UCSB Science Line (2024)

We breathe by expanding our lungs. Thisliterally pulls air into our lungs because we aremaking more space inside our bodies. As long asthe air around us is thick enough we can breathe,regardless of gravity. On Earth, gravity is whatholds our atmosphere. When astronauts go intospace they can breath, because their space shipsand space suits keep the air around them, eventhough gravity is very weak.

Zero gravity has nothing to do with breathing.If there is air, then you can breathe it; if thereisn't air, then you can't.

Gravity on planets tends to attractatmospheres, and this means that planets withgravity may have breathable atmospheres, unlikethe vacuum of space. However, if you have somemeans of keeping an atmosphere without gravity(for example, your atmosphere is contained insideof your spaceship), then there is nothingpreventing you from breathing in zero gravity.

Breathing actually has to do with air pressurerather than gravity. When we inhale air, thediaphragm contracts and pulls down the lungs,creating a "vacuum" inside (lower air pressure inthe lungs relative to the atmosphere outside). Asa result, air from outside your body rushes in andwe complete the inhalation.

That is a very interesting question. Let´sclarify how gravity and air are related and whatthat means for humans being able to breathe. A person needs air (oxygen) to breathe, but aslong as they have it, then it does not matterwhether or not there is also gravity.

The complicated part is that gravity is the forcethat holds us to the ground, and in fact, gravityalso is the force that holds the atmosphere, ourbreathable air, against the earth where we can useit. In space, there is no air because there isn´tany gravity to hold in the atmosphere. BUT, let´s say you are inside of a space ship,which is closed container that holds air thatcan´t escape. That means another force besidesgravity is keeping the air in so you can breatheit. This force is the sealed walls of the spaceship.

So as long as there is air in the space ship, youcan breathe it, even if there is no gravity.