In this world of rapidly advancing science, it can be easy to get swept up by it all and start believing that we know everything and can do anything. This isn’t a new phenomenon- scientists have been predicting that we will achieve functional immortality sometime in the near future for decades, and they’re still saying it, even though we still have no idea how to even begin with that. So it’s good to remember the things that we don’t know, that we don’t understand and just can’t explain no matter how hard we try. We might find out an answer eventually- given enough time to research, hard-working scientists will come up with an explanation eventually- but for now, plenty of things remain mysteries.

Like Gravity. And everything that it does.

Isaac Newton surely wasn’t the first person to observe that gravity exists, but he was the first person to formulate it, document it, and determine exactly what it does. That was a little less than four centuries ago, and while our knowledge of what gravity does continues to grow significantly, we still have absolutely no clue about why or how.

And that’s just the start of it. According to the best model of physics we have, there are four types of forces in the universe which drive pretty much everything that ever happens, has ever happened, and will ever happen. Gravity is just one of them, and the weakest of them all. You need very enormous objects, relatively speaking, even to see gravity happening. The other forces are so powerful that they act on atoms themselves, instead of just large clusters of them. They are Strong Nuclear Force, Weak Nuclear Force, and Electromagnetic Force.

So what causes all of these? Well, we’re still not sure, though we’ve got a slightly better idea of it than gravity. The Strong and Weak nuclear forces appear to be caused by protons (teeny tiny pieces of matter, which make up atoms) and quarks (even tinier pieces of matter, which make up protons) interacting with each other in specific ways.

Electromagnetic force is even easier to explain, because it’s caused by specific particles unique to it: photons. Basically, it’s light (and also heat and radio waves and everything else you think of when you think “energy”. It’s complicated.)

Gravity, on the other hand, doesn’t seem to be caused by anything at all. It just happens, and continues to happen, no matter what other things the tiny amounts of space particles are doing. There isn’t a specific action we can point to as a cause for gravity. For a while, theorists pushed around the idea of a particle called a “graviton” or “gravitron”, but in over a hundred years of poking around in the sub-atomic world we haven’t even seen the tiniest hint of something like that. Besides, that just makes it worse. If gravity is caused by particles, are those particles also acted upon by gravity? After all, everything with mass is affected by gravity. So that explanation just led to more headache, and eventually fell apart.

The point is, nobody has any clue why gravity happens. We can explain exactly what it does, with incredible accuracy- if we couldn’t, we wouldn’t be able to launch spaceships and probes with the incredible precision that we can, or predict the movements of stars and planets. But despite four centuries of research, we just have no clue what actually causes it. But that doesn’t mean physicists have given up, and soon- maybe very soon- we might finally have an answer.