Proving the earth revolves around the Sun - Page 3

Fellow Traveler · 13th August 2015, 03:53 PM

For anyone suddenly thrust back into 1015, they would experience many unforeseen difficulties. You might build a car but there would be no roads suitable or gasoline. I suppose in "Back to the Future" they sidestepped the fuel issue by making the car nuclear.

Ladewig · 13th August 2015, 06:33 PM

Originally Posted by Fellow Traveler

For anyone suddenly thrust back into 1015, they would experience many unforeseen difficulties. You might build a car but there would be no roads suitable or gasoline. I suppose in "Back to the Future" they sidestepped the fuel issue by making the car nuclear.

Why would those difficulties be unforeseen?

RussDill · 13th August 2015, 06:38 PM

Originally Posted by Ladewig

From what I understand about stellar parallax, diameter of the Earth and other measurements of the Earth are irrelevant. What is needed is a very accurate telescope. In fact, with that approach, a calendar is more useful than an accurate clock.

You need the accurate clock if you are going to take accurate measurements of the planets and use that information to create a precise model of the solar system in an effort to champion heliocentrism. But if you are going straight for parallax as your proof, no clock is necessary.

ETA:
Wait. Are you talking about measuring things with the solar system, e.g. the timing of occultations of Jupiter's moons from different points on the Earth? If so, I dont think that would help in directly proving heliocentrism.

Nothing really helps except proof of gravity. Proof of parallax just shows that the stars are moving relative to the Earth, and geocentrism already says that the planets move relative to the Earth.

Craig B · 13th August 2015, 06:44 PM

Originally Posted by RussDill

Nothing really helps except proof of gravity. Proof of parallax just shows that the stars are moving relative to the Earth, and geocentrism already says that the planets move relative to the Earth.

I can't follow your reasoning there. Can you provide more detail? Thanks.

Mader Levap · 14th August 2015, 09:43 AM

Originally Posted by RussDill

Nothing really helps except proof of gravity. Proof of parallax just shows that the stars are moving relative to the Earth, and geocentrism already says that the planets move relative to the Earth.

Paralax would prove that Earth moves around sun, not opposite. You can't have parallax with immobile Earth in center of universe.

If you mean that someone would try to explain away star movement without parallax, then that person would have pretty impossible task, especially if you can show that different stars will have different parallax (since they are at difference distance from our solar system).

sphenisc · 14th August 2015, 10:00 AM

Originally Posted by Mader Levap

Paralax would prove that Earth moves around sun, not opposite. You can't have parallax with immobile Earth in center of universe.

If you mean that someone would try to explain away star movement without parallax, then that person would have pretty impossible task, especially if you can show that different stars will have different parallax (since they are at difference distance from our solar system).

I can't see the problem. The stars are fixed with regard to the Sun. The Sun goes round the Earth - there's your parallax.

Craig B · 14th August 2015, 10:22 AM

Originally Posted by sphenisc

I can't see the problem. The stars are fixed with regard to the Sun. The Sun goes round the Earth - there's your parallax.

But the fixed stars surely were not thought to be in orbit round the sun. They were "fixed" with respect to one another, in orbit round the Earth.

The "hybrid" systems, like those invented by Tycho and others, were desperate improvisations designed to "save the phaenomena" revealed by Tycho's meticulous observations, and at the same time to retain the principle of a static Earth. Did Tycho or anyone else suggest that the Fixed Stars were centred on any body other than Earth? In the Tychonic system, the Sun. Did TB propose that as regards the fixed stars?

Ladewig · 14th August 2015, 12:47 PM

Stellar parallax is the concept that when the Earth is on opposite sides of its orbit, nearer stars seem to shift position in relation to farther stars. The Earth orbiting the Sun is the only possible way to explain this shift. Because the shift is so small, it cannot be detected with the unaided eye and requires powerful telescopes to observe.

While it is a very convincing proof of heliocentrism, it does require very good telescopes. But precise clocks and precise measurements of the Earth are not required.

RussDill · 14th August 2015, 03:58 PM

Originally Posted by Ladewig

Stellar parallax is the concept that when the Earth is on opposite sides of its orbit, nearer stars seem to shift position in relation to farther stars. The Earth orbiting the Sun is the only possible way to explain this shift. Because the shift is so small, it cannot be detected with the unaided eye and requires powerful telescopes to observe.

While it is a very convincing proof of heliocentrism, it does require very good telescopes. But precise clocks and precise measurements of the Earth are not required.

It is not the only way to explain the shift. The stars could just as well be moving in such a way to present the same apparent motion. You can keep adding complexity to a geocentric theory to make it match observation. The heliocentric system needs much less complexity, but that alone doesn't prove it.

You can prove disprove geocentrism two ways. One is gravity.

The other is special relativity and the cosmic speed limit. I think even Jupiter must need to exceed the speed of light to make it around the Earth in a single day at that distance.

WhatRoughBeast · 14th August 2015, 07:37 PM

Parallax is easy to handle. It requires only that the stars are not all fixed, just most of them. A few nearer stars are embedded in one or more moveable spheres which oscillate just enough to give the necessary slight position shifts. Given the number of levels of nested epicycles required to explain the motions of other bodies, it seems like a perfectly reasonable approach.

Ladewig · 14th August 2015, 08:04 PM

[

Originally Posted by RussDill

It is not the only way to explain the shift. The stars could just as well be moving in such a way to present the same apparent motion. You can keep adding complexity to a geocentric theory to make it match observation. The heliocentric system needs much less complexity, but that alone doesn't prove it.

