# Bose–Einstein condensate

state of matter of a dilute gas of bosons cooled to temperatures very near absolute zero
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Bose–Einstein condensate (BEC) is what happens to a dilute gas when it is made very cold, near absolute zero (0 K which equals −273 °C or −459.67 °F). It forms when the particles that make it up have very low energy. Only bosons can make a Bose–Einstein condensate. The gas has extremely low density, about one-hundred-thousandth the density of normal air.

A Bose–Einstein condensate is a change of state. When matter is in the BEC state it has zero viscosity. Superfluidity and superconductivity are both closely connected with the BEC state of matter.

## Theory

Particles have energy. They can have a lot of energy and bounce wildly like in gases; have less energy and flow like a liquid; or have even less energy like a solid. If you take enough of the particle's energy away you get to the tiniest or the smallest amount of energy possible. This is a Bose–Einstein condensate. This makes all of the particles exactly the same and instead of bouncing around randomly in all different directions, they all bounce up and down in exactly the same way, forming something called a 'giant matter wave'.

## History

The Bose-Einstein Condensate was first suggested by Satyendra Nath Bose and Albert Einstein in 1924–25. Seventy years later, its existence was proved.[1] Eric Cornell and Carl Wieman made the first Bose–Einstein condensate in 1995 at the University of Colorado. Cornell, Wieman,and Wolfgang Ketterle at MIT were then given the 2001 Nobel Prize in Physics.[2]

## Experiments

Usually to get anything cold enough to make a Bose–Einstein condensate you have to first trap the boson using magnets and then, by bouncing lasers off them, take all of their energy away (Laser cooling). This still does not get things quite cold enough. Some of the particles will still be bouncing around a lot, and only some will be lying down nicely. The magnetic field is then slowly lowered bit by bit to let the faster bouncing particles out. This just leaves us with the coldest and slowest atoms inside.[3]

## References

1. Levi, Barbara Goss 2001. Cornell, Ketterle, and Wieman Share Nobel Prize for Bose–Einstein Condensates. Physics Today online. [1]
2. http://www.nist.gov/public_affairs/releases/BEC_background.htm
3. "Bose-Einstein Condensate". YouTube. Retrieved October 21, 2011.