite number of trolls on the internet. 🙄

Edited February 21, 2023 by Lorentz Jr

[Boltzmannbrain]

22 minutes ago, Genady said:

What is wrong about it?

Please ignore this post.  I made a mistake.  I need more coffee!

If you only experience 1 week in the ship, then shouldn't your clock/calendar show 1 week?  Going by your clock, in your 1 week you are still leaving Earth.  You need to experience a long painful 10 years to get back to Earth.  

Edited February 21, 2023 by Boltzmannbrain

[Genady]

1 minute ago, Boltzmannbrain said:

If you only experience 1 week in the ship, then shouldn't your clock/calendar show 1 week?  Going by your clock, in your 1 week you are still leaving Earth.  You need to experience a long painful 10 years to get back to Earth.  

And the clock/calendar in the ship will indeed show 1 week.

[Boltzmannbrain]

14 minutes ago, Lorentz Jr said:

Your use of the word "twins" is meaningless. 😄

Apparently there's an infinite number of trolls on the internet. 🙄

So if you can't understand what I am saying, then I must be a troll.  Great attitude, god luck learning anything new. 

11 minutes ago, Genady said:

And the clock/calendar in the ship will indeed show 1 week.

Sorry, I meant that the time dilation does not happen for the people on Earth even though it appears that way from the ship.  The Earth (not the traveler) experiences a long 10 years.  In other words, nobody experiences time dilation; it is only an observation from a different POV.  

Edited February 21, 2023 by Boltzmannbrain