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Comment by PaulAJ | Hacker News Reader

One thing about helium: once its released to the atmosphere its gone forever. Because it is so light it not only heads upwards, the velocity of the atoms is high enough that some exceed the Earth's escape velocity and don't come down. The only helium on Earth is either in tanks or still underground.

Its a finite resource, we are using it up, and we can never make any more until we get to the outer planets.

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>>> ... we can never make any more until we get to the outer planets.

We can. It isn't easy/cheap and may never be totally practical, but it can be done for less than the costs of getting it from the outer planets.

https://en.wikipedia.org/wiki/Fusor

There are also replacements for helium. They aren't exact replacements and do come with their own issues (liquid hydrogen = fire). With effort, they can be used. Hydrogen under vacuum pressure can be made to boil at temperatures close enough to helium for most applications.

Helium can also be recycled, which today rarely happens. It is not generally collected as a gas and re-liquefied. Maybe if its availability goes down, driving its cost up, people might make efforts to recapture the helium they boil.

Most of the time when people make comments like that, they don’t actually mean “impossible” — they mean within the realm of reality. No one is going to be fusing helium in quantities high enough to run MRI machines. It would greatly add to the discussion if we didn’t have to address these red herrings.

Not how we use it now, but the total amount of helium needed to run an MRI machine (with recapture) isn't all that much. Devices like acoustic cold fingers can use a very very small amount of helium to create a steady heat pump. Currently, such devices are not integrated into MRI machines because tubs of liquid helium are cheaper, but there is no reason why we couldn't build a closed-cycle MRI machine that didn't use any net helium.

https://en.wikipedia.org/wiki/Thermoacoustic_heat_engine

https://en.wikipedia.org/wiki/Pulse_tube_refrigerator

Again, not the point of the discussion. MRI was a simple example of how we use helium today. I could have easily said party balloons. It would help any conversation you have in general to avoid nitpicking on insignificant items and keep the discussion on the main point (which, if I have to spell it out, is the quantity of helium required to do various things)

I do understand that when helium is depleted we will probably find other ways to accomplish things, but it’s still silly to be venting a gas that we KNOW has a finite amount over the lifetime of the Earth or using it for party balloons.

There are MRI machines that use nearly zero helium: https://www.medgadget.com/2018/09/philips-helium-free-mri-sy...

Large NMR facilities have started recycling their helium: Yale, Harvard, Madison, UGA.

It wasn't a red herring - the post he replied to reads: "we can never make any more until we get to the outer planets."

Of course not, not when helium is relatively cheap and plentiful. But when we're nearly out of helium, you'd better bet we'll figure it out.

I did the calculations once and the heat generated by helium production equal to use was approximately equal to the total solar radiation on the planet. Cheap and practical don't make the cut, the physics of fusing hydrogen make it impossible.

Farnsworth fusors are primarily interesting nightlights not a source of Helium. Otherwise they would quickly kill everyone in the room when you turn them on.

Even if the entire world was 100% running on fusion power we would still be short orders of magnitude from our current demand. MRI machines can switch to designs that don’t use helium, parties are simply going to have to go without long term.

Which is why I find helium balloons so damn distasteful. Probably the amount of helium used in balloons is not all that significant in reality, but helium balloons are complete vanity throwaways, so it is more of a question of principle and symbol.

No more metallic mylar balloons? Good riddance. https://www.powerprotectionresource.com/articles/439843-myla...

I have found dead, decaying Mylar balloons in nearly every park I’ve ever been to. I found one a mile off the road in panamint valley, and one in sequoia national park.

They suck.

I am a regular wanderer of the Mazatzal Wilderness, one of the most desolate areas left in thw lower 48. In 5 years and 100+ milea of rugged terrain I have found dozens of mylar balloons. Their absence will be welcomed.

Most helium in the universe was created by the Big Bang, or through stellar fusion ("helium" comes from "helios", it was discovered by spectral analysis of the Sun).[1]

Virtually all helium on Earth was formed on Earth, through radioactive decay within its interior, releasing beta particles (helium nuclei). The helum industrially sourced tends to come from natural gas extraction -- the same reservoirs which trap natural gas (methane) also trap helium fairly well.[2]

Molecular hydrogen also exceeds escape velocity. About 1/4 of the water originally present on earth has escaped to space, after being dissociated into hydrogen and oxygen.[3]

________________________________

Notes:

1. https://www.worldcat.org/title/researches-on-the-solar-spect...

