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What are virtual particles? And...

Outplayz
Posts: 1,274
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12/28/2015 1:14:49 AM
Posted: 11 months ago
Don't they still have causation bc of their interaction with other particles?

I am asking this bc in the end of Stephen Hawking's documentary (Into the Universe) he uses that as an example of something that can come into existence without a cause.

I am also wondering... it is energy, but if i am reading it right, it can turn into matter. Again, is this what Stephen Hawking is referring to; that it's a particle of energy that comes out of nothing and can turn into physical matter?

I've been trying to find good sources to read about it, but the ones i have, make it sound like it is still from interactions of particles... Then again i am a layman, so it would be nice to hear about it if someone knows a thing or two more.
tejretics
Posts: 6,091
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1/4/2016 12:15:34 PM
Posted: 11 months ago
A virtual particle is a particle that emerges from a quantum fluctuation of energy in the quantum vacuum. The "uncaused" aspect of them comes from a hypothesis that Heisenberg's uncertainty principle allows for some energy to be borrowed ex nihilo, such that the time in which it is borrowed is lower than Planck time. But the uncertainty principle doesn't entail it, actually. The conservation of energy is fundamental, even in quantum mechanics. In fact, a vacuum state has multiple fluctuations that ensure it isn't actually an "absolute vacuum," and is what physicists call a false vacuum. The Third Law of Thermodynamics does not allow an absolute vacuum state within a closed system.
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Sidewalker
Posts: 3,713
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1/5/2016 7:27:56 PM
Posted: 11 months ago
At 12/28/2015 1:14:49 AM, Outplayz wrote:
Don't they still have causation bc of their interaction with other particles?

Quantum physics can't be explained, at least not logically, but I'm going to try anyway.

Virtual particles come in pairs, a particle and its anti-particle pop into existence in empty space and almost immediately annihilate each other, so it is fair to say that they are interacting, but that is not the cause of their existence.

I am asking this bc in the end of Stephen Hawking's documentary (Into the Universe) he uses that as an example of something that can come into existence without a cause.

Here"s the thing, according to the Standard Model it isn"t a deterministic system, it"s probabilistic, it is a kind of triangulation in which complementary pairs of imperfect concepts " wave/particle, position/momentum, value of a field/its rate of change " are used to home in, as best we can, on phenomena beyond the reach of human ability to directly observe. Because virtual particles result from the probabilistic nature of quantum reality, they are completely unpredictable and consequently, they can be considered to "come into existence without a cause". They certainly interact once they pop into existence, but that interaction isn"t what causes them.

I am also wondering... it is energy, but if i am reading it right, it can turn into matter. Again, is this what Stephen Hawking is referring to; that it's a particle of energy that comes out of nothing and can turn into physical matter?

According to the Special Theory of Relativity matter and energy are two aspects of one and the same fundamental reality, the formula that tells us that is the famous E=MC squared. In quantum physics matter and energy have complementary aspects that can be represented as particles or waves, historically, matter was particles and energy was waves, particle and wave are mutually exclusive properties and consequently, the mathematics of particles and waves are very different. So yes, you could say matter is energy and energy is matter, and it is fair to call it a "particle of energy that can turn into matter". So what Hawking is referring to is the fact that virtual particles appear and disappear in a completely random manner, and consequently, they don"t appear to have a specific cause.

But it isn"t correct to say it"s a particle "that comes out of nothing". The zero energy state of empty space is a physical phenomenon that is full of forces that balance each other exactly, it is a very dynamic and constantly changing state and it just isn"t accurate to consider the complex counterbalancing of positive and negative forces to be equivalent to "nothing". Virtual particles are a disturbance in the energy field of empty space, "perturbation theory" tries to explain their cause, but it doesn"t really.

Theoretically, the Heisenberg Uncertainty Principle doesn"t just apply to the position and velocity of a particle, it also applies to the value and rate of change of a field, and it says the more accurately you know one, the less accurately you can know the other. This isn"t a function of our ability to measure by the way; it is a fundamental feature of reality according to the Standard Model. Consequently, the Heisenberg Uncertainty Principle tells us there is no such thing as an empty space because for there to be a truly empty space the value of the field and its rate of change would both need to be exactly zero; and the standard model, specifically Heisenberg"s Uncertainty Principle says that it can"t be exactly zero. That is the reasoning as to why virtual particles must come into existence in empty space, it isn"t actually considered the cause though, so many consider them uncaused.

Keep in mind, nothing in quantum physics is directly observed, most everything we say we "know" is a function of the mathematics, and it is then supported by secondary or inferred evidence. You asked about the equivalence of matter and energy, it is the particle/wave complementarity inherent in quantum physics and the associated mathematics of the Heisenberg Uncertainty Principle that gives us virtual particles. They come out of the mathematical intersection of the energy "wave" and the matter "particle, specifically the associated Fourier transform which refers to both the frequency domain representation and the mathematical operation that associates the frequency domain representation to a function of time. Functions that are localized in the time domain have Fourier transforms that are spread out across the frequency domain and vice versa, the associated mathematics tells us that there isn"t an exact equivalence in the mathematical transformation, as one side of the equation approaches certainty, the other side becomes less certain, and that is the mathematical essence of the Uncertainty Principle.

So, if the mathematics accurately describes the system, and the Standard Model says it does, then the Uncertainty Principle is a feature of reality and virtual particles must occur in empty space. The secondary or inferred evidence is that this mathematical prediction is explanatory of things like the Casimir Effect, Vacuum Polarization, and the Coulomb Force.

Hopefully this makes it easier rather than harder to understand, I think it"s important to understand where the concepts come from, especially that they aren"t observed phenomena, they come out of the mathematics of the Standard Model. A lot of things about quantum physics that seem so strange are strange because of the mathematical incompatibility of wave and particle and the fundamental conflict between probabilistic and deterministic mathematics.

If you have further questions I"ll be glad to try to clarify, just ask.

I've been trying to find good sources to read about it, but the ones i have, make it sound like it is still from interactions of particles... Then again i am a layman, so it would be nice to hear about it if someone knows a thing or two more.

I know a thing or two, probably just enough to confuse the hell out of you, which is good because, as Richard Feynman said, "If you think you understand quantum mechanics, you don't understand quantum mechanics", therefore if you are still confused, that means you understand :)
"It is one of the commonest of mistakes to consider that the limit of our power of perception is also the limit of all there is to perceive." " C. W. Leadbeater