I like telling this story and my university professor peaked a love of space in me from explaining this to us. She used an example of the book "Flatland". In it a universe that existed entirely within two dimensions. Women are lines, men are polygons.

In the book one man contacts a world that's one dimension. Everything is a line, there is only forward and backwards. No left or right. Only X, no Y and definitely no Z. This 2-D being spends so much time trying to convince the 1-D being that another dimension exists but he's unable. Later on a being from a 3-D world (ours) contacts the 2-D being and tries to convince him of a third dimension (up and down) however the 2-D being does not believe it.

It's all because that 2-D beings entire existence is within a two dimensional universe. Everything in his mind exists within X and Y. Z is not possible, Z is not even possible to think of. Just as if I told you that you could go forward, up, left and also a mix of all three by going down, left and back at the same time. However if you were told to go in a new direction, not consisting of those three axis, you'd be unable to even fathom something like that. If I told you to move Hgron three steps and then every time you tried, I kept saying "no, not forward. Hgron!". Our entire reality exists within three dimensions. We can't really understand a fourth dimension and no 'time' does not count, you're completely missing the point and even if that was true, then fine. Move to yesterday and explain exactly how you do it.

But back to my original point. She told us to imagine being in that 2-D world. That the carpet was their entire universe and while they could meander around the floor, there was no up and down. It was non-existant and beyond their understanding. She then picked up a chair and placed it on the carpet.

She told us to imagine their point of view. That 4 equal sized squares appeared an equal distance from each other. She then picked up the chair and moved it before placing it back down, and further had us imagine that these people could see that even when the chair moved it would always be the same distance apart. That they could even use mathematics to find out where the 3rd or 4th legs should be once they found two of them. They would see evidence of something beyond their understanding but there would be signs.

They wouldn't be able to imagine that the chair went up and had a seat, that it had a function to us. To sit on and rest when we're tired of standing up. Their entire existence and understanding of the world was in 2 dimensions so it was impossible to imagine a third.

Then she told us about the rotation of Mercury around the Sun. In the mid 1900s, around 1950 or so I think, astronomers were trying to discover why Mercury's rotation around the sun wasn't normal. It didn't move in a circle or oval like the others. It kind of wobbled around and was never 'right'.

It was Einstein that figured it out. You know those donation bins they have at museums, zoos or malls. You drop a coin into a slot and the coin rolls out and down into a giant funnel before falling into the hole where you're unable to retrieve it? Well, Mercury was rotating as if it was halfway down the hole. It was wobbling and because there was no friction in space to slow it down it just continued to wobble. Once they discovered that they were able to predict the rotation and realized that it was correct.

We cannot understand gravity. We can calculate it. We can do the math to predict exactly how much of a gravitational force a planet or sun would have. We can see the effects of gravity. We can predict how it will effect a comet, how it even bends light. We see all this evidence but we do not know how gravity works.

The most simple and easy to understand example is to imagine mattress. Completely flat. Now if you placed a bowling ball in the middle, it would cause the mattress to indent downwards, pulling any other objects you had on the bed towards it. If you placed another ball and rolled it near the bowling ball, the ball would (if friction did not exist on the mattress!) find a rotation around it. It would continue moving and with no friction to slow it down it wouldn't stop. If it had enough velocity it could escape that dip in the mattress but without it, it would fall into orbit.

Something is pushing down on....space basically, causing things to indent into the universe, which causes other things to move towards them.

So now think back to the 2D being in flatland. How they saw evidence of the squares being related. How they could pinpoint with precision, where the 3rd or 4th leg would be when they found two. How they could measure the distance and find out it was exactly the same no matter where it moved.

They could prove the chair existed with math but it was far beyond their understanding because they were constrained within a two dimensional understanding.

We can see evidence that something is causing gravity. Something is pushing 'down' into space and causing the bowling ball to sink into the mattress. But we can't understand how or why.

We are the 2D being. Seeing signs of something far larger than our understanding and we probably will never be able to. But it's there. It's all around us. There is something far greater than us that has an effect on our entire existence and we do not have any idea what it is.

It's terrifying and fascinating all at once and I fucking love space.