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Geocentric Thinkers and Heliocentric Theory in the History of Astronomy (Ptolemy and More Models)

Stephanie is a student who enjoys accumulating books and recipes. She wants to be a Wizard when she grows up.

constellations and mythology

constellations and mythology

People have always wondered about the heavens.

Before civilizations developed enough for people to sit down and really think about tough questions, humans came up with complex mythologies to explain the miraculous world we inhabit. It wasn't until the greatest civilizations developed institutions for knowledge and discovery that people began to mix scientific observation in with their cultural beliefs.

Up until the Enlightenment, Astrology and Astronomy were one and the same. It took a few very dedicated people to lead the way to our modern beliefs about the universe, which tie in so closely to our view of ourselves, religion, and God.

Here are the [abridged] stories of some of these people and their ideas that made our modern world possible.

Claudius Ptolemy, as imagined by a Baroque artist.

Claudius Ptolemy, as imagined by a Baroque artist.

Geocentric Theory.

This theory states that the Earth is the center of everything . It makes sense-- If the Earth moved, wouldn't we would feel that movement?

Claudius Ptolemy, a Roman-Egyptian astronomer from the first century, was a chief proponent of the geocentric model, and believed in something that Plato coined as quintessence. Quintessence, or ether, is basically the heavenly stuff that the cosmos are made of, which was taken very seriously in the science community in the Middle Ages. Nowadays, the poetic word quintessence is used to describe the (hypothetical) "dark" energy that is believed to propel the expansion of the universe.

But back to the point.

Ptolemy saw the universe as a series of domes that surrounded the Earth. Each dome contained a heavenly object-- the moon had a dome, the sun had a dome, and each of the known planets had a dome. Eventually, Ptolemy's theory had 88 domes and explained retrograde. But there was a problem...as science advanced and we humans started discovering more and more things circling around in the sky, this theory got way too complicated, leading to it being discredited.

Ptolemy's geocentric theory, the Ptolemaic model.

Ptolemy's geocentric theory, the Ptolemaic model.

Nicolaus Copernicus, or Nikolaur Kopernikus, proponent of the Heliocentric theory,

Nicolaus Copernicus, or Nikolaur Kopernikus, proponent of the Heliocentric theory,

Heliocentric theory.

Heliocentric theory states that the sun is at the center of everything . The radical idea that the Earth revolved around the sun was proposed by a brave astronomer during the 3rd century, but the idea was thrown out by his peers.

The Heliocentric model is truly a development of the renaissance, and was presented by Nicolaus Copernicus, a Polish monk. The funny thing is, this guy didn't even care that much for astronomy- he saw it more as a hobby and focused on math, art, and linguistics. However, he went down in history for sparking the Copernican Revolution, and ideological shift away from Ptolemy's model. His heliocentric theory would later be supported by such great thinkers as Galileo Galilei and Isaac Newton.

heliocentric theory

heliocentric theory

Johannes Kepler, who came up with the Laws of Planetary Motion

Johannes Kepler, who came up with the Laws of Planetary Motion

Joannes Kepler and the Laws of Planetary Motion.

This guy was hired to calculate the orbit of Mars based on a circular model of planetary orbit. Kepler worked on this, but had so much trouble fitting Mars' orbit into this model that he abandoned it, and came up with 3 revolutionary laws of planets in movement.

His first law is the Law of Ellipses. This states that planets travel around the sun in ellipses . What the heck is an ellipse? I could give you the physics textbook definition, but I want you to keep reading, so let me try to explain in plain English.

An elipse is a curve that gets interrupted, but still closes up again. Since it's interrupted, it doesn't form a perfect circle when it closes.

Think of that game, tether ball. The ball goes all the way around the pole, but because of its speed and the pull of the rope, it doesn't form a perfect circle. It forms more of an oval. The path of the ball around the pole is an ellipse. This is similar to the path of planets around the sun.

Tether ball

Tether ball

Drawing an ellipse with two pins, string, and a pencil.

Drawing an ellipse with two pins, string, and a pencil.

As you see here, the ellipse is a closed curve with two center points. In planetary motion, the sun is one of these points.

Second law: A planet moves faster when it is closer to the sun, slower when it is far.

This observation was a true breakthrough in understanding how gravity works, and helped to lay the foundation for Isaac Newton's revolutionary theories.

Take a look at the illustration below, which attempts to demonstrate the effects of gravity. Imagine a penny rolling around inside a circular sink. As the penny gets closer to the drain, it speeds up.

The Earth's gravitational pull, Kepler's Laws of Planetary Motion

The Earth's gravitational pull, Kepler's Laws of Planetary Motion

Third law: the distance from the sun to a planet^3 is equal to the period^2 of the...uhhh???

