Zero Gravity Flight
Stephen Hawking, weightless (courtesy Zero Gravity Corporation)

Guide to Space

What Causes Gravity

19 Sep , 2010 by


Gravity is one the four fundamental forces of the universe and is considered a noncontact force. It is what holds the planets in orbit as well as the very universe itself. It is what keeps us from floating off into space and plays a crucial role in almost every nature process from the ocean tides to the body’s circulatory system. However what causes gravity? What is the mechanism that makes it work? Physicists have only partially answered this question. The first person to comprehensively describe it was Isaac Newton.

Newton gave us the foundations of Physics, Classical Kinematics. Isaac Newton used the universal law of gravitation to describe how gravity works. Thanks to him we know any two objects in the universe that have mass exert a gravitational pull on each other. The greater the mass and the closer the two objects are, the stronger the force of gravity. However this only described the phenomenon in party. It basically was a more detailed description than just something makes any object that is unsupported to fall to the ground. Einstein took the next step in describing it with his Theory of Relativity.

Einstein hypothesized that space and time were one and the same and served as the fabric of the universe. He stated that gravity was simply a curvature in space-time created by a mass object pretty much in the same way a piece of cloth would be curved if it was stretched out and a heft object was placed on it. This curvature in space created by an object with greater mass than the objects surrounding it would cause these objects of lesser mass to fall toward the more massive object.

Even then this only described gravity on the large scale. Newton’s Law of Universal Gravitation correctly states that gravity affected every thing with mass in the universe. This is where quantum physics came in. Quantum physics introduced the existence of even smaller particles than neutrons, electrons, and protons to describe what seemed to be exceptions to classical physics when the interaction of matter is viewed on the micro scale. Quantum physics proposed a theoretical particle called the graviton that controls gravity.

That brings us to our current understanding. Gravity still remains one of the biggest mysteries of physics and the biggest obstacle to a universal theory that describes the functions of every interaction in the universe accurately. If we could fully understand the mechanics behind it, new opportunities in aeronautics and other fields would appear.

We have written many articles about gravity for Universe Today. Here’s an article about gravity in space, and here’s an article about who discovered gravity.

If you’d like more info on gravity, check out the The Constant Pull of Gravity. And here’s a link to an article about Gravity on Earth and Gravity on Space.

We’ve also recorded an episode of Astronomy Cast all about Gravity. Listen here, Episode 102: Gravity.

Cornell Astronomy
Stanford University

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