Sunday, September 15, 2013
NatGeo: "Time Travel: The Truth"
The film starts by introducing time as a dimension in 4-way space-time. We think of places on Earth in two dimensions on a map (postal addresses) but Donald Trump can give us a lesson on air rights. Is the same true of time?
I think that an appreciation of time can affect how we perceive people. A perfect 21-year –old athlete today will, given enough time and living long enough, become an old man – unless he is Clark Kent or an angel, the stuff of science fiction. The reverse is true. I was once a 20 year old, with hair on my scalp and legs. One could imagine a space where every person exists at their own biological best. Again, science fiction. Over time, in our experience, organisms decay because of entropy, and so they must reproduce to overcome it.
The film explains the relationship between mass, energy, gravity and time, and shows how time pass more slowly when under the influence of gravity. Michio Kaku leads off with general explanations. A young professor from Manchester England Brian Cox (not the actor) speaks, followed by Princeton Professor Richard Gott, who proposes how a time machine could be built with massive cosmic strings, but only civilizations with access to the amount of energy in a galaxy could build them. The Lon Mallett demonstrates the possibility of a time machines based on loops of light, since light has energy, which converts to mass and eventually gravity, which can bend time. In nature, a kind of time machine could occur inside a rotating black hole, but you never check out of one. It might also occur with a “worm hole” in space time.
The last part of the film talks about the paradox implicit in backwards time travel – you can’t change the past -- the irreversible nature of the "time arrow of physics." You can walk upstairs but never come down again, safely, except in thought. That is, you can’t undo a crime you just committed one second ago after you pulled a trigger. Your own sense of free will – you own identity – will deal with the punishment and jail, maybe even death row. Until that moment of no return, punishment and jail is what other “free wills” experience – unless you are framed or unjustly prosecuted and convicted for something you didn’t “do”. This can go another direction – into “thought crime”, telepathy, “pre-crime”, or “Minority Report”. Other films to recall are "Time Bandits" (Terry Gilliam, 1981, Embassy) and "The Time Machine", H.G. Wells story, the most recent film coming from Warner Brothers in 2002 and director Simon Wells with Guy Pearce.
But physicists get around this problem by proposing a countably infinite collection of parallel universes. I’m not sure I buy this, except that contemplation of the afterlife makes one wonder. Maybe in “death”, while you cannot “experience” in the normal sense, you know about other universes and your consciousness (or partition of a larger soul) moves to another universe. Maybe because of my karma, I get reborn into a world where Hitler won WWII.