How a jar of Mayonnaise helped overturn our perception of reality. For hundreds of years, we assumed incorrectly that materials, such as paint and mayonnaise remained viscous due to attractive forces that exist between neutral atoms and molecules.

The long held view that properties of such solutions are determined by van der Waals forces - long-range, attractive forces that exist between neutral atoms and molecules.

In the mid twentieth century the theory that was used to explain van der Waals forces, which had been developed by Fritz London in 1932, did not adequately reflect experimental measurements.

Casimir and Polder working at the Philips Research Laboratories in Eindhoven discovered that the interaction between two neutral molecules could be better described and interpreted in terms of vacuum fluctuations eventually leading to his famous prediction of an attractive force between reflecting plates. That is:-

What happens if you take two mirrors and arrange them so that they are facing each other in empty space?

**Background**

In the days of classical mechanics the idea of a vacuum was simple. The vacuum was what remained if you emptied a container of all its particles and lowered the temperature down to absolute zero. The vacuum therefore was/is a region that is devoid of matter or put another way - a volume of space that is essentially empty of matter. It’s what comes to mind when we thought about space as we were growing up.

**Space is shockingly bizarre**

According to quantum mechanics, all fields have fluctuations. That is, at any given moment their actual value varies around a constant, mean value. Even a perfect vacuum has a fluctuating field, the mean energy of which corresponds to half the energy of a photon.

Some 30 years after Paul Dirac formulated the famous Dirac equation, which describes the behavior of fermions and which led to the prediction of the existence of antimatter (however, unable to deal with more than a single electron) Richard Feynman, and others, attempted to take the understanding of the Atom further and help develop the theory of everything.

Their theory, Quantum Electrodynamics (QED) is a far-reaching and more accurate than any previous approximations and underpins almost everything we experience in the physical world – shapes, texture, color, and how everything interacts together.

Here, empty space (a vacuum) buzzes with matter and activity. Here, energy is said to be borrowed from the future and is used in the creation of a particle and an antiparticle. These particles, in turn meet in a fraction of a second and annihilate each other. So energy is borrowed out of nowhere, turned into matter self-destruct and returns back into energy all in a fraction of a second. This is happening everywhere countless times a second.

So according to QED, the everyday matter filling our physical world, the world we see and feel is a kind of left-over from the feverish activities virtual particles get up to in the “empty” void.

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**Further reading**

M Bordag, U Mohideen and V M Mostepanenko 2001 New developments in the Casimir effect *Phys. Rep.* **353** 1 H B Chan *et al.* 2001 Nonlinear micromechanical Casimir oscillator *Phys. Rev. Lett.* **87** 211801 F Chen and U Mohideen 2002 Demonstration of the lateral Casimir force *Phys. Rev. Lett.* **88** 101801 C Genet, A Lambrecht and S Reynaud 2000 Temperature dependence of the Casimir force between metallic mirrors *Phys. Rev.* A **62** 012110 S K Lamoreaux 1997 Demonstration of the Casimir force in the 0.6 to 6 micrometer range *Phys. Rev. Lett.* **78** 5 K A Milton 2001 *The Casimir Effect: Physical Manifestations of Zero-point Energy* (World Scientific, Singapore)

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