2. https://geology.com/articles/helium/

3. http://sciencenordic.com/earth-has-lost-quarter-its-water

> One thing about helium: once its released to the atmosphere its gone forever. Because it is so light it not only heads upwards, the velocity of the atoms is high enough that some exceed the Earth's escape velocity and don't come down.

I'm all for preserving helium, but sensationalist BS doesn't help.

> On the surface of the Earth, the escape velocity is about 11.2 km/s

https://en.wikipedia.org/wiki/Escape_velocity

The thermal velocity (at room temperature) of He is 1.245 km/s

https://en.wikipedia.org/wiki/Thermal_velocity

There is no way that Helium reaches escape velocity without some sort of mechanical assistance.

I've heard it theorized that Helium, because it is prone to float at the outer edges of the atmosphere, is particularly susceptible to being stripped away by solar winds. I don't have sufficient expertise to evaluate this claim, but it seems at least plausible. This can't be happening very much, though, or our atmosphere would much more closely resemble that of Mars, which lacks a protective magnetosphere.

> There is no way that Helium reaches escape velocity without some sort of mechanical assistance.

Thermal velocity is an average - there is a distribution of velocities around this average. It says that right in the article you linked to.

At the high end of the distribution, some Helium atoms will indeed have velocities greater than the Earth's escape velocity.

I had this impression as well, but there's something else going on. If you run the numbers, at T=293, there's a negligible fraction above 5 km/s. The atmospheric loss models typically use an exosphere temperature of T=1000, but again, negligible fraction above 10 km/s.

However, there were some contradictions I couldn't immediately understand. This source [1] says "Only about one in a million helium atoms is lost from Earth via Jeans’ escape.". But it also cites a plot from [2] showing the rule-of-thumb for Jeans' escape: 1/6th the escape velocity vs the RMS thermal velocity. In this case, He has an RMS velocity of 2.5 km/s at T=1000, which is greater than 1.9 km/s.

[1] https://geosci.uchicago.edu/~kite/doc/Catling2009.pdf [2] http://geosci.uchicago.edu/~kite/doc/Catling_and_Kasting_ch_...

Agreed the article is not very clear. From the context of the surrounding paragraph though, I think it means one in a million helium atoms is lost via Jeans’ escape every year. Which would obviously be quite a significant factor on any geological timescale.

Helium does escape the atmosphere, a naive comparison of average heat velocities notwithstanding. The linked articles say as much, along with https://en.wikipedia.org/wiki/Atmospheric_escape

https://en.wikipedia.org/wiki/Atmospheric_escape

I believe it gets much hotter in the upper atmosphere. Though there isn't much actual matter there.

Helium is continuously created by radioactive decay of other elements underground. But it's a slow process; we're using helium at an unsustainable rate.

Didn't we capture most of it from nuclear reactors decades ago?

You may be thinking about He-3. It is extracted during maintenance from tritium in nuclear bombs (tritium is a neutron source but He-3 a most efficient neutron absorber). I think now there is also a spallation plant at Oak Ridge. Yearly production is a few kilograms. Interesting stuff.

Mostly from mining and gas extraction. The source is nuclear decay of natural isotopes.

See e.g. https://www.quora.com/What-are-main-sources-of-helium-gas

Do you really think that if you could buy helium and store it for 100 or 1000 years, you'd make more of a profit than investing the money?

Helium is really hard to store for long periods due to the molecule size. It will permeate almost all containers pretty rapidly.

That's not the point of my hypothetical question, since it has the same rhetorical force in worlds where helium is impossible to store as ones where it's easy. The point is to think about your expectation of helium prices compared to interest rates.

But what - happens if the atoms leave earths gravity well? They get pushed by solar winds, meaning the earth has always left a slight trail of helium atoms, spiraling (in system reference frame) slowly outwards- same goes for all other planets.

So- spacebased, scoop - spiral catching to get this?

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