Recently I wrote a blog entry called “Einstein v the Church v Galileo?” Without reproducing the whole thing, here’s basically what I said: There was once a view that empty space contains stuff – “ether,” a view that there was an absolute backdrop to space against which all motion in the universe could be measured.
Then making one of my central claims, I noted that the dispute highlighted in the notorious Galileo affair – whether the earth moves around the sun or the sun moves around the earth, really only makes sense when we presuppose this “fixed backdrop” view of motion in space.
Next, I drew support for this claim from Albert Einstein. As has been summarised, “Prior to the generation of Einstein’s theory of special relativity, physicists had understood motion to occur against a backdrop of absolute rest (the “ether”), with this backdrop acting as a reference point for all motion. In dismissing the concept of this backdrop, Einstein called for a reconsideration of all motion. According to his theory, all motion is relative and every concept that incorporates space and time must be considered in relative terms. This means that there is no constant point of reference against which to measure motion. Measurement of motion is never absolute, but relative to a given position in space and time.”
I then applied this summary to Galileo’s claim about the earth and the sun. His view had been it was an objective fact that the earth travelled around the sun, and that it was objectively false (i.e. false from all observational perspectives) that the sun moves around the earth. The above summary of Einstein’s theory (or part thereof) means rejecting this pair of claims. It also means rejecting the reverse claims (that it’s objectively true that the sun moves around the earth, and objectively false that it does not). What it does is that it relativises both positions, thus denying that either position is objectively correct. From the earth’s perspective, the sun is correctly observed to move around the earth. From the sun’s perspective, the earth is correctly observed to move around the sun.
The upshot of this is that in making his claim, which he meant to be an objective claim while rejecting another view as objectively false, Galileo was wrong. Although I was challenged by a visitor who claimed that the above is not connected to Einstein’s theory of special relativity, and that Einstein’s theory, as far as he was aware, was never applied to the question of the earth moving around the sun or vice versa, the fact is, as I found more and more to be true the further I looked, is that the above description of motion in space really is associated with Einstein’s theory by scientists, and it really is appealed to in discussions about the earth and the sun.
The reality, of course, is that it really wouldn’t matter if this perspective on Galileo can be connected to Einstein or not (even though it looks like plenty of people do make this connection). This perspective on Galileo is the subject, and it can be analysed and discussed irrespective of how it connects to other theories.
So in short, my claim was as follows: What would be observed if the earth moved around the sun is actually “observationally identical” to what would be observed if the sun moved around the earth. The facts that we actually see in the universe can be correctly described either way.
In future, rather than repeat this, I will just refer to this position as “my claim.” My claim refers to two ideas: that of the earth moving around the sun, which I will call view a), and that of the sun moving around the earth, which I will call b).
You can think of either a) or b) as a model, but the evidence does not favour one over the other. Yes of course it would favour a) over some specific varieties of b) (e.g. the claim that everything else in the universe follows a perfect circular/eliptical orbit, where the earth is at the centre of that circle/elipse, but obviously that view isn’t required in order for one to hold to some form of view b).
Notice also a couple of terms that I deliberately never used in my blog post (and which do not affect my blog post – since I never mentioned them), but which are still relevant: Geocentrism is the ancient view that the earth is the centre of the universe. It wasn’t the view that the earth is the centre of the solar system, since the idea of a solar system exists within a model that is not geocentric. In geocentrism, the moon, the sun, the other planets and the stars all revolve around the earth. Ancient graphical depictions of geocentrism show all the heavenly bodies moving in a perfect circle with the earth at the centre of that circle, like so:
Heliocentrism is the view that the sun, rather than the earth, is at the centre of the universe and that all the heavenly bodies move around the sun.
As you can see from my summary of what my blog post was about, the issue wasn’t so much geocentrism or heliocentrism, but which travels around which: the earth around the sun, or the sun around the earth. That being said, what I am saying can be extended to say that from an observational point of view, the claim that not just the sun but all the heavenly bodies move around the earth is no better or worse supported than its denial.
Although the number of people taking issue with this blog post was tiny (and coincidentally all people who visit the blog of one person in particular), the comments from one visitor (the owner of said blog) were pretty boisterous. First, a whole string of false claims were made about my views. It was claimed that I excused the church (even though I said nothing about the conduct of the church, and also that the church was just as wrong as Galileo). It was claimed that I had said that Einstein accepted geocentricity (the view that it’s an objective fact that the sun orbits the earth). Things, sadly, did not improve, and when I had the audacity to complain about such misrepresentations, and I committed the sin of not changing my mind to agree with my rather outspoken guest, I was told that the issue, really, is that I have anger issues. Yep, the blog just became a therapy session.
