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The Daily Cardinal Est. 1892
Tuesday, May 21, 2024
Helium balloons


Balloons, gravity and runaway helium


Did you ever wonder what happens to helium-filled balloons when you let them go? Well, as they fly up into the sky the atmospheric pressure drops, so the balloons grow larger. Eventually they pop, releasing their helium and falling back to Earth.

But what happens to all the helium? It keeps on rising and never stops!

Helium atoms are so light that Earth’s gravity can’t hold them, so they float away into space. This is why earth, compared to the rest of the solar system, has a miniscule amount of helium.

Helium is the second-most abundant element on Jupiter and Saturn—planets over 100 times as massive as Earth. In fact, they have enough mass that their gravity keeps the helium from being blown away by solar winds.

But this creates quite a quandary when you want to open up the next helium balloon to breathe it in and make your voice sound funny. Isn’t that helium and laughter-filled exhale precious if the helium will float away never to return? As luck would have it, your own planet has solved this problem quite well. Earth is a veritable helium factory, so exhale freely!

If you paid attention in middle school science class you probably remember that matter can never be created or destroyed. So, you’re probably wondering how our own planet can produce helium atoms.

Never fear, though. Earth is not violating the laws of nature. It is actually producing helium atoms as a by-product of the nuclear breakdown of radioactive uranium and thorium atoms that have been in the earth’s crust ever since its formation.

When these unstable atoms decompose, they spit out tiny, fast-moving things called alpha particles. These speedy particles bounce around, heating up the Earth as they slow down. Eventually they grab electrons and become the helium atoms we know and love. These helium atoms collect in Earth’s crust and are pumped out of the ground with oil and natural gas.

Remember this the next time you stroll down the street with a helium-filled balloon: Those are newborn helium atoms in your balloon, resting along their voyage from the centers of radioactive atoms, to pockets in Earth’s crust, to your balloon and finally off into outer space.

Lee has a blog with similarly awesome science blurbs. Check it out at

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