What is the closest to absolute zero that has ever been reached?. What would happen to a substance if it were cooled to absolute zero?
Answer 1:
Absolute zero is defined as zero degrees Kelvin. The closest recorded temperature to absolute zero that I could find is 0.0001K, for helium gas.
Your question about what would happen to an object cooled to absolute zero is a great one! All molecules are constantly in motion (the bonds between atoms are vibrating and changing shape). The speed of this motion is dependent on the temperature of the molecule. As you can probably guess, motion is faster at higher temperatures. Changes in molecule motion with temperature are responsible for phase changes. Water vaporizes at high temperatures because as the water molecules move faster they bump into one another more often, pushing each other away and taking up more and more space, eventually forming a gas (steam). Water freezes at low temperatures because as the water molecules slow down they coalesce, or come together like pieces in a puzzle to form a crystal- like matrix. (Why is ice LESS dense than water, then? If the molecules are moving slower, they should be closer together, right? Ice is less dense than water -- it floats -- because air becomes trapped into the matrix as the water molecules come together.)
Even when water freezes, the molecules are still vibrating. Only at absolute zero do molecules stop moving completely. What sort of phase change would this cause? According to Einstein, who based his work on an Indian physicist Satyendra Nath Bose, this would result in a completely new form of matter.
Albert Einstein speculated that when molecules stop moving, the atoms would fall together and merge into one atom. The individual atoms (oxygen and hydrogen, in the case of water) would loose their identities and form what Einstein called a "superatom", or what we now call a Bose-Einstein Condensate.
Last year, Carl E. Wieman at the University of Colorado in Boulder won the Nobel prise for his work on Bose-Einstein Condensates. To read more about Wieman's work, go to
http://www.news.cornell.edu/Chronicle/02/10.24.02/ Wieman
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