I disagree that one could explain the star shift by describing a star movement, but I am having a difficult time finding the language to describe why. Let me think about it.

Loss Leader · 14th August 2015, 10:37 PM

Originally Posted by Ladewig

I disagree that one could explain the star shift by describing a star movement, but I am having a difficult time finding the language to describe why. Let me think about it.

The problem with all of it is that no breakthrough in science is instantaneous. All the pieces need to come together slowly - technology, observation, theory, etc. You can't prove parallax without telescopes, you can't make telescopes without precise optics, you can't grind lenses precisely without machinery, you can't make good machinery without strong metal alloys, you can't make ...

My advice is, if you go back in time to 1000 AD, have a smoked turkey leg and culture some penicillin.

Craig B · 14th August 2015, 10:50 PM

Originally Posted by WhatRoughBeast

Parallax is easy to handle. It requires only that the stars are not all fixed, just most of them. A few nearer stars are embedded in one or more moveable spheres which oscillate just enough to give the necessary slight position shifts. Given the number of levels of nested epicycles required to explain the motions of other bodies, it seems like a perfectly reasonable approach.

Unless this is a joke, it seems an entirely arbitrary supposition. By that sort of argument you can postulate anything at all. I walk towards a tree, but I can't admit that this is happening because I follow a dogma that holds that I am fixed at the centre of the universe. No problem; I simply propose that the tree is becoming larger.

sphenisc · 15th August 2015, 01:58 AM

Originally Posted by RussDill

It is not the only way to explain the shift. The stars could just as well be moving in such a way to present the same apparent motion. You can keep adding complexity to a geocentric theory to make it match observation. The heliocentric system needs much less complexity, but that alone doesn't prove it.

You can prove disprove geocentrism two ways. One is gravity.

The other is special relativity and the cosmic speed limit. I think even Jupiter must need to exceed the speed of light to make it around the Earth in a single day at that distance.

A non-rotation is different from Geocentrism.

Manopolus · 15th August 2015, 06:38 AM

Originally Posted by Fellow Traveler

Lets suppose you were living say 1000 years ago and had no telescope: What kind of proofs or logic could you give to convince some scientifically inclined person that the Earth rotates around the Sun? Would it be eclipses?

Well, you start with retrograde motion and then do a bunch of math and geometry to explain why it happens. They were already quite aware of planetary retrograde motion at that point in history and had all sorts of problems trying to explain it. That's exactly how Galileo explained it, and the telescope wasn't actually a concrete prerequisite to working it out.

https://en.wikipedia.org/wiki/Retrog...rograde_motion

hecd2 · 15th August 2015, 07:01 AM

There are two sorts of powerful evidence that we have now, which so far haven't been mentioned:

1) Stellar aberration. It is a bigger effect than parallax so easier to measure (and therefore quantified before parallax could be detected). Moreover, it cannot be explained by motion of the source(s) as parallax can. Since it is an effect that is proportional to velocity rather than position, it is 90 degrees out of phase with parallax.
2) Annual doppler modulation of celestial objects. Its phase and amplitude is consistent with stellar aberration. All stars and galaxies in the same direction have the same amplitude and phase of modulation regardless of the distance of the source. Since the speed of light is finite this implies that the modulation is caused by the motion of the earth rather than the sources.

Of course, neither of these pieces of evidence could be detected in 1000CE.

PhantomWolf · 17th August 2015, 06:37 PM

Okay so while it wouldn't prove absolutely that the Earth orbited the sun, it would help...

Since we could use what we know now, and it'd be easy to replicate with the tools available in 1012, I'd use Henry Cavendish's work to use a torsion balance device and then show the derivation of G and then subsequently the Earth's mass. I'd follow this up with using orbital velocity and Hipparchus' parallax based determination of the distance to the moon to show that the moon was not travelling fast enough to orbit the Earth based on a stationary non-rotating Earth. I'd then show from this that a rotating Earth closely matched the observed Lunar passage. From this I could then press for the case that the sun's passage was caused by that same rotation rather than that the sun orbited the Earth. Not fool proof, but it'd be a good starting point.

Ladewig · 17th August 2015, 07:37 PM

Fellow Traveller, are you still here?

Can you tell us what prompted this thread?

Roger Ramjets · 17th August 2015, 08:37 PM

I wouldn't mess with advanced math or trying to make precise measurements. I would just make a working model of the solar system with a glowing sun in the center, and let the 'scientifically inclined person' have a play with it. Pretty soon he would be announcing that he had figured it out!

Ladewig · 17th August 2015, 09:14 PM

Originally Posted by Roger Ramjets

I wouldn't mess with advanced math or trying to make precise measurements. I would just make a working model of the solar system with a glowing sun in the center, and let the 'scientifically inclined person' have a play with it.

Pffft. If you are not going to make your model to scale, what's the point?

Quote:

Pretty soon he would be announcing that he had figured it out!

He? 1000 CE seems like a good time to plant the seeds to equality.

Puppycow · 17th August 2015, 09:20 PM

Originally Posted by Trebuchet

Relative masses of the "geo" and "sol" parts.

Originally Posted by macdoc

Different set of laws of physics tho if the "earth" had the denisity of a few hundred brown dwarf stars....

