Why does gravity pull us down and never up?
Gravity is the explanation issues with mass or vitality are attracted to one another. It’s why apples fall towards the bottom and planets orbit stars.
Magnets appeal to some forms of metals, however they will additionally push different magnets away. So how come you are feeling solely the pull of gravity?
In 1915, Albert Einstein discovered the reply when he revealed his principle of basic relativity. The explanation gravity pulls you towards the bottom is that every one objects with mass, like our Earth, really bend and curve the material of the universe, referred to as spacetime. That curvature is what you are feeling as gravity.
What Is Spacetime?
Earlier than moving into the sophisticated world of gravity, you should perceive spacetime.
Spacetime is precisely what it appears like: the three dimensions of house – size, width, and top – mixed with the fourth dimension – time. Utilizing some very good math, Einstein was the primary individual to appreciate that the legal guidelines of physics work in a universe the place house and time are merged collectively.
What this implies is that house and time are linked – for those who transfer actually quick via house, time slows down for you in comparison with somebody who’s transferring slowly. That is why astronauts – who’re transferring very quick in house – age a tiny bit extra slowly than individuals on Earth.
Matter Makes Gravity Wells, Not Gravity Hills
Keep in mind, gravity is the concept objects within the universe are attracted to one another as a result of spacetime is bent and curved. When Einstein got here up with basic relativity, he confirmed that every one stuff within the universe can curve spacetime – in physics phrases that stuff is mass and vitality.
Since your mind normally thinks concerning the world in three dimensions, it’s actually exhausting to consider the 4 dimensions of spacetime as a single concept. So to make it simpler to visualise, think about the floor of a trampoline. If there may be nothing on it, it’s flat. However for those who stand on the trampoline, it stretches round your ft and creates a valley with you on the middle. If there’s a ball on the trampoline, it will roll towards your ft.
It is a two-dimensional instance of how spacetime works. Your mass stretched the trampoline, creating what is known as a gravity effectively that the ball rolls into. That is similar to how the gravity of a heavy object – just like the Earth – pulls issues such as you and me towards it.
To make issues even weirder, since house and time are linked, time can also be stretched by heavy objects!
Within the film ‘Interstellar,’ the characters go to a planet near a black gap, and whereas they’re there, they age slower than everybody else.
The heavier you might be, the steeper the perimeters of the trampoline effectively. That’s the reason actually large issues within the universe – just like the Solar or black holes – have stronger gravity than Earth.
So why does gravity pull you down and never push you away?
Think about somebody went underneath the trampoline and pushed up. The ball would roll away! This may be a gravity hill, not a gravity effectively. So far as scientists know, matter – or stuff – at all times makes gravity wells and never gravity hills. Scientists can think about issues fabricated from unique matter or vitality that may trigger gravity to push you off into house, however to date, nobody has discovered something that would trigger gravity to push you away from Earth.
Written by Mario Borunda, Affiliate Professor of Physics, Oklahoma State College.
Tailored from an article initially revealed in The Dialog.