Thread: Planets and Retrograde Motion

That is cool! After I saw the tour I played with the controls!

Originally Posted by Oneironaut

Just stumbled upon This and thought it was interesting.

I've never thought about the motion of the other planets, from our perspective, aside from the simple idea of their moving about their own orbits around the sun. Pretty cool.

Makes you realise how hard it was to work out what was going on... it's really not that obvious at all from the perspective of Earth.

That's a really cool site. I've seen a simulation like it once before, in physics class, though. But this one was well made.

Originally Posted by Xei

Makes you realise how hard it was to work out what was going on... it's really not that obvious at all from the perspective of Earth.

And yet some ancient greeks managed :p

Uh... which Greeks?

Originally Posted by Xei

Makes you realise how hard it was to work out what was going on... it's really not that obvious at all from the perspective of Earth.

Definitely. I can hardly imagine how tough it must have been to track them across the sky, when they would loom closer, then further away, from various directions. It's kinda weird, just thinking about it.

Well, plus we didn't even have most of the information above; that thing's two dimensional. When we watch lights cross the sky they only move in one dimension, in a line. We can't tell if they are close or faraway.

Originally Posted by Xei

Well, plus we didn't even have most of the information above; that thing's two dimensional. When we watch lights cross the sky they only move in one dimension, in a line. We can't tell if they are close or faraway.

So can we not tell, in any way, if they are at their closest point, or the furthest point in their own own orbit? They don't appear lighter, or more dull? Or their size never changes, in our point of view? Say, if Jupiter was at its closest point to us, it would look the same if it was waaaaaay out at like 100 degrees (in its own orbit. I know 180 would probably be completely blocked by the sun, yes?) or would we just not see it, that far out, because it would be shrouded by the daytime atmosphere?

Hope that makes sense.

Well clearly we easily have the technology today to do it, but have you ever noticed that Jupiter is 20% brighter than normal..? Probably not; bear in mind that Jupiter's distance from us doesn't vary by a huge amount. How would you go about objectively measuring it, plus taking into account cloud cover etc.? Only a few hundreds of years ago people didn't even have telescopes.

Originally Posted by Xei

Well clearly we easily have the technology today to do it, but have you ever noticed that Jupiter is 20% brighter than normal..? Probably not; bear in mind that Jupiter's distance from us doesn't vary by a huge amount. How would you go about objectively measuring it, plus taking into account cloud cover etc.? Only a few hundreds of years ago people didn't even have telescopes.

Very good point.
I'd actually forgotten how "new to the scene" instruments like telescopes really are. And yea, the brightness of the planet makes such a miniscule change - over such a long period of time - that I suppose it would be rather hard to measure it objectively.

neptune has the coolest perspective. All of the other planets are clustered around the sun. And then pluto comes from out of nowhere and almost smacks into it.

Originally Posted by Xei

Uh... which Greeks?

I don't remember who it was, sorry. But they didn't believe him / them.
I'll try and remember to ask the one who told me, though.

The Greeks did many brilliant things but a heliocentric model of the solar system wasn't one of them.

Erotosthenes of ancient Greece deduced the circumference of the Earth in 200 BC.

Khh, it's mentioned in Carl Sagans Cosmos. The Library of Alexandria is said to have contained a book by Aristarchus of Samos, who deduced that the Sun was the centre of the solar system and not the Earth a full 1800 years before it would be accepted by the world as fact.

Sure takes a long time to convince the world of truth..

Originally Posted by Alextanium

Erotosthenes of ancient Greece deduced the circumference of the Earth in 200 BC.

Khh, it's mentioned in Carl Sagans Cosmos. The Library of Alexandria is said to have contained a book by Aristarchus of Samos, who deduced that the Sun was the centre of the solar system and not the Earth a full 1800 years before it would be accepted by the world as fact.

The circumference of the Earth isn't really related to heliocentrism... actually it's been known for thousands of years that the world was round.

I never knew the Greeks were the first to postulate heliocentrism though, that is interesting...

Originally Posted by Xei

The circumference of the Earth isn't really related to heliocentrism... actually it's been known for thousands of years that the world was round.

I never knew the Greeks were the first to postulate heliocentrism though, that is interesting...

