Oh, oh, oh, oh, oh, oh, oh, oh, oh, hey.

Oh, my life.

Oh, wow. Hello and welcome to the Science of Everything podcast. I'm your host James Fodor. In this podcast, I discuss a wide variety of topics in both the natural and social sciences exploring the many fascinating insights that the scientific method yields about the world around us. Now, the topic for the first episode this week is explaining gravity. So in this episode, I want to look at first the historical background about different theories

of gravity before moving on to explaining Newton's theory of gravity.

And then we'll look at how orbits work, the topic about gravity in space and on the moon,

etc. And finally, we'll have a bit of a look at the tides.

So let's dive into it.

Now, theories about gravity basically go back to the times of the ancient Greeks.

According to ancient Greek, they didn't really have a concept of gravity like we do today as a force, they believed that all objects in the

universe or on earth were made up of four different elements and that different elements had

different natural tendencies to go in different directions. So, for example, fire had a natural

tendency to go upwards, seek the heavens, so to speak. And so if an object had lots of fire

in it, it would tend to go upwards. Whereas if an object had lots of earth in it, it would tend to

sink downwards. And the ancient Greeks also believed that the circle was sort of a perfect form,

a perfect shape. And so circular motion at a constant speed was sort of seen to be perfection,

sort of the universal and natural form of motion.

And so it was believed that all the planets had a circular orbit around the Earth.

And that idea of a geocentric universe was put forth by Aristotle, and later on it was

sort of codified and consolidated in the Ptolemaic model.

Ptolemy lived in, I think, the second century AD, or might have been the first century, and he adopted basically an

Aristotelian worldview of gravity in the orbits, except that more accurate observations of the

planets had showed that there was a phenomenon called retrograde motion. Basically, that means that normally the planets had showed that there was a phenomenon called a phenomenon called retrograde motion.

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