time

[claymore]

is there any law in physics that says that time must always flow forward and never backward

[Campfire]

This is a question I doubt anyone can answer indisputably. The greatest minds of our time (Stephen Hawkins for example) have discussed this and still no definitive answer can be agreed upon by the scientific community.

Theoretically when you enter into discussion on quantum physics and relativism there have been various suggestions it's possible. It is my personal belief it is not possible or that if it is, humans will never be able to harness it in the form of a technology or ability. I'm really not knowledgeable enough on the topic though, suffice to say there is no simple answer.

I believe the general consensus is that time travel is impossible due to the constraints of physics, and any notion of time travel is purely theoretical.

[eyebrows]

er.....have you not seen back to the future?

already been done....sheesh...

catch up sparky...

[Campfire]

Wow. I rescind everything I previously said.

:(

[eyebrows]

see....

scientology!

[jake-the-peg]

There are a couple of interesting points here depending on the precise meaning.

Firstly there is something called T symmetry

http://en.wikipedia.org/wiki/T-symmetry

the T here is time and the principal is that a process that works one way in time should be able to work the other way too.

This symmetry is true only in restricted areas - it fails in quantum mechanics and in terms of entropy.

Entropy is a measure of the disorder in a complete system and the second law of Thermodynamics says that overall Entropy is always increasing and that things are always getting more disordered.

Why that is so is indeed something that has occupied a lot of great minds but have a look at this:

http://en.wikipedia.org/wiki/Arrow_of_time

for an overview

[Physicsgirl]

all you need is a flux capacitor ...... and a Delorean

[Clanad]

I think you probably mean a closed system, don't you jake? Pedantic, I know...