Question for the forum: What would the ancients have needed to determine planetary orbits?

originally posted by: Sinter Klaas

How far would you go, with this instrument as technological advanced possible. Incorrect theories account for the imperfections of the mechanism.
At this point the Greek where already aware that the Sun was going around the Earth right ?

No, they were not great believers in Heliocentrism, though we have mentions of people that proposed non-geocentric, and even heliocentric, theories in Ancient Greece. The works themselves are lost, but other writers did mention them.
Heliocentrism isn't required for the construction and use of the Antikythera Mechanism.

What you are referring to is that they knew the Earth was a sphere.

Harte

originally posted by: Harte

The first thing they would need is a theory of Heliocentrism, which the certainly did not have and almost certainly could never have had, since the Sun, the Moon and planets obviously circled around the Earth.

Armed with heliocentricity, they could have established reasonable estimates of the orbits of visible planets using the same means they were using to plot their positions in the sky - good eyeballs and standard positioning equipment.

I think this is a very good answer!



Armed with the idea that all planets, including our own, orbit the Sun, the above observation (for example) could reveal a lot.

In the same way, observing retrograde motion like above SHOULD probably have made the one or the other sharp thinker come up with the idea of heliocentricity on their own. But, the fact that this idea was taboo for the longest made this science certainly not easier.

a reply to: Hanslune

We might suppose an alien mission descend, took stock of the situation (perhaps they had enabled it at some earlier epoch) and set about an attempt to get humanity off on the right foot. (Such as the way we teach one another the A, B, Cs.)

First, they would say, "All of your silly myths are wrong, earth people. The sun is not the only thing in the sky and it is not the center of the universe. We can show you the way to understand everything, from when the rains come and when to mate your animals (to them own kind). Later, we'll come back and shake up your world again with new revelations."

Thus, with an intense curiosity aroused in the more thinking crowd with that promising carrot, they enticed mankind on a path uncompleted to this day. The method was math (with a tad of philosophy thrown in for steerage).

Since math is true, it was never beaten back, totally ignored or replaced with something better so it survived and supports in some fashion large and small your existence today. You may wonder if that story be true, and wonder if maybe humans would have done it alone. Possibly. I think we would still be herding sheep.

Maybe... they did it to be able to predict astronomical events like eclipses and that one thing where two planets appear to be very close together creating the illusion of one huge bright star, and they used this to trick the masses. The old "look the snake god is eating the sun! We need the sun to live but fortunately our priests are in contact with the snake god and know how to appease him. So do whatever we say quickly. Oh look its working, the snake god is going away! Good thing you listened to us! But the snake god will back and our priests will know beforehand so we can prepare to appease him once more." trick, which can be used in many variations for many different events. They do not need the snake god today, but still celebrate the planets movements because that is the reason they were able to take control over humanity thousands of years ago so they honor it because it is the reason they have their power today. Maybe.

But, the fact that this idea was taboo for the longest made this science certainly not easier.

Copernicus figured out how retrograde motion worked.

But, while heliocentrism did go against the religious grain, It had actually been around for quite a while. But the trouble with it is that it is so very counter intuitive. How can the Earth move? I can't feel it move? And very difficult to prove. That is, until Galileo saw that Venus exhibited phases like the Moon. That's pretty hard to explain with a geocentric model.

a reply to: Aliensun

First, they would say, "All of your silly myths are wrong, earth people. The sun is not the only thing in the sky and it is not the center of the universe

Except, they didn't.
You don't think people are very smart, do you? Projection?

a reply to: Harte

Not really. I thought their combined data and stuff would have paved the pavement for that idea. Around the time they came up with these amazing things. Maybe a little later.

About the sphere idea.

The possibilities seem endless, but as Phage noted Venus is the third brightest object in the night sky and the retrograde motion would catch an ancient astronomers eye.

a reply to: Phage

Howdy Phage

I thought the title might lure you in.

So what are your thoughts on the ancients being able to figure out the elliptical orbits prior to when it was done in historic times? The view I'm seeing here by the early responses is what I would have expected - highly unlikely.

What would be your opinion on the matter?

originally posted by: Phage

But, the fact that this idea was taboo for the longest made this science certainly not easier.

Copernicus figured out how retrograde motion worked.

