It's been argued that, regardless of biomedical advances, true immortality is impossible, simply due to thermodynamics, and the fact that the universe itself is mortal.

Some physicists have come up with a theory that this may not necessarily be so.

That's what I love about physics... you can say something seriously that otherwise would have people calling for the butterfly nets.

Entropy only applies to a closed system. Things go in and out of bodies all the time -- they are not closed. No reason to think that (given the right circumstances and intervention) that they really couldn't last forever.

Not that I think it will happen soon -- or that it will happen ever. But I don't think there is any reason to think it shouldn't, either.