Time travelling

[Guest PSdiE]

A definitive answer on Time Dilation please!

 

According to Einstein's "time dilation" theory, if an object (A) is moving at a relative speed higher than that of another object (B), time travels more slowly for A than for B, correct?

 

OR is it that A (or its passenger) perceives time to travel more slowly than B does (as inferred by many explanations of the Time Dilation effect)? This makes a big difference!

 

If the former is true, then the scenario discussed earlier in this forum would genuinely occur: two twins, one settles down on Earth, the other becomes an astronaut and orbits the Earth at great speed for many years. When the astronaut returns, he has physically aged less than his twin (and has had fewer birthdays). He has effectively travelled to the future (albeit irreversibly).

 

If on the other hand, the only thing that changes is the twins’ perception of time, then when the astronaut returns he will be the same age, but is considerably more bored than his twin because time appeared to travel more slowly for him (i.e., felt like 20 years instead of 10).

 

This has bothered me since a half-baked explanation from my A-level physic teacher! Presumably the authoritative answer depends on whether an atomic clock, flown around the world on a fast jet, registers less time as having passed than a grounded reference clock, once the plane has landed?

 

If this is confirmed to be the case, does anyone know the scale of the time shift? For example, if I have an illness and wish to travel 5 years into the future to increase the chances of a cure being available, how fast a satellite do I need to stowaway on and how long should I count on waiting?

 

Would I also be correct in thinking that (since direction of motion is irrelevant) time also slows down for objects spun in a circle? In which case, I'm off to live on a merry-go-round until they improve anti-wrinkle creams ..

 

Fascinating forum (with the possible exception of 1 vs N dimensional time theories), thank you all.

[Deified]

The answer is "a". Time slows down in gravitational fields and at high velocities. I haven't studied these theories extensively, but I do know that the have to correct the clocks in GPS satellites, because they lag behind earth clocks.

[Ophiolite]

A definitive answer on Time Dilation please!

 

This has bothered me since a half-baked explanation from my A-level physic teacher! Presumably the authoritative answer depends on whether an atomic clock' date=' flown around the world on a fast jet, registers less time as having passed than a grounded reference clock, [b']once the plane has landed[/b]?

 

.

"During October, 1971, four cesium atomic beam clocks were flown on regularly scheduled commercial jet flights around the world twice, once eastward and once westward, to test Einstein's theory of relativity with macroscopic clocks. From the actual flight paths of each trip, the theory predicted that the flying clocks, compared with reference clocks at the U.S. Naval Observatory, should have lost 40+/-23 nanoseconds during the eastward trip and should have gained 275+/-21 nanoseconds during the westward trip ... Relative to the atomic time scale of the U.S. Naval Observatory, the flying clocks lost 59+/-10 nanoseconds during the eastward trip and gained 273+/-7 nanosecond during the westward trip, where the errors are the corresponding standard deviations. These results provide an unambiguous empirical resolution of the famous clock "paradox" with macroscopic clocks."

J.C. Hafele and R. E. Keating, Science 177, 166 (1972)

[Guest PSdiE]

Thanks Ophiolite - THAT'S the study I've been looking for.

Anyone fancy estimating how fast/long my terminally ill satellite stowaway needs to ride for? And does rotational force create the same Time Dilation?

[alext87]

Here's an interesting point:

The mass of an little insect is less than the mass of a human by quite a large factor.

 

Einstein said that the higher the mass the more the object distorts time. Therefore, little insects must be in a slightly different 'time zone' than us as humans.

 

So does that mean when insects watch human move we appear to be travelling faster and when we watch them move they appear to be travelling more slowly.

 

 

Is there a constant link between the mass of an object and the rate of time which they are experiencing?

[ydoaPs]

you got it backwards.

[AtomicMX]

Is there a constant link between the mass of an object and the rate of time which they are experiencing?

Perfect no.

You would have to take in count all the universe. positions and stuff.