BEC - What is it and where did the idea come from?
|When I make the temperature low, they are all in the bottom. What does that mean?|
|The atoms piling up in the bottom is what we call Bose-Einstein condensation, and it happens because this demonstration is built to match Einstein's equations. "What it really means" is probably a question Einstein should have asked, but did not. He did not realize how weird a material would be with all the atoms in one level like this. It means that all the atoms are absolutely identical. There is no possible measurement that can tell them apart.|
|But I can just look and see the different black spots that represent different atoms. How can they be identical?|
|Good point. You have just picked out a mistake in this demonstration. Really, an atom in the lowest energy level is spread out a little, so it looks like a very small fuzzy ball. When you have lots of atoms in the same state, all these fuzzy balls lie exactly on top of each other.|
|Now I can't tell one atom from another; they are all in the same place. But I know that atoms don't really do that. I have tables, chairs, and all these other objects that have their shapes because their atoms are arranged in different places.|
|Now you can see why it was so long before people understood what BEC really meant. Atoms really can all be in the same place like this, but it goes against everything we see around us. It is only at the special incredibly low temperatures needed for BEC that they lose their individual identities and coalesce into a single blob. Some people have called this a "super atom" for just that reason.|
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