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Author Topic: What phenomena do quantum fluctuations in space help to explain?  (Read 2502 times)

Johann Mahne

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Can someone explain, in basic terms, what quantum fluctuations in space are and what phenomena do they help to explain?
Have these fluctuations ever been measured?
How do they affect photons passing and particles passing through space?


 

Offline imatfaal

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deep breath

Quantum fluctuations can be viewed as a manifestation of the Heisenberg uncertainty principle - but not the more usual momentum/position format, the energy/time format. ΔEΔt≥h/2π

From a measurement point of view the HUP standard form is often taken to mean that product of the error on the momentum and error on the position must be greater than planck's constant over 2 pi.  the energy formulation can be seen this way as well - but it is also read as saying that the law of conservation of energy can be "relaxed" as long as the change in energy is so short-lived that the product of the energy and time is less that hbar/2.  This relaxation in energy conservation appears as the spontaneous generation of virtual particle pairs of a positron and electron in what was previously empty space.  There is a much more complicated explanation that does not require any relaxation of conservation of energy.

the casimir effect is generally - although by no means universally - accepted as being driven by either vacuum virtual particles or quantum field fluctutations.  two plates extremely close together in a hard vacuum feel a force (normally towards each other - but it depends on arrangement). 

hawking radiation can be explained heuristically - but not completely wrongly - by virtual particle formation.

there is a huge amount we don't know about this field - it is ongoing to say the least.  much of this area of physics can be viewed in different ways to explain the same thing - I think this is an area which is more often looked at through the lens of fluctuations in the quantum field rather than creation/annihilation of virtual particles. 

How this effects light and particles in the vacuum? - I don't know.  It would be difficult to test as whichever explanation you choose - the phenomenon is omnipresent
 

Offline JP

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There is another reason to believe these fluctuations are real: quantum field theory works incredibly well.  In order for the theory to work at higher energies, where these fluctuations don't matter so much, it has to include these fluctuations.  Because the theory works, we can infer that they're real. 

There is at least one major problem, though.  These fluctuations mean that empty space has energy.  Since the universe is expanding, creating more empty space means creating more energy.  This is one candidate for the mysterious "dark energy" that seems to be making the universe expand faster.  The problem is that the energy calculated from quantum mechanics is way too big for what we observe, so there's something we don't understand yet going on between the small scale and the large scale.
 

Johann Mahne

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Thanks very much for the replies.It's a big sandwich to chew on, but i'll try to check out the basics that were mentioned.
 

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