A white dwarf has the mass of a sun in the volume of the earth. Eventually they become a "black dwarf" in about 10¹⁵ years after they cool down. But there probably wouldn't be many suns left by then. Just a universe full of black holes and black dwarfs, old dead planets and maybe neutron stars. Even the red dwarfs would probably have used up their fuel by then. Maybe a few new red dwarfs will still be being born but I kinda doubt it.

Craig B · 17th August 2015, 09:52 PM

Originally Posted by Puppycow

A white dwarf has the mass of a sun in the volume of the earth. Eventually they become a "black dwarf" in about 10¹⁵ years after they cool down. But there probably wouldn't be many suns left by then. Just a universe full of black holes and black dwarfs, old dead planets and maybe neutron stars. Even the red dwarfs would probably have used up their fuel by then. Maybe a few new red dwarfs will still be being born but I kinda doubt it.

I've been trying to work out exactly what brown dwarfs are, and how they relate to gas giant planets; but I don't think the expression refers to a white dwarf on the way to becoming a black dwarf.

It's astounding how long it takes for white dwarfs to cool down, by the way.

Puppycow · 17th August 2015, 10:04 PM

Originally Posted by Craig B

I've been trying to work out exactly what brown dwarfs are, and how they relate to gas giant planets; but I don't think the expression refers to a white dwarf on the way to becoming a black dwarf.

It's astounding how long it takes for white dwarfs to cool down, by the way.

No, brown dwarfs are different. Think of a brown dwarf as just like a larger version of Jupiter. As a gas giant gets bigger and bigger, eventually it becomes a brown dwarf, then a red dwarf is the next size bigger, then orange and then a yellow dwarf, like our own sun. There is no precise dividing line between any of these. The upper limit for a gas giant planet is about 13 time the mass of Jupiter. Beyond that it is considered a brown dwarf. At some point it becomes massive enough to create a fusion reaction, so it starts to gradually become more like a star than a large planet.

A white dwarf and a black dwarf are completely different: a white dwarf is what is left after a large star goes Nova at the end of its life. It's the remnant of a dead main sequence star.

https://en.wikipedia.org/wiki/Brown_dwarf
https://en.wikipedia.org/wiki/White_dwarf

Craig B · 17th August 2015, 11:27 PM

Originally Posted by Puppycow

No, brown dwarfs are different. Think of a brown dwarf as just like a larger version of Jupiter. As a gas giant gets bigger and bigger, eventually it becomes a brown dwarf, then a red dwarf is the next size bigger, then orange and then a yellow dwarf, like our own sun. There is no precise dividing line between any of these. The upper limit for a gas giant planet is about 13 time the mass of Jupiter. Beyond that it is considered a brown dwarf. At some point it becomes massive enough to create a fusion reaction, so it starts to gradually become more like a star than a large planet.

I'm with you on that. But I have one query left.

A star, even a small star like a "brown dwarf", has independently condensed out of a (larger or smaller) cloud. Jupiter is not like that in origin. It has condensed out of part of a cloud, which may not have the same composition as a whole cloud. Planets may well not. The Earth and the Sun are made of different proportions of materials.

I would therefore expect an independently condensed "brown dwarf" to be different from an expelled "gas giant" even if both bodies have exactly the same mass. So I am tempted to retain the expression BD for the first, and GG for the second.

Is there any sense or value in such a convention?

Puppycow · 18th August 2015, 12:15 AM

Originally Posted by Craig B

I'm with you on that. But I have one query left.

A star, even a small star like a "brown dwarf", has independently condensed out of a (larger or smaller) cloud. Jupiter is not like that in origin. It has condensed out of part of a cloud, which may not have the same composition as a whole cloud. Planets may well not. The Earth and the Sun are made of different proportions of materials.

I would therefore expect an independently condensed "brown dwarf" to be different from an expelled "gas giant" even if both bodies have exactly the same mass. So I am tempted to retain the expression BD for the first, and GG for the second.

Is there any sense or value in such a convention?

I'm afraid this is beyond what I know. Not sure exactly what you mean by "an expelled gas giant". Expelled from what? My own understanding is that all of these bodies condense from clouds of dust and gas, but exactly how large (massive) the resulting lump of matter gets determines whether it is a star or a planet. I'm no astronomer, just a layman who is interested in astronomy.

You are right that the Sun is composed of different elements from the earth. It's mostly hydrogen (71%) and helium (27%), and together those two elements account for 98% of the sun's mass (and 99.9% of the atoms).

The earth OTOH, is mostly made of much heavier elements like iron, oxygen, silicon, etc. and hydrogen and helium are actually relatively rare on the earth. I think mainly that's because there isn't enough gravity on earth to keep hydrogen and helium from floating to the top of the atmosphere because they are lighter than nitrogen and oxygen, and then off into space.

Jupiter is much more like the sun than the earth: it's also mainly made of hydrogen and helium, not heavier elements like the earth.

Quote:

Thus, Jupiter's atmosphere is approximately 75% hydrogen and 24% helium by mass, with the remaining one percent of the mass consisting of other elements. The interior contains denser materials, such that the distribution is roughly 71% hydrogen, 24% helium and 5% other elements by mass.

So the main reason that the earth and the smaller planets are made of different elements than the sun and Jupiter is, simply because they are too small to hold hydrogen and helium, so those mostly float away, leaving only the heavier elements behind.

