[alancalverd]

As relativistic mechanics is now accepted as fundamental, with classical or newtonian mechanics being a special case where v<<c, the question is actually badly phrased.

The meaningful  question is "what causes apparent simultaneity?"

[Zer0]

Hope the OP won't mind me Intruding.

If i am in a spacecraft moving at 1%
Speed of Light...
I'm at the Centre..
Which blinking light would i see first, the front or the back one?

[hamdani yusuf (OP)]

In summary, it says that the difference is due to equivalence principle.

I guess you will never be able to understand the twin 'paradox' with all the different explanations on Youtube.

Eliminating paradox can be done by showing the mistakes in every contradicting explanation, except one.

[hamdani yusuf (OP)]

What it is about has already been well explained. Most you-tube videos on the subject contain mistakes. The one you provide is blatantly wrong in several areas.

Can you find a YouTube video on the subject that doesn't contain mistakes?

[hamdani yusuf (OP)]

As relativistic mechanics is now accepted as fundamental, with classical or newtonian mechanics being a special case where v<<c, the question is actually badly phrased.

The meaningful  question is "what causes apparent simultaneity?"

Is there any experimental evidence showing that traveling twin age less than staying twin, excluding every other effects but their speed?

[hamdani yusuf (OP)]

Hope the OP won't mind me Intruding.

If i am in a spacecraft moving at 1%
Speed of Light...
I'm at the Centre..
Which blinking light would i see first, the front or the back one?

Theoretically, you will see them at the same time.
Practically, you'll see the one you are facing to, except you use some helping devices like a mirror.

[alancalverd]

Is there any experimental evidence showing that traveling twin age less than staying twin, excluding every other effects but their speed?

It is not possible to do so directly. You need to synchronise your clocks, which requires that they are not moving with respect to one another, then accelerate one to the required speed.

You can however calculate and subtract all the effects of acceleration, gravitation etc from any practical observation.

[Origin]

Is there any experimental evidence showing that traveling twin age less than staying twin, excluding every other effects but their speed?

You mean like humidity changes or something?

[Halc]

Eliminating paradox can be done by showing the mistakes in every contradicting explanation, except one.

Even one explanation with a mistake contradicting the theory would still be a wrong one.

Try all the ones that don't contradict relativity. There are many different valid explanations of the twins scenario, and none of them contradict SR or each other. If one claims to be the "one correct" explanation, it is wrong.

Can you find a YouTube video on the subject that doesn't contain mistakes?

The Minutephysics video you linked in post 17 seems reasonable. It isn't the simplest explanation, but it isn't wrong because of that.

Is there any experimental evidence showing that traveling twin age less than staying twin, excluding every other effects but their speed?

It wasn't ever done with human twins, no. There is very much experimental evidence done with say crude clocks, and all done in a way that gravity plays no role, such as in a cyclotron.

If i am in a spacecraft moving at 1% Speed of Light...

Relative to what? I mean, Earth is moving at 1% c relative to something. It is also moving at 95%c relative to something else.

I'm at the Centre.. Which blinking light would i see first, the front or the back one?

If both lights blink simultaneously in the frame of the ship, then since light moves at c relative to that frame, the light will reach the center at the same event.
If the lights blink simultaneously relative to any frame in which the ship is moving, then they probably have different distances to travel in that alternate frame and will thus probably not arrive simultaneously at the detector.

Point is, you didn't say how the blinking lights in the ship are synced. You specified no frame in which they blink at the same time, or if they blink at the same time at all. Maybe they blink hours apart. You don't say.

The meaningful  question is "what causes apparent simultaneity?"

You give zero indication of what you think 'apparent simultaneity' means. It's not a known term. Simultaneity is a convention, an abstraction. There's nothing physical about it, and no empirical test for it. The phrase seems to imply that there's a way to measure it without first presuming an abstract coordinate system.

You need to synchronise your clocks, which requires that they are not moving with respect to one another

Clocks in each other's presence can be synced to the same value at that event, without any requirement of them being mutually stationary.
You need a citation to back this speculation.

