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The title is quite accurate, as helium achieves escape velocity and escapes the Earth's gravity when it is released in the atmosphere, making it one of the rarest elements, in the long-term.

https://www.youtube.com/watch?v=oZkMQkHGj1s https://medium.com/starts-with-a-bang/6757fcdaa283

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Helium is a rare element in Earth, but Helium 4 is the most common isotope: http://en.wikipedia.org/wiki/Helium

> He^3 : 0.000137% *

> He^4 : 99.999863% *

> * Atmospheric value, abundance may differ elsewhere

Of course, but Helium - any isotope - is quite rare and our supply strictly[1] decreases with time.

In fact, both (very useful) isotopes are rare for different reasons. He3 got expensive - enough to seriously impact medical and scientific uses - when we decided a beta-detector was needed across in port. (He4 we just waste in party balloons sigh)

[1] well, almost. Capturing alpha particles works, but good luck filling the LHC or your local MRI scanner from a source that expensive.

I thought the title was misleading enough to warrant a comment. It makes it seem like the Helium-4 isotope is exotic. Losing Helium-4 to the atmosphere is an acceptable research cost. Losing Helium-3 is not.

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