Speed-of-Light Travel and Aging
The most basic measure of time is entropy. The processes of entropy would be much slower at just below the speed of light. Therefore if Mr X is travelling at near the speed of light, then he would age much less quickly than his friends on earth. However, all his biological and physical processes would be slower too. Indeed if we could get our biological processes to slow down without travelling at just below the speed of light, then perhaps we would age much less quickly here on earth too.
Could bodies which have evolved with processes of a certain ‘speed’ cope with such changes? This would also involve the slowing down of our mental (neurological) processes. That is, we would be both mentally slower and physically slower – like human slugs! As a guess, I would say that the human body couldn't cope with such changes. That's unless technological processes which counteracted the negative side-effects (as it were) could also be created.
Is Consciousness Constituted by Physical Processes?
David Chalmers asks an interesting question:
“Is consciousness constituted by physical processes, or does it merely arise from physical processes?”
The consensus position is that consciousness “arises” from physical processes. At first blush, saying that “consciousness is constituted by physical processes” appears to be a reductive position. That is, if x in “constituted by” A, B and C, then that must surely mean the following:
If x = A, B & C
then x can also be reduced to A, B & C.
Nonetheless, if one tackles this from another angle, consciousness can be constituted by physical processes even though it it isn't identical to those processes. Thus, x is constituted by A, B and C, though x is not identical to A, B and C.
Here is a simple example. A house in constituted by bricks and other material objects. Though a house is not identical to the bricks and material objects which constitute it.
This doesn't work for consciousness because there are things true of consciousness which aren't true of brain/physical processes. Having said that, there are things true of bricks and other objects (as well as the sum of bricks and other objects) which aren't true of house which was made out of them. Yet some would say that the house is nothing “over and above” the bricks and other objects. Yes, in physical terms that's correct. However, there are still things true of the house which aren't true of the objects which “constitute it” - and not even true of the sum of the objects which constitute it. So, even though the house is entirely made of bricks and other objects/materials, there are things true of the house which aren't true of the things which constitute it (whether taken individually or collectively).