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# How do particles pop in and out of existence?

What is the mechanism, the reason, the math? How can something just appear into...another something? Could a building just appear downtown? Could a person just appear into your home or workplace?

### 7 Answers

- 1 month ago
The most basic fact of existence is the uncertainty principle. A quantity of energy, multiplied by a quantity of time, must be greater than Planck's reduced constant (a very small number) in order to engage with causation. As a result of that fact, the vacuum state isn't entirely empty. It contains uncaused energy fluctuations having magnitudes that follow some sort of distribution: probably a Planck distribution. Some of them contain enough energy to form conjugate pairs of elementary particles, such as an electron and a positron.

There's some speculation that this mechanism provides for the genesis of universes, when, upon an extremely rare occasion, a fluctuation of energy in vacuum has a magnitude that exceeds the Planck energy, resulting in a quantum black hole that is forbidden by conservation laws to decay by Hawking radiation. Upon reaching the time limit imposed by the uncertainty principle, the quantum black hole detaches from our universe and forms a trivial manifold of one Planck volume. This again violates the uncertainty principle, and the result is a rapid pluralization of quantum states: i.e. the inflation that starts off a new universe.

- Jeffrey KLv 72 months ago
Quantum fields can not be exactly zero in empty space due to Heisenberg Uncertainty Principle. As the fields fluctuate randomly, virtual particles appear and disappear. If they are charged, they come in pairs with their antiparticle.

The probability of something appearing decreases with it's mass. So a building or person is very unlikely to appear.

- 2 months ago
The math and the concept is the easy bit. Over a sufficiently short timeframe there is sufficient uncertainty in the energy to account for a particle, since each particle has mass, and mass has an energy equivalence. Therefore a particle can indeed pop out of "nothing" for a timespan that depends on it's mass. The shorter the timeframe the more massive the particle can be.

Under the right circumstances, there may be a non-zero probability of the particle interacting with it's surroundings during the short time of it's existence. During that time, it may accumulate sufficient energy to promote it to a "real" particle, at the expense of the energy in it's surroundings. Note that conservation of quantum numbers is always required. So for example a positive "real" particle will appear along with a negative one. We see a clear example of this during pair creation where an electron and a positron may pop into existence under the appropriate circumstances. The required energy to promote the pair to "real" particles generally comes from a photon.

All this is very nicely described by the mathematics of quantum mechanics, which has been well tested over the century or so since it was developed.

The difficult part is explaining how it happens and describing the exact mechanism by which it happens. I feel confident that you can safely assume that we can never know the answers to these questions. We would need to peer deep into the quantum world on incredibly short timeframes and over incredibly short distances to do so. The energy is simply not available for us to do this, and the finances are not available even on a global scale to allow us to build the necessary instrumentation. Note that the LHC cost around ten billion dollars to build and even it can't answer these questions. It would require a budget many times that of the LHC to even have the slimmest hope of finding the answer. Are you going to pay for it? Nope, and neither will the world.

So be happy that we can explain exactly what happens, and treat the why and how as examples of unanswerable questions.

- Anonymous2 months ago
From this 3D plane to another, back-and-forth.

Did I just blow your mind?

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- ?Lv 72 months ago
Nobody knows the answer to that yet.

Where it all comes from to begin with, is still the great unknown.

- nebLv 72 months ago
The math is straightforward - the energy-time version of the uncertainty principle is about as simple an equation as you can find. It basically says that the uncertainty in energy is inversely proportional to the amount of time that the change in energy can exist.

So, what the hell does really mean? It means that all fields can exist at a classically zero vacuum energy. But because of the uncertainty principle, the classically zero energy cannot remain at zero quantum mechanically, because remaining at zero energy for two instants of time would violate the uncertainty principle. So, a quantum vacuum must fluctuate its energy - the greater the energy, the shorter the time that it can exist as a fluctuation. The energy that fluctuates into existence are pairs of virtual particles. Large amounts of energy (e.g a building or person) would have an infinitesimal probability of existing for an infinitesimal period of time.

Now, the hard part. Do virtual particles really exist? Many physicists would say no, that virtual particles are simply artifacts of the perturbative solutions required to approximate the difficult equations of quantum mechanics. Of course, then they would turn around and use virtual particles as metaphors in papers they write.

There seems to be evidence they exist, for example, the Casimir effect. The basic idea with the Casimir effect is that virtual particles have constrained wavelengths between two closely spaced metal plates. Since their wavelengths outside the plates are unconstrained, there should be a net pressure pushing the plates together due to a higher virtual energy outside the plates than inside the plates. This has been verified.

My personal ambivalent opinion is that we don’t have a good grasp on quantum reality so I’m open to the existence of virtual particles ( but not virtual humans!)