However, there were other guests, and there was decent discussion had. One of the things that I explained is that the mere fact that view a) isn’t objectively true does not mean that it has no advantages. In particular, I explained that it has the advantage of simplicity as a model. We know, for example, that some stars and planets are much closer to the earth at some times than others – much further than could be explained by the claim that they orbit the earth (i.e. in a nice elliptical path with the earth at the centre). What we would have to posit, therefore is a whole range of paths that form shapes where the earth is not in the exact centre, and some pretty curly lines to boot! A geocentric model, to be sure, is more complicated – so much so that plenty of people might regard it as absurd on that basis. But this, of course, is not the same as saying that it is objectively false, or that view a) is objectively true (I made these points in comment 51 and 58 of the earlier blog on this subject).
Still, there was a lingering comment by my rather outspoken guest. Absolutely no reputable scholars would ever support this claim that I was making, I was told. Actually the claim changed over time. First of all I was told that this person had never seen Einstein drawn on in this issue, but as the subject was further introduced to my visitor, that claimed vanished. Clearly people were indeed drawing on Einstein. But nobody, nobody worth reading anyway, I was told, would make these claims about view a). Anybody who dared to consider agreeing with me would be “lining up with Glenn against everyone else – including all astronomers.” All!
However, another visitor then reproduced a quote from the late Sir Fred Hoyle, the eminent British astronomer – someone who surely counted as a “reputable” scholar in the field. That quote, from Hoyle’s work, Nicholas Copernicus: An Essay on his Life and Work, read:
The relation of the two pictures [geocentricity and heliocentricity] is reduced to a mere coordinate transformation and it is the main tenet of the Einstein theory that any two ways of looking at the world which are related to each other by a coordinate transformation are entirely equivalent from a physical point of view. (p. 78)
My vocal critic who had claimed that absolutely no reputable scholar would support my claim, and that “all astronomers” would surely reject it, reacted immediately. He admitted to never having read Hoyle’s work, but he expressed absolute confidence that Bob was misunderstanding Hoyle.
There was obviously only one way to settle this – actually read Hoyle (what a radical idea – check the source!). Obviously if an argument is plausible, then it doesn’t need Hoyle’s defence, but being able to appeal to someone like Hoyle for support will at very least silence those who say that nobody else supports this view.
Having now actually read the entire chapter in Hoyle’s book from which that quote was taken, I am prompted to add this new blog entry. Call it gratuitous spotlighting of my own vindication, call it what you will. But in fact, Hoyle was endorsing exactly the view that I presented in my previous blog entry: What would be observed if the earth moved around the sun is actually “observationally identical” to what would be observed if the sun moved around the earth. What we actually see in the universe can be correctly described either way. Not only that, but he is not alone among scientists. So first, let’s take a look at what Hoyle said.
The book consists of four chapters and then an epilogue. The chapters are, as one would expect from a work with this title, historical and biographical in nature, and they also detail some of the astronomy/physics/mathematics issues that Galileo dealt with. But then comes the epilogue: “Epilogue from the Twentieth Century,” beginning on page 74. Here is where Hoyle takes advantage of the benefit of the centuries that had passed between Galileo’s time and his own (the book was published in 1973). He throws Einstein into the mix, and turns his attention to the question of whether we can really say that view a) or view b) is really objectively true. The coincidence in subjects between this epilogue and my argument are perfect – he intentionally set out a chapter on exactly the same subject that I was writing about in my earlier blog post. So the first hurdle has been passed: We are on the same page, subject-wise.
Amongst his comments, Hoyle does use the words “geocentric” and “heliocentric,” and he uses the name of Ptolemny in reference tot he former. However, that is because geocentrism is a species of view b), and heliocentrism is a species of view a). He makes it absolutely clear that by including those terms as well, he is not limiting himself only to geocentrism and heliocentrism as defined above. Of this there can be no doubt, as we see thus: In contrasting the two views which, on the whole, he is comparing, (I will continue to use my terms, the a) view and the b) view), he talks about the dominant view as the view “that the Earth really goes around the Sun, not the Sun around the Earth” (p. 75). This is a general position that includes full blown heliocentrism but is not limited to it. OK. We (Hoyle and I) are talking about the question of whether the earth moves around the sun or vice versa, asking whether or not either view can be thought of as objectively correct. The prospects are good that what we find in this chapter and apply to this question, therefore, will not be a case of quote mining and taking statements out of context. Let’s proceed.
Part of the difficulty in conveying Hoyle’s epilogue is that virtually every part of it reads like a deliberate statement of agreement with my position, and I’m not going to quote all of it. Moreover, my guest was so intent on making sure that Hoyle could never be understood by him to agree with me, that he went as far as to say that I would simply put words into Hoyle’s mouth, thereby ensuring that he did agree with me. While this may be a suspicion my guest has come to have based on his usual partners in dialogue, it is not something I do, so I have taken a different approach, as outlined below.