Craig B · 18th August 2015, 05:28 AM

Originally Posted by Puppycow

I'm afraid this is beyond what I know. Not sure exactly what you mean by "an expelled gas giant". Expelled from what? My own understanding is that all of these bodies condense from clouds of dust and gas, but exactly how large (massive) the resulting lump of matter gets determines whether it is a star or a planet. I'm no astronomer, just a layman who is interested in astronomy.

Before studying the rest of your post, I mean this: a body of that mass might have been produced on its own by the collapse of a gas cloud, or it might have at one time been part of a stellar system, and then been thrown out of it by the interaction of binary stars or in some other way.

Would bodies of such disparate origin be the same in composition? That's what I mean.

Chanakya · 18th August 2015, 06:13 AM

Originally Posted by Fellow Traveler

Lets suppose you were living say 1000 years ago and had no telescope: What kind of proofs or logic could you give to convince some scientifically inclined person that the Earth rotates around the Sun? Would it be eclipses?

Nice thought experiment. Here's my lazy answer:

Since you're living 1000 years ago, it would probably be the exact same thought processes that led you, yourself, to that hugely radical notion, that the earth is spherical and that the earth goes round the sun. You'd only need to describe to said scientifically minded person how you yourself arrived at that conclusion.

If time machines enter into the process (of your knowing what you know when living 1000 years ago), so much the better.

Earthborn · 18th August 2015, 05:46 PM

Originally Posted by Puppycow

why would you even think that the earth orbits the sun?

Careful observation?

Quote:

Something would have to put that idea in your head in the first place, almost 5 centuries before it occurred to Copernicus.

Something put the idea in Copernicus head, and that thing was centuries of highly detailed observational data. From Arabs. During the so-called Islamic Golden Age, a lot of astronomical data was recorded by Islamic scientists who were quite familliar with the heliocentric model, and who had no particular religious doctrines favouring geocentridm. Some even toyed with the idea that stars might be suns with their own planets orbiting them.

Even for them, heliocentrism wasn't a new idea. The concept has been floating around for a long time. The ancient Greeks knew about it, even Ptolemy who gave us the geocentric model with epicycles had to deal with heliocentric critics. Who based their ideas on even older Hindu observations.

Craig B · 18th August 2015, 05:57 PM

Originally Posted by Earthborn

During the so-called Islamic Golden Age, a lot of astronomical data was recorded by Islamic scientists who were quite familliar with the heliocentric model, and who had no particular religious doctrines favouring geocentridm.

These scholars may have speculated as you describe, but they did in fact have "particular religious doctrines favouring geocentrism". The Quran expounds a clearly geocentric cosmology.

It even has the sun setting in a muddy pool.

Lo! We made him strong in the land and gave him unto every thing a road. And he followed a road. Till, when he reached the setting-place of the sun, he found it setting in a muddy spring, and found a people thereabout. We said: O Dhu'l-Qarneyn! Either punish or show them kindness. Then he followed a road. Till, when he reached the rising-place of the sun, he found it rising on a people for whom We had appointed no shelter therefrom. Qur'an 18:84-90

The person "Dhu'l-Qarneyn" is, I believe, thought to be a reference to Alexander the Great.

Reformed Offlian · 8th January 2021, 05:48 PM

Originally Posted by Fellow Traveler

Lets suppose you were living say 1000 years ago and had no telescope: What kind of proofs or logic could you give to convince some scientifically inclined person that the Earth rotates around the Sun? Would it be eclipses?

It bears pointing out that Copernicus himself largely argued his case based on classical (i.e., Ptolemaic) data. So, basically, crib the arguments from De Revolutionibus Orbis.

ETA, Sorry, I had no idea how old this thread was until after I responded. No idea why this popped up where it did in my search results.

13th August 2015, 03:53 PM	#81
Fellow Traveler Master Poster Join Date: Jan 2013 Posts: 2,933	For anyone suddenly thrust back into 1015, they would experience many unforeseen difficulties. You might build a car but there would be no roads suitable or gasoline. I suppose in "Back to the Future" they sidestepped the fuel issue by making the car nuclear.
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13th August 2015, 06:33 PM	#82
Ladewig I lost an avatar bet. Join Date: Dec 2001 Posts: 28,036	Originally Posted by Fellow Traveler For anyone suddenly thrust back into 1015, they would experience many unforeseen difficulties. You might build a car but there would be no roads suitable or gasoline. I suppose in "Back to the Future" they sidestepped the fuel issue by making the car nuclear. Why would those difficulties be unforeseen?
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13th August 2015, 06:38 PM	#83
RussDill Philosopher Join Date: Oct 2003 Location: Charleston Posts: 5,426	Originally Posted by Ladewig From what I understand about stellar parallax, diameter of the Earth and other measurements of the Earth are irrelevant. What is needed is a very accurate telescope. In fact, with that approach, a calendar is more useful than an accurate clock. You need the accurate clock if you are going to take accurate measurements of the planets and use that information to create a precise model of the solar system in an effort to champion heliocentrism. But if you are going straight for parallax as your proof, no clock is necessary. ETA: Wait. Are you talking about measuring things with the solar system, e.g. the timing of occultations of Jupiter's moons from different points on the Earth? If so, I dont think that would help in directly proving heliocentrism. Nothing really helps except proof of gravity. Proof of parallax just shows that the stars are moving relative to the Earth, and geocentrism already says that the planets move relative to the Earth.
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14th August 2015, 10:00 AM	#86
sphenisc Philosopher Join Date: Jul 2004 Posts: 5,384	Originally Posted by Mader Levap Paralax would prove that Earth moves around sun, not opposite. You can't have parallax with immobile Earth in center of universe. If you mean that someone would try to explain away star movement without parallax, then that person would have pretty impossible task, especially if you can show that different stars will have different parallax (since they are at difference distance from our solar system). I can't see the problem. The stars are fixed with regard to the Sun. The Sun goes round the Earth - there's your parallax.
sphenisc Philosopher Join Date: Jul 2004 Posts: 5,384	__________________ "The cure for everything is salt water - tears, sweat or the sea." Isak Dinesen

