Dear Mr. Sungenis,

I read with interest your challenge to "prove that the earth revolves around the Sun". Unfortunately, your challenge was too vague for me to decide whether to agree or disagree. The principle difficulty is with the word "revolve". The dictionary defines it to mean "to orbit around a center". However, "center" can be understood many different ways. I will address 5 of them:

It is also not clear whether you expect a challenger to prove that the "centrality" of the Sun is unique or absolute in some way. From the rest of your article, it seems that you regard the "centrality" of the Earth as unique or absolute in some way (which you do not explain). Therefore, I will also address the uniqueness of each concept of "center".

The Observational Center

Does anyone seriously dispute that, observationally, the Sun revolves around the Earth? If anyone might be inclined to make such a dispute, it would be those who live north of the artic circle. According to those who write about the artic from firsthand experience, the Sun "makes distant lazy circles in the southern sky". These circles are entirely above the horizon for a season, and entirely below for another season. To those in the far north or far south, the Sun does not seem to revolve around the Earth.

We know by direct observation from the surface of the Moon, that the Sun also revolves around the Moon. From the Moon, the Earth goes through phases, just as the Moon does when observed from the Earth. These are beautiful and spectacular photos from the Apollo Moon mission. From pictures sent back by Mars landers, we know that the Sun also "revolves" around Mars.

Try this experiment. Have a friend stand "still", and walk around him/her while facing one wall. You will see your friend revolve around you. If you ask your friend, they will report seeing you revolve around them. Now, walk around your friend while keeping your face always toward your friend. Now you will see your friend turning slowly around, while the room revolves around you. Your friend will report that you are revolving around them as before, but with your face always toward them.

When we send spacecraft to the distant reaches of the Solar System, their antennae continually move to point directly at Earth in order to stay in communication. The Earth makes epicycles in the sky around these spacecraft (as do the other planets).

A 3D computer graphics system describes objects by means of coordinates in an arbitrary frame of reference. However, the "center" of the scene is the "camera". The camera itself has coordinates in that same frame of reference, but what you see on the screen is determined by the position of the virtual camera. The coordinates of the virtual camera can be changed at will, so that the viewer seems to fly through the scene.

It should be clear by now that revolution in the observational sense is relative, and that the Earth is not unique in having heavenly bodies revolve around it in the observational sense. Does the Earth revolve around the Sun in this sense? We don't yet have direct observations from the Sun, but the upcoming Solar Probe will provide just that. However, straitforward geometry, without regard for any laws of physics, allows us to compute what a hypothetical observer on the Sun would see. They would see the Earth revolving around the Sun.

So, in the observational sense, the Sun revolves around the Earth, but the Earth also revolves around the Sun. The majority of Scripture passages which you cite describe the motion of the Sun in this sense.

The Geometric Center

Copernicus discovered that if you pretend that the Sun is a fixed point, and plot the positions of the planets (including Earth) relative to the Sun, their positions form an approximate circle with the Sun at the geometric center. Later, Tyco recorded precise positions of the planet Mars, including distance from Earth measured by parallax. Kepler found that the orbit of Mars (around the Sun considered as a fixed point), and indeed that of Earth and the other planets more precisely formed ellipses, with the Sun at one focus.

You can check this by carefully recording the bearing and azimuth of your favorite inner planet every night along with the exact time over the course of at least a year (outer planets will take much longer). If possible, measure the distance to the planet by measuring the bearing and azimuth from two widely separated locations at the same time. You will also need to measure the distance and direction to the Sun. If you are only interested in the Earths orbit, just the Sun positions will do. Each observation of a Sun or planet is a 3 dimensional vector, with its origin at the Earth. For each observation, subtract the Sun's vector from the Earth or planet vector to get Sun relative position. What are your standards of evidence for observations? Is Kepler's data acceptable? Are my kids data from homeschool astronomy acceptable? How about NASA?

It is much easier to go the other direction. Start with your favorite web site or open source solar system model to predict planet motions. These programs use a numerically approximated gravitation model, however, the resulting orbits can be plotted and observed to be ellipses from the Sun's frame of reference. Many of these program conveniently provide a viewpoint from anywhere, including from Earth or a point "above" the Solar System (so you can see the ellipses). Spot check their predictions of the view from Earth with your actual observed position of the planets.

