Dr Karl

Welcome.

It began several thousand years ago with various cultures around the world, ranging from Europe all the way across to China and down into Africa, looking at the stars at night and noticing that those little objects in the sky, some of them moved but most of them did not.

And then they started doing measurements with observatories where they'd have a bunch of sticks in the ground or a building and these are open-air astronomical observatories but with no telescopes as such.

And they just sort of have these two sticks and line them up and say, oh, that thing's moved over there, now it's moved back again.

And then that body of knowledge began to accumulate more and more and

And by the time you get to the 1600s in Europe, we've worked out that if you get some glass or two bits of glass, you can make a telescope and make much more accurate measurements.

So we started getting numbers coming back.

And then around 1666, 65, a couple of things happened in the United Kingdom.

The Great Plague came through, which killed about one third of everybody and there was a Great Fire of London and Isaac Newton, who was one of the great mega brains, was stuck on his farm just trying to keep alive and he was thinking about things and he came up with his law of gravity and it's a remarkably simple equation.

It's not 100% correct.

Einstein had to do a few modifications to it, but not many.

But it was... And from that, and the formula is that the force between two objects of a certain mass is G, which is a gravitational constant, M1 multiplied by M2, so the mass of, say, the Sun, the mass of the Earth, divided by their distance squared.

And that remarkably simple formula, if you then go and apply it through to the different planets one at a time in the solar system and then the different moons...

everything works out.

So it comes from Newton and his law of gravitation, and then Einstein had to come and do a modification in 1915.

Does that kind of get you started, how he worked it out-ish?

Yeah, so the definition of a genius is that they're the sort of person who can look at something that the rest of us look at and they see something different.

So Einstein looks down a microscope and then realises that atoms have to exist.

So there are these people who are just incredibly different from us and I love them to pieces and Newton was one of those.

Thank you, Dr. Zara.