# The Sun-Centered Solar System and Other Baloney

21 October 2013 by Troy McConaghy, posted in Astronomy

The standard story learned by schoolchildren is that Ptolemy (c. 90–168 CE) thought the Earth was the center of the universe, and everyone agreed, for a long time. Then in 1543, Copernicus came along, said the Sun is at the center, and almost everyone changed their mind, although it took a while.

Copernicus

Well, that's baloney.

For starters, there were some ancients who thought the Sun was at the center. Aristarchus of Samos (c. 310–230 BCE) was one.

Moreover, it's completely okay (i.e. not wrong) to say that the center of the universe is at the center of the Earth. Mathematically, we'd put the origin of our coordinate system at the Earth's center of mass. We could make graphs showing how the positions of the Sun, planets, and stars change over time, in our Earth-centered coordinate system. In fact, people who design Earth-orbiting space missions often do exactly that. It's convenient because near the Earth, the main forces are the gravity of the Earth and atmospheric drag. Other forces, like the gravity of the Sun, or the gravity of the Moon, can be treated as small extras, to be worried-about later, if at all.

If you're studying the motions of the Sun and the planets, then you might put the origin of your coordinates at the center of the Sun, but the math gets complicated. It's easier if you put the origin at the center of mass of the entire system (Sun, Jupiter, Saturn, Earth, etc.).

If you're studying the motions of the stars in the Milky Way galaxy, then you might put your origin at the center of the galaxy.

In general, you can put the origin of your coordinate system anywhere at all. There's no wrong place. There are just more- or less-convenient places, depending on what you're doing. You can put it on the peak of Mount Everest for all I care. In fact, you might even attach it to a spacecraft that travels around the solar system. Why not?

To be fair, Copernicus' idea was more than a mathematical trick. It was a questioning of Earth's central place in the universe. The Earth isn't at the center? Humanity isn't in a special place? It was a big change. It made lots of people unhappy.

Rant complete. Carry on.

### References and Suggested Further Reading

The Cambridge Concise History of Astronomy, edited by Michael Hoskin.

### Image Sources

The image is of the painting  Astronomer Copernicus, conversation with God by Jan Matejko. It's public domain. It was at the Jagiellonian University Museum in Kraków, Poland.

Outer Spacing is a blog about space exploration and development. It's written by Troy McConaghy (@TroyMc on Twitter).

## 5 Responses to “The Sun-Centered Solar System and Other Baloney”

Focus on solar system formation. It was a big rotating cloud, where earth, along with other planets, formed gathering grain of dust by grain of dust. Many particles spiraled in the center due to gravitational pull (of the sun-to-be), and many others dindn't. Particles didn't spiraled in into earth, but into the sun. It might be a math trick, but there's some physics behind it too.

(correct me if I'm wrong)
Thanks,
M

Lots of particles, asteroids and comets crashed into the Earth, and they continue to do so. They also crash into Jupiter, the Moon, and so on.

The Sun *is* the most massive thing in the Solar System, but not because it was "at the center." Something had to become the most massive thing.

Astronomy makes me humble in a way no grand organized religion built on superstition ever could. Haldane said it best- "The Universe is not only queerer than we suppose, but queerer than we can suppose."