[hamdani yusuf (OP)]

Is there any experimental evidence showing that traveling twin age less than staying twin, excluding every other effects but their speed?

You mean like humidity changes or something?

Yes. Also other effects like temperature, pressure, electromagnetic radiation, gravitational acceleration and potential.

[hamdani yusuf (OP)]

Even one explanation with a mistake contradicting the theory would still be a wrong one.

Try all the ones that don't contradict relativity. There are many different valid explanations of the twins scenario, and none of them contradict SR or each other. If one claims to be the "one correct" explanation, it is wrong.

Many Youtube videos trying to explain Twin Paradox point out what's wrong in explanations provided by other videos or books. Latter videos try to correct earlier ones while declaring that they still follow theory of relativity, either special or general one.
Some say that special relativity is not adequate to explain the paradox, while the others say that it is adequate. They are contradicting each other.
Some say that Doppler effect must be taken into account, while the others say it's unnecessary.
Some even declare that there is no paradox even without analyzing the situation from the perspective of traveling twin.
Saying that they are equally valid is not a logically sound position.

[alancalverd]

from: alancalverd on 25/12/2023 23:00:44
The meaningful  question is "what causes apparent simultaneity?"

You give zero indication of what you think 'apparent simultaneity' means. It's not a known term. Simultaneity is a convention, an abstraction. There's nothing physical about it, and no empirical test for it. The phrase seems to imply that there's a way to measure it without first presuming an abstract coordinate system.

That's the whole point: simultaneity is a convention. We perceive and describe two nearby events as simultaneous if we receive information from both of them coincidentally, but we know that if the sources are at different distances from us, or indeed travelling at different velocities relative to us, they would not appear simultaneous to an observer for whom the arrangement was symmetrical.

from: alancalverd on Yesterday at 14:46:05
You need to synchronise your clocks, which requires that they are not moving with respect to one another

Clocks in each other's presence can be synced to the same value at that event, without any requirement of them being mutually stationary.
You need a citation to back this speculation.

Synchronisation doesn't just mean showing the same number at a given instant. There is a presumption in "gentlemen, synchronise your watches" that  they will all continue to tick at the same rate for long enough to effectively coordinate the invasion. But relativity tells us that as the army, navy and air force travel at different speeds, they won't be coordinated when they reach alpha centauri.

[Zer0]

Hope the OP won't mind me Intruding.

If i am in a spacecraft moving at 1%
Speed of Light...
I'm at the Centre..
Which blinking light would i see first, the front or the back one?

Theoretically, you will see them at the same time.
Practically, you'll see the one you are facing to, except you use some helping devices like a mirror.

What if i was standing Sideways?
Or
Assume both Blinkers were Synchronised while spacecraft was at Speed 0.

Gradually 1%c is reached.
My left eye tracking Front blinker.
My right eye tracking Back blinker.

Let's say i am Not interested in the Theoretical part of it.
I just wanna know Which one i'd see blinking first/faster?

ps - is there any possible way U could avoid using SR/GR & give a Simplistic answer.

[Origin]

Let's say i am Not interested in the Theoretical part of it.
I just wanna know Which one i'd see blinking first/faster?

If the  lights were synchronized at zero m/s, then no matter how fast you were going they would stay synchronized.  IOW the light from both sources would continue to hit you at exactly the same time.

[Halc]

Many Youtube videos trying to explain Twin Paradox point out what's wrong in explanations provided by other videos or books.

Which means either that these videos are wrong, or they're correct about the mistakes being made by the other videos/books. If they say that their own explanation is the one correct one, then the former is true.

Some say that special relativity is not adequate to explain the paradox, while the others say that it is adequate. They are contradicting each other.

The latter case is correct here. The former claims indeed contradict that, and are wrong.

Some say that Doppler effect must be taken into account, while the others say it's unnecessary.

The latter would be the correct one here. Mind you, the twins thing can be explained by perspectives and appearances, and Doppler needs to be taking into account if you do it that way, but the valid video I mentioned above makes no mention of Doppler, illustrating that indeed not always necessary,.

Some even declare that there is no paradox even without analyzing the situation from the perspective of traveling twin.

