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## how does the earth have this force called gravity?

As all we say the gravity (small g) pulling the things on earth towards the center of the earth, when "Capital G" makes earth stand on the solar system. sorry if i'm confused in..
1.how does the earth have this force called gravity (small g)?
2.where did the force come from?
3.what is the relativity between this Capital G and small g?

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• #### Bryan Maloney30+

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Mar 3 2014: A more physical answer:

"Gravity" is how we perceive "squeezing" by "space-time". That is, all matter disrupts the "elastic fabric" that is "space-time", which is the "fundamental stuff" of the universe. Space-time "wants" to be as "flat" as possible--that is its "natural" state. Matter 'disrupts" this state and so the "space-time" "squeezes" it. It's a very bad analogy, but the actual math is rather tedious.

"G" is the so-called "gravitational constant", which is really just a fudge factor to make some equations look pretty.
• #### Rodrigo P. Feliciano20+

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Mar 8 2014: Thanks, professor!
• #### Bryan Maloney30+

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Mar 1 2014: Because life sucks. A swan is here and gone, but man is tied up to the ground, and he makes the saddest sound, the saddest sound.*

*Paul Simon, 1970
• #### chandru r

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Mar 2 2014: I couldn't understand what are you saying here!
• #### Rodrigo P. Feliciano20+

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Mar 2 2014: Hi Chandru,

Mr. Maloney is humoring you. On a serious note, he's making you think deeper, much, much deeper - maybe SOMETHING much more powerful and difficult to understand than gravity.

Knowledge of Physics, no doubt, makes you an intelligent man - it's a good start. However, will it make you a wise man?

Suggest you reflect on the thoughts of Dr. Nathan Myhrvold, Dr. Stephen Hawking, Dr. Deepak Chopra, and the writings of ancient sages.

Later on you will move on - beyond quantum mechanics, number theory, nanotechnology, and genetics engineering. Your perspective will change. You will discover new frontiers and you may even found a successful company. Or, you may become cynical at some point because of what life throws at you. I hope you won't give up by then.

I believe you show a lot of promise, a man of unlimited potiential. Pursue, pursue, pursue!

P.S.
When I was young, I could walk and run for miles and miles. Now, I can barely walk two miles without gasping for breath. I guess this is due partly to gravity.
• #### chandru r

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Mar 3 2014: Thanks Rodrigo :)
• #### Santokh Saggu10+

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Mar 1 2014: You are not confused , You have asked a very right question . But, I doubt that some scientists may say that your question is irrelevant.

Ask tough questions and face the music.

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Mar 14 2014: Interesting question and conversation here.
I think of Earth with far less gravity. May be more birds and fish, less organisms walking about on land.
I think of Earth with far more gravity. May be more fish and organisms walking about on land, less birds.
Earth's gravity determines organisms that can survive here.
If Earth gravity increased, then it may pull back some materials moved to outer space by humans. Can Earth increase or decrease its gravitational pull?
• #### Darrell Shimel Jr.10+

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Mar 3 2014: chandru,

The real answer is that we are not 100% sure.

Pre-Galileo (early 1600s), people believed heavy things fell faster than light things. A rock falls faster than leaf. Galileo proved that it wasn't the weight, but rather the density (weight to wind resistance ratio).

Newton, (circa 1700) studying force's effect on objects (laws of motion) figured out the Law of Gravity. Any two masses attract directly proportionate to their mass and inversely proportionate to the square of their distance. That is, the more massive something is, the more gravitational force if creates. The force is strongest when things are right next to each other, but falls of as they get further apart.

A scientific law only describes what, not why, so Newton made no guess as to WHY gravity only HOW gravity.

Early 20th Century, Einstein was contemplating our discovery that light did not move like anything else, and came up with The Theory of Special Relativity that described space/time as being relative to velocity. He later expanded this in The Theory of General Relativity, to explain gravity is the result of energy warping space/time. Each object thinks it is traveling in a straight line through space, but space itself is bent by energy.

Einstein's version of gravity predicted that not only mass, but even massless energy such as light would bend and be bent by the warping of space/time. This means Newton's gravity was just a simplified case of the real gravity, the way a circle is a simplified case of a sphere.

In the early 20th century, we were actually aware of 4 fundamental forces of the universe. Electro-magnetic, gravity, nuclear strong and nuclear weak. After explaining gravity as a warping of space/time Einstein spent the rest of his life trying to explain the other 3 using the concepts of relativity. That unifying theory of the 4 fundamental forces (Universal Field Theory) has not been found.
• #### Frank Bierbrauer

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Feb 28 2014: Little g refers to the acceleration due to the force of gravity felt by any object raised above a stable level. Big G is is the constant of proportionality used by Newton in his expression for the force of gravity between two masses separated by a distance r. Gravity itself, according to general relativity, is not a force but rather due to the warping of space-time created by a large mass. Think of space-time as flat away from masses so that a moving small object would simply travel in a straight line since the space it is travelling in does not have any bumps or troughs in it. Remember, it must follow this space. In the presence of a large mass, the space-time around the large mass, e.g. planet, star etc, is curved creating a kind of trough so that a small mass moving in this space must in fact fall down into the trough. If it is moving tangentially then it will still fall into the trough but cannot actually hit it, this is an orbit.
• #### Ariel Ramirez

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Feb 28 2014: As far as I understand it, small g is the acceleration due to Earth's gravity, while Capital G is the gravitational attractiveness of two bodies on each other. In a sense therefore, small g is just Earth's Capital G.
1) All bodies have gravity, not only Earth.
2) according to Einstein, gravity is not a pull but as with other forces, a push from the differing spaces or 'warping' of space.
3) See first sentence. :)
• #### chandru r

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Mar 1 2014: My question is.... Is gravity generated by some sources or it just exists in space..? as far as we know. Like assumption of big bang...as we know how it works, but how is it created?
• #### Ariel Ramirez

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Mar 2 2014: As of now, no one knows. You've just stumbled on one of the great conundrums of physics today.