Who Truly Experiences Slower Time in the Paradox of Time Dilation?

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The discussion centers on the concept of time dilation in the context of special relativity, particularly through the lens of the twin paradox. It highlights that while both twins perceive each other's clocks as running slow during their separation, the twin who accelerates (turns around) experiences less accumulated time due to the change in inertial frames. The conversation emphasizes that the aging difference is determined by the paths taken through spacetime, which can be calculated using proper time metrics. The importance of acceleration in breaking the symmetry of the situation is underscored, as it allows for a definitive comparison of ages upon reunion. Ultimately, the discussion reaffirms that Einstein's postulate regarding relative motion remains valid, even when considering acceleration.
  • #121


swerdna said:
No. I fully accept both statements. I made them. I don't accept sylas’s claim that - “Whether you are in motion or stationary is relative”.

Oh, I see. I believe sylas's claim is simply the traditional short hand for those two statements.
 
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  • #122


atyy said:
Oh, I see. I believe sylas's claim is simply the traditional short hand for those two statements.
Doesn't make it any less wrong.
 
  • #123


swerdna said:
Doesn't make it any less wrong.

:confused: I thought you accepted the 2 statements? Or are you saying that it is not acceptable short hand for the 2 statements?
 
  • #124


atyy said:
:confused: I thought you accepted the 2 statements? Or are you saying that it is not acceptable short hand for the 2 statements?
What are you drinking? Doesn’t make Sylas’s statement - “Whether you are in motion or stationary is relative” any less wrong. Nothing to do with the statements I made. Sylas made that statement before I made mine.
 
  • #125


swerdna said:
What are you drinking? Doesn’t make Sylas’s statement - “Whether you are in motion or stationary is relative” any less wrong. Nothing to do with the statements I made. Sylas made his/her statement before I made mine.

Well, if sylas's statements have the same meaning as statements you consider correct, how can you consider them wrong?
 
  • #126


atyy said:
Well, if sylas's statements have the same meaning as statements you consider correct, how can you consider them wrong?
“Whether you are in motion or stationary is relative” (sylas) and “When you are accelerating you are absolutely in motion (no relativeness required)” (me) are NOT the “same meaning“. Please read at least some of the thread before commenting on it.
 
  • #127


swerdna said:
“Whether you are in motion or stationary is relative” (sylas) and “When you are accelerating you are absolutely in motion (no relativeness required)” (me) are NOT the “same meaning“. Please read at least some of the thread before commenting on it.

So you disagree with the traditional shorthand, which is fair enough. That means you have no problem with special relativity?
 
  • #128


atyy said:
So you disagree with the traditional shorthand, which is fair enough. That means you have no problem with special relativity?
How can sylas’s statement be a shorthand response to my statement when his statement was made first Is he psychic?

Whatever it is that you are drinking I think you really have had more than enough.
 
  • #129


Stationary can only exist in a relative sense and not an absolute sense.

Motion can exist in a relative sense and also in an absolute sense in the form of acceleration.
 
  • #130


swerdna said:
Stationary can only exist in a relative sense and not an absolute sense.

Motion can exist in a relative sense and also in an absolute sense in the form of acceleration.

Sure, that's understandable short hand for the 2 statements. So you accept special relativity?
 
  • #131


atyy said:
Sure, that's understandable short hand for the 2 statements. So you accept special relativity?
You’re just pulling my leg aren’t you. Very funny.
 
  • #132


swerdna said:
You’re just pulling my leg aren’t you. Very funny.

So which part of special relativity don't you accept?
 
  • #133


atyy said:
So which part of special relativity don't you accept?
If you are actually interested read the thread.
 
  • #134


swerdna said:
If you are actually interested read the thread.

Which post? I can only tell you think you disagree with special relativity. I can't tell that you disagree with special relativity.
 
  • #135


swerdna said:
Written in layman-speak . . .

An inertial frame is defined by non-accelerating things that don’t move relative to each other.

Sure. Better: an inertial frame is defined as a frame in which the laws of physics look "pretty", eg. in which Maxwell's equations have their "standard" form. The reason this is better is that you have used "non-accelerating" without specifying whether it is non-accelerating relative to an inertial or a non-inertial frame. Your statement is true if "non-accelerating" is defined relative to an inertial frame. But then you would have used "inertial frame" in the definition of "inertial frame".

swerdna said:
No inertial frame can be stationary relative to any other inertial frame. It follows therefore that all inertial fames move relative to all other inertial frames.

Yes.

swerdna said:
There is absolutely no evidence that anything can ever be absolutely stationary. It follows therefore that no inertial frame can be absolutely stationary.

Yes, provided "absolutely" means "relative to all inertial frames".

swerdna said:
In other words inertial frames are always relatively and absolutely in motion.

Anything wrong with any of this?

This is wrong, if "absolutely" means "relative to all inertial frames", since each inertial frame is not in motion relative to itself, so it is not in motion relative to all inertial frames.
 
  • #136


Is the term “a thing is stationary relative to itself” really valid? Relative is one thing compared to another thing. For a thing to be relative to itself wouldn't it have to have multiple existence? How can a thing be relative to itself? A thing is itself. Stationary only exists as a relative situation so how can it be attributed to a situation that isn’t relative? A thing is in motion when it’s accelerating but acceleration isn’t a relative situation. I know I’ve used this term many times myself, but on reflection I thinks it’s nothing more than a nonsense
 
  • #137


swerdna said:
Is the term “a thing is stationary relative to itself” really valid? Relative is one thing compared to another thing. For a thing to be relative to itself wouldn't it have to have multiple existence? How can a thing be relative to itself? A thing is itself. Stationary only exists as a relative situation so how can it be attributed to a situation that isn’t relative? A thing is in motion when it’s accelerating but acceleration isn’t a relative situation. I know I’ve used this term many times myself, but on reflection I thinks it’s nothing more than a nonsense

I think it's ok.

