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Author Topic: Why does the Universe behave differently when we don't observe it?  (Read 4282 times)

Offline Airthumbs

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I am referring to Young's double slit experiment which seems to be the start of all this! 

And how on earth does light know we are observing it in the first place?  It is almost like the Universe is trying to hide something from us..............  :o


 

Offline MikeS

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I am referring to Young's double slit experiment which seems to be the start of all this! 

And how on earth does light know we are observing it in the first place?  It is almost like the Universe is trying to hide something from us..............  :o
Why does the Universe behave differently when we don't observe it?

When we observe the universe on the macroscopic scale although we are interacting with it we do so without changing anything, or very little.  When we "observe' it on a quantum scale, the only way we can do ti is by interacting with it.  That interaction changes one of the parameters.  How any of this relates to the Bells double slit experiment I haven't a clue.
 

Offline imatfaal

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Whilst what Mike has said is correct (apart from fact that it is Youngs Slits and Bells inequality) it goes much deeper than interaction rather than passive observation.  In another thread MPC posted a link to the wikipedia article on the Delayed Choice Quantum Eraser experiment - it is a remarkably good explanation and might give you an insight to the completely non-classical world of qm.

http://en.wikipedia.org/wiki/Delayed_choice_quantum_eraser#The_experiment

The way the experiment is set up the detection of whether the photon passed through slit a or slit b is removed from the interaction that causes the interference.  After the photon has passed thought the slit apparatus it generates an entangled pair of photons one of which (the signal) might cause the interference pattern, the other of which (the idler) can be measured to see which slot the original photon passed through.  the results are astounding and cannot be viewed from a classical perspective.  I would recommend reading it - and if you have any questions on the results - let me know, if you have any questions on what the hell is going on - join the club
 

Offline MikeS

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Sorry, my brain was over the other side of the universe when I wrote Bells. [:I]
 

Offline Phractality

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I am referring to Young's double slit experiment which seems to be the start of all this! 

And how on earth does light know we are observing it in the first place?  It is almost like the Universe is trying to hide something from us..............  :o

One of the many-worlds interpretations is that the universe behaves in every possible way until we make an observation which determines which of those ways belongs in our own past. Until we know which universe we're in, all the possible universes still exist. They only cease to exist for us when we eliminate them by observation.
 

Offline imatfaal

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Mike - in one particularly warped universe I suppose it was Bells Slits and Youngs Inequality. 
 

Offline MikeS

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imatfaal

Damn.  You've found out where I live.
 

Offline Airthumbs

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That doesn't answer where I live!
 

Offline yor_on

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Well, you could always try to apply 'sum over paths' (Feynman) and see if it makes more sense then :) Or you could try the cheap way out. Just define light as a constant but stop consider it to move. Motion is on the whole one of the most questionable definitions we seem to have. Not that we don't move, but the question seems to be if what we call motion is correctly defined.

Without motion, as something propagating from 'A' to 'B' you can still have a causality chain, well, as a proposition :) And the causality chain may very well translate into what we see as motion, but when pushed to its extremes, as in macroscopically 'speeding' close to 'c', or as in the quantum realm observing 'light paths' the room, and the associated motion, seems intertwined and give us very strange readings.

It could very well be a matter of from where a 'SpaceTime' makes most sense. Then we are exactly where it does, in the 'middle' of it where all effects are able to be defined as linear processes as we've been observing them for the longest time. Newtons world was a very safe one where stuff made sense, at least compared to the one we're exploring today.
 

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