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Sticks
2007-Nov-05, 05:33 PM
It has been said on a non-science forum that


as for your argument that something cannot come out of nothing - Quantum Field theory disproves that

Is this correct?

It came out of a brief discussion about the merits of the Big Bang theory.

I am assuming that we have moved on from the Big Bang to inflationary theory which Fraser and Pamela covered on Astronomy Cast.

antoniseb
2007-Nov-05, 06:15 PM
Depending on the sophistication of the writer, they might be referring to virtual pairs appearing and disappearing before they exceed Dr. Heisenberg's room for doubt.

Jeff Root
2007-Nov-05, 10:39 PM
I should know about this, but don't: Do pairs of virtual particles
"appear out of nothing" (as long as they dissapear again, of course),
or do they require an energy source -- which I surmise would be this
"zero-point energy of the vacuum" that I keep seeing mentioned but
know almost nothing about? If they require an energy source, why
can't they retain that energy to become physical particles? Is it
because they have enough energy to become virtual particles (for
a while) but not enough energy to become physical?

I wrote to physicist Yuvaal Ne'eman a decade or two ago asking
about this. He replied that I should get ahold of his book, 'The
Particle Hunters', but I never got beyond checking out the price
at Barnes & Noble.

-- Jeff, in Minneapolis

Jeff Root
2007-Nov-05, 10:43 PM
Sticks,

What do you mean by "moved on from"? I'd call the inflationary theory
a subset of Big Bang theory.

-- Jeff, in Minneapolis

Spaceman Spiff
2007-Nov-06, 01:59 AM
I am a Ph.D. astronomer; I do not do QFT for a living. However, I think I understand correctly that virtual particle pairs (containing all sorts of quanta) pop in/out of existence via Mr. Heisenberg's famous principle (dE * dt > hbar/2), without any energy source. This is the quantum vacuum - the finite ground state energy in the quantized EM field. However, generally such pairs do require an energy field to become real - and in doing so remove energy from that field equivalent to their rest mass.

re. the big bang - or rather an inflationary big bang - the energy was borrowed from a scalar field that by a chance fluctuation got hung up in a false vacuum state (i.e., not the 'ground state', but an 'excited state'). In this case, the energy required to be borrowed from the vacuum amounts to about ~2 billion Joules (about the same amount of chemical energy in a tank of gasoline). Several good books out there; try Brian Greene's Fabric of the Cosmos.

Spaceman Spiff
2007-Nov-09, 01:18 AM
And by the way - physicists create particles out of the vacuum every day in their particle colliders. The KE of the collision provides the requisite energy to create matter and anti-matter that was never there before, except as virtual particle pairs in the quantum vacuum.

Fraunkensteen
2007-Nov-09, 03:28 AM
Quantum Theory does not say "something comes from nothing", but it does leave an apparent "distasteful" situation hanging there begging for resolution. String Theory does solve this sticky concept. Matter spends time in the Sub-Planck-sized extra 6 dimensions in one of many curled up Yao spaces in the fabric of space-time, and then appear in the flattened out X, Y, Z, / Time dimensions in which we spend our lives, and we suddenly observe them. It's just an illusion, this idea of matter popping up out of nowhere. The matter was always there, only in dimensions we can not yet observe. We can never directly observe sub-Planck distances, but as with other things, we can observe predicted results of events in these spaces and dimensions

Blue Fire
2007-Nov-09, 04:18 AM
Quantum Theory does not say "something comes from nothing", but it does leave an apparent "distasteful" situation hanging there begging for resolution.As has been mentioned before, the vacuum energy is the "nothing".

String Theory does solve this sticky concept. Matter spends time in the Sub-Planck-sized extra 6 dimensionsFirst, String Theory says that strings are planck sized, so you couldn't have SUB-Planck sized matter. Further, the Planck length would be the lower limit of a space dimension - the smallest chunk of space would be a planck length. Second, M-Theory, which ties together the five string theories, uses 7 (not 6) extra space dimensions.

in one of many curled up Yao spacesThat would Calabi-Yau spaces.

