Monday, 23 July 2018

newtonian gravity - Can helium disappear from Earth?


Helium is lighter than air, so it should fly off from Earth. Is it possible that in the future we will run out helium?



Answer



Yes, helium can leave the Earth, and yes, we will run out of helium, but because of different reasons.


When you buy a helium balloon and its contents get released, this helium goes into the atmosphere. It isn't gone, and it could in principle be purified out of normal air. However, the total amount of helium in the atmosphere is so small it is technologically not feasible to reclaim it. At some point the technology might be developed, but it is unlikely to be economical.


On top of that, helium does also escape from the atmosphere. Since it is so light, it drifts naturally to the upper layers, and there it is easily torn away by the solar wind. However, this process will occur on geological timescales, unless we were to waste so much helium that the total atmospheric content changed appreciably. Keep in mind, though, that even if the helium doesn't leave Earth it is lost to us once it's diluted in the atmosphere.



So: yes, we will run out, and yes, it will make everything awful. And yes, you should cringe when you see helium balloons at a childrens' party.


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