Doing Science Science is figuring out stuff and not fooling yourself in the process Richard Feynman Copyright 2009 Pearson Education Inc Think about it Science verus faith Shroud of Turin Science takes the beauty away from nature Science is a philosophy of life Science is revolutionary and can be dangerous Copyright 2009 Pearson Education Inc Copyright 2009 Pearson Education Inc What is our place in the universe Our cosmic address Insert ECP 5e Figure 1 1 Copyright 2009 Pearson Education Inc Star A large glowing ball of gas that generates heat and light through nuclear fusion Copyright 2009 Pearson Education Inc Planet Mars Neptune A moderately large object that orbits a star it shines by reflected light Planets may be rocky icy or gaseous in composition Copyright 2009 Pearson Education Inc Moon or satellite An object that orbits a planet Ganymede orbits Jupiter Copyright 2009 Pearson Education Inc Asteroid A relatively small and rocky object that orbits a star Ida Copyright 2009 Pearson Education Inc Comet A relatively small and icy object that orbits a star Copyright 2009 Pearson Education Inc Solar Star System A star and all the material that orbits it including its planets and moons Copyright 2009 Pearson Education Inc Solar Star System Copyright 2009 Pearson Education Inc Nebula An interstellar cloud of gas and or dust Copyright 2009 Pearson Education Inc Galaxy A great island of stars in space all held together by gravity and orbiting a common center M31 the Great Galaxy in Andromeda Copyright 2009 Pearson Education Inc Universe The sum total of all matter and energy that is everything within and between all galaxies Copyright 2009 Pearson Education Inc How did we come to be Copyright 2009 Pearson Education Inc How did we come to be Copyright 2009 Pearson Education Inc How did we come to be Copyright 2009 Pearson Education Inc How did we come to be Copyright 2009 Pearson Education Inc How can we know what the universe was like in the past Light travels at a finite speed 300 000 km s Destination Light travel time Moon 1 second Sun 8 minutes Sirius 8 years Andromeda Galaxy 2 5 million years Thus we see objects as they were in the past The farther away we look in distance the further back we look in time Copyright 2009 Pearson Education Inc Example This photo shows the Andromeda Galaxy as it looked about 1 2 million years ago Question When will we be able to see what it looks like now M31 the Great Galaxy in Andromeda Copyright 2009 Pearson Education Inc Definition Light Year The distance light can travel in 1 year About 10 trillion kilometers 6 trillion miles Copyright 2009 Pearson Education Inc At great distances we see objects as they were when the universe was much younger Copyright 2009 Pearson Education Inc Can we see the entire universe Copyright 2009 Pearson Education Inc Thought Question Why can t we see a galaxy 15 billion light years away Assume the universe is 14 billion years old A Because no galaxies exist at such a great distance B Galaxies may exist at that distance but their light would be too faint for our telescopes to see C Because looking 15 billion light years away means looking to a time before the universe existed Copyright 2009 Pearson Education Inc Thought Question Why can t we see a galaxy 15 billion light years away Assume the universe is 14 billion years old A Because no galaxies exist at such a great distance B Galaxies may exist at that distance but their light would be too faint for our telescopes to see C Because looking 15 billion light years away means looking to a time before the universe existed Copyright 2009 Pearson Education Inc What have we learned What is our place in the universe Earth is part of the solar system which is the Milky Way Galaxy which is a member of the Local Group of galaxies in the Local Supercluster How did we come to be The matter in our bodies came from the Big Bang which produced hydrogen and helium All other elements were constructed from H and He in stars and then recycled into new star systems including our solar system Copyright 2009 Pearson Education Inc What have we learned How can we know what the universe was like in the past When we look to great distances we are seeing events that happened long ago because light travels at a finite speed Can we see the entire universe No The observable portion of the universe is about 14 billion light years in radius because the universe is about 14 billion years old Copyright 2009 Pearson Education Inc 1 2 The Scale of the Universe Our goals for learning How big is Earth compared to our solar system How far away are the stars How big is the Milky Way Galaxy How big is the universe How do our lifetimes compare to the age of the universe Copyright 2009 Pearson Education Inc How big is Earth compared to our solar system Let s reduce the size of the solar system by a factor of 10 billion the Sun is now the size of a large grapefruit 14 cm diameter How big is Earth on this scale A B C D an atom a tip of a ball point pen a marble a golf ball Copyright 2009 Pearson Education Inc Let s reduce the size of the solar system by a factor of 10 billion the Sun is now the size of a large grapefruit 14 cm diameter How big is Earth on this scale A B C D an atom a tip of a ball point pen a marble a golf ball Copyright 2009 Pearson Education Inc The Solar System Mercury Venus Earth moon Mars Jupiter Saturn Uranus Neptune Pluto Nearest star 8 paces nonpariel 7 paces mini M M 6 paces mini M M 5 cm nonpariel 11 paces pinhead 79 paces chocolate caramel 93 paces small chocolate caramel 207 paces M M 233 paces M M 204 paces nonpariel 5500 km Copyright 2009 Pearson Education Inc The Solar System Mercury 8 paces Venus 7 paces Earth 6 paces a clove moon 5 cm Mars 11 paces pinhead Jupiter 79 paces chocolate caramel Saturn 93 paces small chocolate caramel Uranus 207 paces M M Neptune 233 paces M M Pluto 204 paces nonpariel Nearest star Copyright 2009 Pearson Education Inc How big is the Milky Way Galaxy The Milky Way has about 100 billion stars On the same 10 billion to1 scale The Size of the Milky Way Copyright 2009 Pearson Education Inc Thought Question Suppose you tried to count the more than 100 billion stars in our galaxy at a rate of one per second How long would it take you A a few weeks B a few months C a few years D a few thousand years Copyright 2009 Pearson Education Inc Thought Question Suppose you tried to count the more than 100 billion stars in our galaxy at a rate of one per second
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