The Cosmic Engine

Solar System

Universe

Venus

Mercury

Earth

Mars

Jupiter

Saturn

Uranus

Neptune

Planets

Gravity

Sun is a starPowered

by nuclear reactions

Millions of stars (suns)

Billions of galaxies

Milky Way

Stars orbit galactic centre

GravityGalaxy

Universe is expanding

Scale of the Universe

http://primaxstudio.com/stuff/scale_of_universe/

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 aroundEverything revolved around the Earth

Helio-centric: Helio = sun Centric = centred around

Everything revolves around the sun

It all started with Aristotle & Aristarchus

~330BCAristotle: Philosopher – Sun, moon, planets & stars orbit Earth on crystal spheres Geo – centric

~240BCAristarchus: Philosopher – Earth & planets orbit the sun on crystal spheres, stars

are on a fixed sphere very far away.

Helio– centric

Claudius Ptolemy - ~120AD

Geo-centric

It explained retrograde motion of planets

Based on evidence, not philosophy

It worked!

It became part of religious doctrine

Ptolemy

Nicolaus Copernicus 1473 - 1543

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

Copernicus

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

Tycho Brahe

Johannes Kepler 1571 - 1630

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

Kepler

Galileo Galilei 1564-1642Used 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”!)

Galileo

Sir Isaac Newton 1642-1727

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

Newton

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.