14th August 2015, 12:47 PM	#88
Ladewig I lost an avatar bet. Join Date: Dec 2001 Posts: 28,036	Stellar parallax is the concept that when the Earth is on opposite sides of its orbit, nearer stars seem to shift position in relation to farther stars. The Earth orbiting the Sun is the only possible way to explain this shift. Because the shift is so small, it cannot be detected with the unaided eye and requires powerful telescopes to observe. While it is a very convincing proof of heliocentrism, it does require very good telescopes. But precise clocks and precise measurements of the Earth are not required.
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13th August 2015, 06:44 PM	#84
Craig B Penultimate Amazing Join Date: May 2011 Posts: 22,841	Originally Posted by RussDill Nothing really helps except proof of gravity. Proof of parallax just shows that the stars are moving relative to the Earth, and geocentrism already says that the planets move relative to the Earth. I can't follow your reasoning there. Can you provide more detail? Thanks.

14th August 2015, 09:43 AM	#85
Mader Levap Graduate Poster Join Date: Dec 2012 Posts: 1,576	Originally Posted by RussDill Nothing really helps except proof of gravity. Proof of parallax just shows that the stars are moving relative to the Earth, and geocentrism already says that the planets move relative to the Earth. Paralax would prove that Earth moves around sun, not opposite. You can't have parallax with immobile Earth in center of universe. If you mean that someone would try to explain away star movement without parallax, then that person would have pretty impossible task, especially if you can show that different stars will have different parallax (since they are at difference distance from our solar system).

14th August 2015, 10:22 AM	#87
Craig B Penultimate Amazing Join Date: May 2011 Posts: 22,841	Originally Posted by sphenisc I can't see the problem. The stars are fixed with regard to the Sun. The Sun goes round the Earth - there's your parallax. But the fixed stars surely were not thought to be in orbit round the sun. They were "fixed" with respect to one another, in orbit round the Earth. The "hybrid" systems, like those invented by Tycho and others, were desperate improvisations designed to "save the phaenomena" revealed by Tycho's meticulous observations, and at the same time to retain the principle of a static Earth. Did Tycho or anyone else suggest that the Fixed Stars were centred on any body other than Earth? In the Tychonic system, the Sun. Did TB propose that as regards the fixed stars?

14th August 2015, 03:58 PM	#89
RussDill Philosopher Join Date: Oct 2003 Location: Charleston Posts: 5,426	Originally Posted by Ladewig Stellar parallax is the concept that when the Earth is on opposite sides of its orbit, nearer stars seem to shift position in relation to farther stars. The Earth orbiting the Sun is the only possible way to explain this shift. Because the shift is so small, it cannot be detected with the unaided eye and requires powerful telescopes to observe. While it is a very convincing proof of heliocentrism, it does require very good telescopes. But precise clocks and precise measurements of the Earth are not required. It is not the only way to explain the shift. The stars could just as well be moving in such a way to present the same apparent motion. You can keep adding complexity to a geocentric theory to make it match observation. The heliocentric system needs much less complexity, but that alone doesn't prove it. You can prove disprove geocentrism two ways. One is gravity. The other is special relativity and the cosmic speed limit. I think even Jupiter must need to exceed the speed of light to make it around the Earth in a single day at that distance.
	__________________ The woods are lovely, dark and deep but i have promises to keep and lines to code before I sleep And lines to code before I sleep

14th August 2015, 07:37 PM	#90
WhatRoughBeast Graduate Poster Join Date: Apr 2011 Posts: 1,449	Parallax is easy to handle. It requires only that the stars are not all fixed, just most of them. A few nearer stars are embedded in one or more moveable spheres which oscillate just enough to give the necessary slight position shifts. Given the number of levels of nested epicycles required to explain the motions of other bodies, it seems like a perfectly reasonable approach.

