Apparent contradiction in time dilation

[Julius Ceasar]

TL;DR Summary

This video here 8.50 to 9.50 minutes , shows an apparent contradiction in time dilation, in the "twins paradox" the clock that is accelerated is relative, i.e. from earth the space ship moves but from the space ship the earth moves, i know time dilation is a real thing used in real applications like gps hence I say an apparent contradiction but the point is that a clock cannot be both faster and slower.

This video here <link deleted> 8.50 to 9.50 minutes , shows an apparent contradiction in time dilation, in the "twins paradox" the clock that is accelerated is relative, i.e. from Earth the spaceship moves but from the spaceship the Earth moves. I know time dilation is a real thing used in real applications like gps hence I say an apparent contradiction but they seem to make a fair point that a clock cannot be both faster and slower.

Note: Link to aether theory crackpottery deleted by Mentor

 

[Doc Al]

The "twin paradox" is a standard, well-known result of relativity -- not a contradiction to it. That video is nonsense if it claims otherwise.

There are many, many threads discussing the twin paradox on this site. Or just pick up any relativity text. Dive in!

 

[omega_minus]

The video says acceleration is not accounted for in relativity. This is nonsense. This is another video of someone "proving" relativity is wrong by mis-stating the theory entirely. Accelerations matter even in SR. The ship (earth or rocket in this case) that accelerates in one direction and then turns around has a fundamentally different experience than the one that stays in the same frame of reference. It is the turning around that marks the asymmetry. This event occurs instantly for the accelerating body (the ship is present at the event of the turn around) but takes a while for this event to travel to the Earth (earth won't see the turn around event until the light relaying the information arrives there) By this time, the ship will almost be back to Earth (for a relativistic trip near speed c) So the Earth will see the return trip taking very little time. Since time will appear to move faster than normal for the objects approaching one another (search term: doppler effect time dilation) the Earth only sees time moving fast on the ship for a short time, but the ship will watch the Earth approach for the same amount of time as the outbound leg of the voyage. So time will run faster on Earth from the rocket frame of reference for a longer time. Hence more time will elapse on Earth than the rocket. Note that neither one is "right". It is perfectly acceptable for different times to elapse for different observers. It's the so-called spacetime interval that is preserved. They're are better explanations than this but it gives an idea of whence the apparent "paradox" comes from. In fact, it is not a paradox. If it didn't occur, that would mark an actual paradox.

 

[Vanadium 50]

I'm not going to waste 19 minutes of my life watching a YouTube video titled "AETHER FIELD IS THERE - THIS CHANGES EVERYTHING!" It is almost certainly crackpottery.

 

[Orodruin]

Summary:: This video here 8.50 to 9.50 minutes , shows an apparent contradiction in time dilation, in the "twins paradox" the clock that is accelerated is relative, i.e. from Earth the spaceship moves but from the spaceship the Earth moves, i know time dilation is a real thing used in real applications like gps hence I say an apparent contradiction but the point is that a clock cannot be both faster and slower.

This video here 8.50 to 9.50 minutes , shows an apparent contradiction in time dilation, in the "twins paradox" the clock that is accelerated is relative, i.e. from Earth the spaceship moves but from the spaceship the Earth moves. I know time dilation is a real thing used in real applications like gps hence I say an apparent contradiction but they seem to make a fair point that a clock cannot be both faster and slower.

Please read my forum signature.

 

[phinds]

I'm not going to waste 19 minutes of my life watching a YouTube video titled "AETHER FIELD IS THERE - THIS CHANGES EVERYTHING!" It is almost certainly crackpottery.

Why is the word "almost" in this sentence ?

 

[omega_minus]

Yeah, I skipped to the time stamp and didn't get very far. As a word of advice, avoid any video that says "ether, Aether, or free energy"

 

[Dale]

the clock that is accelerated is relative

Velocity is relative, but (proper) acceleration is not. All inertial frames agree which twin accelerated.

 

[Orodruin]

Yeah, I skipped to the time stamp and didn't get very far. As a word of advice, avoid any video that says "ether, Aether, or free energy"

Unless it has the word "disproving" just before it.

 

[Doc Al]

I'm not going to waste 19 minutes of my life watching a YouTube video titled "AETHER FIELD IS THERE - THIS CHANGES EVERYTHING!" It is almost certainly crackpottery.

Indeed. (I could only take about 20 seconds of it.) Accordingly, I will delete the link.

 

[Julius Ceasar]

This is another video of someone "proving" relativity is wrong by mis-stating the theory entirely.

It is perfectly acceptable for different times to elapse for different observers. It's the so-called spacetime interval that is preserved.

This is a cautionary tale to anyone looking at these kinds of videos, i thank you all.

 

[Mister T]

If you want to see a simple but concise explanation of the twin paradox go to YouTube and search for "Hewitt Twin Trip".

The entire analysis involves the Doppler effect, and although it's not stated, the rocket speed is $0.6 \ c$.

 

[FactChecker]

a clock cannot be both faster and slower.

If I am stationary and the traveling clock is moving to my left, then my judgment of his clock is by comparing his time to my times to MY left. On the other hand, he is judging my clock by comparing its progress with his times to HIS left (assuming we are facing each other). So we are both making judgments based on different sets of times. That is how each observer thinks that the other person's clock runs slower.

 

[Julius Ceasar]

If you want to see a simple but concise explanation of the twin paradox go to YouTube and search for "Hewitt Twin Trip".

Good sing along time song for hipsters here with kooky 1974 animation, educational though about light flashing 5 times on out journey and 20 times on in journey. An observer sees the Doppler effect at shorter or longer intervals depending on direction of travel. Nice and easy.

 

[Nugatory]

but the point is that a clock cannot be both faster and slower.

This apparently paradoxical result comes from from failing to include the relativity of simultaneity in the analysis.

Look at https://www.physicsforums.com/threads/special-relativity-time-issues.846242/post-5307390 and https://www.physicsforums.com/threads/weird-time-dilation-question.883303/post-5552719 for an explanation.

 

[Julius Ceasar]

So what's going on here is that relativity of simultaneity allows the two observers to disagree about what clock A reads at the same time that clock B reads 12:30 PM, and that allows them both to correctly conclude that the other clock is the slower one.

I like this, it explains it well.