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Asked by anawesomepersonlol to Rob, Claire on 25 Jun 2013.
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Robert Woolfson answered on 25 Jun 2013:
Helium is a gas that we can filter from mines underground. It’s fairly rare, but is incredibly useful for getting things very cold. The coldest temperature possible is called 0 Kelvin or absolute zero, which is -273 Celsius. Given water freezes at 0 Celsius, that’s extremely cold.
Helium, when cooled to a liquid, can be used to cool other things down. Most helium can take things down to about 4 Kelvin, which is pretty cold. However, there is an extremely rare part of helium, Helium-3. This is ridiculously expensive (about £2000 per litre), but when used with normal helium can cool things down to 0.002 Kelvin, or within a fraction of absolute zero.
We need things extremely cold when we study some areas of quantum mechanics in the real world because any heat basically scrambles the effect.
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Claire Lee answered on 25 Jun 2013:
One of the very useful applications for liquid helium is its use to cool the magnets in MRI machines – these are the machines that hospitals have to get fantastic pictures of your insides, better than an xray. The magnets need to be superconducting to get to the magnetic field they need. Its the same for the LHC – we also use liquid helium to cool the magnets that bend the protons around the ring. We need something like 96 tonnes of liquid helium for that!
The world’s supply of helium is running low, though, and soon we’ll need to find it elsewhere. I think the moon is said to have more helium than earth – maybe we better go mine the moon!
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