How does gravity work?
354581
Stand under stepladder\nget friend to drop brick\nouch!\nthis is how it works
46750
It depends on who you ask (sort of).\n\nAccording to Newton gravity is a force proportional to the mass of the two objects involved, and inversly proportional to the square of their distance.\n(To see the relevant equations go here: \nhttp://scienceworld.wolfram.com/physics/Gravity.html )\n\nFrom our perspective we typically drop things much less massive than the Earth (apples, bicycles, pizzas) and very close to the surface of the Earth (that is, almost at the same distance from the Earth's center) the result is that things fall with the same acceleration 9.8 m/s^2 regardless of their mass. In other words, drop an apple and a bulldozer from the same distance and (if air resistance is ignored) they will hit the ground at the same time.\n\nHowever, if you ask Einstein then the nature of gravity is more complex (although in the limit of apples and bulldozers near the surface of the Earth, the same 9.8 m/s^2 pops out of Einstein's theory).\n\nAccording to Einstein's Theory of General Relativity gravity is a "warping" of space time. Mass will bend space-time, and this bending will influence the way in which other objects move.It is sort of summed up in the expression: "Mass tells space what to do, and space tells mass where to move."\n\nSo for Einstein, in some sense, there is no force of gravity (although it certainly seems that way if you fall out of a building).\n\nIf you ask leading physics people today they will say that Einstein was on the right track all right, but General Realtivity stills needs to be work nicely with the other major idea of modern physics, Quantum Mechanics.\n\nThere is still a long way to go in making QM and GR part of a single consistent theory. But it is a very powerful goal since it would unite gravity with the forces which are explained quite well with QM (electromagnetism, the strong nuclear force, and the weak nuclear force.)\n\nIn QM forces are carried by force particles. Photons, for instance, are the force carrying particles of electromagnetism. The force carrying particle of gravity - something which has not been discovered - is called the graviton. So, in modern physics, if you have a graviton then you are back to gravity being a force. \n\nOf course efforts to successfully unite GR and QM are still going on. String theory, is one way that is popular these days.\n\nSo the answers are:\nNewton - gravity is a force based on mass and distance\nEinstein - gravity is the warping of space-time\nUltra-Modern - gravity is a force carryed by gravitons
330093
These answers are correct, in that inertia is only present during acceleration.   This is why countless designs to create gravity-like conditions on spacecraft don't work, because they try basing them on acceleration, which will not work when objects inside the craft appose each other in any way...IE, a person moves.  Now to get to what humans are confused about.  Gravity is not a force at all, but simply the consequence of the local slope of the universe, in a direction the human eye cannot see: time.  You stick to the floor not because gravity is pulling you down, but because that is the shortest distance between today and tomorrow.  In the mid 1950s, the Manhattan project had has its goals to crack the anti-gravity mystery.  Many publications were abundant during the early 50's.  By 1957, it completely stopped.  The Kinemassic Force field generator is probably the most known and only accepted anti-gravity generator ever created by humans.  This design has been arrived at by several scientists in the last 10 years.  When charged, the generator creates a gravitational field that is non-magnetic based.  Uses include artificial gravity, and propulsion.  This methodology is likely the future of space travel, and also disproves the Newtonian view of gravity in the universe.
816746
I can't understand your question but, nothing moves with the aid of gravity, rather, things stop moving because of other forces acting upon them, e.g. drag, friction, etc. In space, there is no gravity (or much much less than on earth), which is why if you set a ball in motion in space, it would theoretically keep going forever, unless something got in it's way.
658894
Gravity is a property of all particles that possess mass. It is just a fundamental force that at the present can not be explained scientifically to a complete extent.\n\nAny particle that possesses mass (which is basically everything apart from light) has its own gravitational potential which stretches off into infinity. Any other mass which enters this field is subjected to a mutually equivalent force. Obviously then, all matter in the universe is simultaneously interacting with all other mass\n\nIt is proposed that a particle called the graviton carries the force between all massive particles, however this has yet to be identified.\n\nAnother theory is that gravitational waves are constantly being emitted by all objects, and these carry forces.\n\nEinstein proved in his general relativity paper that the presence of mass curves space time and what we observe as a force is merely a particle taking the shortest route through space. This is the current view of gravity\n\nGravity is made purely by the presence of mass, exactly what 'form' it takes is not yet proved.
1132052
Gravitation and gravity are the same thing.  Gravity is one of the four fundamental forces, so yes, gravitation is a force.
1130053
As mentioned in other replies, physicists don't yet have all of the "how" questions answered. Einstein, in the General Theory of Relativity, pretty much nailed the underpinnings of the current theoretical understanding of gravity. Here is my attempt at the "nutshell." I'll start with an analogy. Let's say you are driving somewhere in the midwest or plains states--essentially flat ground, with a few rolling hills. Let's say you stop your car at the top of a slight rise. As you look around you, you see flat land in every direction. You're sitting on essentially a two-dimensional plane. Taking your foot off the brake, you notice the car starting to roll forward. Your initial observation about the 2-dimensional "space" you were sitting on isn't quite accurate. The 3rd dimension (altitude) has come into play, and gravity is pulling your car into the swale. What Einstein said (and how he came up with this back in the early 1900's is incredible) was that our THREE dimensions are really a slightly inaccurate description of the world (and universe) we inhabit. A fourth dimension, time, is part of the "fabric" of our surroundings. As in the case of that slight "warp" in the 2-dimensional farmland that led to a noticeable effect on your car, Einstein said that warps in the space-time continuum are experienced as gravity. As you know, Einstein was into the "energy = mass" thing big time, and you know that mass is tied up with gravity as well. If you want to get more cozy with these related concepts, I strongly recommend David Bodanis' book, "E=mc2: A Biography of the World's Most Famous Equation" -- available as a "BooksOnTape." It's exciting, full of cool anecdotes about the heroes of 20th century physics, and... NO MATH, just concepts. Best of luck!
