Transcript
0:00 is our solar system right here you can see the planets going around the sun in nearly perfect circles and if we zoom in closer here's earth and we're going around the sun with the other planets this is a heliocentric model and it makes sense but in the past we used to think the earth was the center so this is the model if earth was the center of our solar system and you'll notice as they move the planets move in really
0:21 weird ways looks like jupiter saturn and uranus are kind of dancing with each other up there and if we zoom in closer to earth we can see the different planets move in really weird ways mercury in the sun are kind of spinning around mars is doing something funny let's look at mercury by itself so here's mercury and the earth it's kind of spinning in this weird little circle this would be really confusing to people in the past they're trying to figure out
0:44 what's going on you can see it's going one direction and then it goes backwards relative to our vision so in the night sky it would move like this and then it would start moving the other direction and move further this way it wouldn't make any sense to him next if we look at the sun this actually makes sense this goes in a nearly perfect circle that's logical because if the earth roughly goes in a circle around the sun then the
1:04 sun would go roughly in a circle around the earth now if we add mercury now you'll notice what's happening is mercury is just going around the sun essentially and as the sun goes around the earth mercury goes around the sun so this orange circle represents the path of the sun around earth and this red circle represents the path of mercury around the sun and you can see how closely that is approximating it it's not exact because i'm not a rocket
1:27 scientist and i did do these formulas by hand so you can tell i'm not perfect if we get rid of the sun and just think of this as two circles this looks like a circle going around a circle that's called an epicycle and that is how ancient astronomers dealt with this weird behavior is they created epicycles if we zoom out the same thing is true for say jupiter so this orange circle is the inner circle and this red one is the
1:50 epicycle for this orange one so the center of this red circle is going around this orange circle and jupiter moves very slowly but it's moving along that red circle and the center of this red circle is just rotating around this orange circle so this one's also an epicycle so using multiple epicycles was the way that ancient astronomers would explain this weird behavior that they saw from earth then one day someone came along and said wait a second if all of
2:15 these are going in circles around the sun why don't we just put the sun in the middle and that is when they discovered that everything came together super clean but they weren't able to say that for a really long time because you'd be a heretic if you said that the earth wasn't the center of the universe