Question: what if helium makes our voices normal and oxygen makes them deeper?

Hywel Owen answered on 19 Jun 2012:

Not sure what you mean by this question. It’s true that breathing air with a lot of helium in it makes your voice higher-pitched than if nitrogen is usually in the air. Air on Earth is about 80% nitrogen and about 20% oxygen. Air on any planet is usually likely to have more nitrogen than helium, since helium is much lighter and tends to escape away into space – nitrogen is held down more by the Earth’s gravity.