Q: Do virtual particles violate the laws that energy can be created or destroyed? Have virtual particles ever been observed? In any other instance can energy ever be destroyed or created?

Posted on June 7, 2010 by The Physicist

Physicist: Almost. There’s a version of the uncertainty principle that says that the amount of energy and the amount of time involved in an event can’t both be certain.  You can think of this version of the uncertainty principle as the universe making clerical errors.
Generally a virtual particle will pop into existence, do whatever it does, and then pop out before the universe catches it.
For example: the gluon (pronounced “glue on”) is the virtual particle that holds the nucleus together. But the time that it can exist is so short that it can’t even get from one side of the nucleus to the other. This is a big part of why big atoms fall apart (uranium, plutonium,…).
Unfortunately, only “real” particles can be measured. Virtual particles have to be inferred. We can observe gluons by introducing enough energy that they don’t have to rely on clerical errors to exist (I’m talking about particle accelerators here).  But virtual particles can only be detected in terms of the effects they have on other particles (like holding an atom together).
Aside from the uncertainty principle, everything obeys conservation of energy. And even with the uncertainty principle the extra energy gets ironed out faster than you can blink.

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6 Responses to Q: Do virtual particles violate the laws that energy can be created or destroyed? Have virtual particles ever been observed? In any other instance can energy ever be destroyed or created?

  1. ToadLicker says:
    January 30, 2012 at 11:50 am

    If energy is conserved where dose the energy from photon redshift due to space expansion go?

  2. Aerandir says:
    July 5, 2012 at 5:37 am

    So is it fair to say that on very short time scales the law of conservation of energy gets sort of ommited?

  3. Error: Unable to create directory uploads/2024/11. Is its parent directory writable by the server? The Physicist says:
    July 5, 2012 at 12:46 pm

    It gets “fuzzy”.

  4. Xerenarcy says:
    April 3, 2014 at 10:53 pm

    @toadlicker
    according to current theory it doesn’t disappear. a simple way to think of it: because the space between the you and the incoming photon is growing, as well as yourself (since you exist as a volume of space, which too must expand with space), the photon would appear to cover only half as much distance per time as it should. to state it another way, if space has doubled, you would not be able to measure it with a physical ruler, for the ruler too has doubled in length; the photon would appear to then travel half as fast as it should.

    because velocity is relative, it is equivalent to stating: i am looking at a photon while moving away from the source at c/2, by the time the photon arrives. as we know, light travels at c in all reference frames, and receding reference frames (looking at something getting farther from you) are redshifted.

    in saying that i have reservations about whether space actually expands vs how light behaves over large distances / timescales.

    @aerandir
    i would say that energy still must be conserved even with the uncertainty relations, but it can manifest in very counter-intuitive ways. for example, the range of the fundamental forces depends on the lifetime of their relevant virtual force carrier particles, which can ‘exist’ for a duration inversely proportional to their mass before violating uncertainty limits (hence defining the distance at which the virtual force carrier ‘source’ can affect neighboring objects / particles).

    that is not to say that energy is violated by particles that spontaneously come into existence, as you could argue that they should appear in pairs. eg, you won’t see a virtual electron without a virtual positron manifesting somewhere else – so long as the universe maintains zero-sum on conserved properties you can have as many particles involved as you like (and indeed this forms part of the problem of numerical calculations in QM, often giving diverging infinite sums until renormalization steps in).

  5. Andrew Peterson says:
    November 26, 2016 at 5:50 pm

    We tend to conservation of laws, because we hanker after the false promise of certainty. Lee Smolin nicely argues that our laws of Physics are evolving as our universe changes, so let’s let go of the concept of universal laws. Quantum mechanics has given us vacuum energy and virtual particles, and the Casimir effect has given us photons that can be made to pop into existence out of the vacuum. So we may reasonably predict that the conservation of energy is not absolute. So what? Far more important is the concept that different forms of energy are inter convertible, though not absolutely.

  6. Benjamin Grimes says:
    October 2, 2019 at 7:20 pm

    That seems to imply that from the perspective of “The universe is a simulation”, virtual particles may exist between the tick-times of the simulation — i.e. the simulation never sees the conservation of energy violation because it applies it (and all other mechanics rules) to the simulated system once per tick. To put it another way, it would be the same as changing a variable value from an expected value, to an unexpected value and back to an expected value in the time between when the system wrote it and when it reads it again.

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