When you see the sun, it rises in the morning and sets at night, correct? Have you ever wondered why this process occurs?
Of course we know that the Earth orbits the sun and rotates so that we receive a sunrise and a sunset on a daily basis. For a long time, however, human civilizations had a different theory about how the universe worked. Instead of us revolving around the sun, they believed the Earth was orbited by its star.
It was a radical change to believe that the Earth wasn’t the center of the universe. The heliocentric theory is the idea that we accept as truth today: that we’re the ones who are orbiting. “Helio” means “sun” and “centric” means “at the center.”
As with many foundational scientific theories, there are multiple individuals who helped to develop what we believe to be fact today. Individuals such as Galileo, Copernicus, Aristarchus, and Kepler all contributed to this theory.
Ancient Greece and the Foundations of Heliocentric Theory
Around 270 BC, Aristarchus looked at the sun. He calculated how big the star must be and then how big the Earth would likely be. His determination? That the Earth was much smaller than the sun. Therefore, in his mind, it would not be possible for the star to be orbiting the planet. The planet had to be orbiting the star.
His work was not readily accepted by the scientific community at the time. This was because around the same time, a mathematician and astronomer named Pythagoras developed models that measured the distance from Earth to our planets with incredible accuracy. He based his mathematical models on the idea that the Earth was the center of the solar system (or universe) and since his math seemed to add up, those theories were given preference.
It would be how people viewed the universe for nearly 1,500 years. It would not be until the Renaissance when the heliocentric theory would be given another serious look.
Copernicus, The Renaissance, and the Growth of the Heliocentric Theory
Europe saw 300 years of incredible progress from about 1300 to 1600. After the Middle Ages, wealth and trade were expanding, societies were thriving, and this allowed people to focus on culture instead of self-perseverance as a top priority.
One of the unique aspects of the Renaissance is that many in Europe believed that their current civilizations had cultural roots in Rome and Greece. This caused many people to begin studying the works of the ancient scientists and philosophers. One of those who took an interest in the ancient works was a fellow named Nicholas Copernicus.
Copernicus would take the work of Aristarchus and expand upon it. In a book he published called De Revolutionibus, Copernicus proposed a model to explain the universe as he saw it. He saw the Earth revolving around the sun and offered geometric equations in order to prove the heliocentric theory was an accurate representation of how the universe worked.
Copernicus also contributed several additional ideas in his work that might seem like common sense today, but shattered the accepted ideas of his time. Here are just some of the claims that Copernicus made.
- The distance from the Earth to the sun was a shorter distance than the Earth to other stars.
- The Earth rotates around the sun, as does every other planet in our solar system.
- Not only does the Earth rotate, but it also spins on an axis that is titled.
- Both the stars and the Earth were moving at the same time.
The work of Copernicus started a revolution. Not only was his work highly regarded, but it encouraged many others to embrace astronomy. Even the Catholic Church, which held the belief that the Earth was the center of the universe at the time, didn’t condemn the work of Copernicus outright.
The Church would list the book as “restricted,” however, and it would be a designation that would last until 183=5.
Johannes Kepler and a Model of the Solar System
Born in 1571, Johannes Kepler expanded upon the work of Copernicus by bringing the entire known solar system into the heliocentric theory. Instead of just having the Earth revolve around the sun, Kepler proposed that every planet in the solar system had its own orbit.
But something wasn’t right. At the time, the idea of an orbit was circular in nature. Through the observation of the planetary positions made by others, Kepler realized that a circular orbit wasn’t possible. Once he realized this, Kepler understood that orbits were more elliptical in nature. He verified this through his own observations.
Yet his own observations showed that the orbits of the various planets were not the same. Mars, he realized, had an orbit that was less eccentric. This allowed him to calculate the elliptical orbits for all of the planets at the time and then produce an accurate model of the solar system based on the heliocentric theory.
Once the model was developed, Kepler then realized that if the sun was placed at one focus of an elliptical planetary orbit, the model matched the observations that he and others had made from the night sky. This helped Kepler to develop the laws of planetary motion, which has allowed us to this day to be able to predict and match planetary positions in our solar system and the movement of planetary bodies in other systems.
Galileo vs Catholicism: Proving the Bible and Science Could Work Together
Galileo Galilei took on those who didn’t believe in the heliocentric theory. A common point of opposition was the fact that no one had been able to observe stellar parallax at the time. By 1615, the curiosity that many had over the work of Copernicus was beginning to fade, with the Roman Inquisition eventually stating that heliocentric theory was “foolish” and “absurd.”
Galileo wouldn’t give up his views. His observations through his telescope proved to him that the Earth orbited the sun. He also observed four of the moons of Jupiter and used the work of Kepler to accurately predict their orbits around that planet. He also confirmed the eccentricity of the orbit of Mars, which could only be explained by Mars orbiting the sun instead of it orbiting the Earth.
Galileo began to teach the heliocentric theory as the only correct theory for how the universe worked. Those who believed that the geocentric theory was accurate felt threatened by this shift in perspective, including some of those at the top of the Roman Catholic Church. An investigation into the heliocentric theory was ordered.
After the Roman Inquisition, Galileo would publish a work called Dialogue Concerning the Two Chief World Systems. In his work, many within the Catholic Church felt like Galileo was attacking the Pope and the Jesuits, so he was found in suspect of heresy and told to recant.
Even when he recanted, however, Galileo reportedly said, “And yet it moves,” in defiance of the Church’s orders.
This placed Galileo under house arrest. During this time, he wrote Two New Sciences, which helped to further his observations about the universe. He would remain under house arrest for the rest of his life, ordered to read penitential psalms for years.
Eventually the work of Galileo would be vindicated and the idea that heliocentric theory and the Bible could work together was validated.
How the Heliocentric Theory Was Finally Proven
The final proof of the validity of the heliocentric theory occurred in 1838. F.W. Bessel discovered the first observed stellar parallax and, for good measure, actually found two instances. Their parallax was consistent with the orbital motion of the Earth around the sun, which then created a new debate: how close was the sun to the center of the universe?
Today we understand that the universe is incredibly vast. The distance between our galaxy and others is something that right now seems insurmountable. We are simply a pale blue dot that is orbiting one star out of a countless number of them.
From the beginnings of what we would consider an advanced human civilization, we have questioned our place in the universe. The idea that we are just one small part of it instead of being the central component of it has long been influenced by religion, new world creationism, and a certain amount of arrogance.
If God is able to create all of this that we can directly observe, why can’t he create a living universe that is filled with a wide variety of life? Why would this vast universe be created only for humanity?
We have many questions that still need to be answered. This is why the foundations of the heliocentric theory and those who discovered it are still important today. By understanding how our planet works, we can understand other planets. This allows us to understand other solar systems and ultimately how the universe works at a fundamental level.
There are more discoveries waiting to be made. Let’s make them.