h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Wouldn't timetravel violate the second law of thermodynamics (Which is about the preservation of energy)?
Travelling back in time would remove mass from the current universe without releasing its mass energy first and thus not preserving the amount of energy, iirc. Is there a way around this or am I just completely wrong

BTW - First post, so 'ello everybody!

It's the first law actually, and I think it could be generalised so that time travel wouldn't violate it. I mean, if a mass (e.g. me) leaves a room and enters another room, it isn't violated. So why not allowing to leave a certain time and entering another one?

I think that if a mass simply left this time and went into the past, it would violate the first law of thermodynamics: during the time when there are two "copies" of whatever time-traveled, the universe has a surplus mass-energy equal to the mass of the time-traveled object. The solution would be to replace the mass you're time-traveling with an equal mass from wherever the destination time is. For example, if I go into the past to 1950, a me-sized chunck of matter must move from 1950 to 2002 to compensate.

Of course, conservation of energy issues are far from the greatest problem with time travel...

But, presumably, you would not change your position in space, just time. A trip of six months would cause you to appear at least 190 million miles from the Earth.

And, also, Einstein's unification of space and time (spacetime) says that by moving in space you are moving in time (and vice versa).

That moving in space means moving in time is trivial -- everybody knows that from everyday life. However moving in time without moving is space *is* possible, even after Einstein.

Lets just say that you could travel back in time, and you can, as you leave a strong gravitational field, your time speeds up. However, i feel that the thermodynamics laws used previously, have been used out of context. Why does it apply, it makes no sence. The transferance of a human body, is just a plausable as sending energy through time, unless you send someone at absolute zero back in time.

Although I already said this in a different thread somewhere around here. If the out universe is just a part of a multiverse, and in traveling back in time you travel into a parallel universe, then matter is being conserved. Because universe A is not one less person, while universe B is one more person. But the multiverse still has the same amount of matter in it. On a different outlook, if time travel is possible that means time has no beginning or end. Considering time travel not being possible, then there is nothing after the present. As in, time is being created right now, and there is nothing ahead of right now until later. However if it's possible for us to have visitors from the future that means that a future already exists before we actually got to it, meaning there will always be a premade future. If that is the case, then subtracting matter from one place in time, and putting it into another wont upset anything because the timeline as a whole still has the same amount of matter on it.

A question I am curious about is why is this law of conservation a law anyway? How do we know matter and energy must always be replaced if destroyed? I don't see how this law can be proven without time travel, since humans don't yet have the ability to either create or destroy matter or energy.

read stuff on relativity and thermodynamics

I have, read tons on it. All they ever say is ... because of the law of conservation ... never actually telling my how we know that.

Well the law of conservation isnt so much a law, as an assumption that makes the universe balanced when another solution cant be discovered

Well that will help me sleep at night. I was never comfortable calling it a law.

I am aware that this may not be the most appropriate place to post this, but I am too lazy to find a better location.

Three years ago I was reading some books on physics, cosmology, and other such related subjects (at that point I was in dire need of a social life). I came across one - I cannot remember if it was Saberhagen or Hawkings that authored the book - and it mentioned a theoretical quantum particle known as the tachyon. This particle had the unique property of being just faster than the speed of light at its slowest point. According to the book, the particle would increase in speed with the addition of mass.

The book doesn't give the equation to figure out the energy required , but assuming that it is the exact opposite of a light particle, it would seem that energy would equal mass times the square root of the speed of light. I am no Physicist, so I could be mistaken on the formula.

I realize that there would be problems, even if we could successfully prove the existence of tachyons, in harnessing them. I leave that up to the ones with the PhDs.

Someones, left a blue floppy disc on my desk.......