But, while heliocentrism did go against the religious grain, It had actually been around for quite a while. But the trouble with it is that it is so very counter intuitive. How can the Earth move? I can't feel it move? And very difficult to prove. That is, until Galileo saw that Venus exhibited phases like the Moon. That's pretty hard to explain with a geocentric model.

True and to see Venus would require technology, in this case a telescope to determine. So what capacity in lenses did the early civs have?

My first impression is that they had none at all.

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Just one more question at what point had mathematics advanced enough that an elliptical orbit could be calculated?

originally posted by: Hanslune

originally posted by: Phage

But, the fact that this idea was taboo for the longest made this science certainly not easier.

Copernicus figured out how retrograde motion worked.

But, while heliocentrism did go against the religious grain, It had actually been around for quite a while. But the trouble with it is that it is so very counter intuitive. How can the Earth move? I can't feel it move? And very difficult to prove. That is, until Galileo saw that Venus exhibited phases like the Moon. That's pretty hard to explain with a geocentric model.

True and to see Venus would require technology, in this case a telescope to determine. So what capacity in lenses did the early civs have?

My first impression is that they had none at all.

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Just one more question at what point had mathematics advanced enough that an elliptical orbit could be calculated?

Hans , like I said that would have been at the point that newton laid down the basics of dynamic physics, and codified calculas. Until you have those computational techniques, describing an elliptical orbit is impossible.

originally posted by: bigfatfurrytexan
a reply to: Hanslune

Too bad the majority of Pythagoras' work was destroyed.

"There's music int he spheres"

Yes so much was lost, I've posted this before but it is an interesting piece of work, a list of a lot of known lost works

Lost works of the Classical era

a reply to: Hanslune

I think it would have been possible but it requires several important factors to do so; very accurate observations, a very good mind, and a mind not constrained by convention. Tycho made very accurate observations and had a very good mind but he could not allow for heliocentrism. He did come up with a model which would fit his observations but it was an amazing kludge. Had he not been so constrained, perhaps he would have come up something closer to reality.

A knowledge of gravity is not required. Kepler produced his laws of orbits with no such knowledge, just observation (actually those of Tycho).

We know that humans have been observing the sky for a very long time, and doing so with high precision. I think it could have been done but until science entered the picture, I don't think it would have. And, until the advent of telescopes, there would have been no way to prove it was the correct model anyway.

a reply to: Hanslune

oh wow....thanks hans!

I think Pythagoras was the first to concoct heliocentrism. It is ascribed to one of his studies (i can't recall the name)....but everything I have seen from Pythagoras was that he was onto it.

He may not have nailed the orbit of the sun...but the spacing of the planets and the heliocentric concept seems to be there. With the planetary placement, I believe his model was accurately predictive.

The concept of heliocentrism isn't enough to calculate orbital distances. Ancient cultures, like Babylon, the Chaldeans, Hindu, and Greeks were good at compiling statistical data on planetary movement, well enough that by 1000-800 BCE Babylonians were well adept at predicting eclipses and Greeks circa 400-500 BCE had determined the "epicycle" of planetary motion well enough to create the Antikythera device.

But orbital radius was not defined until Kepler developed his three laws of motion. Kepler studied the orbits of the planets and found that the time period of a planet's orbit squared in years is equal to the distance from the sun cubed in AU (which is the distance from the Earth to the sun). T squared = Radius cubed. All observable planets could then have their orbital radius calculated as a function of Earths, in AUs.

However the distance of the Earth to the sun (AU) was not determined until 1672 when Giovanni Cassini, using a telescope, determined the distance between Mars and the Earth by parallax - in effect, Cassini, located in Paris, and a colleague stationed in French Guiana, both measured the position of Mars against background stars at a predetermined time. In effect they were creating a gigantic triangle with the Earth's radius as one known leg and the angle between the others now known from their observations. They could then calculate the long leg to Mars. For this calculation to do them any good though, they had to perform it when Mars was exactly in opposition to the sun - forming a straight line of sun - Earth - Mars. They calculated it to around 7% of the modern measurement of 78,000,000 KM. Knowing this they then performed a simultaneous equation 78,000,000 = M - E (where earlier they had already determined M as 1.524 AU). This then gave them the distance of Earth to the sun and consequently to all the other planets.

