Physics Notes

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Preliminary Physics Topic 4

THE COSMIC ENGINE
What is this topic about?
To keep it as simple as possible, (K.I.S.S.) this topic involves the study of: 1. THE HISTORY OF OUR UNDERSTANDING OF THE UNIVERSE 2. HOW THE UNIVERSE BEGAN (THE "BIG BANG" THEORY) 3. LIFE-CYCLES OF THE STARS 4. ENERGY FROM THE SUN, & ITS EFFECTS ON US

but first, let’s revise...
The Structure of the Universe
The EARTH is a PLANET. The Earth and 7 other planets (plus dwarf planets, moons, asteroids, comets, etc) are in orbit around the Sun. The SUN and all these things in orbit around it, make up our "SOLAR SYSTEM". Everything stays in orbit around the Sun because of gravity. The SUN is a STAR. Energy is being produced inside it, due to NUCLEAR REACTIONS. The Sun is one of over 100 billion stars that make up our GALAXY. Each star in the night sky is another "Sun" within our galaxy, the "MILKY WAY". Our Sun and the other stars of the Milky Way are orbiting around the galaxy’s centre because of gravity. Beyond our galaxy are billions of other galaxies. The distances involved are immense and unimaginable! We have good reason to believe that the entire Universe is EXPANDING, with the space between galaxies increasing. Other, distant galaxies

This topic begins with a little history, then gives you an introduction to modern Astronomy. Along the way you’ll learn about nuclear reactions and finish up with a look at the Sun, its many radiations and how they affect the Earth.

Our Galaxy, the Milky Way Sun

Mercury Venus Earth Jupiter

Position of our Sun in the galaxy

Mars Neptune

Our understanding of the Universe is very recent. Just 100 years ago we had no idea of the vastness of the Universe or what was going on inside the Sun. We had no knowledge of the life and death of a star. We’re still learning... Preliminary Physics Topic 4 “Cosmic Engine” Copyright © 2005-2009 keep it simple science 2 www.keepitsimplescience.com.au

Saturn

Uranus

Our Solar System
1

Pluto

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keep it simple science

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CONCEPT DIAGRAM (“Mind Map”) OF TOPIC
Some students find that memorising the OUTLINE of a topic helps them learn and remember the concepts and important facts. As you proceed through the topic, come back to this page regularly to see how each bit fits the whole. At the end of the notes you will find a blank version of this “Mind Map” to practise on.

Geocentric & Heliocentric Models

Evidence for the Big Bang Big Bang Theory Formation of Matter, Stars & Galaxies

A Little History

How the Universe Began
Temperature & Colour of Stars

THE COSMIC ENGINE

Life Cycles of the Stars

Brightness & Distance. Inverse Square Law

Energy from the Sun

HertzsprungRussell Diagram

Nuclear Reactions & Radioactivity Impacts & Effects on Earth

Stages in a Star’s Life

Energy Sources in Stars

Radiation from the Sun

Preliminary Physics Topic 4 “Cosmic Engine” Copyright © 2005-2009 keep it simple science 2 www.keepitsimplescience.com.au

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keep it simple science

Copying is permitted according to the Site Licence Conditions only

1. HISTORY OF OUR UNDERSTANDING OF THE UNIVERSE Different Models of the Universe First, be aware that our understanding of galaxies and the true extent of the Universe was only discovered within the last 100 years. Prior to that, any theory or model of the Universe really only dealt with our Solar System. The stars were thought to be outside the Solar System, but relatively close to it. Over the centuries there have been TWO main models of the Universe competing for acceptance.

Historical Summary
up until about 1700 AD

Aristotle
Thought that:

~330 BC Geocentric Theory

The Sun, Moon, planets & stars are carried on invisible crystal spheres rotating around the Earth. This basic concept was believed...
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