quote:

*Originally posted by Nieuwenhove*

quote:

*Originally posted by Ben*

If time is said to slow down for an object which is moving fast relative to another object, does this mean that for a planet in a solar system on the outskirts of a spinning galaxy (which is moving fast) that time appears slower than for a planet in a solar system near the centre of a galaxy (which is moving more slowly)?

Will this effect make a difference to the time experienced on each of the planets over hundreds of millions of years?

Nobody seems to have mentioned that these time dilations are relative ! Suppose star A moves faster than star B, then both have a velocity relative to each other. A person on a planet near star A will see another person near star B ageing slower (maybe a microsecond over a lifetime) while a person near star B will see the other person (near star A) ageing slower. Now, I have used an argument from special relativity which is not really applicable since we are dealing with accelerated motion. There is some similarity here with the twin paradox, though it is more complicated here. So, one should use general relativity here which will become quit complicated. Any suggestions ?

Yes, this was already covered even in this forum (see THE TWINE paradox:

http://www.thenakedscientists.com/forum/topic.asp?TOPIC_ID=5174).

It's called

__EHRENFEST PARADOX__:

http://en.wikipedia.org/wiki/Ehrenfest_paradox See also:http://en.wikipedia.org/wiki/Born_coordinates

quote:

Summary

Observers riding on a rigidly rotating disk will conclude from measurements of small distances between themselves that the geometry of the disk is non-euclidean. Regardless of which method they use, they will conclude that the geometry is well approximated by a certain Riemannian metric, namely the Langevin-Landau-Lifschitz metric. This is in turn very well approximated by the geometry of the hyperbolic plane (with the constant negative curvature -3w^2). But if these observers measure larger distances, they will obtain different results, depending upon which method of measurement they use! In all such cases, however, they will most likely obtain results which are inconsistent with any Riemannian metric. In particular, if they use the simplest notion of distance, radar distance, owing to various effects such as the asymmetry already noted, they will conclude that the "geometry" of the disk is not only non-euclidean, it is non-Riemannian

I have to say that, unfortunately, I was not able to fully understand everything said in those files.

This is what I have understood, someone correct me if I'm wrong:

1.Even on a circular ring which rotates with constant speed, it's not possible to assign a unique time to all the travellers along the ring.

2.The geometry of the ring is not euclidean (flat) anylonger, so circumference = 2*(pi)*R it's not true anylonger (so, not even v = omega*R is true anylonger) ; specifically, the radius R should be greater than the circumference.

3.Not even something simple has the radius R has a unique meaning: from an observer in the center of the ring it has the value R, for an abserver travelling along the ring, it has another value!