That would be correct. There is not paradox no matter how you look at it. It only becomes paradoxical if one drags in biases from outside of relativity theory.

Saying that they are equally valid is not a logically sound position.

I didn't say all the 'explanations' mentioned above are equally valid, since several make incorrect assertions. So I agree with this statement, but nobody is claiming all these statements are valid.

simultaneity is a convention.

Simultaneity at a distance is a convention. Simultaneity at one event is tautological physical fact.

We perceive and describe two nearby events as simultaneous if we receive information from both of them coincidentally, but we know that if the sources are at different distances from us, or indeed travelling at different velocities relative to us, they would not appear simultaneous to an observer for whom the arrangement was symmetrical.

All this is irrelevant to two clocks passing and syncing at some event at which both are present. The sources are zero distance away, and very much appear simultaneous to any observer, even those not present at the event of their meeting at speed. To suggest otherwise to imply that the light from the two respective objects travels at some speed other than c.

Synchronisation doesn't just mean showing the same number at a given instant.

Yes it does. That's exactly what it means.

There is a presumption in "gentlemen, synchronise your watches" that  they will all continue to tick at the same rate for long enough to effectively coordinate the invasion.

I never claimed the two passing clocks would stay in sync in any given frame. Which clock runs faster would be a frame dependent thing.

But relativity tells us that as the army, navy and air force travel at different speeds, they won't be coordinated when they reach alpha centauri.

Yes. That's pretty much the twins thingy, with everybody taking different worldlines between two mutually common events.

What if i was standing Sideways?

Relativity theory isn't in any way about the limits of human physiology.  A human can detect perhaps a 20th of a second difference in arrival of two pulses. Any less than that and they'll appear simultaneous to a human. Your train example will produce differences on the order of nanoseconds.

Assume both Blinkers were Synchronised while spacecraft was at Speed 0.

OK, that's a good frame reference. They are (or were at at least) synced relative to the frame in which the speed of 1%c is eventually measured.

Gradually 1%c is reached.
My left eye tracking Front blinker.
My right eye tracking Back blinker.
Let's say i am Not interested in the Theoretical part of it.
I just wanna know Which one i'd see blinking first/faster?

You'll see the one in front blink first if you were a high precision measuring device. As a human, you'd never be able to detect the nanosecond difference.

ps - is there any possible way U could avoid using SR/GR & give a Simplistic answer.

That seemed pretty simple to me. It even works in Newtonian mechanics, so I managed to answer without using SR/GR.

If the  lights were synchronized at zero m/s, then no matter how fast you were going they would stay synchronized.

Not true. Them being synced is a frame dependent thing, and after acceleration, they'd be synced in neither the train frame nor the original frame, although at 0.01c, they'd be really close to being in sync in the original frame.

IOW the light from both sources would continue to hit you at exactly the same time.

Sorry but no. The front one hits you first since you're moving toward it in the frame in which the two blinks are synced.

[Origin]

Not true.

You are absolutely right, sorry for misleading anyone!

[varsigma]

Can you find a YouTube video on the subject that doesn't contain mistakes?

Yes, you can.

Look for lectures on special relativity by people like Susskind, or any from the likes of MIT or UC. Google is your friend; just type in the right words.

[hamdani yusuf (OP)]

Which means either that these videos are wrong, or they're correct about the mistakes being made by the other videos/books. If they say that their own explanation is the one correct one, then the former is true.

Anyone who put their efforts to make and upload videos on YouTube most likely think that they're correct, at least when they are being uploaded.

[hamdani yusuf (OP)]

Some say that special relativity is not adequate to explain the paradox, while the others say that it is adequate. They are contradicting each other.

The latter case is correct here. The former claims indeed contradict that, and are wrong.

If general theory of relativity isn't necessary to explain twin paradox, will using it anyway cause a double counting?

[alancalverd]

If the relativistic calculation (a) predicts the experimental result and (b) degenerates to the classical formula when v << c, it is presumed correct. The scientific process is to adopt it until we have  an experimental result that contradicts it. Philosophy is bunk.