Relativity and time question for physics enthusiasts

[DWW]

In my limited knowledge of relativity, the faster you approach the speed of light, your time (in relation to the Earth?) should slow down or something correct?

Astronauts witness this every time they go up, even if it is just in nanoseconds of difference.

My question is:
If you could travel 99.9% the speed of light (185,814 miles per second) and you went to Proxima Centauri which is approximately 4 light years away--if you went there and back (it will take a little more than 8 light years because you are not the speed of light) what would be the difference (in time) between you and the earth?

 

[Heisenberg]

Using those numbers, the time on Earth relative to you would be about 14.1 times as fast. So for every 14.1 seconds in Earth, you'd experience 1 second. The formula for time dilation is d(tau) = dt * sqrt(1-(v^2/c^2)) if you want to figure it out for yourself (and double check my numbers ).

 

[foofoo]

plenty of java based calculators out there
try this one
link

 

[DWW]

Originally posted by: Heisenberg
Using those numbers, the time on Earth relative to you would be about 14.1 times as fast. So for every 14.1 seconds in Earth, you'd experience 1 second. The formula for time dilation is d(tau) = dt * sqrt(1-(v^2/c^2)) if you want to figure it out for yourself (and double check my numbers ).

Thanks!

.. lets see 14.1x8 years (thereabouts) = 112.8 years (everyone you know would be dead)

gee that'd suck

 

[Jzero]

"I may be a geek, but at least I'm not a physics enthusiast."

 

[DWW]

Originally posted by: Jzero
"I may be a geek, but at least I'm not a physics enthusiast."

Heh who wrote that (since its quoted I'm guessing someone else authored it)?

And physics is the only science

 

[Jzero]

Originally posted by: DWW

Originally posted by: Jzero
"I may be a geek, but at least I'm not a physics enthusiast."

Heh who wrote that (since its quoted I'm guessing someone else authored it)?

And physics is the only science

I just made it up as far as I know. I was just thinking to myself that a physics enthusiast has got to be one step down from LARPers in the geek pecking order.

 

[DWW]

Originally posted by: Jzero

Originally posted by: DWW

Originally posted by: Jzero
"I may be a geek, but at least I'm not a physics enthusiast."

Heh who wrote that (since its quoted I'm guessing someone else authored it)?

And physics is the only science

I just made it up as far as I know. I was just thinking to myself that a physics enthusiast has got to be one step down from LARPers in the geek pecking order.

I just googled for LARP and I'll have you know that physics is at least interesting, LARP is just... (I guess I shouldn't throw stones heh)

Heisenberg Can you recommend any good books on relativity?

 

[Heisenberg]

Originally posted by: DWW
Heisenberg Can you recommend any good books on relativity?

That gonna depend on what your background is like. How much physics/math have you had?

 

[DWW]

Originally posted by: Heisenberg

Originally posted by: DWW
Heisenberg Can you recommend any good books on relativity?

That gonna depend on what your background is like. How much physics/math have you had?

Very limited ;( Haven't taken physics since high school and as for math I stopped at Calculus I

 

[Heisenberg]

Originally posted by: DWW

Originally posted by: Heisenberg

Originally posted by: DWW
Heisenberg Can you recommend any good books on relativity?

That gonna depend on what your background is like. How much physics/math have you had?

Very limited ;( Haven't taken physics since high school and as for math I stopped at Calculus I

Hmmm. I'm sure there are a lot of "layman" books on relativity in any book store, but I don't read hardly any of those so I can't really recommend one. I'm not a big fan of those books anyway, because they tend to skip a lot of the math, which is like leaving out half the material IMHO. If you're comfortable with time derivatives and vectors, any modern physics textbook should have a section of basic relativity. "Modern Physics" by Serway, Moses, and Moyer is the book I used and has a whole chapter on relativity. If you have a good feel for basic kinematics, it should be fairly readable.

 

[TuxDave]

Originally posted by: DWW

Originally posted by: Heisenberg
Using those numbers, the time on Earth relative to you would be about 14.1 times as fast. So for every 14.1 seconds in Earth, you'd experience 1 second. The formula for time dilation is d(tau) = dt * sqrt(1-(v^2/c^2)) if you want to figure it out for yourself (and double check my numbers ).

Thanks!