Ok look. Take the average distance between the sun and any planet and cube it. The number you come up with is the same as the time it takes that planet to revolve around the sun squared.

Creepy? I guess so.

One side note about Kepler...his mom was put on trial for being a witch, and imprisoned for over a year before the charges were dropped!

You can't write about the history of astronomy without mentioning Galileo.

The famous and beloved Galileo Galilei was a contemporary of Kepler. It is a common misconception that Galileo invented the telescope, but this is not true. However, he did take the marine telescope, which was commonly used by sailors, and used it to see things in the sky. He discovered that Jupiter had moons revolving around it, which he likened to a mini solar system. This discovery was another blow against Ptolemy's geocentric theory, which was supported by the church at the time.

Galileo also observed sunspots, and was the first person to conclude that the Milky Way was in fact a big collection of stars.

And weird mathematical relationships between planets and orbits and the like aren't the only creepy things going on here! Galileo died in January, 1642. In December of that same year, Isaac Newton was born. Just as spine-tingling as the ideas these guys came up with!

Tito Lessi, Galileo and Viviani

Tito Lessi, Galileo and Viviani

Urbain le Verrier, who calculated the existence of Neptune.

Urbain le Verrier, who calculated the existence of Neptune.

The guy who guessed that Neptune existed.

This dashing French fellow on the right actually predicted the existence of Neptune ( ok, so he didn't exactly guess). This was before anyone ever observed Neptune in the sky. He actually calculated this by studying irregularities in Uranus' orbit. He concluded that these interruptions must be the result of another planet whose gravity was pulling on Neptune. If you ask me, this guy has earned a place in history.

Of course, there have been many more.

I'm leaving out obvious characters, like Isaac Newton and Albert Einstein, who have contributed loads to the science of astronomy. But I'm also leaving out many others who are not so well-known, but whose ideas became the foundations of modern science.

All photos were taken from Wikimedia commons.

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Stephanie Das (author) from Miami, US on November 08, 2012:

@cclitgirl- Yea, I think lots of people learn about astronomy when they are very young, and some of it sticks and some of it doesn't. I think its fun to learn about people's visions of the world anyway. Thanks for the comment!

Cynthia Calhoun from Western NC on October 02, 2012:

Interesting hub on the history of astronomy. I learned about many of these people in school, but it's great to get a refresher. I forgot about how people thought about heliocentric concepts and I didn't know Ptolemy thought of celestial objects that had domes - no wonder that theory got discredited. Thanks for sharing this. Voted and tweeted.

Stephanie Das (author) from Miami, US on May 30, 2012:

Hey Civil War Bob,

I'm glad you enjoyed the hub...it is certainly a fun topic to ponder, and I love to think about how people came up with these ideas in the first place. Thank you for the comment, also, the dog hangs with me while I do my own stargazing. :)

Civil War Bob from Glenside, Pennsylvania on March 02, 2012:

Well done hub, stephaniedas. You started my thinking on various aspects of astronomy that I haven't considered since my high school days back in the 60s. Great photo of the dog, too!

Stephanie Das (author) from Miami, US on February 25, 2012:

Hi Astraveda,

That is an awesome question, though I'm not sure I have an answer for you. I have always found my info from books and magazines, so I don't know much about the online astronomy world. If you could find that information anywhere, ti would be on the NASA website, though. Seems like a pretty difficult thing to figure out, as scientists still haven't mapped out all of the universe. Write bac if you figure something out!

ASTRADEVA on February 20, 2012:

what can you tell me of the timelines of the epochs of time, i.e. where we were in the galaxy at a certain (earth)time, is there a web address concerning this topic,


Stephanie Das (author) from Miami, US on January 22, 2012:

So true! We owe it to our ancestors that we have been able to advance as far as we have, and every day we lay the foundation for the future, whether they be positive or negative. What a great comment!

Carinae Majoris from London, United Kingdom on January 13, 2012:

This is the testament to human thought. Humans never come up with the correct theory straight away, but after years and years of careful deliberation, we can now conclude we are part of a heliocentric model. Brilliant!

Stephanie Das (author) from Miami, US on September 28, 2011:

I know, you look at the evidence they had and it's like, "Wow, this guy was a genius!". I think its incredible when someone can come up with something that everyone else thinks is foolish and promote it, like Copernicus and Galileo did.

Christopher Wanamaker from Arizona on September 28, 2011:

It's really amazing to think about these scientists and the things they were able to come up with using only primitive instruments and observation. I love ready about this stuff.