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I Still Don't Get Virtual Particles
11/01/06
I Still Don't Get Virtual Particles
Having gone back and read about virtual particles once more, I must say that they have become less, rather than more clear.
Werner Heisenberg came up with the idea that electrons repels each other via means of virtual photons. Hideki Yukawa came up with the concept of an idea of a similar exchange particle in 1935 for the glue that binds the nucleus together.
The math can be made to work, but as with so many other similar phenomena, many explanations can converge on the same answer.
The intuitiveness of particles bouncing basketballs off one another, as in how electrons repulse one another, is attractive. When you switch to attraction instead of repulsion, as would be the case with electrons attracting positrons, or electrons attracting protons, or protons attracting protons in the nucleus, the model loses a lot of its intuitive nature.
Some attempts at an explanation:
- FAQ page at University of California
- A thread on sci.physics.research
- Forum postings on electrostatic attraction
- Fun postings on Advanced Physics
There are also those who attempt alternate explanations:
- Emission-Absorption-Scattering
- At Stanford, perhaps they're just part of the quantum probability equations, and maybe they're not there at all
I've found it interesting that the question is not totally nailed down after 70-odd years. I suppose in a way, it's heartening to know there's a lot more to discover.
Virtual particles are probably something that the math can be understood as, but I would hazard a guess that they're not the real answer to why charges attract and repel.
I think it will come right back to finding an explanation for quantum mechanical wave equations. If an electron can 'interfere with itself' and land according to a probability wave, then the same driving force is likely to give probability equations where neutrons and protons hang around in a nucleus with a probability of 100% - or if less, then decay of the nucleus will happen.
If only we could understand what that was, if there is a reality underneath the probability calculations to be found. It will be a while, longer if we continue to subscribe to "shut up and calculate" :)
6 comments
Try this link:
http://thisquantumworld.com/ht/content/view/40/41/
Ooh. Graphics! How much storage space do you have on here? Hmm?
Ulrich: Hi there, Ulrich :)
Objective fuzziness doesn’t cover off the question of virtual particles, but that certainly wends its way into other questions I was going to throw up here for discussion (like “why are there such a thing as orbitals?", “why do p orbitals have the shape they do” abd “why do orbitals hybridize?"…
…but I figured two such postings in a row would make Adam’s head shake too much :)
I’ll be reviewing Penrose’s giant book at some point once I finally digest it (which I can’t possibly in its entirety - I do not have the math)
Adam: Yes, graphics! I’ve got about a gigabyte on here. Mind you, those images are about 6 Kb apiece, so it doesn’t matter too much to that quota :)
I threw together the images in Xara. I bought it; it was just really useful for prototyping the initial card game art and playing around with diagrams (as shown :). Though it’s good for putting together the card game pieces, I really wish I could automate the thing through an API of some sort, since most of the cards can be automatically generated from four images I create :) (I may just figure out whether I can consume any particular vector format it puts out and make a program to do that, though)
Hi Ritchie! I was referring to this passage:
You may have come across claims to the effect that an electron (say) is actually made up of an infinite number of particles — a “bare” electron plus an infinite swarm of “virtual” photons and “virtual” particle-antiparticle pairs, which are said to be “vacuum fluctuations” of the surrounding radiation and matter fields. This is the kind of tale spun by those who fail to heed van Kampen’s warning: “Whoever endows Ψ [the quantum-mechanical wave function] with more meaning than is needed for computing observable phenomena is responsible for the consequences.”
Ulrich - Ah, I understand now. Right near the top in a blockquote, and I entirely missed it :)
I’m of two minds on van Kampen’s warning. On the one hand, the likes of virtual particles are treated as utterly real by a great number of practitioners - when in fact as an artefact of the equation, that’s only one means to get to it. Leaving that as an absolute truth, means that be will be stuck in a surprisingly stagnant enterprises.
On the other hand, I don’t believe we will get anywhere if we just “shut up and calculate". If we never try to figure out what Ψ means, then we will be stuck in a surprisingly stagnant enterprise.
Thank goodness those aren’t the only two options :)
Besides, Heisenberg died in 1976. I think the responsibility wave that resulted is one that decoheres to a different person if you ever try to measure someone’s blame state.
There’s that and van Kampen being taken with a grain of salt, as I see you do from time to time :) -
http://koantum.wordpress.com/2006/08/13/more-van-kampen-bashing/
Hi Ritchie.
In the beginning “shut up and calculate” may have been a fruitful policy. Now it’s time to stop calculating and start thinking. The meaning of the mathematical formalism of quantum mechanics is not found by writing down another formula. Nor is transmogrifying mathematical symbols or computational devices into physical entities or processes (such as “virtual particles") the way to beat sense into quantum mechanics. The recognition that quantum mechanics is nothing but a probability calculus is the sine qua non for finding a sensible ontology. At any rate, thus says I.
