Something from nothing

Posted on December 14, 2011

VIrtual Photons
It is an oft-quoted truism of theists in arguments with atheists that “You can’t get something from nothing.” Like many such truisms, it turns out it is not true at all.

If you happen to be moving close to the speed of light, you most certainly can indeed pull energy out of absolutely nothing. This discovery confirms – at last – a 41 year old prediction on how to pull energy from empty space and produce light.

Long ago it was established that empty space is not really empty at all, but a surging mass of particles that pop into existence and promptly remove themselves again. According to quantum mechanics, that weird but amazingly accurate theory of the very small, even a total vaccum does not have zero energy but must show fluctuations in energy around the zero level. These fluctuations show themselves as the short-lived “virtual” particles that fizz around even in empty space.

English: Photon is a particle or wave? The pho...Strange though they sound, these short-lived virtual particles – usually photons – have long been proven in experiments demonstrating the Casimir Effect in which two parallel mirrors set close together will feel a pull towards each other. This happens because the space between the mirrors limits the number of virtual photons that can appear between them while outside the gap between mirrors there is no such limitation. Since there are more photons outside the mirrors than within, the pressure of light radiation on the outside pushes the two mirrors together.

Chris Wilson and collegues at Chalmers University of Technology in Gothenburg, Sweden have now taken this well-tested experiment further and pulled photons from out of the void in a process they call the “dynamical Casimir Effect.” According to Wilson, “It was a difficult technical experiment. We were very happy when it worked.”

English: Illustration of the Casimir effect.

The effect only requires a single metal mirror, but it must move at close to the speed of light through the sea of virtual photons in the void. Because the mirror is a conductor, the electromagnetic photon particles will absorb some of the kinetic energy of the mirror. This will then be radiated away by producing pairs of real photons.

Obviously, flinging a metal mirror about at near lightspeed is a bit beyond present capabilities, so the experiment instead involved a superconducting electrical circuit with an oscillator that rapidly changed the distance an electron must travel through the circuit. The movement of the electron is determined by the location at which the circuit’s electrical field falls to zero. Controlling all of this, the team used a superconducting quantum interference device.

With this SQUID, the team changed the distance from the electron to the zero-field so fast that the electron appeared to move at a quarter the speed of light. This arrangement was enough for the circuit to emit real photons, coming in pairts, right out of the vaccum.

Full details of the experiment take a pop over to Nature at the web address on this link and read far more – and in far more detail – than can be provided here.