But suppose it's not, that would still not make an inertial frame in motion relative to itself, so an inertial frame would not be in motion relative to all inertial frames, so it would not be in "absolute" motion, where "absolute" means "relative to all inertial frames".

Also, "acceleration is not relative" or "acceleration is absolute" is the traditional short hand for "acceleration is the same relative to all inertial frames".
 
  • #138


If I designed a 3D space (a big one) in a computer, then would relativity apply there to the objects I placed in it?
I was trying to work it out in my mind the other night, but got confused. Let's say I designed in a velocity of light (information) too. Probably no takers.. it was just a thought.
 
  • #139


swerdna said:
Is the term “a thing is stationary relative to itself” really valid? Relative is one thing compared to another thing. For a thing to be relative to itself wouldn't it have to have multiple existence? How can a thing be relative to itself? A thing is itself. Stationary only exists as a relative situation so how can it be attributed to a situation that isn’t relative? A thing is in motion when it’s accelerating but acceleration isn’t a relative situation. I know I’ve used this term many times myself, but on reflection I thinks it’s nothing more than a nonsense

BTW, I can't resist - have you heard of the man and his Ba? I think he tells his Ba not to leave him. Naively I understand a man's Ba to be himself, so the man is telling himself not to leave himself - how can that be? :confused: :smile:
 
  • #140


p764rds said:
If I designed a 3D space (a big one) in a computer, then would relativity apply there to the objects I placed in it?
I was trying to work it out in my mind the other night, but got confused. Let's say I designed in a velocity of light (information) too. Probably no takers.. it was just a thought.
What, you mean like a simulation? Not necessarily... the appeal of simulating things on the computer is that you can program in any physical laws you want. You could make your virtual world follow the laws of relativity if you want, or you could make it follow the laws of nonrelativistic mechanics (but then you'd run into trouble with Maxwell's equations, if EM fields existed in your virtual world).
 
  • #141


atyy said:
I think it's ok.

But suppose it's not, that would still not make an inertial frame in motion relative to itself, so an inertial frame would not be in motion relative to all inertial frames, so it would not be in "absolute" motion, where "absolute" means "relative to all inertial frames".
That made me laugh - thanks. You say suppose it's not okay to use the term then you immediately use the term!

atyy said:
Also, "acceleration is not relative" or "acceleration is absolute" is the traditional short hand for "acceleration is the same relative to all inertial frames".
Thanks for the clarification.
 
  • #142


atyy said:
BTW, I can't resist - have you heard of the man and his Ba? I think he tells his Ba not to leave him. Naively I understand a man's Ba to be himself, so the man is telling himself not to leave himself - how can that be? :confused: :smile:
As I walked upon a stair I saw a man that wasn’t there. He wasn’t there again today. I wish that man would go away.

ETA - If you leave me can I come too?
 
  • #143


swerdna said:
As I walked upon a stair I saw a man that wasn’t there. He wasn’t there again today. I wish that man would go away.

ETA - If you leave me can I come too?

:smile: :confused: :smile: :confused: :smile: :confused: :smile:
 
  • #144


But seriously . . . The important thing (to me at least) about it not being valid to say “a thing is stationary to itself” is that you then can’t use a single thing as a definition of stationary.

ETA - This means a non-accelerating thing is always moving in a relative sense.
 
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  • #145


swerdna said:
But seriously . . . The important thing (to me at least) about it not being valid to say “a thing is stationary to itself” is that you then can’t use a single thing as a definition of stationary.

But whether or not an inertial frame has 0 or undefined velocity relative to itself, that doesn't make it true that an inertial frame has a defined non-zero velocity relative to all inertial frames, since it would have either 0 or undefined velocity relative to itself.
 
  • #146


swerdna said:
ETA - This means a non-accelerating thing is always moving in a relative sense.

Sure, if relative means "relative to at least one inertial frame, but not relative to all inertial frames".
 
  • #147


atyy said:
:smile: :confused: :smile: :confused: :smile: :confused: :smile:

I understand your laughter but not your confusion.

“have you heard of the man and his Ba? I think he tells his Ba not to leave him. Naively I understand a man's Ba to be himself, so the man is telling himself not to leave himself”

“As I walked upon a stair I saw a man that wasn’t there. He wasn’t there again today. I wish that man would go away.”

“If you leave me can I come too?”

These are all a nonsense. I’m suggesting that “a thing is stationary relative to itself” is no less a nonsense
 
  • #148


atyy said:
Sure, if relative means "relative to at least one inertial frame, but not relative to all inertial frames".
If one inertial frame is not moving relative to another inertial frame then they are the same inertial frame.
 
  • #149


atyy said:
But whether or not an inertial frame has 0 or undefined velocity relative to itself, that doesn't make it true that an inertial frame has a defined non-zero velocity relative to all inertial frames, since it would have either 0 or undefined velocity relative to itself.
If "a thing is stationary relative to itself" is not a valid statement you can't use it. How can a thing be relative to itself?
 
  • #150


BTW, there is a very pedantic construction. We don't start by assuming frames to be either stationary or in motion relative to each other. A frame is just a coordinate system for space and time. An inertial frame is a coordinate system in which eg. Maxwell's equations take their standard form. Then one only talks about whether things (like a car, but not a whole frame) are stationary or moving relative to a frame. Consider a thing P that is stationary in inertial frame X, but moving in inertial frame Y. We can assign a velocity to frame X relative to frame Y by saying that it is the velocity of P in frame Y, where P is any thing that is stationary in frame X. In this way, we can define the velocity of a frame X relative to itself by saying that it is the velocity of P in frame X, where P is any thing that is stationary in frame X.
 
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