What goes up must come down. It's certainly true on Earth. On Earth, gravity is a constant influence on our lives. Unfortunately, with gravity being constant it affects us even when we don’t want it to. You know, those times when you trip and belly flop into the pool in front of the entire PE class. Or is that just me? What goes up must come down, so I suppose it is time to lead you down the black hole that is gravity.
Gravity is a force. A force is anything that can alter the velocity of an object. However, gravity is not any old force. Gravity is one of the four fundamental forces. Just to make sure you understand the gravity of this situation, gravity, along with the other 3 fundamental forces, governs how all particles and objects in the universe interact. While gravity is the weakest of the four fundamental forces, gravity is a big deal; it stretches across billions of miles and holds the cosmos together. Without gravity, the universe would just be lukewarm cosmic soup. Despite its lack of strength, gravity is a powerful force especially on a cosmic scale as it is always attractive. Gravity always pulls mass together. Gravity lacks a negative version. Anti-gravity does not exist. Gravity never cancels itself out, thus it is easily observable across large distances.
Newton’s theory of gravitation
If gravity is always attractive, how come we don’t just stick to each other like magnets? The answer lies within Newton’s theory of gravitation. The force of gravity between two objects can be calculated through the equation shown above. The force of gravity is denoted as F. The masses of the two objects are denoted as m1 and m2, and the distance between the centers of both objects is r. Okay, not too hard, it’s still simpler than the quadratic formula, but what is that capital G? That G is used to represent the universal gravitational constant. It equals 6.67408 × 10-11 assuming you are working with SI units. The gravitational constant is infinitesimally small. On Earth, it is almost impossible to see gravity’s effect on two objects with the naked eye, unless the objects have large masses. Compared to the force of gravity between you and the Earth, the attraction between you and your friend is practically nothing. In the void of space, large masses are few and far between. Just two atoms, stuck together by gravity, can eventually form a planet, a star, or even a black hole, although it may take a while.
When we first theorized the existence of black holes, we regarded them as impossible, just a quirk in our understanding of physics, but as time passed we realized that black holes are an important part of our expanding universe. Black holes are regions where gravity is so strong that nothing, not even light, can escape. A black hole is created when an object collapses and is compressed to a radius smaller than its Schwarzschild radius. The Schwarzschild radius is the minimum radius a sphere with a known mass needs to become a black hole. Yes, even a feather can become a black hole if it is compressed hard enough. In reality, feathers do not spontaneously collapse and become black holes (I hope not, at least). However, stars collapse when they run out of fuel. As a star collapses, it shrinks. Once it shrinks too much it becomes a black hole. The general rule of thumb is that any star with a solar mass greater than 2-3 solar masses will collapse into a black hole, where one solar mass is the mass of the Sun.
While it may seem as if we know everything there is to know about gravity, the truth is that we know almost nothing. Gravity is a concept we are only beginning to understand. When James Clerk Maxwell unified electricity and magnetism, he changed the world. Maxwell’s equations allowed us to bend electricity and magnetism to our will. Without them, you wouldn’t have a device to read this article, and the Internet would be a dream that died long before it was conceptualized. In 200 years, human society will think of us as oblivious little children, who could barely grasp the concepts we are dreaming of. Maybe one day we will fully understand gravity and learn to bend gravity to our will, as our ancestors learned to bend electricity to theirs. All we can do for now is to continue exploring gravity in the search for the next big breakthrough.
Gravity is a concept that stretches the human mind like a black hole stretches the fabric of space-time. We’ve only scratched the tip of the stellar nebula that is gravity. Many of our theories are just partial, they work in some cases, but break down in others. Every discovery, every theory, every hypothesis, even if wrong, brings us closer to understanding gravity, and by extension, the nature of our universe.
Post By: Armaan G.
Photo credits: ESO/L. Calçada/M.Kornmesser, CC BY 4.0 <https://creativecommons.org/licenses/by/4.0>, via Wikimedia Commons
Sources:
5) A Brief History Of Time, Stephen Hawking