So I'd say what the ancients needed to calculate orbital distances are:

Empirical data based on observations of planetary motion (which they had at least by 800 BCE). They would need to know the time a planet takes to complete one orbit.

A telescope

Radius of the Earth

Latitudes and Longitudes

Instantaneous communication between observers at far points of the globe

Math (*)

Latitudes and longitudes were needed to make the Earth-Mars observation. This calculation alone, made by Cassini, is very complex, and well beyond anything noted in ancient mathematics. (see Distance to Mars.

(*) The math involved alone would seem to exclude ancient civilizations from having the ability to calculate orbital radii. Scalar vectors, Algebra, Trigonometry, the use of Degrees radians, etc. (although some basic forms of algebra and trig do show up in some form in those cultures.)

Please note none of this begins to touch orbital mechanics.

originally posted by: Harte

originally posted by: Hanslune
First off I don't have the math(s) ability to answer this question myself so if I could call upon the many gifted posters here to answer it.

One see's claims that the ancient knew the orbits of the inner (and outer) planets.

So what instruments, mathematics and skills would be required to obtain that information? The Europeans and others seemed to have worked on this problem for centuries until they resolved it.

So having placed the question I back away and hope that those more gifted by Saint Hubertus can answer it.

The first thing they would need is a theory of Heliocentrism, which the certainly did not have and almost certainly could never have had, since the Sun, the Moon and planets obviously circled around the Earth.

Armed with heliocentricity, they could have established reasonable estimates of the orbits of visible planets using the same means they were using to plot their positions in the sky - good eyeballs and standard positioning equipment. They had the former, and they built the latter (stone circles, the edges of ziggurats, etc.) However, they could not have begun to do this without having the concept that these bodies orbited the Sun.

This is why Europeans had the various layers of "crystal spheres" turning around the Earth for so many years, with the planets turning little circles on their individual spheres; until moons were observed to be going around Jupiter.

Harte

You mean like the 95% deluded ppl that
belive in god or gods....

You are so wrong...

There are ppl that know better..

The oldest telescope was probably a cave wall but the predictability level in the time of Brahe probably helped.

en.wikipedia.org.../File:Horrocks_observing_the_1639_transit_of_Venus_by_Eyre_Crowe.jpg

So that means ancient observations from places like Newgrange 5000+ years ago might have been possible.

www.mythicalireland.com...

originally posted by: Harte

originally posted by: Hanslune
First off I don't have the math(s) ability to answer this question myself so if I could call upon the many gifted posters here to answer it.

One see's claims that the ancient knew the orbits of the inner (and outer) planets.

So what instruments, mathematics and skills would be required to obtain that information? The Europeans and others seemed to have worked on this problem for centuries until they resolved it.

So having placed the question I back away and hope that those more gifted by Saint Hubertus can answer it.

The first thing they would need is a theory of Heliocentrism, which the certainly did not have and almost certainly could never have had, since the Sun, the Moon and planets obviously circled around the Earth.

Armed with heliocentricity, they could have established reasonable estimates of the orbits of visible planets using the same means they were using to plot their positions in the sky - good eyeballs and standard positioning equipment. They had the former, and they built the latter (stone circles, the edges of ziggurats, etc.) However, they could not have begun to do this without having the concept that these bodies orbited the Sun.

This is why Europeans had the various layers of "crystal spheres" turning around the Earth for so many years, with the planets turning little circles on their individual spheres; until moons were observed to be going around Jupiter.

Harte

Man I was hoping someone would say this Great post!

Now if we could just get someone to pull that curtain aside, I'd like to see the Wizard so he can tell us the reason for all the lies.

Your all assuming the Solar System as witnessed today - has always been that way.
I'd like to know what evidence exists that provides these assurances?


Have the orbits changed? Are the observations of 'Gods' (Planets) - the answer to 99% of ancient mans endeavours?
Are the tiny images we see today at certain times of the year in the sky - relevant to ancient man's unwaivering depictions/worship>?



Great thread topic!

a reply to: 131415

Are you proposing one of the 'billiard ball' scenarios then?

For lurkers there were earlier theories that the solar system we see now was quite 'active' during ancient times, with Venus popping out of Jupiter, Mars running around, etc. One of the better known of these theories was covered in a book called, 'Worlds in Collision' written by Immanuel Velikovsky and first published April 3, 1950. There were others too.