So, you think you know what gravity is?
That lovely, simple, embracing thing called gravity.
So simple to understand. I mean, it is a force of attraction, the bigger something is, the more gravity it has.
Drop an apple and it falls to the ground every…. single….. time.
You know it.
I know it.
So why on Earth did I think it was a good idea to learn a bit more about it?
WHY DID I DO THAT?
This post comes with a warning…. If you want to think gravity is that wonderfully simple force that is easy to understand, stop now, seriously, stop.
Well, I did warn you.
What is gravity?
Gravity is probably the most well known of the four fundament forces (Weak interaction, Strong Interaction, Gravity and Electromagnetism) and, ironically, the easiest to understand at a basic level.
At its base, it is a mutual attraction between two masses. This attraction is what holds planets to suns and people to planets. It is always attractive and the force it has depends on the mass of the object.
Questions were asked, such as “How did gravity interact with other things at a distance?” For example, how does the gravity of Earth interact with the gravity of the Moon.
But nobody at the time could figure that out, and since Newton’s Model was so accurate, the problem was ignored.
Problems did appear with Newton’s Law if you had more than two objects though.
It is an exceptional formula if you only have two objects like Earth and Moon, Sun and Earth, apple and Earth. But add in a third object and the application of the Law became complex, if not impossible, to solve exactly.
This meant that, while Newton’s Law was extremely good, it was incomplete.
Einstein and gravity.
He mooted that gravity was more like a bending of space. Meaning that the gaps between objects had substance and could be curved.
A tiny bit like standing on a trampoline. (When you gain the basics of the trampoline analogy, it helps with the concept of gravity. But when you learn more about gravity, you end up discovering that the trampoline analogy is terrible. But it is a good place to start)
If you have a large object on the trampoline, it bends the layer. If you roll a ball towards the object the ball follows the curves of the trampoline.
It looks like it is attracted to the object, but in fact, it was following the curves instead.
Using this concept, if you add a second object to the trampoline, like an Earth and Moon, you can roll a ball onto the trampoline and follow the path of the ball between them.
It also means that if you place a sun in the middle, then roll in an Earth, the Earth spins around the curve. With the Moon spinning around the gravity curve of the Earth.
Basically, small things move in relation to the big things.
Earth moves in relation to the Sun. Moon moves in relation to the Earth.
This means that mass tells space how to bend and space tells mass how to move.
At best, gravity is the shape of space as determined by the mass in it.
Now to the basic problem with the trampoline analogy.
Trampolines are 2D surfaces. Space is 3D.
Now you have the basic idea of space curving in 2D, here is a short video on what it looks like in 3D.
Now you understand that, lets mess you up again.
Gravity is not a force like the other forces. It is the stage that the universe stands on in a 3D way.
The stage is not fixed though. It is in continual motion, bends, warps and things move around on it.
We can’t see what Dark Matter/ Dark Energy is, our understanding of math is not detailed enough, the calculations are too massive, and the mathematical models keep breaking down because of gravity.
We also can’t test ideas either and the evidence can’t be put together. (How do you prove Dark Matter when you can’t see it? The best we can do is say that the nothing is something and we do not know what the something is, but it is there because we can’t see it).
We are trying to see it with particle accelerators, but we are unable to make them big enough. And if we did, there is always the small risk that we create a black hole on Earth. That would be very bad.
Since black holes have a lot of gravity going on around them, science is looking at them closely to learn more. Better to look at a distance when it concerns black holes.
Science attempted to give gravity a particle called a graviton, but that is not working so far. Although it would be nice if we could point to something and say “That is gravity”
If our understanding of gravity needs something to bend and the big things are invisible, why not look at the small things, like atoms.
When we do that we discover that atoms are basically very small things with large spaces around them, that we only have matter because of the forces around the atom, then what is gravity working through? Looking at small things produces the same issues as looking at big things, there is more nothing than something.
Dark Matter, even though the universe is full of the stuff, is proving a problem to see, and our understanding of gravity will remain weak until we see Dark Matter and Dark Energy.
Matter and Energy swap around, so even that is annoying.
At the moment, Dark Matter makes up about 25% of the universe, Dark Matter makes up 70% of the universe, and the rest is what we can actually see.
Then there are the ideas that atoms themselves are made of waves. Waves need something to wave through and we can’t see it.
This means that gravity is the fabric of space, and space is made of Dark Matter and Dark Energy that we have no idea on what it is.
Personally, when I explain gravity to people who ask, I stick to the trampoline first, then explain the 3D part, then talk about how the fabric of space is made mostly of Dark Matter and Dark Energy and that is what gravity appears to work through.
If more questions are asked, I end up repeating this….. “I don’t know, but it is fun not knowing”.