Time dilation and stem cells therapy

[myuncle]

I believe in the future stem cells will cure everything and stop the aging process, and I also think that any mammal travelling at high speed would be affected by failing organs and a weaker immune system (just my opinion).
So, two people of the same age are on Earth. They are identical twins, twin A and twin B, they are 20 years old. Twin A boards a spaceship and begins to travel near the speed of light, Twin B remains on earth. 40 years later Twin B, still on earth is now 60 years old but thanks to stem cells he looks and functions still like a 20 years old. Twin A has just returned to Earth and (unless he died in the first few hours) he looks much older than Twin A because he didn't take any stem cells.
Any thought on this?
Thanks.

[bcrowell]

I believe in the future stem cells will cure everything and stop the aging process, and I also think that any mammal travelling at high speed would be affected by failing organs and a weaker immune system (just my opinion).
Motion is relative, so you can't get physical effects based on constant-velocity motion. If you want to get started on understanding relativity, a good book is Relativity Simply Explained, by Gardner.

[yuiop]

I believe in the future stem cells will cure everything and stop the aging process, and I also think that any mammal travelling at high speed would be affected by failing organs and a weaker immune system (just my opinion).


There is no such thing as travelling at high speed "per se". The twin "travelling" away from Earth is equally entitled to consider himself to be stationary and the Earth is "travelling" away from him. To assume that travelling at high speed by itself causes ageing is to assume that there is such a thing as absolute motion which is an anathema to the Special Relativity. I suspect you are thinking of the negative health aspects experienced by cosmonauts that remained in space for long periods in weightless conditions. This aspect can be overcome by having the twin travelling away from Earth continuously accelerate with a proper acceleration of 1 G (or have a rotating rocket) so that they experience artificial gravity similar to remaining on Earth.

P.S. The secret of immortality is telomerase (in mice anyway). See http://news.google.co.uk/news/more?pz=1&cf=all&ned=uk&cf=all&ncl=dyDAUl_sjOpYdkMF2bgmOTRVTpGlM