Such is the problem with time... And the fact that everyone ignored this thought at first.

I think it may only seem that way through the lens of modern Western society. We tend to date discoveries back to the people who were inspired by the texts of the Greeks which reentered Europe a few hundred years back. The Greeks themselves probably didn't ignore it.

Originally Posted by Xei

I think it may only seem that way through the lens of modern Western society. We tend to date discoveries back to the people who were inspired by the texts of the Greeks which reentered Europe a few hundred years back. The Greeks themselves probably didn't ignore it.

Perhaps, and that is the problem with time.. What we know is only barely scratching the surface of their society.

It's really quite sad that we experienced the "Dark Ages", who knows how far more advanced we could possibly be...

Who's 'we'?

If you consider Western Europe to be the totality of human culture then perhaps, but otherwise, the Arabs went through a golden age of collecting and building upon the knowledge of previous cultures.

Originally Posted by Xei

Who's 'we'?

If you consider Western Europe to be the totality of human culture then perhaps, but otherwise, the Arabs went through a golden age of collecting and building upon the knowledge of previous cultures.

We as in general, Europe was the driving force after the dark ages... was more my point.

And I guess I am of European descent... Italy etc.. So more of the We as in my own personal blood my bad.

My point is really that there was never a 'Dark Age' for mankind. It has been a relatively steady progression. So questions like 'where would we be if there hadn't been a Dark Age'... who knows, perhaps we'd be even further back. The Arabs brought to light some extremely important stuff for science and mathematics (starting with our number system...).

Originally Posted by Xei

My point is really that there was never a 'Dark Age' for mankind. It has been a relatively steady progression. So questions like 'where would we be if there hadn't been a Dark Age'... who knows, perhaps we'd be even further back. The Arabs brought to light some extremely important stuff for science and mathematics (starting with our number system...).

Yes but the majority of the progress we saw in the 20th, 19th, 18th etc.. century was caused by European descendants, even the non-progressive movements were mostly caused by European descendants... I don't doubt the intelligence and accomplishments of the Arabs but they didn't proliferate theirs as widely nor did they accomplish the same technological feats.. My point was, the "dark ages" happened for Europe, and surrounding areas.. Where their was a stunt in technology growth especially compared to the Romans/Greeks(sure their were a few inventions... I forgot exactly..) but generally the population was poor, uneducated, didn't shower... sawed peoples legs off to fix everything, leeched everything.. My point was... if European culture didn't experience such a dramatic shift from the Roman Empire of glory to what was the shambles of the middle ages in Europe... Who knows how much information was lost and never recovered, or recovered thousands of years later? And who knows how many great minds went to waste.

The Romans were facist pigs who didn't contribute one iota to the wisdom of mankind.

The 'progress' of the Renaissance was essentially Europe absorbing the achievements of the Arabs, who had gathered and built upon the achievements of previous civilisations. This was then exceeded in Europe in the following centuries. Nowadays the phenomenon has spread and become a pretty much global one.

Originally Posted by Xei

The Romans were facist pigs who didn't contribute one iota to the wisdom of mankind.

The 'progress' of the Renaissance was essentially Europe absorbing the achievements of the Arabs, who had gathered and built upon the achievements of previous civilisations. This was then exceeded in Europe in the following centuries. Nowadays the phenomenon has spread and become a pretty much global one.

The Romans have a multitude of problems, violence and a thirst for conquer for one.. but I would hardly say they didn't contribute one iota to the wisdom of mankind. I feel them more akin to the American population. (We've contributed much good and much evil to this world)

And the original progress was started by European, and far more has been accomplished by the Europeans afterwards. But as is obvious the way the world works is changing, and many more cultures are catching up, and perhaps passing us... It's a race to the bottom. It's obvious that Arabs had a great many achievements and helped us with formulas/etc.. that helped us develop our technological marvels.

Imagine if their was no need for a renaissance if after the fall of the Roman Empire if Europe didn't fall into it's cycle of ignorance... We could be that much more advanced. After all you said the Arabs worked off of old cultures more specifically probably European culture, had they no need because those fallen cultures ancestors could have easily kept the line of progression going.