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The origins of the Universe • The Earth is part of a Solar System. • The Solar System is centred on the sun. • The Solar System is also made up of nine planets, 60 moons (1978 - we thought 42 moons), thousands of minor planets or asteroids, hundreds of comets and millions of meteors. • The Solar System is a small part of a group of millions of stars called a Galaxy. • This Galaxy is called the Milky Way. • This Milky Way is one of millions of other Galaxies in the Universe. People who study the Universe are called Astronomers. In the study of the HEAVENS (Astronomy) -- many names came up through History . The following are a list of famous Astronomers: • ARISTARCHUS (Greek) (310 - 230 B.C.) • PTOLENMY (140 A.D.) • COPERNICUS (1473 - 1543) • TYCHO BRAHE (1546 - 1601) • KEPLER (1571 - 1630) • GALILEO GALILEI (1564 - 1642) • ISAAC NEWTON (1642 - 1727) • Time does not permit us to study each one’s accomplishments, but for the origins of the Universe and the Solar System, two other Astronomers must be looked at: • PIERRE DE LAPLACE (1796) • G. P. KUIPER There are four theories to the origin of the Universe and our Solar System: 1) Nebular Hypothesis (created by Pierre De LaPlace) • Pierre De LaPlace imagined a globe of hot, glowing gases in space, rotating slowly. This globe due to its rotation contracted (Centripetal Force). As the globe contracted, it rotated faster. • The faster rotation caused the globe to flatten out into a disc. • As it shrank, this left rings of gas around it. Diagram A on the next slide. • These rings separately began to rotate and revolve. These rings eventually contracted to form the solid planets. Diagram B on the next slide. A B 2) Proto Planets (created by G.P. Kuiper) • G.P. Kuiper suggested that rather than rings, big chunks of gas were left behind. • These chunks or clouds were called “Proto Planets”. • Because of their mass and gravitational pull, these chucks of gas began to spin around one another. The bigger chunks attracted smaller pieces. These Proto Planets condensed to form planets and moons. See the diagram on the next slide. 3) Dualistic Theory • This theory states that the sun was once a very large star and that either of the two following scenarios occurred: a) Another star was once very close to the sun and it eventually blew up (went super nova). The explosion threw out debris. This debris created the planets. Diagram A on the next slide. b) Another star came very close to our sun. The gravitational pull of this other star tore chunks out of our sun. These chunks eventually became the planets. The star then moved on through the Universe. Diagram B on the next slide. A B 4) Big Bang Theory (created by group of Astronomers) • This theory states that the universe began approximately 15 to 20 billion years ago when a big ball of gas (from a giant cloud) ripped apart in a “ big bang”. It is the most widely accepted theory. • As this “big bang” or explosion occurred, chunks of gas were left behind from the centre of the explosion outwards. • This gas clustered together (Centripetal force) and this began the formation of the planets, stars and galaxies. Diagram A on the next slide. • Diagram B takes the theory a step further, it illustrates that the Universe will eventually reach a point where it will begin to contract and close in on itself eventually exploding again and starting the process all over again. A B • Years ago The Big Bang Theory was just an Hypothesis. In other words it had no facts or evidence to back it up. But in the early 1900’s Astronomers started to find evidence that pointed to a Big Bang. • In 1922, astronomer Edwin Hubble observed that the universe was expanding. The most distant galaxies he could see through his telescope were moving away at about 40 000 km per second! • This observation led to what is now called Hubble’s Law, which states that the velocity at which a galaxy is moving away from us is proportional to the distance of the galaxy from us. That is if galaxy B is twice as far away as galaxy A, it is receding twice as fast as galaxy A. • Wow, imagine the Universe is expanding. Where is it going? • Albert Einstein hypothesized that the Universe began as a small ‘Cosmic Egg’ the size of the head of a needle perhaps? This egg exploded with such force that the fragments are still flying out from the center of the explosion. • Russian physicist George Gamow in the 1940’s first coined the term ‘Big Bang’ when he hypothesized that the radiation accompanying the explosion should still exist as radio waves. • In 1964 two physicists found this radio-wave radiation. • Based on what we have learned about the expanding universe, it is conceivable that we can actually see in the past. Light travels at a speed of 299 792 km per second. A light year is the distance light travels in one year (approx. 9.5 trillion km). • So, if we look at a star one light year away, the light we would see would have been created a year earlier. The closest star to our solar system is Proxima Centauri. It is 4.3 light years away (40X1012 km). How far in the past would you be seeing if you viewed this star? • Most stars are further than Proxima Centauri. Stars in our galaxy are as far as 80 000 light years from the sun. Stars in distant galaxies are billions of light years away. If the universe was created 15 billion years ago, light created when the universe was born may still be seen today! The many galaxies in our universe. Our galaxy - The Milky Way - looks like this (It is a Spiral Galaxy): Our Solar System is found somewhere here.