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/sci/ - Science & Math

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3528273 No.3528273 [Reply] [Original]

/sci/, I'm a layman who is curious about space like most other people. I've wondered about the implications of relativity on interstellar space travel. Correct me if I'm wrong but the faster a body travels, the slower time goes. But is this time relative to the body travelling at high speeds or outside the body? For example, a new space ship can go at .75c and reach a hypothetical star within 10 years at that speed. Will it feel like 10 years to the crew in the craft? Also, suppose that it does, and that the crew takes another 10 years to come back to Earth. How much time will have passed on Earth? Will it be 20 years or more?

Sorry for my ignorance, just trying to understand this better.

>> No.3528310

At .75c, time should feel 1.5 times slower. So to the crew, it would feel like 6.66 years have passed when on earth 10 years have gone by. So 20 years will have passed on earth.

Play with the time dilation calculator on this for a while, you'll notice that the closer you get to 1 the closer the time dilation gets to infinity.

http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/tdil.html

>> No.3528306
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3528306

bumping, come on /sci/

>> No.3528320

Time slows down from the obervers frame of reference. The traveller would not notice time slowing down in his reference frame.

>> No.3528331
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3528331

>>3528310

This is fucking sweet! Thanks brah

>> No.3528342

Ive always wondered. So if you are moving at 0c, as in, you are perfectly still in interstellar space. Would you experience an infinite amount of time?

>> No.3528354

>>3528342

You have it backwards. If you were moving at c, you would experience infinite time.

>> No.3528362

I do not have the power of latex, but...

the dilation equation is T = t / (sqrt(1 - vsquared/csquared))

where v is velocity, c is the speed of light in a vacuum, t is fixed time and T is relative time.

>> No.3528364

>>3528310
>you'll notice that the closer you get to 1 the closer the time dilation gets to infinity.

Welp could it be said then that particles like photons that travel at c are basically "outside time" (from a hypothetical travellers perspective)?

>> No.3528379

>a new space ship can go at .75c

I'm going to assume you mean from the Earth's perspective, because otherwise that's a meaningless figure.

The crew can't actually feel any difference in the flow of time, but the Earth will appear to have aged faster than they did while they were in transit.

>>3528342

Your question is meaningless because there's no privileged reference frame in the universe. There's no single stationary point and you can't be at zero velocity relative to everything.

>> No.3528382

>>3528364

Photons aren't "outside" time or they wouldn't exist, but they don't experience the passage of time themselves.

>> No.3528392

>>3528342
When you manage 0c let us know.

>> No.3528400

Ok, so if we send a probe to alpha centauri at .999 C, how long would it appear to take from our perspective?

>> No.3528401

>>3528342
No, you would only experience infinite amount of time in comparison to the person going c. Since we are all going basically 0c with respect to each other, we base all of our time off of that.

>> No.3528405

So if, for the sake of argument, you have two objects in space. They are moving relative to each other at .75c.... How do you know which one is actually moving and therefore experiencing time dilation? There is nothing else to compare them to.... this is fucking with my mind. how know

>> No.3528404

>>3528400
4 years (assuming AC is 4 light years away), however, if you attached a clock to the probe, the clock would say it only took like a day.

>> No.3528430

>>3528405
>How do you know which one is actually moving and therefore experiencing time dilation?

Both. The trick is acceleration, not constant velocity.

>> No.3528436

>>3528382

If they don't experience time, how come they change?

>> No.3528437

>>3528430

I think you're thinking of 'G force'. Relativity certainly depends on velocity, constant or otherwise.

>> No.3528440

>>3528405

Which one accelerated to create that differential? That'll be the one to experience time dilation.

If they both accelerated, then they'll both experience time dilation relative to their acceleration.

>>3528436

They don't. If you're referring to scattering or something of that nature, the photon is actually destroyed by absorption and a completely new one emitted with new properties determined by quantum mechanical effects.

>> No.3528448

>>3528437

Gravity and acceleration are the same thing.

>> No.3528488
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3528488

>>3528448

Well then, I'll just gravity my car as I go to the shops, then gravity the goods as I put them in the bags, then gravity my car back home.

>> No.3528493

>>3528488

You have no idea how close to right you actually are.

>> No.3528501

>>3528488

Your mass increases when you accelerate, so yeah, you kind of do gravity.

>> No.3528508

>>3528440
>not sure if gets it
Better explanation: http://en.wikipedia.org/wiki/Twin_paradox
And as it has been said, no one "experiences time dilation". If you're traveling at near light speed you don't notice the difference, time passes normally, your lifespan doesn't increase. Once you come back you will have made a leap in the future, that's all.

>> No.3528517

>>3528508

You can't perceive it, but you're undergoing it. Hence why you come back having aged less than your twin.

>> No.3528522

>>3528501
>>3528493

While their similarities might be interesting, it's not useful to conflate the two. The four fundamental forces of the Universe are not strong nuclear, weak nuclear, electromagnetic, and acceleration. Acceleration can be *consequence* of gravitational force, but then it can also be the consequence of charge. I'm sure we're just talking terminology here, but it's important. Especially when concepts are being explained to a non physics enthusiast.

>> No.3528557

>>3528517
Both twins are undergoing it.

>> No.3528671

>>3528557

That goes without saying, since it's relative (and apparently involving relatives).