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Eppur si muove. But why? - the period of cosmography
Eppur si muove. But why?
This might turn out a bit embarrassing, but I'm rather curious to see what replies I'll get. Over the weekend I realised that if I would be in trouble to give sound answers if, confronted by one of those fanatics of ignorance, I were challenged to explain how it is that we know that the Earth rotates on its axis and orbits the Sun. I tried to recall what I was taught in school about the matter, but I only could remember that they told us that people used to be frightfully ignorant and superstitious, and implicitly dumb, until science came along and showed us the truth; nothing though as to why the truth was true. I don’t intend to debate well established facts, but rather to see how far these facts are accepted mainly on Science’s authority. If your LJ friends are the kind of people who care for this kind of questions, kindly point them to this entry. So, this is not a quiz but a poll it's not about giving the right answer but about telling what you learned:
What proof do we have that Earth rotates on its axis?
What proof do we have that Earth revolves around the Sun?
Did you learn this in school? College? Or in self study?
17 comments or Leave a comment
juggzy From: juggzy Date: September 26th, 2011 08:48 pm (UTC) (Link)
I was trying to answer this, but then an over-sensitive track pad lost my terribly rational and non-egotistic thoughts.

In short, it's not a matter of proof - taken from the viewpoint of the Earth as a basic frame of reference, you could argue that the Earth does not rotate and that everything in the Universe rotates around us, with varyingly complex patterns.

It's just that the notion that the Earth rotates and orbits the sun is much simpler and hence is a much more fruitful and fertile ground for further predictions.
jackfirecat From: jackfirecat Date: September 26th, 2011 10:08 pm (UTC) (Link)
Ha! I was thinking about what to say and talked it through with a friend tonight - often thoughts fall into better shape when you have to say them out loud - you sometimes discover what you were thinking - and then I come home to post my proud discovery of my thoughts and find it's already been done.


Occam's razor.

It's not untrue (as Juggzy says) that the earth revolves around the sun. If you're on the earth, it is a fact that in your frame of reference it does, it's only if you want a simpler version to eliminate those tricky epicycles, which also happens to be true for an external observer, that - anyway she just said that in fewer words.
anselmo_b From: anselmo_b Date: September 28th, 2011 07:24 am (UTC) (Link)
Thank you for your reply and sorry for the lost text. I wrote a very lengthy reply meant for all of you in the form of two comments to the original post. Read it or ignore it as you wish.
jackfirecat From: jackfirecat Date: September 26th, 2011 10:42 pm (UTC) (Link)
proof? They explain the known facts (seasons/sun rises and falls) in a logically consistent way. If a better explanation were to be posited, I would be interested in knowing of that.

I take it on trust that no-one has posited a better version which is being kept from me, by a cabal who all agree to misinform us, because my understanding of the world is that people in science are constantly trying to overturn shibboleths ('Darwin was wrong!' on New Scientist cover whenever anything happens in biological science which wasn't known to someone writing in the late nineteenth century) to make new discoveries/ their careers.

Occam's razor in a social wissenschaft sense too - that a lot of people would have to be actively lying to me/not representing themselves correctly, in a conspiracy, in a completely unbelievable way, for it not to be true/ the best version we have in current knowledge - in a we've got the photos from space - unless they were faked - sort of way.

(I haven't done any experiments myself to prove to myself that the earth is round - which I know is not one you asked, but in that case I know what the experiment would be - but I believe it nevertheless despite my day-to-day experience of it being more-or-less flat)
anselmo_b From: anselmo_b Date: September 28th, 2011 07:25 am (UTC) (Link)
Thank you for your comment. I wrote a very lengthy reply meant for all of you in the form of two comments to the original post. Read it or ignore it as you wish.
joculum From: joculum Date: September 27th, 2011 03:12 pm (UTC) (Link)
Curiouser and curiouser. Of course the trickster David Eagleman pointed out, in his refutation of the usefulness of Occam's razor, that if you are only looking at the apparent motion of the sun and the other stars (I quote Dante on that, of course) a stationary Earth is the simplest explanation until you try to work out the mathematics, at which point you end up with all those epicycles. The seasons are only explained by the tilt of the axis, of course, not even the distance from the sun...and trying to remember an experiment that would convince the more simple-minded skeptics really is embarrassing...Foucault's pendulum demonstrates the rotation of the earth, but only if you already have the theory; otherwise you have a mystical-looking pendulum knocking things over for no immediately obvious reasons.
anselmo_b From: anselmo_b Date: September 28th, 2011 07:25 am (UTC) (Link)
Thank you for your comment. I wrote a very lengthy reply meant for all of you in the form of two comments to the original post. Read it or ignore it as you wish.
anselmo_b From: anselmo_b Date: September 28th, 2011 07:21 am (UTC) (Link)

