What is a Virtual Particle?

When you combine quantum mechanics and relativity, it tells us that for every particle that exists in nature, it turns out there is a possibility, in fact, a likelihood, that out of empty space, particle/anti-particle pairs will be created spontaneously and they’ll exist for a little while and then they’ll disappear.  They’ll disappear in a time scale so short you can’t measure them.  And in fact, it’s related to something called the Heisenberg Uncertainty Principle in quantum mechanics.

If they exist for a time so short that the Heisenberg Uncertainty Principle says there’s no way you can really know they were there then they don’t violate anything.  Quantum mechanics is kind of as I often say like the White House or corporate America, if you can’t measure it, anything goes.  And so these virtual particles are really particles that simply are created from empty space, particle anti-particle pairs that exist for a time-scale so short that you can’t observe them by any measurement, but they’re there.

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