and one thing they saw that really screwed things up was this like imagine you were tracking the planets okay I'm gonna get some a blank space down here imagine you were tracking the planets and these were the background stars okay and let's say oh my froze up let me just reboot that there we go so that's the background stars and you are gonna track the planets from day to day to day to day and let's say you were tracking Mars for example if you tracked Mars and if this was how you thought things worked Mars would just spin around the earth in a simple circle and so if you were standing on the earth looking up that should mean that Mars should grow across the stars in a perfect straight line right you would expect Mars to go across the stars like this maybe it's here in January and then July so what's with the month after January January February basically you should go across the stars like this January February March April May June blah blah blah blah blah nice straight line but if you really watch Mars every single day every once in a while this is gonna happen check this out let me zoom in a little bit here we go for a few months it'll go one direction so January February March and then Oh for a little while it'll actually turn around and go backwards across the sky for a few months and then it'll turn around and go the main direction again so most of the time Mars goes one direction across the sky but every once in a while for a little bit it'll turn around and go backwards okay and we call that retro motion and Mars is not the only planet that does it so here we go retrograde motion that's when a planet looks like it goes backwards for a little while okay so the ancient Greeks had to figure out how do we explain this how do we get the mark how do we get Mars to go backwards in our system right and that was hard for them to do it was hard for them to figure this out and the person that figured it that the first person to come up with an explanation for this which we now know is wrong because it's based in the ancient Greek system but the first person to come up with an explanation for this that worked sort of was a guy named Ptolemy okay I'll write his name down Ptolemy's Ptolemy and by the way the the P is silent so when you're saying this guy's name it's just Ptolemy okay just Ptolemy this was an ancient Greek he was a mathematician and scientist and he came up with a way to explain retrograde motion okay so what did he do he kept the earth in the center so right off the bat we know he's wrong but the ancient Greeks were pretty sure that the earth wasn't moving so let's keep the earth in the middle I'll put a little eye on it for the earth okay and he kept a glass ball for every planet every single planet still had a glass ball I'm just gonna draw it for one planet but every planet had another one of these okay now remember in the old system before Ptolemy the ancient Greeks thought that the planet was attached to this ball and that that ball just spun okay here's what Ptolemy added he added a second glass ball he attached a smaller glass ball to the big glass ball and he said that the planets were attached to one of those so each planet had one big glass ball and one smaller glass ball on it that it was actually attached to so that little dot that might as well be Mars okay and he called this extra glass ball and epicycle so his explanation for retrograde motion was epicycles now how does this fix things well here in his version the big glass ball stayed still and the little glass ball rolled on the big glass ball okay like a tire like imagine that this ball was a tire and that Mars right here this little planet is a nail in the tire okay now if we do that and this ball is allowed to roll what's going to happen well when Mars is on top of this little ball it's gonna roll forward but which way will Mars go when it spins down to the bottom of this little ball which way will Mars be going it's moving forwards when it's on top of the ball but which way will it move when it gets to the bottom of the little ball backwards yeah it's easier for me to show you guys a picture from the book for this get right here there we go so on here as the as the little glass ball rolls on the big one every time the planet moves underneath the tire it'll move backwards for a little bit every time it moves under the tire it moves backwards for a little bit so in our little picture that I was drawing what's gonna happen is that as the planet goes around the Earth it's gonna loop underneath like this over and over again so instead of going around the earth in a perfect circle it goes in a curlicue shape right like spaghetti right and that way if you're underneath this if you're underneath this part it's gonna look like the planets going one way but if you're underneath that part it's gonna look like it's going backwards so every once in a while it'll go backwards forwards backwards and that people are pretty satisfied with that explanation because it's didn't throw out the whole system but it still could show the planet going backwards sometimes but here's the thing we got better at mapping the Stars okay we got better at mapping the Stars and if this is what's happening if this was right let's say let's say it took five months between this retrograde motion and this retrograde motion if there was five months between this retrograde motion in this retrograde motion when would the next one happen when would the next one happen if it took five months from that backwards motion to that backwards motion when would this next one happen don't overthink it five more months yeah and then five more months to the next one and then five more months to the next one if this was the whole explanation then and that ball spun at one speed which that's what they assumed was happening that meant that the retrograde motion should always happen like a clock it should always happen in the same amount of time but as we got better at mapping the Stars we realized it was irregular it didn't always take the same amount of time to start going backwards and so what they had to do was tweak it again okay they tweaked it another time so here we go so how do they fix it they still have the earth in the middle they really love that part and they're still not figuring out that that is the reason they keep having to fix the problem that's the problem that they haven't realized yet but how did they fix it so they still had the glass ball for each planet they still had the epicycle that was rolling on it but the planet wasn't attached to that the fix was there's another glass ball on that glass ball and that's what the planet is attached to so the littlest glass ball can roll on the medium glass ball and the medium glass ball still rolls on the big glass ball so now the planet goes around us like this okay yeah so so this is something right this is something and it was more accurate at predicting when retrograde motion would happen it was more accurate at predicting when the planets would go backwards until until they got better at mapping the stars again and so they had to tweak it again they had to tweak it again after this anybody want to guess let's guess here how did they tweak it what did they add to this to try to make it more right what was the next week I bet you can guess marbles Greeks had more balls there we go there's another ball and that worked a little bit better but it didn't work perfectly so they added another ball and they added another ball and they added another ball in another ball in another ball they added between like 20 or 25 balls to each stack and the planet was attached to like the very top of that stack and so this whole stack was just swinging around swinging around big stack of balls just tons and tons of glass balls somebody stole the joke that I usually make about this it's like total ball ception total ball ception here and here's the thing Mars was not the only one and that means that this the planets were going around the earth like a crazy mess like the path of the planets was just ridiculous and at this point people are like is the solar system really this complicated right they started to realize this was a little bit wrong also check it out if these things are made out of glass or crystal and every single planet had a giant precarious stack of them that they're all swinging around like crazy what could happen if that were true if every planet was swinging another a tall stack of glass around glass or crystal that would be a big problem yeah yeah it could break right it could break if this was what how things were set up if those glass stacks got too tall they could slam into each other and then break and then if they broke the planets would fall onto the earth at least that's what the ancient Greeks thought so around this time people were starting to think maybe you may be weird like going in the wrong direction with this whole thing and unfortunately I think they would have maybe considered going back to the heliocentric model at this point but before they could come up with that idea they their Society collapsed okay Greek society and fell apart and you know things were on fire not because of this it was for other historical reasons take a history class for the details but if your society is on fire are you probably going to worry about this are you probably going to worry about why the planets go backwards sometimes in the sky is that going to be top of your list of like worries under a collapsing Society no no at that point your job is just to survive again and so probably you didn't worry too much about explaining the sky right so yeah actually most of this information may have been lost to us forever Society collapsed really bad at the time things were burning libraries were burned down most of the information was lost in Greece itself the only reason we know that the ancient Greeks thought any of this is that before their society collapsed they visited the Middle East some of their scholars and some of the scholars from the Middle East actually visited Greece as well and there was cultural exchange and idea exchange and so luckily for us libraries in the Middle East where society wasn't collapsing they were able to hold on to all of this work and actually improve on it over time they were able to in the Middle East to make better and better star charts over and over and over and over again who forgot to write down the ball through they wrote it down and it was saved if nobody wrote it down we wouldn't know it today right now check this out so we're gonna kind of skip forward a lot a bit a lot in the in the timeline here because not a lot of work was done on this for hundreds of years after the ancient Greece other than people making better and better star charts and having to make tiny little tweaks like this but nobody was interesting and changing the central problem which was that the earth was the Earth's just not at the same