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The Cosmic Engine
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Millions of stars (suns)
Mercury Planets Venus Earth Gravity Mars Powered by nuclear reactions Sun is a star Jupiter Solar System Saturn Uranus Neptune Millions of stars (suns) Milky Way Galaxy Stars orbit galactic centre Gravity Billions of galaxies Universe Universe is expanding
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Scale of the Universe
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A Little History Up until 200 years ago, it was all about the solar system. 1500 year battle over geo-centric vs helio-centric Geo-centric: Geo = earth Centric = centred around Everything revolved around the Earth Helio-centric: Helio = sun Centric = centred around Everything revolves around the sun
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It all started with Aristotle & Aristarchus
~330BC Aristotle: Philosopher – Sun, moon, planets & stars orbit Earth on crystal spheres Geo – centric ~240BC Aristarchus: Philosopher – Earth & planets orbit the sun on crystal spheres, stars are on a fixed sphere very far away. Helio– centric
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Claudius Ptolemy - ~120AD Geo-centric
It explained retrograde motion of planets Based on evidence, not philosophy It worked! It became part of religious doctrine
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Ptolemy
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Nicolaus Copernicus Helio-centric model – Earth & planets orbit the sun on crystal spheres It was simpler, and possibly more “correct”, but it didn’t work any better, therefore it was largely rejected. Also rejected for religious reasons
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Copernicus
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Tycho Brahe 1546-1601 Believed in a geo-centric universe
He made amazingly accurate measurements (without the aid of a telescope) Kepler was his student (begrudgingly!) and he used Tycho’s results for the next great step in astronomy
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Tycho Brahe
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Johannes Kepler Used Tycho’s data and worked with Copernicus’ model Made the leap from circular to elliptical orbits His model worked, but there was no mechanism to hold the solar system together It was therefore largely rejected
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Kepler
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Galileo Galilei 1564-1642 Used the first telescope in 1609
3 significant observations: Moons of Jupiter Phases of Venus Craters on the moon Heavens not “perfect” Labelled a heretic and forced to recant. He was only forgiven in 1992 (and then “pardoned”!)
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Galileo
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Sir Isaac Newton Newton changed EVERYTHING in physics (and in maths!) In this story, he proposed the first theory of gravity – this was the missing piece of the Kepler model He was also able to predict the model that Kepler had proposed – this is science at its best
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Newton
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But this is only the beginning…
It took another 200 years to start to understand the universe outside of the solar system. They hadn’t even begun to explain nebulae, galaxies, black holes, quasars, pulsars and all the other cool things in the universe.
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