Quantum Mechanics & other strange phenomena

#1
Wave particle duality, entanglement, quantum tunneling. Let's discuss the strangest things in science in this thread!

I'd like to try and form a simple and easy to read layman's guide to cover each topic, if anyone has any good links or websites for QM then post them here.

DC
 
#2
Haven't got a clue what the above means but I'd like to know whether a time machine would ever be feasable? I suppose we'll never be able to go back into the past as that would mean we'd have those from the future visiting us. And if we could go into the future that would mean we could get the technology for a time machine and bring it back into the past. So I suppose one will never be made!

Anyway, back to quantum physics.

erm mechanics.
 

ancienturion

LE
Book Reviewer
#3
If light travels for ever (we know it does because light from stars is millions of years old) then surely it is only necessary to use Heisenberg's Uncertainty Principle in quantum physics in order to travel faster than light. Travellers would then be able to view the past.
 

ancienturion

LE
Book Reviewer
#4
Anyway, didn't Richard Feynmann have something to say about this. I'll have to have a root around and see if I can find my copies of his books.
 
#5
I don't know about a time machine fit for humans but this may interest you:

THE laws of physics seem to permit time travel, and with it, paradoxical situations such as the possibility that people could go back in time to prevent their own birth. But it turns out that such paradoxes may be ruled out by the weirdness inherent in laws of quantum physics.

Some solutions to the equations of Einstein's general theory of relativity lead to situations in which space-time curves back on itself, theoretically allowing travellers to loop back in time and meet younger versions of themselves. Because such time travel sets up paradoxes, many researchers suspect that some physical constraints must make time travel impossible. Now, physicists Daniel Greenberger of the City University of New York and Karl Svozil of the Vienna University of Technology in Austria have shown that the most basic features of quantum theory may ensure that time travellers could never alter the past, even if they are able to go back in time.

The constraint arises from a quantum object's ability to behave like a wave. Quantum objects split their existence into multiple component waves, each following a distinct path through space-time. Ultimately, an object is usually most likely to end up in places where its component waves recombine, or "interfere", constructively, with the peaks and troughs of the waves lined up, say. The object is unlikely to be in places where the components interfere destructively, and cancel each other out.

Quantum theory allows time travel because nothing prevents the waves from going back in time. When Greenberger and Svozil analysed what happens when these component waves flow into the past, they found that the paradoxes implied by Einstein's equations never arise. Waves that travel back in time interfere destructively, thus preventing anything from happening differently from that which has already taken place (www.arxiv.org/quant-ph/0506027). "If you travel into the past quantum mechanically, you would only see those alternatives consistent with the world you left behind you," says Greenberger.

"This is a very nice idea," says physicist Avshalom Elitzur of the Weizmann Institute in Rehovot, Israel, who also suggests that further work in the area could help to clarify the nature of time itself. "Time is a very mysterious thing."
No paradox for time travellers - physics-math - 18 June 2005 - New Scientist

DC
 

ancienturion

LE
Book Reviewer
#7
Do you mean 'view the past' or actually go back into the past in a physical form?
View it rather than be able to go back into the past in a physical form. However, if the speed could be matched to that of the travelling information then perhaps one might be able to interact.
 
#8

rampant

LE
Kit Reviewer
Book Reviewer
#9
If light travels for ever (we know it does because light from stars is millions of years old) then surely it is only necessary to use Heisenberg's Uncertainty Principle in quantum physics in order to travel faster than light. Travellers would then be able to view the past.
Does it, the universe is not infinate and will eventually end due Heat Death, Entropy (according to the Heat Death Theory anyhow), no energy, no motion meaning that even photons may not be able to travel.
 
#10
Was Einstein right ? Or Heisenberg ? Or were they both right depending on which point of view you take ?
 
#11
If light travels for ever (we know it does because light from stars is millions of years old) then surely it is only necessary to use Heisenberg's Uncertainty Principle in quantum physics in order to travel faster than light. Travellers would then be able to view the past.
Entanglement is the only known phenomena to travel faster than light (as far as I know). This is a very odd situation where two atomic substances can be said to be 'entangled' or connected in some way. As soon as they are connected then manipulation on one immediately effects the other, no matter how far apart they are separated. You could spin one electron and the other one would behave in exactly the same way instantaneously even if it was on the other side of the universe. I don't think anyone's figured out why this is the case yet but it's certainly bizarre.

Spooky quantum entanglement disturbed - Technology & science - Science - msnbc.com

DC
 

ancienturion

LE
Book Reviewer
#13
So one day we may actually be able to find out everything in our history which we can only guess at at the moment. Bearing in mind the advances we've made in the last 100 years alone, in 10000 years (if humans are still roaming the earth) then I suppose anything could be possible.
If ever we do then history will have to be totally rewritten which will upset a lot of people who have written it down (or altered it) to suit themselves.
 
#14
Entanglement is the only known phenomena to travel faster than light (as far as I know). This is a very odd situation where two atomic substances can be said to be 'entangled' or connected in some way. As soon as they are connected then manipulation on one immediately effects the other, no matter how far apart they are separated. You could spin one electron and the other one would behave in exactly the same way instantaneously even if it was on the other side of the universe. I don't think anyone's figured out why this is the case yet but it's certainly bizarre.


Spooky quantum entanglement disturbed - Technology & science - Science - msnbc.com

DC
I understand scientists conduct these experiments in controlled labs (or wherever) but how can they say they'd react the same billions of miles apart unless actually carrying out an experiment in this fashion?
 
#15
Was Einstein right ? Or Heisenberg ? Or were they both right depending on which point of view you take ?
Regarding what? Quantum Mechanics and General Relativity? I believe that's the biggest problem in science at the moment because the two theories don't really fit together. Quantum objects behave very differently from classical Newtownian objects and no-one seems to know why. You don't see your cup of tea appearing in two places at once, but in the Quantum world this sort of thing is a normal occurance.

Regarding the time travel discussion, you could consider that light travels at a constant speed and this has an effect on what we see by the time it reaches our eyes. If a planet is 10 light years away we will see that planet as it was 10 years ago, if it's 100 light years away we'll see it as it was 100 years ago. Now it would be interesting to turn that upside down, what do those guys on the other planet see if they look at earth? They certainly wouldn't see me typing this thread, they'd see Britain as it was in 1910 with a vast empire and battleships sailing about the place, I wouldn't even exist! If they were situated a million light years away they'd be able to look at earth and see dinosaurs running about. Theoretically if they were able to record what they saw via a telescope and beam it to us on a laser then it would be possible for us to view the past just as we do with video cameras. The only problem is that it would take a million years for it to reach us.

Mind blowing stuff when you ponder it for a while!

DC
 
#16
I understand scientists conduct these experiments in controlled labs (or wherever) but how can they say they'd react the same billions of miles apart unless actually carrying out an experiment in this fashion?
Good question and I don't have an answer, I guess it's in theory. If it can be instantaneous in a lab a few metres apart perhaps they concluded it would work at any distance?

DC
 

ancienturion

LE
Book Reviewer
#18
The last time I listened to Feynmann he was going on about quarks.
 
#20
Got quite a good vid here without the faintly annoying American narrative you get on Youtube, the first vid is just a general intro but 2/3 get into the interesting details:

[video=youtube;0ey2uVPmAPE]http://www.youtube.com/watch?v=0ey2uVPmAPE[/video]

[video=youtube;lQXQR8unfqU]http://www.youtube.com/watch?v=lQXQR8unfqU&feature=related[/video]

[video=youtube;W6rT5I1nRlQ]http://www.youtube.com/watch?v=W6rT5I1nRlQ&feature=related[/video]


DC
 
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