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why do we need gravity to live

Original When I was young, I dreamed about traveling to space and enjoying the wonders of weightlessness. I wanted to eat bubbles of water and bounce off the ceiling. I planned to take a nap on the wall and then play a 360б game of leapfrog. And the back-flips!! Oh, how I dreamed of doing innumerable, flawless back-flips. You see, I have never been particularly aerobatic (falling generally comes much easier to me), but in space, well, it seemed that anything is possible there. And if IБm being honest, I still dream about floating around among the stars. Sometimes, gravity seems like such a drag. But what if it didnБt exist? What if we all woke up one day and discovered that, suddenly, there was no more gravity? Before we embark on this little thought experiment, first, a definition:
Б is a force of attraction that exists between any two masses, any two bodies, any two particles. Gravity is not just the attraction between objects and the Earth. It is an attraction that exists between all objects, everywhere in the universe. Б Let s say you are walking down the road beside a friend. Even though you may not be aware of it, there will be an incredibly slight gravitational attraction between the atoms in your body and the atoms in your friendБs. The same is obviously true for objects that are floating about in space. Really large objects that have a lot of mass (like planets) exist because matter is gravitationally attracted to other matter. In essence, gravity makes matter clump together; it forms the planets and stars and black holesБand everything else that makes life so terribly interesting. Original At the most basic level: gravity is related to mass, which is related to matter. The more matter, the higher the mass; the higher the mass, the higher the gravitational pull. Gravity on Earth never changes because the mass of the Earth never changes. Essentially, huge chunks of our planet arenБt being ripped out from under our feet (which is, I think, generally a good thing). A change in mass great enough to result in a change in gravity isn t going to happen anytime soon (thankfully, a large portion of our planet isnБt going to up and disappear).


But let s ignore physics. Suppose that, one sunny day in May, the planet gives off a frightening БPOPБ and gravity. goes away. Obviously,. You would float; that chair that you are sitting in would float; the device that you are using to read this would float; the desk or table youБre using would float everything (is what IБm getting at here), everything would float. This might sound like a bit of fun. But, unfortunately, we would lose one of our best friends: the Moon. Of course, EarthБs gravity is the only thing keeping the Moon in orbit. Without it, it would float off into space. Oh, and of course weБd all die. The most important things held to the Earth by gravity are the atmosphere and our water. Without gravity, the air in the atmosphere isnБt compelled to stick around, so it would immediately begin drifting off into space. EarthБs oceans, lakes, and rivers would also depart. I imagine that it would be horrifying (and probably a little amusing) to see fish and whales floating in bubbles of water high in the sky. But of course, weБd be drifting off the planet along with them. Fortunately, we wouldnБt have too long to be horrified because, without air and water, none of us would last very long. б But what if there was never any gravity? What if electromagnetism, the strong interaction, and the weak interaction were all exactly as we know them, but the fourth force, the one that pulled together a bunch of rocks to form Earth and keeps us all from drifting off into the cosmos, what if it never existed? Then, for all intents and purposes, there would be no universe. Or rather, the universe would be completely flat and featureless. There would be no stars or planets, no black holes to boggle the mind. No you, and definitely no me. So, as long as we have gravity we canБt fly. But we can existБand thatБs something There s nothing like a nasty cold to make you appreciate good health. The same goes for the state of the universe: Tweaking just one of the fundamental physical laws or constants, normally perfectly fine-tuned at the right values to allow stars, planets, atoms and life as we know it to flourish, could turn things very different quite unpleasantly so.


Imagining such a bizarro universe may heighten your appreciation for the norm. Consider, for example, how horrifically unrecognizable the universe would be if it had formed with just three fundamental forces instead of four if electromagnetism, the strong interaction and the weak interaction were all exactly as we know them, but that fourth force, the one that pulled together a bunch of rocks to form Earth and still keeps your feet firmly planted on the planet, never existed. What if there was? Picture a barren wasteland. According to James Overduin, a physicist at Towson University in Maryland who specializes in gravitation, a universe without gravity would be completely flat and featureless. Overduin explained that gravity is just another term for the how steep or shallow the fabric of the universe is in a given place (and thus how likely objects are to fall toward the source of curvature). Just as a bowling ball placed on a trampoline curves its surface, it is the presence of matter and energy that cause space-time to curve. So, if the universe can t curve (because gravity doesn t exist), then there can be no matter or energy within it. This would be a boring universe, Overduin told Life s Little Mysteries, a sister site to LiveScience. [ In the interest of not being boring, let s consider an alternative scenario: What if the universe formed with gravity and developed normally up until a certain moment in space-time, and what if then, suddenly, gravity switched off? According to Overduin, Einstein proved that you can t change the value of the gravitational constant known as G doing so simply doesn t work mathematically, so there s no way for physicists to do it and still make sense of what would happen next. However, there are two alternative ways to switch gravity off, while letting all the other physical laws of the universe keep working. One way to scoot around the constant is to manipulate a lesser-used physics model (but one that nonetheless produces an equivalent picture of the universe as Einstein s), which considers G to be a field that permeates space-time, rather than a constant.


Called a scalar field, it works just as well as G in describing the way the universe works, except that mathematically, unlike the constant, its strength is allowed to vary in time and space. Dialing down the scalar field to zero everywhere would essentially flatten the universe. Objects would no longer be drawn toward each other, because there would be no sloping surface for them to fall down. Instead, they would fly off in whatever direction gravity was keeping them from going. Back to the trampoline analogy, deleting gravity would cause the trampoline to suddenly flatten, and the bowling balls would roll every which way. Alternatively, you could get rid of the Higgs field, a field permeating all space that is generated by the. All elementary particles get their masses from their interactions with this field, kind of like being slowed down by passing through a thick syrup, Overduin said. If the Higgs field instead dropped to zero, the syrup would have no thickness and all elementary particles would zip around freely and become massless. Having no mass, they d be unable to curve space-time, so there would be no gravity. On top of that, they d start moving at the speed of light, ditching the other particles they used to hang out with inside atoms. If gravity suddenly disappeared in either of the dramatic fashions described above, what would happen here on Earth? I would expect that [Earth s] constituents, including its atmosphere, and oceans, and us, etc. , would drift apart or even fly apart, assuming that the Earth would still be spinning, he said. We d be gasping for air, but that would be the least of our problems: we d also be grasping for the very atoms in our bodies, and even the rapidly scattering particles in those atoms, all the while lamenting the way times had changed! Follow Natalie Wolchover on Twitter @. Follow Life s Little Mysteries on Twitter @, then join us on.

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