Is it true that there is no way of proving that the earth goes around the sun?

Question

Is it true that the only reason Copernicus is preferred to Ptolemy (i.e. the heliocentric theory over the geocentric) is that it makes the math a lot simpler? Is there any empirical proof that the earth goes around the sun, apart from Ockham's razor? (I.e. the simplest explanation, accounting for the relevant facts, is the preferred one.)

In response to the first answer, that's right--I asked it under philosophy as well. But it would be interesting to get the views of any science people who want to contribute.

Well, it goes back to the Galileo controversy, and the problem that Galileo had with the church: he insisted that heliocetrism was a fact and not a hypothesis (or a theory). The church would have accepted heliocentrism in the latter conceptual framework. There is no doubt that heliocentric-based math is immeasurably less complicated than geocentric-based math. But why is the simpler to be preferred over the complex? I guess I'm getting at the difference between fact and theory. (There is something similar going on today in the conflict between neo-Darwinism and Creationism.) NB I'm asking this question out of philosophical interest. Since people are prone to jump to conclusions in these forums, I should point out that I am neither a Creationist nor a geocentrist.

Answer 1

No, the simpler maths is not the only reason heliocentrism is preferred. There are three observations that support Earth moving and not the sun, one of which you can make youself with binoculars, one of which needs a telescope, and one of which needs very sensitive optics indeed.

The simplest observation is that we can see other systems of smaller bodies orbiting larger bodies. The four Galilean moons of Jupiter can be seen through binoculars, and you can see that they move around Jupiter. With telescopes and more modern space probes you can see other moon systems. So, we see smaller bodies orbiting larger ones. Earth is smaller and less massive than the sun, so it makes sense to say Earth goes roundthe sun and not vice versa.

The next that you can see for yourself is that other planets must go around the sun for their appearances to make sense. Mercury and Venus especially show phases and sizes that cannot be explained any other way, and even the outer planets show noticeable changes in size that puts them either round the sun or in a very eccentric orbits indeed. Ptolemy did not have that information to work with. Nor did anyone else until the telescope came along.

The next, only comparatively recently observed, though postulated very early on (and the unobservable nature of which was a headache for Copernicus and Galileo) is stellar parallax. Nearer stars move against more distant stars in a manner consistent with Earth moving in a big circle about 186 million miles across.

Accepting heliocentrism over geocentrism is not just a question of simplifying mathematics, but of fitting direct observations of the physical world into the model.

Answer 2

No, that is not true. The main reason people at the time could not prove Copernicus right was that they could not measure stellar parallax. All the scientists knew Earth orbiting the Sun would cause a parallax, but none was seen. That is because the stars are MUCH farther away than anyone expected, so the parallax was too small to measure with the telescopes available at the time. Modern telescopes can measure the parallax easily. That is actually the primary method we use to measure the distance to the stars.

The other reason Copernicus' theory was not immediately accepted was that it did not explain the motions on the planets as seen in the sky any better than Ptolemy, because he assumed all the planets orbited in circles. This error was corrected by Kepler who showed the planets orbit in elliptical orbits.

Answer 3

Wow... I thought we were past that by the 1800's. You can tell that the earth is orbitting the sun from space fairly easilly by just looking out the window. The way Copernicus found out is that he noticed that, from different areas of the earth, and at different times of the year, the sun would be at different points of the sky that it would have been at, let's say a month before-hand. When he "did the math" the only way that could make sense at all is that the earth apparently orbited the sun. Now, why don't we try and prove the earth isn't flat.

Answer 4

I would say it depends on what you mean by "proof" and "goes around". ( I hope we can all agree on "Earth" and "Sun"). Mach's principle and Ockham's razor both suggest that the simple explanation that fits all the observations, is the truth.

If the sun "goes around" the earth (using the most common-sense meaning of "goes around"), then it can be shown that the universe has a net rotation. Also, the earth would be in a privileged position in the universe. All the equations of motion, for all the objects in the universe, would have terms for "how far is this object from the Earth".

But if the earth goes around the sun, then we can preserve the non-rotating universe, and the earth is just an ordinary planet.

Answer 5

It's all relative. The Sun goes around you. You go around the sun.

It could all be an illusion, but occam's razor suggests that given our senses, all the satellite data, all the astronomical observations, all the confirmation of Einsteinian and Newtonian mechanics and every other physical confirmation that the Sun and Earth rotate around each other in accordance with well established theories might just be consistent with reality rather than it being an unexplained giant cosmic hoax.

That is the nature of science. Test the hypotheses, promote hypotheses that survive multiple tests to being theories and go with the most likely explanation.. the one supported by the data, not ludicrous explanations of the fevered imagination of lunatics and gullible religious people willing to believe what's in a book rather than the world about them.

Answer 6

Absolutely. It makes sense that the most massive body in the Solar System -- the Sun, by a long way -- should organize the behaviour of the lesser components. Universal Gravitation does a superb job of predicting the motions of the Solar System, and relativity even better. There is no reason to believe in a geocentric model, if one is inclined to believe scientific observations at all.

Answer 7

The world has launched a lot of satellites over the years and they have travelled to each of the eight planets. Sometimes their paths take them close to one planet to get a gravitational assist and direction change to sling shot them toward their goal at a faster rate than they were going before. Some of those convoluted paths have used the earth for a gravitational shift. If the planets, including the earth, were not in orbit around the sun, none of this would work.

Answer 8

Well, if the geocentric idea of the solar system were correct then none of the space probes to the planets would have worked properly with sun-centered programming in their guidance systems.

Another thing is, if the sun were not the gravitational center of the solar system then the planets would not vary in size in accordance with their position relative to the sun as seen from the earth. They would stay the same size all the time as seen from the earth (neglecting orbital eccentricities, of course).

Answer 9

In the sens that it is technically possible to describe the Earth as being the center of the Solar System, sure it's true. It's just insanely complicated.

It is possible to prove that the Sun is by far the dominant mass of the two objects, and that the barycenter of the orbit does in fact lie within the Sun. Beyond this, you can show that the Earth is undergoing greater acceleration, and so on.

Answer 10

Well, to be frank, trying to justify an Earth-centered solar system isn't just complex, it's impossible. It's not just the relationship between the Earth and sun, it's the other seven planets, along with the countless number of comets, asteroids, and Kuiper Belt Objects. In an Earth-centered model, the varying degrees of retrograde orbits would have to be explained for every one of these objects. Good luck trying to come up with a model for THAT system.