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 ac

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.