I am not going to let some pencil necked geek
tell me what I can and can not do in the past...
Posted on 06/17/2005 12:06:22 PM PDT by LibWhacker
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.
Paradox explained
Although the laws of physics seem to permit temporal gymnastics, the concept is laden with uncomfortable contradictions.
The main headache stems from the idea that if you went back in time you could, theoretically, do something to change the present; and that possibility messes up the whole theory of time travel.
Clearly, the present never is changed by mischievous time-travellers: people don't suddenly fade into the ether because a rerun of events has prevented their births - that much is obvious.
So either time travel is not possible, or something is actually acting to prevent any backward movement from changing the present.
For most of us, the former option might seem most likely, but Einstein's general theory of relativity leads some physicists to suspect the latter.
According to Einstein, space-time can curve back on itself, theoretically allowing travellers to double back and meet younger versions of themselves.
And now a team of physicists from the US and Austria says this situation can only be the case if there are physical constraints acting to protect the present from changes in the past.
Weird laws
The researchers say these constraints exist because of the weird laws of quantum mechanics even though, traditionally, they don't account for a backwards movement in time.
Quantum behaviour is governed by probabilities. Before something has actually been observed, there are a number of possibilities regarding its state. But once its state has been measured those possibilities shrink to one - uncertainty is eliminated.
So, if you know the present, you cannot change it. If, for example, you know your father is alive today, the laws of the quantum universe state that there is no possibility of him being killed in the past.
It is as if, in some strange way, the present takes account of all the possible routes back into the past and, because your father is certainly alive, none of the routes back can possibly lead to his death.
"Quantum mechanics distinguishes between something that might happen and something that did happen," Professor Dan Greenberger, of the City University of New York, US, told the BBC News website.
"If we don't know your father is alive right now - if there is only a 90% chance that he is alive right now, then there is a chance that you can go back and kill him.
"But if you know he is alive, there is no chance you can kill him."
In other words, even if you take a trip back in time with the specific intention of killing your father, so long as you know he is happily sitting in his chair when you leave him in the present, you can be sure that something will prevent you from murdering him in the past. It is as if it has already happened.
"You go back to kill your father, but you'd arrive after he'd left the room, you wouldn't find him, or you'd change your mind," said Professor Greenberger.
"You wouldn't be able to kill him because the very fact that he is alive today is going to conspire against you so that you'll never end up taking that path leads you to killing him."
LOL
No. If at some time in the future you are going to go into the past, then at this moment, you have already been in the past. You can't change anything.
I am not going to let some pencil necked geek
tell me what I can and can not do in the past...
Gibberish...
Maybe it was better you met her then, rather than meeting and marrying her 10 years from now, right before you clear $5 million investing in an upstart anti-graviton manufacturer.
In your case, perhaps that's what God wants you to believe.
Usually, if you can't understand something, it's not that thing that's stupid.
"In your case, perhaps that's what God wants you to believe."
Perhaps. What does that say about what God wants you to believe, though?
"not that thing that's stupid". A bit grammatically challenged, are you? There was nothing of substance in that article.
If you aren't rich in Wal-Mart stock today, then according to this model, you wouldn't be able to go back and buy Wal-Mart stock. "Something" would prevent that.
Back to the drawing board.
The proposition put forth is that the fact of your existence makes it impossible to alter the past in such a way as to make your existence cease. That is, since you are here now, you are here and there is no way that the past exists which makes you not be here. Cause here you are.
To put it another way, it is impossible for you to have the desire or ability to go back and kill your father, because you obviously didn't, cause you're here.
SD
for example, the elements and molecules that made up michael fox in 1980 were somewheres else 100 years earlier and will be somewheres else 100 years from now...
for better or worse, we are essentially creatures limited to the 'here and now'
Hey people, I just tried it and this article is baloney. What happens is you get thrown into a parallel alternate universe that exists by virtue of your meddling.
I don't think I'll miss my original universe though-- I mean, I can live without President Gore and the Pope divorcing her third husband.
How do we know that killing them as infants would not lead to even worse horrors arising in their place?
" But then by simply going into the past you would be changing something, the air you breathe ?"
Oh... sort of like the old butterfly flapping it's wings in China thing, any change -no matter how minor- will affect a chaotic system in seemingly unpredictable and increasingly complex ways? You do have a point. Not sure that it would preclude time travel into the past, but this would make it seemingly much more difficult, close to impossible.
I thought they had been discontinued.
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