14th August 2015, 08:04 PM	#91
Ladewig I lost an avatar bet. Join Date: Dec 2001 Posts: 28,036	[ Originally Posted by RussDill It is not the only way to explain the shift. The stars could just as well be moving in such a way to present the same apparent motion. You can keep adding complexity to a geocentric theory to make it match observation. The heliocentric system needs much less complexity, but that alone doesn't prove it. I disagree that one could explain the star shift by describing a star movement, but I am having a difficult time finding the language to describe why. Let me think about it.
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14th August 2015, 10:37 PM	#92
Loss Leader I would save the receptionist. Moderator Join Date: Jul 2006 Location: Florida Posts: 27,719	Originally Posted by Ladewig I disagree that one could explain the star shift by describing a star movement, but I am having a difficult time finding the language to describe why. Let me think about it. The problem with all of it is that no breakthrough in science is instantaneous. All the pieces need to come together slowly - technology, observation, theory, etc. You can't prove parallax without telescopes, you can't make telescopes without precise optics, you can't grind lenses precisely without machinery, you can't make good machinery without strong metal alloys, you can't make ... My advice is, if you go back in time to 1000 AD, have a smoked turkey leg and culture some penicillin.
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14th August 2015, 10:50 PM	#93
Craig B Penultimate Amazing Join Date: May 2011 Posts: 22,841	Originally Posted by WhatRoughBeast Parallax is easy to handle. It requires only that the stars are not all fixed, just most of them. A few nearer stars are embedded in one or more moveable spheres which oscillate just enough to give the necessary slight position shifts. Given the number of levels of nested epicycles required to explain the motions of other bodies, it seems like a perfectly reasonable approach. Unless this is a joke, it seems an entirely arbitrary supposition. By that sort of argument you can postulate anything at all. I walk towards a tree, but I can't admit that this is happening because I follow a dogma that holds that I am fixed at the centre of the universe. No problem; I simply propose that the tree is becoming larger.

15th August 2015, 01:58 AM	#94
sphenisc Philosopher Join Date: Jul 2004 Posts: 5,384	Originally Posted by RussDill It is not the only way to explain the shift. The stars could just as well be moving in such a way to present the same apparent motion. You can keep adding complexity to a geocentric theory to make it match observation. The heliocentric system needs much less complexity, but that alone doesn't prove it. You can prove disprove geocentrism two ways. One is gravity. The other is special relativity and the cosmic speed limit. I think even Jupiter must need to exceed the speed of light to make it around the Earth in a single day at that distance. A non-rotation is different from Geocentrism.
sphenisc Philosopher Join Date: Jul 2004 Posts: 5,384	__________________ "The cure for everything is salt water - tears, sweat or the sea." Isak Dinesen

15th August 2015, 06:38 AM	#95
Manopolus Metaphorical Anomaly Join Date: Jan 2010 Location: Brownbackistan Posts: 7,547	Originally Posted by Fellow Traveler Lets suppose you were living say 1000 years ago and had no telescope: What kind of proofs or logic could you give to convince some scientifically inclined person that the Earth rotates around the Sun? Would it be eclipses? Well, you start with retrograde motion and then do a bunch of math and geometry to explain why it happens. They were already quite aware of planetary retrograde motion at that point in history and had all sorts of problems trying to explain it. That's exactly how Galileo explained it, and the telescope wasn't actually a concrete prerequisite to working it out. https://en.wikipedia.org/wiki/Retrog...rograde_motion
	Last edited by Manopolus; 15th August 2015 at 06:43 AM.

15th August 2015, 07:01 AM	#96
hecd2 Muse Join Date: Oct 2013 Posts: 927	There are two sorts of powerful evidence that we have now, which so far haven't been mentioned: 1) Stellar aberration. It is a bigger effect than parallax so easier to measure (and therefore quantified before parallax could be detected). Moreover, it cannot be explained by motion of the source(s) as parallax can. Since it is an effect that is proportional to velocity rather than position, it is 90 degrees out of phase with parallax. 2) Annual doppler modulation of celestial objects. Its phase and amplitude is consistent with stellar aberration. All stars and galaxies in the same direction have the same amplitude and phase of modulation regardless of the distance of the source. Since the speed of light is finite this implies that the modulation is caused by the motion of the earth rather than the sources. Of course, neither of these pieces of evidence could be detected in 1000CE.
hecd2 Muse Join Date: Oct 2013 Posts: 927

17th August 2015, 06:37 PM	#97
PhantomWolf Penultimate Amazing Join Date: Mar 2007 Posts: 20,278	Okay so while it wouldn't prove absolutely that the Earth orbited the sun, it would help... Since we could use what we know now, and it'd be easy to replicate with the tools available in 1012, I'd use Henry Cavendish's work to use a torsion balance device and then show the derivation of G and then subsequently the Earth's mass. I'd follow this up with using orbital velocity and Hipparchus' parallax based determination of the distance to the moon to show that the moon was not travelling fast enough to orbit the Earth based on a stationary non-rotating Earth. I'd then show from this that a rotating Earth closely matched the observed Lunar passage. From this I could then press for the case that the sun's passage was caused by that same rotation rather than that the sun orbited the Earth. Not fool proof, but it'd be a good starting point.
	__________________ It must be fun to lead a life completely unburdened by reality. -- JayUtah I am not able to rightly apprehend the kind of confusion of ideas that could provoke such a question. -- Charles Babbage (1791-1871) Last edited by PhantomWolf; 17th August 2015 at 06:42 PM.

17th August 2015, 07:37 PM	#98
Ladewig I lost an avatar bet. Join Date: Dec 2001 Posts: 28,036	Fellow Traveller, are you still here? Can you tell us what prompted this thread?
	__________________ I lost an avatar bet to Doghouse Reilly.

17th August 2015, 09:14 PM	#100
Ladewig I lost an avatar bet. Join Date: Dec 2001 Posts: 28,036	Originally Posted by Roger Ramjets I wouldn't mess with advanced math or trying to make precise measurements. I would just make a working model of the solar system with a glowing sun in the center, and let the 'scientifically inclined person' have a play with it. Pffft. If you are not going to make your model to scale, what's the point? Quote: Pretty soon he would be announcing that he had figured it out! He? 1000 CE seems like a good time to plant the seeds to equality.
	__________________ I lost an avatar bet to Doghouse Reilly. Last edited by Ladewig; 17th August 2015 at 09:17 PM.

