Look at space under a microscope and what do you see? Nothing. Magnify 1,000 times. Nothing. Magnify 1,000,000 times. Still nothing. Magnify 1,000,000,000 times. Absolutely nothing.
At this point, the average person would probably be satisfied with the conclusion that space is, in fact, nothing. This makes intuitive sense, after all, and besides, we're already far beyond the magnification power of real microscopes.
Quantum physicists aren't average people, however. Armed with theoretical microscopes, they keep on magnifying, gazing deeper and deeper into empty space until out of nothing, they suddenly see something.
That something is a roiling collection of virtual particles, collectively called quantum foam. According to quantum physicists, virtual particles exist briefly as fleeting fluctuations in the fabric of spacetime, like bubbles in beer foam.
"The 'bubbles' in the quantum foam are quadrillions of times smaller than atomic nuclei and last for infinitesimal fractions of a second—or in 'quantum-speak', the size of a Planck Length for a Planck Time," Eric Perlman, a Professor of Physics and Space Science at Florida Institute of Technology, says.
Something so utterly small has obviously not been directly observed. So why can we be very sure this quantum foam exists? One of the greatest pieces of evidence for it was predicted back in 1947 by Dutch physicists Hendrik Casimir and Dirk Polder. Fermilab senior experimental physicist Don Lincoln explained the so-called "Casimir Effect" for PBS:
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