Helium, and similar
Discussion
Most of it would over a long enough time scale, drift off that is.
For it to escape the earth it needs a velocity greater than escape velocity, average thermal velocity is sqrt(3kT/m) where k is Boltzmann's constant and m the molecular mass. Room temperature, this means helium is whizzing around at ~1km/sec which is much less than the 11km/sec escape velocity. Even up at ~40 miles high in the atmosphere, where it'll be much hotter, it's average thermal velocity is still too low.
The key word in this is 'average' though. The velocities follow a Maxwell-Boltzman distribution so there are a bunch of molecules in the high velocity 'tail' which do have a high enough velocity. This is why there's a slow 'leak' of helium over time out of the atmosphere. Countering this (a bit) is more helium being produced via radioactive decay.
For it to escape the earth it needs a velocity greater than escape velocity, average thermal velocity is sqrt(3kT/m) where k is Boltzmann's constant and m the molecular mass. Room temperature, this means helium is whizzing around at ~1km/sec which is much less than the 11km/sec escape velocity. Even up at ~40 miles high in the atmosphere, where it'll be much hotter, it's average thermal velocity is still too low.
The key word in this is 'average' though. The velocities follow a Maxwell-Boltzman distribution so there are a bunch of molecules in the high velocity 'tail' which do have a high enough velocity. This is why there's a slow 'leak' of helium over time out of the atmosphere. Countering this (a bit) is more helium being produced via radioactive decay.
Edited by hairykrishna on Tuesday 16th October 20:12
e600 said:
Why is there any helium left, why hasn't it all drifted off to space? Discuss.
Commercial helium is a byproduct of natural gas extraction - it forms constantly (but slowly) in gas fields via radioactive decay. So in times of lower gas use (recessions), available helium also drops. There has also been a number of planned and unplanned shutdowns at processing plants this year, which has exacerbated the problem. But really the main reason for difficulties is because the US stockpiled helium for many years (for use as a lifting gas) and then started selling it off way below the market value. This stock is now running out, and so prices and useage rate will have to correct.Maybe, by the time it is due to 'run out' we will have nuclear fusion plants sorted, then it will be a waste product hence a new leftist organisation called the "Helium Trust" will insist on a new helium tax of 80p in the pound, helium credits and have adverts on television with a helium monster causing global warming cooling high-pitched talking and so on and so forth... 
wattsie_2004 said:
Maybe, by the time it is due to 'run out' we will have nuclear fusion plants sorted, then it will be a waste product hence a new leftist organisation called the "Helium Trust" will insist on a new helium tax of 80p in the pound, helium credits and have adverts on television with a helium monster causing global warming cooling high-pitched talking and so on and so forth...
Well at least we can laugh about that one.This was on Qi i think or it was mentioned,I think they said it would all run out by 2046(around then can't remember exact date).as was said the us gave it away cheap as its costly to store then realised they should keep it.once its gone I wonder what they'll use for the mmi scanners as they use helium to cool it down I think they said.
As a diver I can tell you helium is getting very expensive, party ballon wasters irritate me, I am being priced out of diving with it yet you can use ltrs of the stuff for stupid party ballons! Surely sooner or later it will become a restricted item to provide stocks for medical, military and industrial use only.
Sadly the next least narcotic gases are not as friendly to breath as Helium :-(
Sadly the next least narcotic gases are not as friendly to breath as Helium :-(
It is fantastically useful stuff. I've been helium leak testing all week.
As the price goes up, as the yanks cease to flood the market, the problem will solve itself I think. At the moment there's no real incentive for making MRI's etc all that 'helium efficient' in that it doesn't matter if you lose some because it's so cheap. This will change - much more recycling rather than 'never mind, just top it up'. It's already happened with Helium-3 in some applications after US homeland security essentially bought it all to make their neutron detectors with and caused the price to go through the roof.
As the price goes up, as the yanks cease to flood the market, the problem will solve itself I think. At the moment there's no real incentive for making MRI's etc all that 'helium efficient' in that it doesn't matter if you lose some because it's so cheap. This will change - much more recycling rather than 'never mind, just top it up'. It's already happened with Helium-3 in some applications after US homeland security essentially bought it all to make their neutron detectors with and caused the price to go through the roof.
Gene Vincent said:
There is no shortage of helium, it is just that journalists are thick and can't grasp even the simplest of realities.
There was a minor hiccup in '05/06 due to a major converter complex going off stream due to corrosion.
The rest is just hype to put up the price and boost profits.
errr...There was a minor hiccup in '05/06 due to a major converter complex going off stream due to corrosion.
The rest is just hype to put up the price and boost profits.
the US has a large stockpile but is selling it off well below its true market value because the law there says they have to get rid of their stockpile.
it's recovered mostly from oil wells I think.
helium doesn't stay in the atmosphere, its produced slowly, and we're using it up.
hopefully we'll get those high temp superconductors in time to save us any bother but you never know...
http://www.bbc.co.uk/programmes/b01j6t0n
listen from 21:45 to the end, my friend at Culham is explaining the actual situation.
listen from 21:45 to the end, my friend at Culham is explaining the actual situation.
Gassing Station | Science! | Top of Page | What's New | My Stuff