Full transcript
0:00The A-Z of isms... geocentrism.
0:04Until the 16th Century,
0:06geocentrism was a prevailing theory of what the universe looked like.
0:10Geocentrism is the belief that the Earth,
0:12our home planet,
0:13is at the centre of the universe.
0:15Everything else revolves around us.
0:18This seemed obvious to ancient astronomers,
0:20after all they observed the sun and the moon, the planets and the stars,
0:24to move across the sky as we go forward through time,
0:27just like we do today.
0:29So this must mean that the Earth is in the centre of it all, right?
0:32Wrong!
0:34The earliest geocentric models of ancient Greek
0:37philosophers/scientists/general all-rounders
0:38such as Plato and Aristotle in the 4th Century BC
0:42placed a stationary Earth at the centre
0:44with the planets and the stars moving around us on circles or spheres.
0:49The thing is, the simple geocentric model
0:52couldn’t quite explain all that we see when we watch the skies.
0:56For a start, the planets change brightness,
0:59which shouldn’t happen
1:00if they're always the same distance from the Earth.
1:03Second, the paths of Mars and Jupiter through the sky
1:06sometimes appear to go backwards for a time,
1:08which shouldn’t happen
1:09if they're travelling round in these neat little circles.
1:12Despite this, the theory had such a hold
1:14and astronomers were so convinced by it
1:16that they spent hundreds of years making all sorts of modifications
1:20to try and make the general theory fit.
1:23And as needlessly complicated as it now seems to modern astronomers,
1:27this version of the universe proposed by Ptolemy in the 2nd Century,
1:30was almost universally accepted for hundreds of years.
1:33But not everyone was happy.
1:35As far back as the 3rd Century BC,
1:38Aristarchus of Samos
1:39had suggested that the Sun was in the centre of the universe.
1:42And in the years that followed Ptolemy's work
1:45both European and Islamic scientists
1:47started to question aspects of his geocentric model.
1:50Finally in the 16th Century,
1:51Polish astronomer Copernicus published his model of the universe,
1:55which also put the Sun, not the Earth, at the centre of it all.
1:59This is known as heliocentrism,
2:02and for the first time, mainstream science took note.
2:05Today we know that even heliocentrism doesn’t tell the full story.
2:09While the Sun may be at the centre of our solar system,
2:12it is just one of over a hundred billion stars
2:15in our Milky Way galaxy,
2:17which is itself one of over a hundred billion galaxies
2:19in the observable universe.
2:22Not only do we have to contend
2:23with being just one of probably countless planets out there,
2:26modern cosmology tells us that the Earth and our solar system
2:29doesn't even occupy a special place in the universe.
2:33And in fact, it turns out that there is no centre to this universe at all.
2:43Thanks for watching.
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2:49See you again soon!