[CZARCAR (OP)]

cooling effects a molecular slowdown.
traveling near speed of light also effects an aging slowdown per einstein? wouldnt the slowed aging also involve a molecular slowdown?

[Mr. Scientist]

cooling effects a molecular slowdown.
traveling near speed of light also effects an aging slowdown per einstein? wouldnt the slowed aging also involve a molecular slowdown?

Theoretically, yes.

[Bored chemist]

The speeds of molecules are typically about the speed of sound, rather than the speed of light. The effect due to relativistic effects would be tiny.

[Geezer]

Surely that is the actual reason for the slower aging associated with relativistic effects? As clocks travel, they slow down (relative to static clocks). Why would molecules be any different?

[CZARCAR (OP)]

The speeds of molecules are typically about the speed of sound, rather than the speed of light. The effect due to relativistic effects would be tiny.

it would seem that the slowed aging of the traveling twin would be due to a slowed metabolism & molecular activity therein associated?

[Geezer]

it would seem that the slowed aging of the traveling twin would be due to a slowed metabolism & molecular activity therein associated?

I believe that is correct. For the traveler, time itself is passing more slowly than it is for the stationary twin. Therefore, all activity - atomic, molecular, etc., etc., is relatively slower. Of course, the traveler is completely unaware of this. In fact, it is impossible for the traveler to measure any difference in the rate at which time elapses.

(At least, that's my understanding! I'm an engineer, not a scientist.)

[Geezer]

Theoretically, yes.

The predictions of the theory have been confirmed experimentally on many occasions. GPS systems have to take the effect into account.

http://en.wikipedia.org/wiki/Hafele%E2%80%93Keating_experiment

[CZARCAR (OP)]

 if so i am looking at 2 opposites to find the same result=?
1-energy removal via cooling on earth results in slowed molecular activity
2- increased energy of the faster spaceship results in slowed molecular activity

[Soul Surfer]

You are forgetting one important thing RELATIVITY the effects of time dilation ONLY apply to objects that are travelling at high speeds with respect to each other therefore the individual molecules in an object are travelling at low velocities with respect to each other and there is no significant change. travelling near the speed of light has absolutely no effect on the molecules in the object that is travelling at high speed.  It is this vital fact that the laws of physics are the same everywhere and for objects travelling at high speed and the velocity of light is fixed that creates these relatavistic effects.

[CZARCAR (OP)]

You are forgetting one important thing RELATIVITY the effects of time dilation ONLY apply to objects that are travelling at high speeds with respect to each other therefore the individual molecules in an object are travelling at low velocities with respect to each other and there is no significant change. travelling near the speed of light has absolutely no effect on the molecules in the object that is travelling at high speed.  It is this vital fact that the laws of physics are the same everywhere and for objects travelling at high speed and the velocity of light is fixed that creates these relatavistic effects.

the traveling twin returns younger than the stationary twin, the metabolic rate must have slowed?

[Soul Surfer]

No it has NOT it is just that the fast moving twin has moved through LESS TIME than the stationary one because it has moved through MORE SPACE. The critical difference between the lives of the two twins is the acceleration and deceleration that is required to go quickly.

This may be counterintuitive but it is correct

[Geezer]

travelling near the speed of light has absolutely no effect on the molecules in the object that is travelling at high speed.

I don't think so. If it has no effect, how do you explain the difference between the two clocks in the well known experiment? Bear in mind, these are atomic clocks.

Relatively, less time has elapsed for the traveler. The metabolic rate will be the same for both twins from their perspective because, from their perspectives, there has been no change in the rate at which time passes. However, because their relative elapsed times are actually different, the relative amount of metabolization must indeed be different.

[RD]

... the relative amount of metabolization must indeed be different.

half-lifes are different, e.g. muons ...

When a cosmic ray proton impacts atomic nuclei of air atoms in the upper atmosphere, pions are created. These decay within a relatively short distance (meters) into muons (the pion's preferred decay product), and neutrinos. The muons from these high energy cosmic rays, generally continuing essentially in the same direction as the original proton, do so at very high velocities [~0.998c]. Although their lifetime without relativistic effects would allow a half-survival distance of only about 0.66 km at most, the time dilation effect of special relativity allows cosmic ray secondary muons to survive the flight to the earth's surface.

http://en.wikipedia.org/wiki/Muon#Muon_sources

[Soul Surfer]

The extended life is only from our stationary point of view.  The fast moving muon decays in the same time as if it was stationary from its point of view.  this proves that the fast moving particle does not experience itself a slowing down of time

[CZARCAR (OP)]

does jetlag have biophysical effects? might this apply?

[Geezer]

does jetlag have biophysical effects? might this apply?

Well, jetlag does have effects, but not for this reason. At aircraft speeds the effects are incredibly small, and very difficult to actually measure (see experiment referenced above).

[Geezer]

The extended life is only from our stationary point of view.  The fast moving muon decays in the same time as if it was stationary from its point of view.  this proves that the fast moving particle does not experience itself a slowing down of time

Precisely! That's why it's called RELATIVITY. There is no way to measure "time" per se. We evaluate time based on the motion of things in space, be they pendulums or electrons. Because of this, a stationary muon (if there can be such a thing) and a fast moving muon will decay at different rates RELATIVE to each other. Likewise with humans. "Absolute" time is an illusion that we have created for ourselves.

In the case of the twins, who's to say the traveler's life is "extended"? From his perspective, everything is quite normal, except that his twin suddenly seems to look a lot older than he does (because he is!). From the traveler's perspective, his stationary twin's life has been considerably "shortened", even although from the perspective of the stationary twin, it has not been.

[CZARCAR (OP)]

assuming an unchanged metabolic rate & that the twins' hearts are good for 100 ticks, the twins rejoin @ 99 ticks & both die on the next tick [heart worn out]. the traveling twin will have died "younger"?

[CZARCAR (OP)]

similarly? each twin has a block of ice, the ice in the ship would melt in less time/faster than the ice on earth?

[Geezer]

assuming an unchanged metabolic rate & that the twins' hearts are good for 100 ticks, the twins rejoin @ 99 ticks & both die on the next tick [heart worn out]. the traveling twin will have died "younger"?

If each twin was good for 100 ticks of their tickers, assuming the travelling twin moved through space really fast, he might only have reached 97 ticks when he meets with his twin again, but the stationary twin would be at 99 ticks.

From each twin's perspective, his metabolism is unaffected and identical to his twin. However, their relative metabolisms really are different. The stationary twin will expire 2 second sooner.

The term "rate" could be confusing. The metabolic rate of each twin is equal relative to each ones frame of reference, but it is not equal relative to each other's frames of reference. Time really does pass more slowly for the traveller relative to the static twin, but because time itself passes more slowly, it is impossible for the traveler to know it is passing more slowly within his frame of reference. How could he know? Everything is effected.

For example, if the static twin could magically observe his traveling twin, he would notice that the twin's voice is a bit deeper than usual because he is hearing it relative to his timeframe. However, the traveler would not notice anything unusual at all. Frequency is a function of time, so even although the waves are stretched from the static twin's perspective, they are not stretched from the travelers perspective.