Part I

First of all thank you all for your replies. What Juggzy and Jackfirecat say is exactly what I'd thought for the last couple of decades, convinced by the geometric argument, that you can build the model around any point of view you want, and also by the (un-rigorously understood) notion from physics that time, location and movement are relative. Now, for the past year I've been especially curious about antique cosmology, the spheres, the Ptolemaic system – I even bought myself an expensive new translation of the Almagest which I found for the most part to be a boring collection of instructions for computing the movement of celestial bodies. And by trying to understand it, I came to realize that a geocentric model is wrong in an absolute and physical manner. The problem with it is that if the Earth doesn't rotate but instead everything moves around it, then anything that is more than eight light hours away from it must move faster than light in order to complete an orbit in 24 hours, and that would be a violation of our current understanding of the universe. Therefore although a geocentric model is good enough for describing astronomical phenomena in the solar system, it also implies false laws of the universe. But this implied that I had been wrong all this time in believing that different geometric models of the universe built from different frames of reference could all be equivalent. And that of course raised the question of how it could have come to this. If I'd been consciously aware of proofs for the correctness of the heliocentric, heliostatic or whatever it is that we should call our currently accepted model, I could have tested other models against them and have realized that things are not really quite as relative as I'd thought they were. Therefore either I'd missed something in school, or else and worse, I'd not even been taught certain things. I wrote my entry in an attempt to find out whether I was alone in my ignorance. Can it be that the shape of the solar system and the universe has become so fundamental to our worldview that it is assumed that explanations are not required?
In any case the questions I asked seem to be regarded as a bit weird or freaky. I tried them on a few colleagues at work and they reacted as if I was up to something by apparently questioning (which I'm not) such obvious things. But no one could come up with a proof for Earth's movements though one or two mentioned the refutation of the flat Earth. In our age it's rather easy to look for information, and after posting here I went and found a couple explanations that I found satisfying because they can be understood and probably even observed by anyone; I'll get to them at the end. The funny thing is that I'd read about these experiments before, and that I knew that they were set up for proving Earth's movements, but that I'd evidently never made the connection the other way around, that is, recalling them when looking for such proofs. This is probably due to the fact that I learned of them after school and in separate contexts.
anselmo_b From: anselmo_b Date: September 28th, 2011 07:21 am (UTC) (Link)

Part II

The reconfiguration of the heavens is pretty much the foundation myth of our modern rationalistic worldview and yet it would seem that the average layperson has, if at all, only the vaguest idea of how it came about or what it actually means. The one single thing that I hear repeatedly about it is that the Church burned or wanted to burn Galileo for discovering that the Earth circles the Sun. And that is quite often conjoined with the belief that people used to believe that the Earth is flat until Columbus' time. In fact, barely a week goes by when I don't hear at least one of these misconceptions in a documentary or in a more or less serious tv show. I have the growing feeling of living in a culture where we are educated to ask for rational explanations of everything and anything excepting those things which science set out to explain in the first place; a culture that dismisses offhand anything that smacks of mysticism and embraces with mystic faith anything labelled 'Rationalized'.
The last of course is a wild exaggeration and a generalization unfair to many people who do try to get a picture of the world as complete as possible, but I must say that I was quite shocked about the ease with which I had been holding my assumptions to be true and the smugness that I felt from believing that at least I knew better than most people out there.
You can't be skeptic enough about what you think you know.
And finally the proofs which I looked up after making the original post: for Earth's rotation, Joculum already mentioned Focault's pendulum. It's good enough for me; it can be understood by anyone and observed in a lot of places. We have one here in Munich which I showed to my kids ages ago (it's really funny how I couldn't make the connection). And for Earth's movement around the sun, the parallax effect that occurs when a nearby star is observed from opposite points of Earth's orbit.
Thank you all again for bearing with me and sharing your thoughts. I wish there had been more comments, but apparently my entry only appealed to people whose usernames start with 'J'.
jackfirecat From: jackfirecat Date: September 28th, 2011 07:20 pm (UTC) (Link)

Re: Part II

Sorry, I wondered if I was off-topic, given that you asked what proofs do we know. (I couldn't think of any.)