in the fabric of space-time, and then appear in the flattened out X, Y, Z, / Time dimensions in which we spend our lives, and we suddenly observe them. It's just an illusion, this idea of matter popping up out of nowhere. The matter was always there, only in dimensions we can not yet observe. We can never directly observe sub-Planck distances, but as with other things, we can observe predicted results of events in these spaces and dimensionsI'm assuming this is your own particular opinion and not a matter of the predictions of string/superstring/M-Theory which to my knowlege says no such thing regarding the "illusion" of matter popping out of nowhere. I believe that Matter, according to string theory, in any of the extra curled up dimensions would still be detectable and would exert effects like mass and gravity in our own 3 large dimensions since those extra curled up dimensions would have to exist within the 3 large ones, not separate from them. [Every time you move your finger, your finger traverses continually through all the extra curled up dimensions] Also according to string theory, we could never observe sub-planck distances since "distance" (as a measure of space) would cease to have meaning in much the same way as "sub-letter" would have no meaning when considering the basic constituents of language: paragraphs are composed of sentences, sentences are composed of words, words are composed of letters of the alphabet, letters are composed of ???? Ya just can't go any further since letters aren't made up of anything - they are the basic constituents, period.

Tim Thompson
2007-Nov-09, 05:29 AM
It has been said on a non-science forum that ...
as for your argument that something cannot come out of nothing - Quantum Field theory disproves thatIs this correct?
That depends on what you mean by "nothing". Vacuum fluctuations are fluctuations of the quantum field that quantum field theory is named after. I submit that "nothing" and "quantum field" are not synonymous. If one chooses to define the quantum field as "nothing", then indeed the virtual particles come from "nothing". But i don't think much of that way of thinking.


I am assuming that we have moved on from the Big Bang to inflationary theory which Fraser and Pamela covered on Astronomy Cast.
As already mentioned, inflationary theory is a subset of Big Bang cosmology.

Spaceman Spiff
2007-Nov-09, 03:34 PM
Quantum Theory does not say "something comes from nothing", but it does leave an apparent "distasteful" situation hanging there begging for resolution. String Theory does solve this sticky concept. Matter spends time in the Sub-Planck-sized extra 6 dimensions in one of many curled up Yao spaces in the fabric of space-time, and then appear in the flattened out X, Y, Z, / Time dimensions in which we spend our lives, and we suddenly observe them. It's just an illusion, this idea of matter popping up out of nowhere. The matter was always there, only in dimensions we can not yet observe. We can never directly observe sub-Planck distances, but as with other things, we can observe predicted results of events in these spaces and dimensions

Ok - but that (as corrected by Blue Fire) is an interpretation of "String Theory's" explanation of the quantum vacuum. It may be right, it may be wrong, but we don't yet know - and no plausible experiment has yet been proposed to test this model. Thus it does not enjoy the status usually associated with a "scientific theory". QFT as it now stands is a viable, fertile, and fruitful scientific theory because it makes predictions that have been tested and that can be tested.

Spaceman Spiff
2007-Nov-09, 03:42 PM
As already mentioned, inflationary theory is a subset of Big Bang cosmology.

Or it may be that the "Big Bang Theory" is a subset of "Inflationary Theory".
:)

trinitree88
2007-Nov-09, 03:57 PM
And by the way - physicists create particles out of the vacuum every day in their particle colliders. The KE of the collision provides the requisite energy to create matter and anti-matter that was never there before, except as virtual particle pairs in the quantum vacuum.

Spaceman Spiff. True...and they are created every minute of the day by our constant shower of cosmic rays. The collisions that produced particle/antiparticle pairs were first seen in cloud chambers, with the positron(anti-electron) first identified, then the anti-proton, etc. (I know you know this, I'm just elaborating for forum teaching) It is also possible that the same types of reactions seen in silver halide cosmic ray emulsions, and early cloud chambers, can equally well occur in any body part, including the central nervous system. As photoreceptors of the eye can detect a few photons of a few electron volts in energy...occasionally you may "see" things that don't exist, or have one of those spastic nerve impulses due to an incoming Gev cosmic ray or two. Fortunately the background...~ 8-12 events per minute at my lattitude and altitude is pretty light(Boston). :shifty:Pete

Kaptain K
2007-Nov-20, 01:59 AM
Fraunkensteen,

You are pushing the boundaries! Reread the rules.

Fraunkensteen
2007-Nov-20, 04:12 AM
Fraunkensteen,

You are pushing the boundaries! Reread the rules.


I know the post was cynical , but what was the main reason(s) my post was deleted?