632008
Gravity, its weight, friction\nThat's about it.
533693
Gravity is a very weak force.  Think of a fridge magnet.  A small magnet, or large for that matter, will stick to a fridge despite the gravity from the entire earth pulling it down.
775838
Okay so this will pretty much be an explanation from a classical physics type of view so we can talk about gravity as a force.\n\nYou're totally right.. gravitational acceleration is a bit of a different experience than another kind might be such as acceleration from a surface pushing on your feet or a rope pulling you through your hands.  If you were in space falling freely towards a body (planet.. whatever you want.. anything with mass) because of gravity you wouldn't feel any acceleration at all.. even a fancy accelerometer would feel nothing.  \n\nThe simple answer is that if you are accelerated by being pulled on by a rope you're holding (instead of gravity.. so you're at some place in space with so little gravity you can forget it for this experiment) you will feel it because the pull of the rope is transferred through your body as a strain between all your molecules.  They're all hanging on to each other and getting pulled along by each other and your nerves can feel this strain.\n\nIf it's a push then it's pretty similar... you're in space, some place with negligible gravity, in an elevator with a rope pulling it in what you could call the "upwards" direction.. ie your head is pointing in the direction of acceleration.. and you're inside it with the floor of it pushing on your feet.. you can FEEL it! why? because the force starts at your feet and is transferred through all the tissues in your body compressing you and your nerves.. and you feel it.\n\nYou don't feel the gravitational acceleration because it accelerates every single atom in your body exactly the same way.  They all speed up just the same way as each other and there is no force needed between them.\n\nThink about it like this... if you were in the space elevator again and you were actually made of just a bunch of tiny pieces of stuff all unattached to each other... lake say you were made of sand or something all just floating there undisturbed at first... then the elevator started accelerating! what would happen? well you would end up all mushed against the elevator floor in a big pile.. why? because you had no internal structure to keep you stuck together... if you do have this internal structure with your bones and flesh all stuck together, like you do, then they would all be fighting to cling together and not squish together or tear apart and avoid mushing up on the bottom floor.  You're a solid structure.  Those stresses in your tissues are what you feel.. it's the attachment between all your little pieces being pushed on or pulled on in every little bit of you that you can feel.\n\nHope this helps!
616852
Gravity is the basic force. There is also a positive feedback effect; the more massive a cluster becomes, the more strongly it draws other particles and clusters toward it.
623233
It's gravity that keeps everything in place. And ya'll, don't be hatin' on this persn, it's just a question!
1093836
Centrifugal force and gravity.
21267
Gravity is the force of attraction between massive particles. Weight is determined by the mass of an object and its location in a gravitational field. While a great deal is known about the properties of gravity, the ultimate cause of the gravitational force remains an open question. General relativity is the most successful theory of gravitation to date. It postulates that mass and energy curve space-time, resulting in the phenomenon known as gravity.\n\nGravity is acceleration.  means that (if the mass is unvarying) there must be a force that causes a mass to accelerate. For a rocket ship, that is the rocket engine. For the earth, it is the compression of the mass between something on the surface of the earth and the earth's center of mass. The acceleration is in relation to spacetime in that the weight one feels is one's resistance to deviating from one's path in spacetime. The same holds true in the rocket ship except that a rocket engine supplies the force to accelerate an occupant from his spacetime path. There is no difference between the weight he feels because of gravity or the rocket.
1171587
Gravity is one of the universal forces of nature. It is an attractive force between all things. The gravitational force between two objects depends on their masses, which is why we can really only see gravity in action when at least one of the objects is very large (like the Earth).\n\nIsaac Newton was the first scientist to define gravity using math. There will be a larger pull due to gravity if the objects' masses are larger and if the objects are closer together.\n\nOne thing we can do with Newton’s law is calculate an escape velocity for the Earth. That is the speed something has to go for it to escape the gravity of Earth. This number for Earth is about 11 km/s. This means that if you could throw a baseball at 11 km/s, it would never come down!
919025
Let's clear up our terms a little bit.\n\nGravity only generally occurs between things of mass.  And it is pretty much independant of what the mass is doing.  And I say pretty much because there are things that can create or destroy mass... but in a general sense it all comes down to the mass.\n\nNow, as astronomical bodies form, they tend to get a spin.  Because of the conservation of angular momentum, things that suck up more mass tend to have more spin than others.  These are, however, tendancies, NOT necessities.\n\nCase in point - the Earth.  Because of the tides, the spin of the Earth is slowing down.  We used to have twelve-hour days millions and millions of years ago, but now they're twice as long.  Has this affected the force of gravity?  Not a bit.  The same mass is present, and it's causing the same amount of gravity.\n\nWhat your friend may be confused by is what is sometimes called centrifugal force (a physicist would probably just call it inertia, though).  Although gravity pulls us down to the centre of the Earth, the motion of spin carries us away from the centre, counteracting gravity.  This means if you take a tool to measure gravity near the equator, you'll get a lower reading then you will when you measure it at the axis.  The force of gravity hasn't changed at all, but the spin is creating another force that is mitigating gravity's effects.  On Earth, this force is pretty small, but it's concievable that it could amount to a huge amount on a fast-enough spinning object... say, a space station with almost no gravity, but which was spinning fast to simulate gravity but pulling out instead of in.\n\nSo in a literal sense, you are completely right.  Gravity has ONLY to do with mass (well, mass and distance).  In a squishier sense, your friend is sort of right, in that spin can change the APPARENT force of gravity in local areas and that objects with large gravities also tend to have large spins.\n\nHope that helps!
1069669
gravity is stronger, leave it down