New model 'permits time travel'

[emad]

By Julianna Kettlewell
BBC News science reporter

The concept of time-travel is laden with uncomfortable paradoxes
If you went back in time and met your teenage parents, you could not split them up and prevent your birth - even if you wanted to, a new quantum model has stated.

Researchers speculate that time travel can occur within a kind of feedback loop where backwards movement is possible, but only in a way that is "complementary" to the present.

In other words, you can pop back in time and have a look around, but you cannot do anything that will alter the present you left behind.

The new model, which uses the laws of quantum mechanics, gets rid of the famous paradox surrounding time travel.

http://news.bbc.co.uk/1/hi/sci/tech/4097258.stm

[Moochy]

1. Observation affects subject?

So, what about "just having a look around" ? I suppose that if you are in the past and occupying a volume of space, that you have in fact altered the past. Those air molecules destined to be present in your viewing location, before you started your time travelling trip, would be displaced by your body, and thus, you've affected the past.

"I wish, I wish I did not kill that fish" Homer Simpson, bummed about his Time Travelling woes.

[bigendian]

2. UFO'S?

I have thought for a long time that flying saucers were actually time travellers. The lack of formal contact, the ability to move in the blink of an eye from one place to another, changing shape, etc.
It makes sense if you are operating from another time frame.

[sui generis]

3. so, . . .

if I sent my dog back in time as the observer with knowledge of teh present would the probabilities collapse just the same?

What if I sent a robot with a bomb back in time? Would it technically have knowledge of the present?

This theory's main premise is the observational collapse of a probability wave function; it's downright victorian.

I would probably have to dredge up Occam's razor on this one - there are too many "if / then's" for it to be plausible.

[hyphenate]

4. Time travel

(if the physics part of it is ever worked out!) is not as ingrained as that model, and I disagree strongly with their contention that you could not "change" the past.

While there are many theories about what you could or couldn't do, it's not really a matter of CHANGING anything, it's a matter of choosing NOT TO CHANGE anything lest something horrific happen as a result of change down the line.

Of course, since TV and movies always try to go the "protagonist" and "antagonist" routine, it's always more a matter of setting "right" what the bad guy has done wrong.

[progmom]

5. this was the basic premise behind the Time Traveler's Wife

...which was an excellent book.

[ET Awful]

6. Well, theoretically, it would be impossible to change anything

because if you travel back in time, your presence there existed at that time and always existed at that time.

If you were to travel back and in any way effect events, that effect will already have happened in your "present" (for lack of a better term).

History is a constant, it has already happened. In any potential time travel, you are simply occupying a spot in history that you have always occupied, the time has already passed. You have no memory of the time because that history has not become part of your present or future yet, but if you were in a public place, there may very well be a record of your presence.