17th August 2015, 09:20 PM	#101
Puppycow Penultimate Amazing Join Date: Jan 2003 Location: Yokohama, Japan Posts: 25,738	Originally Posted by Trebuchet Relative masses of the "geo" and "sol" parts. Originally Posted by macdoc Different set of laws of physics tho if the "earth" had the denisity of a few hundred brown dwarf stars.... A white dwarf has the mass of a sun in the volume of the earth. Eventually they become a "black dwarf" in about 10¹⁵ years after they cool down. But there probably wouldn't be many suns left by then. Just a universe full of black holes and black dwarfs, old dead planets and maybe neutron stars. Even the red dwarfs would probably have used up their fuel by then. Maybe a few new red dwarfs will still be being born but I kinda doubt it.
	__________________ A fool thinks himself to be wise, but a wise man knows himself to be a fool. William Shakespeare

17th August 2015, 09:52 PM	#102
Craig B Penultimate Amazing Join Date: May 2011 Posts: 22,841	Originally Posted by Puppycow A white dwarf has the mass of a sun in the volume of the earth. Eventually they become a "black dwarf" in about 10¹⁵ years after they cool down. But there probably wouldn't be many suns left by then. Just a universe full of black holes and black dwarfs, old dead planets and maybe neutron stars. Even the red dwarfs would probably have used up their fuel by then. Maybe a few new red dwarfs will still be being born but I kinda doubt it. I've been trying to work out exactly what brown dwarfs are, and how they relate to gas giant planets; but I don't think the expression refers to a white dwarf on the way to becoming a black dwarf. It's astounding how long it takes for white dwarfs to cool down, by the way.

17th August 2015, 10:04 PM	#103
Puppycow Penultimate Amazing Join Date: Jan 2003 Location: Yokohama, Japan Posts: 25,738	Originally Posted by Craig B I've been trying to work out exactly what brown dwarfs are, and how they relate to gas giant planets; but I don't think the expression refers to a white dwarf on the way to becoming a black dwarf. It's astounding how long it takes for white dwarfs to cool down, by the way. No, brown dwarfs are different. Think of a brown dwarf as just like a larger version of Jupiter. As a gas giant gets bigger and bigger, eventually it becomes a brown dwarf, then a red dwarf is the next size bigger, then orange and then a yellow dwarf, like our own sun. There is no precise dividing line between any of these. The upper limit for a gas giant planet is about 13 time the mass of Jupiter. Beyond that it is considered a brown dwarf. At some point it becomes massive enough to create a fusion reaction, so it starts to gradually become more like a star than a large planet. A white dwarf and a black dwarf are completely different: a white dwarf is what is left after a large star goes Nova at the end of its life. It's the remnant of a dead main sequence star. https://en.wikipedia.org/wiki/Brown_dwarf https://en.wikipedia.org/wiki/White_dwarf
	__________________ A fool thinks himself to be wise, but a wise man knows himself to be a fool. William Shakespeare Last edited by Puppycow; 17th August 2015 at 10:05 PM.

17th August 2015, 11:27 PM	#104
Craig B Penultimate Amazing Join Date: May 2011 Posts: 22,841	Originally Posted by Puppycow No, brown dwarfs are different. Think of a brown dwarf as just like a larger version of Jupiter. As a gas giant gets bigger and bigger, eventually it becomes a brown dwarf, then a red dwarf is the next size bigger, then orange and then a yellow dwarf, like our own sun. There is no precise dividing line between any of these. The upper limit for a gas giant planet is about 13 time the mass of Jupiter. Beyond that it is considered a brown dwarf. At some point it becomes massive enough to create a fusion reaction, so it starts to gradually become more like a star than a large planet. I'm with you on that. But I have one query left. A star, even a small star like a "brown dwarf", has independently condensed out of a (larger or smaller) cloud. Jupiter is not like that in origin. It has condensed out of part of a cloud, which may not have the same composition as a whole cloud. Planets may well not. The Earth and the Sun are made of different proportions of materials. I would therefore expect an independently condensed "brown dwarf" to be different from an expelled "gas giant" even if both bodies have exactly the same mass. So I am tempted to retain the expression BD for the first, and GG for the second. Is there any sense or value in such a convention?

