Most of the Universe is pretty empty — that’s why we call it “space” — Lol, sounds literal right? But most of us have not thought about it that way.
If I were to magically transport you someplace randomly in the cosmos, the chances are you’d be a million light years from the nearest substantial object. Evolving on a planet has warped our sense of physics. If I throw an object away from me, it comes back. That’s bizarre! It should just keep going, moving away from me at a constant speed. Instead though it goes up, slows, stops, then falls back down toward me.
The difference between living on a planet and being in deep space is gravity. Gravity from an object goes on forever, but it gets weaker rapidly with distance. A zillion light years away, the Earth’s gravity is fantastically weak, but here on Earth it’s literally a force to be reckoned with. And in some places it can be a lot stronger than what we experience right here. For most of history, gravity was just a fact of life, neither understood nor examined terribly closely.
In the mid 1600s, researchers like Robert Hooke and Isaac Newton began examining it utilizing math — actually, these two men got into a sharp fight over who thought of what first. Be that as it may, whoever it was who initially hit the nail on the head, now we have a vastly improved comprehension of how gravity functions.
One thing before we get to gravity.
An essential idea that surfaces a great deal is mass. It’s a bit tricky to define, but you can think of it as how much stuff makes up an object. I know, that’s not very scientific sounding, but it’s not a bad way to think about it. Something with more mass has more stuff in it. Size doesn’t really play into this; two objects can have the same mass but one can be much larger than the other. In that case, the bigger object’s mass is more spread out, so we say it has lower density, where density is how much mass is inside a given volume.
In science terms, mass reveals to us how much a question opposes having its movement changed. A protest with more mass is harder to move than a question with less mass, which is truly clear on the off chance that you’ve at any point took a stab at pushing on a toy auto versus a genuine truck.
In any case, mass is additionally characterized utilizing gravity. Everything that has mass also has gravity and can inflict this force on another object. The amount of force you feel from the gravity of an object like a planet depends on three things:
How much mass it has?
How much mass you have?
How far away you are from it?
Distance dominates here;
the force of gravity weakens with the square of the distance. Double your distance from an object and the force of gravity drops by 2 x 2 = 4 times. Go 10 times more distant away and the compel drops by 10 x 10 = 100 times.
Gravity is likewise appealing: It can just attract things, not repulse them. In any case, how it draws in things, is the place it gets fun. In the event that I hold up a stone and let go of it, it tumbles to the ground. What might be hard to see is that it gets faster the longer it drops. Forces accelerate objects, so the longer the force acts, the more the object’s velocity changes – in this case getting faster. If I drop a rock from higher up, it’ll move faster when it hits the ground. Other forces act on moving objects, as well, like friction and air resistance, counteracting gravity, making this acceleration hard to see. But in space, the force of gravity becomes very clear.
Two objects that have mass will attract each other. If there are no other forces acting on them, they’ll accelerate toward each other until they meet. Remember, though, that the force of gravity depends on those masses. If one is really massive, and the other not so much, then in more practical terms the massive one will pull in the less massive one. The more massive one does move, but much less than the other one.
When objects are free to move under the effects of gravity, we say they are in orbit. The simplest kind of orbit may not be what you think: It’s actually just a line! When you drop a rock, it’s very briefly in orbit. Ignoring things like the Earth’s rotation (which adds a bit of sideways motion) it’s close enough to say the rock just falls straight down, and is stopped because the Earth itself gets in the way. That’s not a terribly interesting orbit!
So what if, instead of dropping the rock, we throw it? That gives it a little bit of sideways motion, so instead of hitting the ground at my feet, it hits a bit farther away. If I throw it harder, it moves horizontally even more before it hits.