Home >> Science & Nature >> Astronomy

What Generates Gravity?

Gravity is the constant natural force between two objects. All objects have mass. That mass, in turn, is the generator of gravitational attraction. Gravity is what holds people and the atmosphere on Earth. Gravity is what a rocket must overcome when it leaves Earth. First described in 1666 by Isaac Newton, gravity is the basis for astronomy and physics. Newton's theories about the nature of gravity held for 250 years until Einstein put forth the theory of general relativity in 1915.

Newton's Law of Gravity
- Professor Bangalore Sathyaprakash of Cardiff University states, "According to Newton's relatively simple picture, gravity is a force that works between two objects." The formula for determining the force of gravity is F = G(M1*M2)/R^2) where G is the gravitational constant, M1 is the mass of the first object, M2 is the mass of the second object and R is the distance between them. The closer the two objects are, the greater the force of gravity between them.
Mass
- Mass is different than weight. Mass is a measurement of how much matter is contained in an object. Conversely, weight is the measurement of how hard gravity is pulling on an object. Mass is a constant. An astronaut has the same mass when he lands on the moon as he did when he was on Earth. However, because the moon has less gravity, he weighs only about one-sixth as much.
Force
- Unlike magnetism, which can attract and repel, gravity is an always-attractive force. All objects exert gravity and are acted upon by gravity. It is universal and unavoidable. The greater the mass, the greater the gravitational force the object generates. Earth exerts gravity on every person. Each person also exerts reciprocal gravity on the planet. However, because there is such a huge difference in mass, (a person has a mass of about 70 kg, whereas the Earth's mass is about 6 * 10^24 kg), even six billion people do not affect the movement of Earth.
Science
- The problem with Newton's original theory is that it did not encompass and account for all the other immutable forces, such as the speed of light. Newton's theory held that gravity was constant and instantaneous. However, nothing can travel faster than light, not even gravity. This is one of the paradoxes addressed in Einstein's theory of general relativity. In the years since Einstein, physicists, such as Stephen Hawking, have struggled to reconcile gravity with quantum physics.

Astronomy