Articles

Force from Nothing ?

In Uncategorized on June 6, 2010 by Sukrit

What happens if you take two mirrors and arrange them facing eachother in empty space ? You first reaction would be nothing ofcourse. But what if i told you that those 2 mirrors would attract eachother. Sound crazy doesn’t it ? Guys from MIT just proved it experimentally. This effect being another manifestation of vacuum energy is called the Casimir Effect.

Where does this force come from ? Even though the idea of the Casimir force seems very counterintuitive it is fairly well understood. This lack of understanding stems from our classical notion of vacuum thinking of it as empty space. However as i have explained in other articles the vacuum is teeming with fields and particles flipping in and out of existence. This imparts a certain level of energy to the vacuum called vacuum or zero point energy. With this in mind the effect is easily explained.

An important physical quantity when discussing the Casimir force is the “field radiation pressure”. Every field – even the vacuum field – carries energy. As all electromagnetic fields can propagate in space they also exert pressure on surfaces, just as a flowing river pushes on a floodgate. This radiation pressure increases with the energy – and hence the frequency – of the electromagnetic field. At a cavity-resonance frequency the radiation pressure inside the cavity is stronger than outside and the mirrors are therefore pushed apart. Out of resonance, in contrast, the radiation pressure inside the cavity is smaller than outside and the mirrors are drawn towards each other.It turns out that, on balance, the attractive components have a slightly stronger impact than the repulsive one and the mirrors attract one another: Casimir Force.

Casimir force is a force from nothing really. Its just a manifestation of vacuum. The recent renewal of interest in Casimir forces comes primarily from 2 areas Nanoscience and Exotic Theoretical physics. At distances below a micrometre the Casimir force becomes the strongest force between two neutral objects. Indeed at separations of 10 nm – about a hundred times the typical size of an atom – the Casimir effect produces the equivalent of 1 atmosphere of pressure.

The new and exotic theories of physics prophesizing 10-11 dimensions of space predict that the effects of gravity would be different from those described by general relativity at the smallest scale. Precise measurement of Casimir force can help strengthen this claim.

Sukrit

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