At the subatomic level, particles interact not only with one another, but with the quantum fields inherent to space, both owing to the presence of charged sources and also to the quantum vacuum of (otherwise) empty space itself. (IQOQI/HARALD RITSCH)

Quantum Fluctuations Were Experimentally Proven Way Back In 1947

Often viewed as a theoretical, calculational tool only, the Lamb Shift proved their existence.

If you spend enough time listening to theoretical physicists, it starts to sound like there are two separate worlds that they inhabit.

1. The real, experimental-and-observational world, full of quantities and properties we can measure to high precision with a sufficient setup.
2. The theoretical world that underlies it, full of esoteric calculational tools that model reality, but can only describe it in mathematical, rather than purely physical, terms.

One of the most glaring examples of this is the idea of virtual particles. In theory, there are both the real particles that exist and can be measured in our experiments, and also the virtual particles that exist throughout all of space, including empty space (devoid of matter) and occupied (matter-containing) space. The virtual ones do not appear in our detectors, don’t collide with real particles, and cannot be directly seen. As theorists, we often caution against taking them too seriously, noting that they’re just an effective calculational tool.

But virtual particles do affect the real world in important, measurable ways, and in fact…