Why does the Earth still have helium?

[purpler]

It’s lighter than air, chemically inert (for the most part), and the Earth has been around for 4.7 billion years. In all that time, why hasn’t all the helium bubbled out and away to the upper stratosphere?

[Lemur866]

New helium is being made through radioactive decay, and some of this gets trapped in helium-tight spaces underground.

[Exapno_Mapcase]

Helium

Helium makes up about 0.0005% of the earth’s atmosphere. This trace amount of helium is not gravitationally bound to the earth and is constantly lost to space. The earth’s atmospheric helium is replaced by the decay of radioactive elements in the earth’s crust. Alpha decay, one type of radioactive decay, produces particles called alpha particles. An alpha particle can become a helium atom once it captures two electrons from its surroundings. This newly formed helium can eventually work its way to the atmosphere through cracks in the crust.

Just in case you’re asking this because creationists use the presence of atmospheric helium to argue for a young earth, see Radiometric Dating from The Evolution Evidence Page

[PBear42]

Wikipedia can be your friend: Helium.

[purpler]

@Exapno Mapcase

Just in case you’re asking this because creationists use the presence of atmospheric helium to argue for a young earth, see …

Thanks for that info! I realize you don’t know me, because i’ve been mostly lurking on these boards for years and not posting much (i read them voraciously, though), but i got quite a good laugh out of your mild insinuation that i might be a YEC. I do have three of them in my family, though, and it does make Thanksgiving conversation rather…strained.

PBear: i did check Wikipedia right before asking, but somehow i missed the paragraph about radioactive decay. I’ll read more thoroughly next time.