Age slow when approaching light speed?

[Adz]

Hey all,

I have another question. I was recently learning about how you would age slower the close you got to travelling at the speed of light. My friend replied

"I personally think that idea of ageing slower the nearer you get to the speed of light is silly, for lack of a better word. Ageing is a process that occurs as a result of biological changes taking place within the body itself irrespective of how fast you may be travelling."

I believe he is wrong, but could some people point me in the right direction?

Cheers,

Adam

[brianb]

Your aging rate will remain unaltered if you measure your age by a clock which is travelling at the same speed that you are. You will appear to age more slowly by the standards of someone who has a large velocity relative to you.

This is counterintuitive but the effect is measurably real - some mesons are observed in the solar wind even though their rest lifetime is only microseconds, yet they can travel for at least 8 minutes (by our clocks) without decaying because of their velocity which is very close to the speed of light.

[mikeknowle]

Yes, it depends on the reference point....it's all relative (boom-boom).

Time, in this context is a funny one to explain as it's not absolute, but is a perception measured from the observer's point-of-view. Not an issue normally as we all at travelling at the same velocity.

Mind you, we don't have to go far to see its effects - the satellites that broadcast the GPS signals for our SatNavs have relativistic compensations built in....otherwise the location plot would be well off.

[themos]

If you appear to travel at near light-speed, then you would appear to age slower.

If you appear to sit still, you would appear to age normally.

Sadly, we all appear (to ourselves) to sit still, so no funny time distortions.

[ronin]

Depends which you are, the one at near the speed of light or the one at rest.

In each case your time is normal, the other one is either fast or slow.

[brianb]

Depends which you are, the one at near the speed of light or the one at rest.

In each case your time is normal, the other one is either fast or slow.

Let's be accurate about this.

There is no state of rest, only relative motion.

If you move relative to a frame of reference, your clock and the reference clock will appear to run at different rates.

That's all there is to it - and that's all Einstein needed to generate the whole of the Theory of Special Relativity.

[Ad Astra]

The difference in the rate at which time passes is only different when you compare to someone in a different frame of reference.

So, if you are traveling at 0.9 c away from Earth, then your friend on Earth will age more rapidly than you do because you are moving fast relative to him.

As far as you are concerned - the days and hours on the spacecraft will seem normal to you. However, when you turn around and return home to Earth, you will be much younger than the friends you left behind.

How much younger you are depends on only two things,

1. How close to light speed did you get?

2. How long were you traveling that fast?

By the way, biological or mechanical - all clocks are subject to relatavistic effects.

Dan