An Introduction to Gravitation in Physics
DownloadThe gravitational force (also known as gravitation) is one of the four fundamental forces in physics and is responsible for the attraction between objects. In fact, every mass has an associated gravitational field that exerts an attractive force on other masses and pulls them toward each other. This phenomenon was first discovered by Isaac Newton, after which it was then extended upon by Albert Einstein’s theory of general relativity, explaining how gravity can affect the curvature of space-time itself. This blog post will take you through an introduction to gravitation in physics, its applications and how it works.
Assumptions of the Equivalence Principle
In Newtonian physics, gravitational attraction is presumed to be an instantaneous action at a distance between two bodies. In other words, both objects would feel a pull from each other as soon as they were close enough for gravity's effects on space-time itself (rather than any sort of interaction between them) to be felt. However, because it is impossible to detect that space-time has been affected by something (like gravity), we instead use action at a distance for all interactions of gravity until we can build a theory that explains it more thoroughly. That's one reason Einstein had such trouble with Newtonian physics - it assumes so much without explaining why or how.
The Equivalence Principle
One of Einstein’s greatest contributions to physics was his realization that gravity and acceleration are one and the same. Here, we explore how much Newtonian gravitation is a manifestation of accelerated motion. One of Einstein’s greatest contributions to physics was his realization that gravity and acceleration are one and the same. Here, we explore how much Newtonian gravitation is a manifestation of accelerated motion. The reason physicists can call accelerating an object gravitational is because both phenomena obey what's known as Newton's second law: F = ma, or force equals mass times acceleration.
Newton's Law of Universal Gravitation
The Law of Universal Gravitation is a physical law that states that every particle attracts every other particle in the universe with a force that is directly proportional to the product of their masses and inversely proportional to the square of their distance apart. This formula also works for Jupiter and all its moons, or between you and any other person (if you are big enough). It explains why objects fall on Earth, why planets orbit suns, and why galaxies move. It's one of three fundamental forces (along with electromagnetism and weak nuclear force) that shape our universe.
Einstein's General Theory of Relativity
To paraphrase Albert Einstein, Everything is relative, but gravity isn’t. General relativity describes gravitation—the force that attracts objects toward one another. In general relativity, gravity isn’t a force at all; it’s actually a manifestation of spacetime curvature (how much space bends and curves around an object) caused by mass. The more massive an object is, or the more matter it contains, the greater its gravitational pull.