How can gravity be explained in a simple nutshell?

Question

I am pretty intelligent, but I have a hard time understanding how and why gravity exists.

Answer 1

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!

Answer 2

Some good explanations here, but none of the "nutshell" ones quite hit it, though the curved space-time thing is close.

Nutshell: any energy/mass attracts all other energy/mass. The generated acceleration falls off with distance, and is proportional to the mass that is doing the attracting.

The why it exists is not known, it is just the way the universe is. The how it works gets beyond the nutshell stage and itself is not well understood at the extremely microscopic scale (aka quantum gravity.)

Answer 3

I think you have to stop thinking of gravity as a "force".Gravity is caused by the effect objects with mass have on the surounding space. Try to imagine streching out a square peice of nylon. Then place a heavy rock in the center. Imagine the effect the rock will have. It will sink a little in the center. This is how object affect their surounding space. Now roll a small marble from one of the ends of the nylon and you will see that the marble follows the curve the rock made on the fabric and the marble will roll down in a circular motion towards the rock. This is my modest attempt of showing how a space time continuim works.

Answer 4

Gravity keeps the nut inside that shell from falling up into space when the nutshell is split open; it also makes that same nut want to go to the center of the earth at all times. pretty weighty question but applies to all...

Answer 5

Gravity is there because large masses bend space create a curve that other masses can orbit in. The curve pulls objects in but we can not see the curve with our eyes.

Answer 6

An apple falls DOWN and doesnt Go UP!Thats gravity.

Answer 7

I could tell you in Newtonian way. If it is not there, you could not play your favorite game. The ball or whatsoever would go to the orbit if you throw it up. It helps us stay where we are. As a matter of fact all object have graviattional force, Bigger (heavier) have bigger force of atraction. That's why one can jump 6 time futher in moon.

Answer 8

Any 2 objects that have mass will also have gravity. Period.

Answer 9

It is a very weak attraction that exist between all objects inversly proportional to the mass and distance

Answer 10

Someone (*) once said "Space-Time tells matter how to move. Matter tells space-time how to curve".

Given that, I think you could then say that Gravity is "how they talk to each other".

(conveniently ignoring any specific details, which are not completely known yet ...)

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(*) quote attributed to JA Wheeler (Misner, Thorne, and Wheeler)? or Ernst Mach?