Gravity, in the form of gravitational waves, is on a lot of people's minds at the moment. We have all experienced the force of gravity. It is what happens to you when you jump up into the air. Disappointingly for anyone with ambitions to be Supergirl or Superman, we tend to fall right back down to the ground. But what if we could switch gravity off?
Physics is adamant that this could never actually happen. But that has not stopped people exploring the idea. Here, based on the collective wisdom of several experts, is the best guess at what would happen to you if gravity suddenly vanished.
Jay Buckey, a physician and one-time NASA astronaut, explored how the absence of gravity affects the human body in a short Ted-Ed lecture. Wounds take longer to heal and the immune system loses its strength
Buckey says that our bodies are adapted to an Earth-like gravitational environment. If we spend time living where gravity is different, such as on board a space station, our bodies change.
It is now an established fact that astronauts lose bone mass and muscle strength during stints in space, and their sense of balance changes.
An absence of gravity brings other problems. For reasons not entirely clear, our red blood cell count falls, bringing on a form of "space anaemia". Wounds take longer to heal and the immune system loses its strength. Even sleep is disturbed if gravity is weak or absent.
That is just what happens after a short visit to space. "What if you were to grow up without gravity?" Buckey asks. "What about the systems that depend on gravity like your muscles, or your balance system, or your heart and blood vessels?"
There is good reason to believe the human body would develop differently.
Buckey points to an experiment in which a cat grew up with one eye permanently hidden behind an eyepatch. The cat was rendered blind in the eye as a result. The circuitry that would have connected it to the brain's vision processing regions failed to develop, because the eye was not processing any visual information: a very literal example of the old phrase "use it or lose it".
Earth's atmosphere and its oceans, rivers and lakes would be one of the first things to drift away into space. It seems likely that the rest of our bodies would respond similarly. If gravity was not around for our hearts, muscles and bones to respond to, our organs would almost certainly develop in different ways. That said, if gravity did get switched off we would have more pressing things to worry about than the long-term effects on human development.
Scientists have explored the immediate physical consequences of losing gravity. The first problem is that Earth is rotating at high speed, rather like the way a weight on a string rotates if you spin it around your head. Switching off' gravity is analogous to letting go of the string. Things not attached to the Earth in any other way would fly off into space in a straight line that would take them away from the surface of the Earth.
A lack of gravity would eventually take its toll on our very planet. Earth itself would most likely break apart into chunks and float off into space.
A similar fate would befall the Sun. Without the force of gravity to hold it together, the intense pressures at its core would cause it to burst open in a titanic explosion. The same thing would happen to all the other stars in the Universe. However, because they are so far away, it would be years before the light from their death throes reached you.
Eventually there would be no clumps of matter, like stars or planets, anywhere in the Universe. There would just be a diffuse soup of atoms and molecules, drifting around not doing anything much.
This scenario – which just to repeat, could never happen – illustrates just how fundamental gravity is to the workings of the Universe. Without it, nothing interesting like planets could ever exist. Oh, and of course we'd all die.
Gravity is one of four fundamental forces that govern our Universe. The other three are just as crucial. Without electromagnetism and the strong and weak nuclear forces, atoms themselves would fall apart. But gravity is the only one that is truly a household name, which is perhaps why we are so fascinated by ideas like antigravity – and why the discovery of gravitational waves is so exciting, even if it never touches any of our lives directly.... we know it is making the universe work and holds it all together.