What If There Were No Gravity?

Gravity is one of those things most of us take for granted in our daily lives. Specifically, two aspects of it: the fact that it is always there and the fact that it never changes. On this latter point, if the Earth’s gravity were ever to change significantly, it would have a huge effect on nearly everything, as so many things are designed around the current state of gravity.

Before looking at changes in gravity, however, it’s helpful to first understand what gravity is. Gravity is an attractive force between any two atoms. Let's say you take two golf balls and place them on a table. There will be an incredibly slight gravitational attraction between the atoms in those two golf balls. If you use two massive pieces of lead and some amazingly precise instruments, you can actually measure an infinitesimal attraction between them. It is only when you amass a gigantic number of atoms together, as in the case of the planet Earth, that the force of gravitational attraction is significant.

The reason why gravity on Earth never changes? Because the mass of the Earth never changes. The only way to suddenly change the gravity on Earth would be to change the mass of the planet. A change in mass great enough to result in a change in gravity isn't going to happen anytime soon.

So, what would happen if we were able to flip a switch and turn the Earth's gravity off for a day? The end result of what would happen may surprise you. Read this HowStuffWorks article to find out more.

How Weightlessness Works

What is often called weightlessness — especially in reference to astronauts on a space shuttle, for example — is actually more appropriately termed microgravity. You are not actually weightless, because the Earth's gravity is holding you and everything in the shuttle in orbit. You are actually in a state of free-fall, much like jumping from an airplane except that you are moving so fast horizontally that, as you fall, you never touch the ground because the Earth curves away from you. Likewise, because the shuttle and all of the objects in it are falling around the world at the same rate, everything in the shuttle that is not secured floats.

To put it in real-life context: When you stand on a bathroom scale, it measures your weight because gravity pulls down on you and the scale. Because the scale is resting on the ground, it pushes up on you with an equal force — this equal force is your weight. However, if you were to jump off a cliff while standing on a bathroom scale, both you and the scale would be pulled down equally by gravity. You would not push on the scale, and it would not push back against you. Therefore, your weight would read zero.

While microgravity looks like fun, as we’ve seen in pictures of astronauts floating around inside the space shuttle or International Space Station, it actually places great demands on your body. Initially, you feel nauseated, dizzy and disoriented. Your head and sinuses swell and your legs shrink. In the long term, your muscles weaken and your bones become brittle. These effects on your body could do severe damage on a long voyage, such as a trip to Mars. And the longer you stay in microgravity, the more your muscles and bones weaken.

For a closer look at how your body responds to this experience, read this article from HowStuffWorks.