Few things in life are as constant, vital, and mysterious as gravity. Gravity is the force that brought the materials of the solar system together, is the element that keeps Earth spinning around the sun, and is the power that keeps us grounded on our planet. However, as omnipresent as gravity is, it has long defied precise definition. Let’s take a look at some of the dominant theories of how gravity works.
The facts of gravity
Gravity is an observable phenomenon and because of this, we can describe what it will do with precision on a surface level. We know that objects with more mass exert a stronger influence of gravity on objects around them. We also know that gravity gets weaker with distance.
Supermassive objects such as the sun can exert massive gravitational forces over huge distances, which is enough to keep objects as large as planets in orbit around them. However, those gravitational forces are not strong enough to overcome large objects’ inertia and pull them toward the sun to be destroyed.
Newton’s Theory of Universal Gravitation
Isaac Newton, the revolutionary mathematician, observed the natural behaviors of gravity and used them, along with his pioneering work in physics, to craft the Theory of Universal Gravitation. According to legend, Newton was reading under an apple tree when an apple hit him on the head and led him to wonder why the apple was inclined to fall to the ground in the first place.
Without digging into the complicated mathematics that support his theory, Newton's reasoning states that gravity is an entity that acts on everything in the universe. Every object creates a gravitational attraction to every other object that is proportional to its mass. The largest objects exert the greatest gravitational force and draw smaller objects toward them.
Newton’s theories are supported by solid math and physics. They explain most observable interactions between gravity. It's no wonder that they remained unchallenged as the explanation of gravity for centuries.
Einstein’s Theory of Relativity
During the early 20th century, Albert Einstein introduced the Theory of Relativity and altered our perception of how gravity works forever. The crucial difference between Einstein’s understanding versus Newton’s theory is the belief that gravity is not a force at all. Rather, it’s a result of the curvature of space time — an imperceptible fourth dimension.
Using advanced physics and methods of observation unavailable to Newton, Einstein found that massive objects create a dimple in the space time fabric that defines our universe. These depressions in that fabric also explain why gravity has an effect on massless particles such as light.
Modern explanations of gravity
Although Einstein's Theory of Relativity is difficult to understand for most people, it is still accepted by the scientific community as the most accurate mathematical representation of gravity. In recent years, scientists have theorized the existence of gravitons, which are particles of gravity that are attracted to one another. They offer a convenient theoretical explanation of gravity, but have yet to be observed well enough to be definitive.
Another potential explanation is the existence of gravitational waves, which are theorized to be created when an object is accelerated. Again, while the math adds up, there is not enough observational evidence of these waves for them to become accepted as fact.
While we may not yet know exactly how gravity works, we know that it is there and we know that it is complex. Like many of the great scientific endeavors of humanity, the pursuit of that knowledge has helped us learn more about our world than even Isaac Newton imagined.