Did this really happen?

[caveman]

I heard that someone did an experiment with two atomic clocks, one stayed in London and one went around the world in the opposite direction to the spin of the earth at mach1. When it got back to London it had lost more time than it normally would in a millennia(fraction of a second). I can't remember where I heard this but it has been playing on mind if it was true, surely some military jets can do about mach4 then time travel would be possible(if impractical)?

 

[Jack D]

How could the clock 'speed up'? It would be slower, due to the effect of time dilation.

 

[Janus]

Yeah, this was done a while back, as one of the proofs of relativistic time dilation. No 'time travel', though, in the popular sense of the term. If you're interested, there are plenty of popularised books on relativity which give a basic overview of the theory and its implications.

Going mach 4 would produce more time dilation, but still no time travel.

 

[djayr42]

I believe this is what you are looking for: http://www.pbs.org/wgbh/nova/einstein/hotsciencetwin/test.html


this is a transcript http://www.pbs.org/wgbh/nova/transcripts/2612time.html

possible things of interest http://www.pbs.org/wgbh/nova/time/through.html

<This message has been edited by djayr42 (edited 29 June 2000).>

 

[The Doctor]

....

<This message has been edited by The Doctor (edited 01 July 2000).>

 

[djayr42]

If you were to take one of those clock and spin it so that the apperant gravity is twice the normal gravity, you would think it would an affect on time as measured by the clock. If there is no effect then there seems to be something missing using apparant gravity. As far as I know it has been proven that the farther you are from a large gavitional force the weaker that force becomes and time will move slower as compared to being closer to that gravitional force.

 

[Janus]

Well, AFAIK, fission is not dependent on magnetism. But, in any case, you could just do the test again with maser clocks. No fission there. Relativistic time dilation has been proven in many ways, many more elegant than this one. Using the planes, there's a lot of messy math to sort out, seperating the dilation due to gravity and that due to speed, and all the acceleration etc.

djayr42: Spinning something doesn't actually increase the 'apparent gravity'. It gives you a pseudoforce somewhat like gravity, but which falls off with the inverse of your distance from the "floor", rather than the inverse square like gravity. So the effects would naturally be somewhat different than that of gravity.

Oh, and you got it backwards: the closer you are to a massive object (like Earth), the slower time goes for you. That's why time is said to stop in a black hole.

 

[Guest]

Fortunately fission is not how atomic clocks work, however they do use magnetic fields and If not properly shielded these magnetic fields could be affected.

 

[The Doctor]

...?...

<This message has been edited by The Doctor (edited 01 July 2000).>

 

[Guest]

Janus:
Many scientist belive time dilation equals time travel and that the clock experiment proves this. Why do you disagree?

 

[Janus]

Time~Master, I agree with your statement. But the phenomenon most people imagine when one says "time travel" is something like stepping through a portal which leads instantaneously to another time. Not just making your clock run slower or faster than someone else's. I agree it's a moot point, but I like to draw the distinction, just so that no-one gets the wrong impression.