Virtual Particles and Fluctuating Mass

Virtual particles are constantly popping in and out of existence. I heard that we have virtual particles in us so why doesn't our mass keep fluctuating?
- Zahra (age 18)
United States of America

Physicists often say things like "Virtual particles are constantly popping in and out of existence" but it isn't true. The field of the virtual particles doesn't actual fluctuate in time unless something else (a real particel) comes along to interact with it. The same basic argument applies to a simple harmonic oscillator- a mass on a spring. Quantum mechanics says that the position of the mass is spread out, but it would be wrong to say that it's fluctuating around. The position spread is fixed unless something comes along and interacts with it.

Things generally don't have a precise value of mass (i.e. energy). Rather, they have a small spread of values. But that spread isn't changing. A very precise "measurement", a type of interaction with the measurement apparatus, can make the mass take on a narrower spread, somewhere in the range of the broader pre-measurement range. The new narrow spread won't change without a new interaction. Repeating the same measurement interaction will give the same result again.

Mike W.

(published on 12/28/2016)