.. lets see 14.1x8 years (thereabouts) = 112.8 years (everyone you know would be dead)

gee that'd suck

Something doesn't seem right in that answer. Isn't it more like while the earth sees you travel for 8 years, you only experience 8/14.1 years?

 

[DWW]

Originally posted by: TuxDave

Originally posted by: DWW

Originally posted by: Heisenberg
Using those numbers, the time on Earth relative to you would be about 14.1 times as fast. So for every 14.1 seconds in Earth, you'd experience 1 second. The formula for time dilation is d(tau) = dt * sqrt(1-(v^2/c^2)) if you want to figure it out for yourself (and double check my numbers ).

Thanks!

.. lets see 14.1x8 years (thereabouts) = 112.8 years (everyone you know would be dead)

gee that'd suck

Something doesn't seem right in that answer. Isn't it more like while the earth sees you travel for 8 years, you only experience 8/14.1 years?

I wouldn't think so (could be wrong). It takes light 4 years just to get here from there. If you were going near (99.9%) the speed of light it would take just over 4 light years (4 light years is an approximation of its distance). If you experienced 8/14.1 that would be FTL (Faster Than Light) which is impossible short of warping space-time I think (worm holes or Alcubierre warp)

 

[RaynorWolfcastle]

You could try Feynman's "Six Not-So-Easy Pieces", I read it a few years back and I thought it was accessible enough that anyone who's interested enough in the subject to put up with a little math would be able to understand it.

 

[Descartes]

I love physics, and although I can follow a considerable amount of the mathematics involved, I generally choose "lighter" texts for my casual reading. By casual I don't necessarily mean pop science texts (although I sometimes enjoy them as well), but something in between. The best general treatment of relativity I've read is Relativity and Its Roots. It was simply a pleasure to read. I think you could start there and work your way up.

 

[rgwalt]

Originally posted by: TuxDave

Originally posted by: DWW

Originally posted by: Heisenberg
Using those numbers, the time on Earth relative to you would be about 14.1 times as fast. So for every 14.1 seconds in Earth, you'd experience 1 second. The formula for time dilation is d(tau) = dt * sqrt(1-(v^2/c^2)) if you want to figure it out for yourself (and double check my numbers ).

Thanks!

.. lets see 14.1x8 years (thereabouts) = 112.8 years (everyone you know would be dead)

gee that'd suck

Something doesn't seem right in that answer. Isn't it more like while the earth sees you travel for 8 years, you only experience 8/14.1 years?

I'm not sure about that answer either. If you were going very close to the speed of light (from the Earth's reference frame), the Earth would view the trip as taking 8 years. You would experience less time due to length contraction (I think?) Your trip would be shorter aboard the ship, but 8+ years would pass on the Earth.

R

 

[Descartes]

Originally posted by: rgwalt

Originally posted by: TuxDave

Originally posted by: DWW

Originally posted by: Heisenberg
Using those numbers, the time on Earth relative to you would be about 14.1 times as fast. So for every 14.1 seconds in Earth, you'd experience 1 second. The formula for time dilation is d(tau) = dt * sqrt(1-(v^2/c^2)) if you want to figure it out for yourself (and double check my numbers ).

Thanks!

.. lets see 14.1x8 years (thereabouts) = 112.8 years (everyone you know would be dead)

gee that'd suck

Something doesn't seem right in that answer. Isn't it more like while the earth sees you travel for 8 years, you only experience 8/14.1 years?

I'm not sure about that answer either. If you were going very close to the speed of light (from the Earth's reference frame), the Earth would view the trip as taking 8 years. You would experience less time due to length contraction (I think?) Your trip would be shorter aboard the ship, but 8+ years would pass on the Earth.

R

You experience less time due to time dilation according to the Lorentz transformation. Length contraction is also a Lorentz transformation.

 

[DWW]

Originally posted by: Descartes

Originally posted by: rgwalt

Originally posted by: TuxDave

Originally posted by: DWW

Originally posted by: Heisenberg
Using those numbers, the time on Earth relative to you would be about 14.1 times as fast. So for every 14.1 seconds in Earth, you'd experience 1 second. The formula for time dilation is d(tau) = dt * sqrt(1-(v^2/c^2)) if you want to figure it out for yourself (and double check my numbers ).

Thanks!

.. lets see 14.1x8 years (thereabouts) = 112.8 years (everyone you know would be dead)

gee that'd suck

Something doesn't seem right in that answer. Isn't it more like while the earth sees you travel for 8 years, you only experience 8/14.1 years?