Recall my earlier statement that the reason one might prefer to use theory a) over theory b) is simplicity. Theory b) is difficult to work with, and is, well less useful. It has less utility as a model, hasn’t been as handy at predicting things. It involves all the same physical facts, but changes the way that we look at them in a way that will appear less neat, but this does not make it untrue, nor does it make theory a) true. Now observe Hoyle’s epilogue, reproduced here in full on the grounds that this is an out of print book that is sufficiently hard for some people to locate that this may be the only way you will get to read this chapter in full.
HERE is the chapter in pdf format. Read it, then read on.
You might disagree with Hoyle. That is fine. But if, after reading Hoyle, you maintain that he does not support my view then you either did not understand it, you have not understood me, or, unfortunately, you are not telling the truth. Hoyle explicitly and clearly affirmed that we can treat either the sun or the earth as the centre of rotation of the other, and that neither observational model is more objectively right in any meaningful physical sense. He also noted, as I noted prior to discovering this book, that view b) is less convenient to handle, and that much progress has been made using model a). He even adds that it is Einstein’s theory that lends further support to the b) view, further vindicating that claim on my part.
OK, so we’ve passed a hurdle. There does (did) exist at least one eminent astronomer who supports my thesis (and therefore supports the thesis that Galileo’s claim, which was meant to be taken as objectively true, was wrong). Are there others, perhaps? In fact there are.
The internationally renown astrophysicist George Ellis makes the following comments when discussing the big bang model. He makes the point that there are a range of models in cosmology that could well be correct and which are fully compatible with the evidence. Guess which example he picks?
“People need to be aware that there is a range of models that could explain the observations,” Ellis argues. “For instance, I can construct you a spherically symmetrical universe with Earth at its center, and you cannot disprove it based on observations.” Ellis has published a paper on this. “You can only exclude it on philosophical grounds. In my view there is absolutely nothing wrong in that. What I want to bring into the open is the fact that we are using philosophical criteria in choosing our models. A lot of cosmology tries to hide that.”
W. Wayt Gibbs, “Profile: George F. R. Ellis,” Scientific American, October 1995, Vol. 273, No.4, p. 55.
Albert Einstein and L. Infeld, from The Evolution of Physics (New-York: Simon and Schuster (1938), 212.
Can we formulate physical laws so that they are valid for all CS [coordinate systems], not only those moving uniformly, but also those moving quite arbitrarily, relative to each other? […] The struggle, so violent in the early days of science, between the views of Ptolemy and Copernicus would then be quite meaningless. Either CS could be used with equal justification. The two sentences:
“the sun is at rest and the earth moves”
“the sun moves and the earth is at rest”
would simply mean two different conventions concerning two different CS.
Note the example they chose to use: the movement of the sun around the earth, or vice versa. The dispute between the two positions is rendered meaningless, say Einstein and Infeld, since either can be expressed with equal justification.
This quote is used in the article by Galina granek of Haifa University in “Einstein’s Ether: E. Annual Motion of the Earth,” Apeiron, 8:3, July 2001. See it online here.
I wish I could locate the source of this quote from Ernst Bloch, where he makes the following comment about the impact of Einstein and relativity on the issue of the earth moving around the sun:
From the moment that…movement is no longer produced towards something, but there’s only a relative movement of bodies among themselves, and therefore the measurement of that [movement] depends to a great extent on the choice of a body to serve as a point of reference, in this case is it not merely the complexity of calculations that renders the [geocentric] hypothesis impractical?
Enough quotes, the concept has been communicated clearly enough already. The quotes were just to dmonstrate that I am far from being the only person to say this.
This page is quite helpful for those still struggling with the idea. It shows an animation showing how we can simply change the centre of our diagram, depict the earth as not moving (as we now do with the sun), and then just let the other objects resume their normal movements as before. They are all moving around the earth, and no observations would be any different from before.
Prompted by Hoyle, then, I have gone looking to see if in fact any reputable scholars would support the point that I have made. In fact they do. Granted, given that I am talking about something that is observationally identical with what believers in view a) already believe, there’s not likely to be a lot of motivation to re-describe the motion of the planets. I have no problem with that, especially given the fact that I do not deny the fact that the earth moves around the sun. As long as people are willing to be clear and say “but that’s not a more objectively true model than a model with the earth at the middle,” because in fact it really is all relative, then astronomers can keep going about their business.
But insofar as Galileo made his claim into an objective knock down to the alternative, he was still wrong. Sorry Ken. 😉