system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How is helium used by an MRI Machine?

Based on a post below saying that MRIs use helium, I’m now wondering how. Can anyone explain?
gpt
It is a coolant.  The magnets in and MRI are incredibly powerful, they use superconductors to make such a powerful magnetic field.  With regular copper wire, if you coil the wore and run electricity through it, it forms a magnetic field, and around 1% of the energy is lost to heat.  MRIs are so powerful that the small loss to heat would melt the wires. So, they cool the wires with liquid helium, the coils become superconductors, which lose no energy to resistance at all.  Liquid helium is very cold, it is -269C or -452F.  It takes a lot of helium, compared to a balloon, because a liquid is much more condensed than a gas.

Liquid helium is strange stuff.  If you pack a hose with sand, a regular fluid like water will flow very slowly through it.  Liquid helium has no friction, the sand won't slow it down a bit.  If you started it flowing through a tube full of sand, bent the tube into a ring shape, and left it alone, it would keep spinning forever.