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Would things be the same if the Sun was orbiting Earth and the Earth was in the center of the Solar System, or would there be any big difference?

It seems like why people before thought the Earth was the center of the Solar System since it didn't conflict with their experience.

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    $\begingroup$ Hi, izkch, and welcome to Astronomy Stack Exchange! I've edited your question to fix the capitalization and grammar; I've also assumed that you're referring to the center of the Solar System - feel free to edit again if I've been mistaken. That said, I'm not sure that your question is on-topic here, as we generally don't deal with hypothetical astronomical scenarios unless they focus on understanding a concept from astronomy. $\endgroup$
    – HDE 226868 ♦
    May 9, 2018 at 13:58
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    $\begingroup$ You can happily write the equations of motion with the Earth at the center. They will be very ugly. $\endgroup$
    – Carl Witthoft
    May 9, 2018 at 15:37
  • $\begingroup$ Yes, that's what I meant as well, so I interpret the question as asking, if our experiences gibe with us being at the center of the solar system, is there a way to frame the laws of physics such that we can use that language correctly? It wasn't easy-- but Einstein pulled it off. $\endgroup$
    – Ken G
    May 9, 2018 at 15:54
  • $\begingroup$ HDE 226868 hi and thanks for editing, Carl Witthoft think I'd like that Ken G yeah $\endgroup$
    – izkch
    May 9, 2018 at 18:50
  • $\begingroup$ Question better suited for Worldbuilding SE $\endgroup$
    – jean
    Jun 8, 2018 at 16:50

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It depends on what you mean by "in the center" or "switch places." If you physically moved the Earth to where the Sun is, and the Sun to where the Earth is, and gave each the speed that the other had while keeping the same reference frame, this would do tremendous violence to all the other planets in the solar system (though the Earth would continue to orbit more or less the same).

However, if what you are talking about is simply the language of what you call the center, then you are talking about changing to a different set of coordinates where the Earth is at the stationary center of your coordinate system. Doing that presents no problems, and nothing is different except the language you are using to talk about what is going on. One of the great things Einstein did was to reframe the laws of physics in a form that was independent of coordinates, allowing us to forever separate what the laws say is happening from the language we use to talk about what is happening (i.e., our chosen coordinates). So it all comes down to whether you think "being in the center" is a real thing, or just the language of some coordinate system. If the former, then no, things would not be at all the same, if the latter, then yes, they'd be exactly the same, if you are careful to use coordinate-independent laws like general relativity.

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    $\begingroup$ I love people who downvote but have no idea what they are talking about. $\endgroup$
    – Ken G
    May 9, 2018 at 15:27
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    $\begingroup$ That may be true, but shouldn't we assume the best, and find the interesting question that is there? $\endgroup$
    – Ken G
    May 9, 2018 at 16:40
  • $\begingroup$ OP? I didnt downvote though I wasnt even here? $\endgroup$
    – izkch
    May 9, 2018 at 18:51
  • $\begingroup$ thank you for your answer Ken G, the upvote doesnt show because this account is new and my reputation is less than 15 $\endgroup$
    – izkch
    May 9, 2018 at 18:52
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    $\begingroup$ The language for putting numbers to what you see is called a "coordinate system." Before Einstein, every physics law was only true in specific coordinates that were generally different from the coordinates that describe what we as observers actually see, requiring a layer of translation between what we see and what agrees with the laws. Einstein fixed that, so although his system is difficult, if we use it, the laws describe exactly what we see with no translation. It made the center of the solar system an arbitrary concept. $\endgroup$
    – Ken G
    May 10, 2018 at 13:12
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As @Ken G noted, it all depends on what you are asking. I think the question is, "What would happen all apparent motions of the heavenly bodies and all phenomena we see on Earth remained unchanged and yet the Earth was stationary and the Sun (and everything else, I guess) revolved around it?"

The answer is, nothing need change except that the laws of physics would get hugely more complicated -- unrecognizably more complicated -- or else they would turn out to be essentially arbitrary. It's perfectly possible to rewrite Newtonian (or Einsteinian) mechanics so that there's an arbitrary non-moving and non-accelerated body, but the force laws get very complicated and there are messy "extra" forces.

We have an inbuilt prejudice (which I should make clear I share) that, their effectiveness at describing nature being equal, the simpler the laws of physics are, the more likely they are to be true. The Earth going around the Sun yields simple laws of nature. Having the Sun going around the Earth requires contorted, ugly laws of nature, but theories can be constructed each why that yield the same result.