Your original was Sun-centric and Axial-tilt, not rotation (nor flat, which is easier). Doesn't Focault's (I've seen one in a Glasgow shopping mall - neat!) just do rotation not axial-tilt?

I like your faster-than-light Tellus-centric-roundabout disproof! but it goes wider than our narrow system - the same problem would exist if everything rotated about the sun.

Isn't axial not only 'it's a good explanation of seasons' (there could be others) but also, we have photos from space which show it?

Edited at 2011-09-28 07:22 pm (UTC)
jackfirecat From: jackfirecat Date: September 28th, 2011 07:39 pm (UTC) (Link)

Re: Part II

oh, pardon me, you did ask 'rotates' not 'tilt' I just failed the paper by addressing a different question than the one that was asked.
anselmo_b From: anselmo_b Date: September 29th, 2011 07:59 am (UTC) (Link)

Re: Part II

Off topic is not an issue and I wasn’t chiding you (or anyone for that matter) I was just pointing out that the two questions seem commonly to get associated. And remember, I couldn’t think of any proofs either when I wrote the original post. I’m grateful to have gotten any feed back at all.

Yes, Foucault’s does only rotation as far as I know (but I wasn’t after axial tilt anyway)

Dilletantism has its moments too :) Yes, it would. It just blows away the illusion that it’s all a matter of POV.

I wasn’t after axial but, even though I didn’t say so, I was hoping for low tech pre-spaceflight pre-Michelson-Morley experiment (funny that that’s being mentioned at crowleycrow’s too) and Einstein (that’s why I didn’t feel satisfied with my own answer to axis rotation) solutions.

Thanks a lot too for pointing to here, I really appreciate that.

Nice trick that of replying to invisible quotations. I hope I managed as well as you.
jackfirecat From: jackfirecat Date: September 29th, 2011 06:51 pm (UTC) (Link)

Re: Part II

>Nice trick that of replying to invisible quotations. I hope I managed as well as you.

I understood the reply, so if you understood mine, you must've.
jackfirecat From: jackfirecat Date: September 29th, 2011 07:14 pm (UTC) (Link)

Re: Part II

parallax effect: cool! That lack of being able to detect it was used against Heliocentism (implying, if H. true, a huge, unlikely distance of void between us and the eighth sphere), even cooler. Thanks for making me look it up on wikip.
oldbloke From: oldbloke Date: September 28th, 2011 10:06 pm (UTC) (Link)
We of course have film of the Earth rotating on its axis, ever since we've had spacecraft with cameras. Unless somebody wants to argue that the ballistics we all believe send things in straight lines mysteriously cause spacecraft to spiral out from Earth.
For the sun-earth system, it is as others say a case of how to make the mathematics simplest to express. In fact of course the whole lot is moving with the Milky Way, which is revolving about its centre and also hurtling though intergalactic space, so the actual paths from the viewpoint of, say, Betelgeuse, is a bit more complex. But when you're dealing with local stuff, is makes sense to assign (relative) immobility to the most massive of the objects involved.
anselmo_b From: anselmo_b Date: September 29th, 2011 08:03 am (UTC) (Link)
Thanks a lot for your feedback. I posted two quite lengthy comments with my thoughts on the matter.
dyvyd From: dyvyd Date: October 23rd, 2011 04:06 am (UTC) (Link)
Operational proof also exists. Astronauts have watched the earth rotate from space. Scientists have successfully plotted the course of spacecraft to the moon, Mars, and other planets, all based on the models of planetary motion we currently have. If it works, it's proof enough for me!
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