Is the Sun the geometric center of the Solar System? The answer is yes by direct observation of the position of the planets relative to the Sun. Furthermore, the Sun is the only body in the Solar System which is at the center of simple circles and ellipses formed by the motion of the other bodies. The other bodies (including Earth) lead to more complicated motions when considered as the geometric center. Note that this says nothing about whether the Earth or the Sun is actually moving, only that their positions relative to the Sun form simple geometric shapes.

So in the geometric sense, the Earth revolves around the Sun.

The Sun as geometric center provides a much simpler and easier method of predicting the motions of the planets. Copernicus was humble man, and did not claim that the Sun was the "center" in anything but this obvious geometric sense. As a result, his theory was accepted, with reservations, by the reigning Aristotelians as a mathematical shortcut for the computation of epicycles. The reservation was that some might see this geometric centrality of the Sun as implying something more.

The Teleological Center

Why does the Sun revolve around the Earth (or vice versa)? This is not something that can be proved by scientific observation. However, the Scripture makes it very clear that the Sun and Moon at least were created for the benefit of Mankind. Are the Earth and Mankind unique in this respect? The Scripture does not explicitly rule out the possibility of other physical rational beings - however, our explorations so far have made it very unlikely that such beings are to be found within our Solar System. Hence, I would agree that Mankind (and therefore the Earth, his home) is the "center" of the Solar System (but not necessarily the universe).

So, in the teleological sense, the Sun revolves around the Earth.

The Earth as the teleological center was in hot dispute after Copernicus. Bruno audaciously proclaimed that not only was the Earth not the "center" of the Solar System, but the Sun itself was only one of multitudes of other suns with planets of their own! He was burned at the stake in 1600 for his blasphemy. Before you judge the actions of the Church in this matter, keep in mind, that Bruno was explicitly using his astronomical theories and geometrical facts as evidence of a religious assertion. His syllogism went something like this:

(I think there is a problem with premise 2.) Now, I don't agree with burning heretics at the stake, but Bruno's religious doctrine was certainly heretical.

A little later, Galileo showed Pope Urban the moons of Jupiter through a telescope. The Pope saw and understood that this was contrary to the assertion of the Aristotelians that the heavenly bodies were perfect spheres. He expected trouble, and earnestly counseled Galileo on six occasions to adopt the humble spirit of Copernicus and avoid directly contradicting the reigning Orthodoxy. Galileo did the opposite, and called his opponents "simpletons". The Pope managed to save Galileo from the fate of Bruno (Galileo was willing to "recant"), but he spent the rest of his life under house arrest and his writings no longer had the approval of the Church. (This, of course, made his writings even more popular.)

The Gravitational Center

Determining the center of gravity of the Solar System depends on not only the geometry of the positions of the Sun and planets (which we can directly observe), but also on Newton's laws of motion. From the geometry and Newton's laws of motion, we can directly calculate the mass of the Sun and Planets. I am not sure if you would accept Newton's laws of motion. They have been reliable when directly tested on Earth. They have been reliable when directly tested in space on journeys to the Moon, Mars, Jupiter, and other planets. However, while the position of the Sun and planets relative to Earth can be directly observed, it is difficult to directly measure the mass of the Sun. But if you do, then the center of gravity for the Solar System lies within the Sun.

So, in the gravitational sense, the Earth revolves around the Sun - but this result depends on Newtons laws of motion.

The Cosmic Center

If I had to guess which kind of "center" you have in mind, my first choice would be the cosmic center. In other words, you believe that the Earth provides a fixed, unique frame of reference that is not arbitrary. This theory is not without merit. Before the Michelson Morley experiment, most scientists believed in an absolute frame of reference called the "aether". The Earth was believed to move through this aether. The Michelson Morley experiment proves that the Earth is not in fact moving through the aether. Einstein's conclusion was that there is no absolute frame of reference. However, one logical possibility that has not been ruled out is that the Earth is fixed at the center of an absolute frame of reference. Another theory is that the aether is a discete media with local currents like an atmospheric wind. There are also those who claim that the Michelson Morley experiment actually does detect an aether wind, but that a vast conspiracy has concealed this fact from the general public. There are many other theories.

So, in the cosmic sense, there are many competing theories, but in none of them is the Sun at the center of the Cosmos.

In conclusion, your challenge needs to be more specific before anyone can properly decide on its merits. You need to specify what kind of "revolution" is being talked about, and whether its uniqueness is in question.