Image: Wikimedia Commons/Emok, MissMJ

February 12, 2013

Something from Nothing? A Vacuum Can Yield Flashes of Light

“Virtual particles” can become real photons–under the right conditions

By Charles Q. Choi

A vacuum might seem like empty space, but scientists have discovered a new way to seemingly get something from that nothingness, such as light. And the finding could ultimately help scientists build incredibly powerful quantum computers or shed light on the earliest moments in the universe’s history.

Quantum physics explains that there are limits to how precisely one can know the properties of the most basic units of matter—for instance, one can never absolutely know a particle’s position and momentum at the same time. One bizarre consequence of this uncertainty is that a vacuum is never completely empty, but instead buzzes with so-called “virtual particles” that constantly wink into and out of existence.

These virtual particles often appear in pairs that near-instantaneously cancel themselves out. Still, before they vanish, they can have very real effects on their surroundings. For instance, photons—packets of light—can pop in and out of a vacuum. When two mirrors are placed facing each other in a vacuum, more virtual photons can exist around the outside of the mirrors than between them, generating a seemingly mysterious force that pushes the mirrors together.

This phenomenon, predicted in 1948 by the Dutch physicist Hendrick Casimir and known as the Casimir effect, was first seen with mirrors held still . Researchers also predicted a dynamical Casimir effect that can result when mirrors are moved, or objects otherwise undergo change. Now quantum physicist Pasi Lähteenmäki at Aalto University in Finland and his colleagues reveal that by varying the speed at which light can travel, they can make light appear from nothing.

Read more: Something from Nothing? A Vacuum Can Yield Flashes of Light: Scientific American.

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