Friday, February 4, 2011

Does backward time travel violate the conservation of energy?

The law of conservation of energy basically states:

the total amount of energy in an isolated system remains constant over time (is said to be conserved over time).

Now imagine that a time traveler, Welles, goes into his time machine at time t` in order to go back 50 years to time t. We can think of Welles as a bundle of particles with mass, or its equivalent, packet of energy, as special relativity suggests with a inertial reference frame. What happens to that energy packet after t`? The state of the universe before t` had a constant amount of energy but after t`, its total energy is less by the amount composed of Welles. The inertial reference frame which traced his path through spacetime simply ends (where it goes backward in time, perhaps "doubling back") before that time. Thus the total energy of the isolated system (the universe) after t` is less than the time before making the total energy of the universe not constant over time.

Now when Welles appears at t, the total energy of the universe would appear to be increased after t (but before t`) by the amount composing of Welles.

Angels and Demons

Imagine if a nation of psychopaths were to appear on some land. These people are anti-social to the extreme and are out to destroy the rest of the human race. They have no higher goal and they seem to be no convincing them against their evil ways. There may be ways of convincing them to renounce those ways but no one has yet to find a way to convince them. They have developed sophisticated war technologies and are about to wage war on the rest of Mankind. Mankind seems to have adequate ground to kill many of them in self-defense or to incapacitate or incarcerate the rest. They would have no justified moral grounds to complain against such treatment.

Now imagine a nation of angels, of perfectly moral beings that were to appear on some land. They have also developed very sophisticated war technologies but their reasoning for doing so is to protect themselves from attack from the rest of Mankind. What principled, non hypocritical grounds would we have against a proposal by them to kill and/or capture and incapacitate us?

Personal identity

There are still some neo Lockean personal identity theorists around like Michael Tooley. I don't support such a view. I mentioned in a previous post that I supported a brain identity criterion (that the self is a phase sortal of the brain). One way that occurred to me in how to "settle" this is using XPHI. As I pointed out in another previous post, XPHI isn't that impressive to me but it might go some ways to convince those on this issue who see more value in it than myself. The following dilemma might be posed to a sample of people:

You have a brain disease that will destroy your brain in a few weeks. You have the option of either taking a drug that will cure you of the disease but will result in the deletion of all your current memories,personality and other unique character traits but will allow you to start anew by learning and forming new memories. Alternatively, you can have your brain state recorded by a brain scanner and "implanted" into a new brain inside another body without any of its own memories. The new brain will be activated as soon as your old brain is destroyed by the disease. This person which has the new brain will begin to act and behave and think just like you now but she will have a different brain.

Those who choose to have their brains scanned and the information "programed" into the new brain might have their intuitions in line with neo Lockean accounts while the ones that would choose to take the drug (and hence lose all their memories, etc but keep their physical brains) are closer to the brain theorists.

My review of Killing in War

By Jeff McMahan here.