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What is the Casimir Effect?

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What is the Casimir Effect?

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The Casimir effect is a small attractive force which acts between two close parallel uncharged conducting plates. It is due to quantum vacuum fluctuations of the electromagnetic field. The effect was predicted by the Dutch physicist Hendrick Casimir in 1948. According to the quantum theory, the vacuum contains virtual particles which are in a continuous state of fluctuation (see physics FAQ article on virtual particles). Casimir realised that between two plates, only those virtual photons whose wavelengths fit a whole number of times into the gap should be counted when calculating the vacuum energy. The energy density decreases as the plates are moved closer which implies there is a small force drawing them together.

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The Casimir effect refers to the tiny attractive force that appears between two uncharged plates in a vacuum. This Casimir force is only measurable when the plates are extremely close together (several atomic diameters). This force was predicted in 1948 by Hendrik Casimir, a Dutch theoretical physicist. It was experimentally verified in 1958 by Marcus Spaarnay, again at Philips in Eindhoven while he was studying the properties of colloidal solutions. The recognized cause of the Casimir effect is the quantum vacuum fluctuations (zero-point fluctuations) of the electromagnetic field between the plates. The attractive force occurs because, as quantum theory indicates, even a so-called vacuum contains a multitude of virtual electromagnetic particles and anti-particles in a continuous state of fluctuation. This is known as the vacuum energy. Because the gap between the plates constrains the possible wavelengths of the virtual particle pairs, there are fewer virtual particles within the spac

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The Casimir effect is a small attractive force that acts between two close parallel uncharged conducting plates. It is due to quantum vacuum fluctuations of the electromagnetic field. The effect was predicted by the Dutch physicist Hendrick Casimir in 1948. According to the quantum theory, the vacuum contains virtual particles which are in a continuous state of fluctuation (see physics FAQ article on virtual particles). Casimir realised that between two plates, only those virtual photons whose wavelengths fit a whole number of times into the gap should be counted when calculating the vacuum energy. The energy density decreases as the plates are moved closer, which implies that there is a small force drawing them together.

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Northeastern University experimental particle physicists Stephen Reucroft and John Swain put their heads together to write the following answer. To understand the Casimir Effect, one first has to understand something about a vacuum in space as it is viewed in quantum field theory. Far from being empty, modern physics assumes that a vacuum is full of fluctuating electromagnetic waves that can never be completely eliminated, like an ocean with waves that are always present and can never be stopped. These waves come in all possible wavelengths, and their presence implies that empty space contains a certain amount of energy–an energy that we can’t tap, but that is always there. Now, if mirrors are placed facing each other in a vacuum, some of the waves will fit between them, bouncing back and forth, while others will not. As the two mirrors move closer to each other, the longer waves will no longer fit–the result being that the total amount of energy in the vacuum between the plates will

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The Casimir effect is a small attractive force which acts between two close parallel uncharged conducting plates. It is due to quantum vacuum fluctuations of the electromagnetic field. The effect was predicted by the Dutch physicist Hendrick Casimir in 1948. According to the quantum theory, the vacuum contains virtual particles which are in a continuous state of fluctuation (see physics FAQ article on virtual particles). Casimir realized that between two plates, only those virtual photons whose wavelengths fit a whole number of times into the gap should be counted when calculating the vacuum energy. The energy density decreases as the plates are moved closer which implies there is a small force. drawing them together. The Casimir force between two plates of area A separated by a distance a can be calculated to be: pix pi h-bar c F = ———– A 240 a4 where h-bar is Planck’s constant over two pi and c is the speed of light. The tiny force was measured in 1996 by Steven Lamoreaux. His

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