reply to post by Lawgiver
Let's just say time travel is so improbable that it isn't even worth discussing. The idea of time travel breaks pretty much every physics law there
is, but here are a couple of simple laws.
Matter/Energy can neither be created nor destroyed, they can only be converted - Well, I'd even argue this one a bit, but the standard model says
otherwise and time travel means the destruction of mass/energy in your original time line and the creation of mass/energy in your destination time
Conservation of energy - Move someone from their time to another time, you move their energy with them which gives a net gain at their destination
time and a net loss at their source time which changes the total energy of the universe.
Conservation of matter - Move someone from their time to another time, you move their mass which gives a net gain at their destination time and a net
loss at their source time which changes the total mass of the universe.
There is also the problem of mass/energy persistence or the distribution of that energy or mass over time. If you travel back 200 years, weigh 200
pounds and carry 500 btu's of energy, then that 200 lbs and 500 btu's get added to the universe for 200 years and then hopefully a reset of some kind
occurs. That may not seem like a big problem, but if there are millions of entities doing this, that could become problematic. But, take another
scenario of permanent migration to the future in which case the mass and energy stay in the future until the final throws of entropy. There are other
iterations of this problem, eg. you travel to the past for 30 years and return to your original time line. Once back, you travel back again to the
first day of the first month and you stay for 30 days, then 29, then 28, etc., in 30 days you've just increased the mass energy transfer of your first
month in your 30 years in the past by 6000%.
Even if you could leave your own time line and return at the same instance you left, you still deposit that mass and energy in the past or the future
for the duration of the time you exist in the past or future, which of course increases the total mass/energy of the universe. If you look at all the
possibilities and probabilities, time travel is ridiculous.
Another example, you have a full meal, go back in time and take a crap depositing that mass/energy (turd) in the system, you decide to leave and come
back to your time without eating an equivalent meal to produce an equivalent crap when you get back to your original time. Now you've left probably
500 grams of turd in the past which will be added to the universe forever and you can't get rid of that nasty old turd. Can you imagine the mountain
of time-displaced turds if a whole bunch of entities behaved this way?
Even traveling between parallel universes/realities would create almost exactly the same problem because you would be changing the mass/energy
relationship in your originating universe and the parallel universe (especially if you left a turd behind, you'd have "persistence of turd" ad
So, before you can even start looking at some viable and rational theory of time travel, you have to first look at the universe as a structure, or
not. If the universe is a closed finite system, then the laws seem to apply. If the universe is open ended, then there may not be a problem with the
creation and destruction of mass/energy. Or maybe the universe is based on total mass/energy over total time, which still may or may not create a
Cheers - Dave
edit on 10/22.2013 by bobs_uruncle because: (no reason given)