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/sci/ - Science & Math

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2081238 No.2081238 [Reply] [Original]

Would someone be kind enough to explain exactly how/why time dilation works?

I've been fascinated by it since I read about the twin paradox where one twin goes into space for a certain amount of time while the stays on earth. When twin A gets back a lot more time has passed on earth and his twin is a lot older than him. And yet you can have real-time communication with the shuttle and time is experienced at the same pace.

>> No.2081244

Could this theoretically be a way to time travel? Supposing we had the technology to be going 99% the speed of light and were able to stay up there for extended periods of time. Perhaps even raising children. Whenever they finally got back to earth, it could be far into the future, sort of. Could it work?

I am not well versed in the rules of physics. So maybe don't be too technical and also if this is something I'm an idiot for not understanding, please don't be to hard on me.

>> No.2081253

>>2081244
it can be used to travel time, but only forward at different speeds.

>> No.2081267

Why is the twin paradox called a paradox?

>> No.2081275

>>2081253

Well forward is the good part. I mean sure it would be neat to go back in time. But we know how that went already and frankly I'm not impressed.

>> No.2081276

if you have real-time communication then twin B will hear and see twin A in slow motion. It happens to allow everyone, no matter how fast they are going to measure the speed of light as c. That the speed of light is constant for everyone comes from the principle of relativity, that is, that it is impossible to know if you are standing still or moving at a constant rate. If you could measure the speed of light and get a different value depending on how fast you are going it would violate this.

>> No.2081279
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2081279

>>2081267
Trollface's paradox is the correct name

>> No.2081290

Backgound: The speed of light is a constant in all interial frames of reference. It doesn't matter if you are standing still or traveling .99 the speed of light and turn your headlights on. You measure light moving relative to you at a constant speed in a vacum.

Time dialation is a direct result of the above fact. Lets say I have two mirrors with a light beam bouncing between them. I measure (in the same reference-frame as the mirrors) the time it takes for the light to bounce from mirror to the other is exactly 1 light-millisecond. Now suppose these mirrors are actually on a spaceship moving through space. To you, the light is moving straight up and down between the two mirrors and distance between them is fixed. But to someone on earth it appears that the light is really moving in a zig-zag pattern (picture the line on Charlie Brown's shirt). When measured, the distance the travels on each trip between mirrors will be larger than the distance you measured on the ship. But since we both measure the speed of light to be a constant, and speed is just distance / time (d/t), then since d is larger in the ground measurement, t must also be larger.

>> No.2081293

>>2081267
because he twin A looks younger than twin B from B's perspective and twin B looks younger than twin A from A's perspective. Same as if you stand far from someone else and you look small from his perspective and he looks small from your perspective.

>> No.2081301

>>2081290
Pretty much this.

Everything is relative to the fact that the speed of light (c) is constant at every inertial frames of reference.

Then you go into theoretical experimentation... etc. and prove it.

>> No.2081319

>>2081238
The shuttle travels at a max of 7 km/s, which is the speed for low-earth orbit. That's about 1/50,000 the speed of light, so not fast enough to measure any time differences without very precise measuring equipment. But if you took an atomic clock on the shuttle, and then compared it to one that was left in one spot on earth, you'd definitely be able to measure the difference.

>>2081267
It seems paradoxical at first, because both twins are moving at the speed of light relative to each other -- a symmetrical situation -- but when they meet one has aged more than the other -- an asymmetrical situation. But it's not really a paradox; it's not symmetrical because one had to accelerate to go back in the opposite direction. Since special relativity only works in a fixed inertial reference frame, whatever frame you choose the one who accelerates must go through less time than the one who doesn't.

>> No.2081382

>>2081276

Crazy stuff man. If there was real time video communication as well, I assume it would also appear to be slo-mo. That's pretty cool.

>>2081290
>>2081301
>>2081319
>>2081293

Ah thank you. I get it now. I just couldn't get that from the wikipedia article etc.