18th August 2015, 12:15 AM	#105
Puppycow Penultimate Amazing Join Date: Jan 2003 Location: Yokohama, Japan Posts: 25,738	Originally Posted by Craig B I'm with you on that. But I have one query left. A star, even a small star like a "brown dwarf", has independently condensed out of a (larger or smaller) cloud. Jupiter is not like that in origin. It has condensed out of part of a cloud, which may not have the same composition as a whole cloud. Planets may well not. The Earth and the Sun are made of different proportions of materials. I would therefore expect an independently condensed "brown dwarf" to be different from an expelled "gas giant" even if both bodies have exactly the same mass. So I am tempted to retain the expression BD for the first, and GG for the second. Is there any sense or value in such a convention? I'm afraid this is beyond what I know. Not sure exactly what you mean by "an expelled gas giant". Expelled from what? My own understanding is that all of these bodies condense from clouds of dust and gas, but exactly how large (massive) the resulting lump of matter gets determines whether it is a star or a planet. I'm no astronomer, just a layman who is interested in astronomy. You are right that the Sun is composed of different elements from the earth. It's mostly hydrogen (71%) and helium (27%), and together those two elements account for 98% of the sun's mass (and 99.9% of the atoms). The earth OTOH, is mostly made of much heavier elements like iron, oxygen, silicon, etc. and hydrogen and helium are actually relatively rare on the earth. I think mainly that's because there isn't enough gravity on earth to keep hydrogen and helium from floating to the top of the atmosphere because they are lighter than nitrogen and oxygen, and then off into space. Jupiter is much more like the sun than the earth: it's also mainly made of hydrogen and helium, not heavier elements like the earth. Quote: Thus, Jupiter's atmosphere is approximately 75% hydrogen and 24% helium by mass, with the remaining one percent of the mass consisting of other elements. The interior contains denser materials, such that the distribution is roughly 71% hydrogen, 24% helium and 5% other elements by mass. So the main reason that the earth and the smaller planets are made of different elements than the sun and Jupiter is, simply because they are too small to hold hydrogen and helium, so those mostly float away, leaving only the heavier elements behind.
	__________________ A fool thinks himself to be wise, but a wise man knows himself to be a fool. William Shakespeare

18th August 2015, 05:28 AM	#106
Craig B Penultimate Amazing Join Date: May 2011 Posts: 22,841	Originally Posted by Puppycow I'm afraid this is beyond what I know. Not sure exactly what you mean by "an expelled gas giant". Expelled from what? My own understanding is that all of these bodies condense from clouds of dust and gas, but exactly how large (massive) the resulting lump of matter gets determines whether it is a star or a planet. I'm no astronomer, just a layman who is interested in astronomy. Before studying the rest of your post, I mean this: a body of that mass might have been produced on its own by the collapse of a gas cloud, or it might have at one time been part of a stellar system, and then been thrown out of it by the interaction of binary stars or in some other way. Would bodies of such disparate origin be the same in composition? That's what I mean.

18th August 2015, 06:13 AM	#107
Chanakya Join Date: Apr 2015 Posts: 2,598	Originally Posted by Fellow Traveler Lets suppose you were living say 1000 years ago and had no telescope: What kind of proofs or logic could you give to convince some scientifically inclined person that the Earth rotates around the Sun? Would it be eclipses? Nice thought experiment. Here's my lazy answer: Since you're living 1000 years ago, it would probably be the exact same thought processes that led you, yourself, to that hugely radical notion, that the earth is spherical and that the earth goes round the sun. You'd only need to describe to said scientifically minded person how you yourself arrived at that conclusion. If time machines enter into the process (of your knowing what you know when living 1000 years ago), so much the better.
Chanakya Join Date: Apr 2015 Posts: 2,598

18th August 2015, 05:46 PM	#108
Earthborn Terrestrial Intelligence Join Date: Aug 2001 Location: Terra Firma Posts: 6,291	Originally Posted by Puppycow why would you even think that the earth orbits the sun? Careful observation? Quote: Something would have to put that idea in your head in the first place, almost 5 centuries before it occurred to Copernicus. Something put the idea in Copernicus head, and that thing was centuries of highly detailed observational data. From Arabs. During the so-called Islamic Golden Age, a lot of astronomical data was recorded by Islamic scientists who were quite familliar with the heliocentric model, and who had no particular religious doctrines favouring geocentridm. Some even toyed with the idea that stars might be suns with their own planets orbiting them. Even for them, heliocentrism wasn't a new idea. The concept has been floating around for a long time. The ancient Greeks knew about it, even Ptolemy who gave us the geocentric model with epicycles had to deal with heliocentric critics. Who based their ideas on even older Hindu observations.
	__________________ Perhaps nothing is entirely true; and not even that! Multatuli

18th August 2015, 05:57 PM	#109
Craig B Penultimate Amazing Join Date: May 2011 Posts: 22,841	Originally Posted by Earthborn During the so-called Islamic Golden Age, a lot of astronomical data was recorded by Islamic scientists who were quite familliar with the heliocentric model, and who had no particular religious doctrines favouring geocentridm. These scholars may have speculated as you describe, but they did in fact have "particular religious doctrines favouring geocentrism". The Quran expounds a clearly geocentric cosmology. It even has the sun setting in a muddy pool. Lo! We made him strong in the land and gave him unto every thing a road. And he followed a road. Till, when he reached the setting-place of the sun, he found it setting in a muddy spring, and found a people thereabout. We said: O Dhu'l-Qarneyn! Either punish or show them kindness. Then he followed a road. Till, when he reached the rising-place of the sun, he found it rising on a people for whom We had appointed no shelter therefrom. Qur'an 18:84-90 The person "Dhu'l-Qarneyn" is, I believe, thought to be a reference to Alexander the Great.
	Last edited by Craig B; 18th August 2015 at 06:02 PM.

8th January 2021, 05:48 PM	#110
Reformed Offlian Critical Thinker Join Date: Apr 2020 Location: USA Posts: 349	Originally Posted by Fellow Traveler Lets suppose you were living say 1000 years ago and had no telescope: What kind of proofs or logic could you give to convince some scientifically inclined person that the Earth rotates around the Sun? Would it be eclipses? It bears pointing out that Copernicus himself largely argued his case based on classical (i.e., Ptolemaic) data. So, basically, crib the arguments from De Revolutionibus Orbis. ETA, Sorry, I had no idea how old this thread was until after I responded. No idea why this popped up where it did in my search results.