I'm not sure about that answer either. If you were going very close to the speed of light (from the Earth's reference frame), the Earth would view the trip as taking 8 years. You would experience less time due to length contraction (I think?) Your trip would be shorter aboard the ship, but 8+ years would pass on the Earth.

R

You experience less time due to time dilation according to the Lorentz transformation. Length contraction is also a Lorentz transformation.

Any clue how much time you would experience? (Would it be the way someone suggested above, 8/14.1 years?)

 

[silverpig]

Light takes 8 years round trip. You travel at 99.9% light speed, you do the trip in 1/0.999 of 8 = 1.001001001 years from earth's perspective. To you in the ship this would be 8/14.1 = 0.567 years.

So you basically travel 8 ly in 0.567 years

This doesn't violate relativity though

 

[Descartes]

Originally posted by: DWW

Originally posted by: Descartes

Originally posted by: rgwalt

Originally posted by: TuxDave

Originally posted by: DWW

Originally posted by: Heisenberg
Using those numbers, the time on Earth relative to you would be about 14.1 times as fast. So for every 14.1 seconds in Earth, you'd experience 1 second. The formula for time dilation is d(tau) = dt * sqrt(1-(v^2/c^2)) if you want to figure it out for yourself (and double check my numbers ).

Thanks!

.. lets see 14.1x8 years (thereabouts) = 112.8 years (everyone you know would be dead)

gee that'd suck

Something doesn't seem right in that answer. Isn't it more like while the earth sees you travel for 8 years, you only experience 8/14.1 years?

I'm not sure about that answer either. If you were going very close to the speed of light (from the Earth's reference frame), the Earth would view the trip as taking 8 years. You would experience less time due to length contraction (I think?) Your trip would be shorter aboard the ship, but 8+ years would pass on the Earth.

R

You experience less time due to time dilation according to the Lorentz transformation. Length contraction is also a Lorentz transformation.

Any clue how much time you would experience?

Heisenburg would be the man to put this on a proper quantitative footing, but what he already stated above is accurate:

y = 1/sqrt(1 - v^2/c^2)

where 'y' is gamma.

y = 1/sqrt(1 - 0.9^2) = ....

Ah hell.

 

[DWW]

Originally posted by: silverpig
Light takes 8 years round trip. You travel at 99.9% light speed, you do the trip in 1/0.999 of 8 = 1.001001001 years from earth's perspective. To you in the ship this would be 8/14.1 = 0.567 years.

So you basically travel 8 ly in 0.567 years

This doesn't violate relativity though

I had better read up That is nuts BTW heh.

 

[hjo3]

To get a time dialation of 14.1:1, you'd have to travel at 0.997481865463213 C. To get to Proxima Centauri, 4.3 ly away (yeah, screw sig figs), and back would take 8 years, 32 weeks, and 3 days. But you would only experience 31 weeks and 6 days. So everyone on Earth would be 8 years and 4 days older than you when you returned.

 

[DWW]

Originally posted by: hjo3
To get a time dialation of 14.1:1, you'd have to travel at 0.997481865463213 C. To get to Proxima Centauri, 4.3 ly away (yeah, screw sig figs), and back would take 8 years, 32 weeks, and 3 days. But you would only experience 31 weeks and 6 days. So everyone on Earth would be 8 years and 4 days older than you when you returned.

:Q

 

[Heisenberg]

Edit: N/m, I'm a dumbass.

 

[RaynorWolfcastle]

Originally posted by: Heisenberg

Originally posted by: silverpig
Light takes 8 years round trip. You travel at 99.9% light speed, you do the trip in 1/0.999 of 8 = 1.001001001 years from earth's perspective. To you in the ship this would be 8/14.1 = 0.567 years.

So you basically travel 8 ly in 0.567 years

This doesn't violate relativity though

I agree, but you have to be careful about how you word things. To YOU on the ship, the trip would still take 8 years. It's not like you'd see your watch suddenly run slow as you sped up. To everyone on earth, it would also take 8 years, but you'd have only aged 0.567 years to them when you returned.

I haven't done any relativity stuff in a while but somehow that doesn't sound right... If you experience that it takes 8 years to make the trip you age 8 years, right?

I'm under the impression that the traveller would only feel the trip to be 0.567 years long because of length contraction, no? Admittedly, I could be completely in left field about this