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Let us suppose that "a wizard did it". The law of gravity no longer applies and the motion of the sun is entirely due to magic.

First off what about the other planets? If they continue to orbit about the centre of the solar system, they would not move across the sky in the looping orbits that they seem to take. Venus and Mercury would not remain near the sun.

If the planets were to move in exactly the same way across our sky, then their routes through space would have to be complex looping affairs. The wizard would be busy.

What about the stars? If the Earth is not orbiting the sun then they wouldn't have the yearly wobble in their position. The wobble is tiny but important in measuring the distance of the stars.

A wizard whold have to move the whole universe around in a 150million km circle each year for things to be exactly the same

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  • $\begingroup$ The "wizard" is called a coordinate system. That is how we obtain language like "what is moving in a circle and what isn't." But general relativity is built to be coordinate independent, so none of that language corresponds to anything physical. This is why Hoyle once said "we can take either the Earth or the Sun, or any other point for that matter, as the center of the solar system." What Hoyle is talking about is the difference between a choice of coordinates, and some kind of statement of absolute truth. Until you know which you are doing, asking "what is the center" is meaningless. $\endgroup$
    – Ken G
    May 9, 2018 at 15:25
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Laws of gravity would require a massive rewrite, and Earth would likely in turn be orbiting Sputnik.

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  • $\begingroup$ If Laws of Gravity change that means you are changing how matter clumps to form stars, planets and galaxies meaning the entire universe can be a very different place $\endgroup$
    – jean
    Jun 8, 2018 at 16:47
  • $\begingroup$ @Jean 3 Yes. The scenario would make everything screwy. $\endgroup$
    – Wayfaring Stranger
    Jun 8, 2018 at 20:49
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    $\begingroup$ There is no need to change the laws of gravity, the ones we already have allow the Earth to be the stationary center of the universe. The physics was made "coordinate independent" by Einstein, and where the Earth is and what it is doing is purely a matter of choosing coordinates. Can anyone give any other meaning to "the Earth is at the stationary center" than "put the origin of our coordinates at Earth and get the correct motion for everything else?" I welcome anyone coming up with any other scientifically demonstrable statement for what that language means, they won't find it possible. $\endgroup$
    – Ken G
    Jul 8, 2018 at 20:52
  • $\begingroup$ This would be better as a comment, imo. $\endgroup$
    – Sir Cumference
    Jul 8, 2018 at 22:46
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Would things be the same if the Sun was orbiting Earth and the Earth was in the center of the Solar System, or would there be any big difference?

Such a model is impossible when combined with visual observations, much as the Earth could not be flat and coincide with the effects of gravity and the observations made when traveling.

The geocentric model of the universe was first proposed in the 6th century BC by Anaximander. In the 2nd century AD the Ptolemaic model was developed to explain the observed motion of the moon and planets using an equant (a sort of barycenter).

By the 10th century AD scholars started to doubt the Ptolemaic model and from the late 16th century onward, it was gradually superseded by the Heliocentric model of Copernicus, Galileo and Kepler.

In 1783 the observations of William Herschel, Friedrich Bessel, and other astronomers showed that the sun, while near the barycenter of the solar system, was not at the center of the universe.

There is a video called "Ptolemaic Planetary model" by YouTube user rufjunk which demonstrates how the geocentric and heliocentric models would appear.

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So, to answer your question let's go to 322 BCC where Earth was at the center and all stars and planets revolves around it. But planet used to show unusual behavior. They use to retrograde (https://en.m.wikipedia.org/wiki/Apparent_retrograde_motion).

So, in retrogration, unlike stars, motion the planets seems to move forward then backward and again forward. To understand this go to link above.

Later to explain retrogration of planets let's go to 3rd century of BC where in the Hipparchian and Ptolemic Astronomy they used concept of epicycle to explain retrogration of planets.

(https://en.m.wikipedia.org/wiki/Deferent_and_epicycle)

So, in epicycle, there is one orbit where some invisible thing is revolving, now on this invisible thing, imagine another orbit. It is like orbit of moon in our present solar system, but we can't see earth, and in this model the orbit of moon is similar to orbit of planets. (See link for better explanation)

Now, with this we can explain retrogration motion of planets. But it lack precision. So what we can do is, introduce epicycle within an epicycle, and epicycle within it... And so on, and use FFT (Fast Fourier Transformation) to decide radius of orbits of various epicycles to match observation data.

Now you have a system where Earth is at center, stars move around it. So, do the Sun. And planets moves in FFT epicycles.

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