Why does gravity pull us down instead of up?
Gravity is the reason objects with mass or energy are attracted to each other. This is why apples fall to the ground and why planets revolve around stars.
Magnets attract some types of metals, but can also repel others. So why do we only feel gravity?
In 1915, Albert Einstein discovered the answer with his general theory of relativity. The reason gravity pulls you to the ground is because any object with Earth-like mass actually bends or curves the fabric of the universe called space-time. That curvature is what is felt as gravity.
What is space-time?
Before we get into the complex world of gravity, we need to understand space-time.
As the name suggests, spacetime is a combination of the three dimensions of space (length, width, and height) and the fourth dimension (time). Using exceptional mathematics, Einstein was the first to realize that the laws of physics operate in the universe. space and time merge.
What this means is that space and time are connected. When you move very quickly through space, time moves more slowly than for someone who is moving slowly. This is why astronauts travel so fast through space. Aging a little slower than people on Earth.
Matter does not create gravitational hills, but gravitational springs.
Recall that gravity is the idea that objects in the universe are attracted to each other because space-time is curved and curved. When Einstein came up with the theory of general relativity, he showed that all objects in the universe can bend space-time. In physics terminology, matter is mass and energy.
Your brain normally thinks of the world in three dimensions, so it’s very difficult to think of the four dimensions of space-time as a single idea. To help you visualize it, imagine the surface of a trampoline. If nothing is placed on it, it is flat. However, when you stand on a trampoline, the trampoline stretches out beneath your feet, creating a valley around you. When a ball is on the trampoline, it will roll towards your feet.
This is a two-dimensional example of how space-time works. Your mass stretched the trampoline, creating a so-called gravity well into which the ball would roll. This is very similar to the way the gravity of a heavy object like the Earth pulls things like you and me towards it.
Even more strangely, space and time are connected. Time is also stretched by heavy objects.!
In the movie “Interstellar”, the characters go to a planet close to Earth. Black HoleAnd while there, they age more slowly than others.
The heavier the weight, the steeper the sides of the trampoline will be. This is why really huge objects in the universe, such as the sun and black holes, have stronger gravity than Earth.
So why does gravity pull you down instead of pushing you away?
Imagine someone gets under a trampoline and gets pushed up. The ball rolls away! This would be a gravity hill, not a gravity well. As far as scientists know, matter, or objects, always create gravity wells, but not gravity hills. Scientists can imagine something made of exotic matter or energy that would force gravity to push you into space, but so far they have discovered nothing that would force gravity to push you away from Earth. There are no people.
Written by Mario Borunda, Associate Professor of Physics, Oklahoma State University.
Adapted from an article originally published in conversation.