In Medieval Europe, the physical universe could be divided into two parts: the Earth and earthly events (chaotic and temporary) and the heavens (structured and eternal). That’s a bit of an over simplification, but the idea was that the Earth and heavens were governed by different rules. In the heavens the stars were fixed and eternal. The motion of the planets were thought to move in circles about the fixed Earth, as did the Sun and Moon. The heavens were ordered and could be described through geometry. Earth, on the other hand, was plagued by weather, disease, and strife. These happened in ways no one could easily predict. Some things, such time and the seasons, could be determined, but then these were determined by the regular motions of the heavens.
Two things changed this view. The first was rise of accurate astronomical measurements. As astronomers grew more skilled it became clear that the motions of the planets were not simple, nor circular. The stars were not fixed and permanent. Even the Earth was found to be just another planet, and it orbited the Sun with all the others. The second was the rise of the physical sciences. Newton gave us an understanding of motion as it applied on Earth, and this was followed a growing understanding of chemistry, thermodynamics, and electromagnetism. We began to understand the rules that governed physical phenomena here on Earth, and over time we could see that the same rules applied to the heavens.
This led to our modern view of the universe, that the rules governing physical phenomena are universal. In other words the scientific laws and theories we develop through experiments here and now apply throughout the cosmos. We are not limited to astronomy alone. We don’t simply observe the heavens and wonder. We can take our celestial observations and combine them with our observations of earthly physics to truly know what is out there. Galaxies, black holes, supernova, planets. We know they exist, and we know what they are. We can prove it.
Recently an image traversed the net under the phrase “rules to live by”. As seen below, it lists six fundamental scientific equations. The image gives a summary of each, but I’ll list my own summary here:
1. Mass and energy are intimately connected.
2. Gravity is heavy.
3. What you see depends upon your point of view.
4. Magnets, how do they work?
5. Black holes have a fever.
6. Everything happens at a cost.
To understand the universe it is useful to gain an understanding of each of these rules. So over the next six days we’ll explore each of these equations in turn. What they say, what they mean, and what they tell us about the universe.
We’ll start with the first one. It’s Einstein’s most famous equation. It changed the political landscape of the world, and it gave us a true understanding of the stars. But to hear that story, you’ll have to tune in next time.