Really, just how important and significant are you…………? Cosmology The study of the contents, structure, and evolution of the universe from the beginning of time……to the future. Was Monty Python right? “that’s orbiting at 19 miles a second” Calculate if this is in any way an accurate figure? What data do you need to do this? Earth – Sun distance = 9.29x107 Miles Year = 365.25 days Calculation Orbit Radius = 9.29x107 miles Circumference= distance travelled= 2πR = 2 x π x 9.29x107 = 583707915 miles Speed = Distance ÷ Time (Time =365.25 days) Speed = 1598105 miles/day or 18.5 miles per second…Pretty close!!! Our Solar System Lets start closer to home…. watch the video “Our Solar Sytem” and make notes. Cosmology Projects/Presentations The Earth, Moon and Sun The Moon The Solar System Stars & Constellations Each group will also have to explain one topic from Cosmology Mathematics. The Earth, Moon & Sun Night & Day Seasons Solar Eclipses Solar Flares Aurora Borelalis The Moon The Phases of the moon The Dark Side Moon Lunar Eclipse Tides Solar System Model Demonstration of the size and scale of our solar system Constellations Identify the Great Bear, The Big Dipper, The Plough Identify the North Star (Polaris) Orion and The Horse Head Nebula Taurus Plaeides Casseopia Star Maps Cosmology Mathematics Astronomical units (AU) Parsecs (pc) Light years (ly) Ellipses Cosmology 1 Our Solar System How it all started…… ‘Heliocentric’ Solar System ‘Geocentric’ versus Ptolemei & Aristotle Earth is the centre of the universe Copernicus (1609/1637) Present idea of planets rotating around the sun Cosmology Kepler’s Laws (1609) Describe the motion of the planets around the sun. Kepler I The orbit of a planet around the sun is an ellipse with the sun at one focus. Kepler II 2 A line joining a planet and the sun sweeps out equal areas in equal times. clack for K2b Movie Click Picture for K2a Movie Kepler III Describes a relationship between the radius of the planets (average distance to the sun) and the time taken for one complete orbit. T2 is proportional to R3 Click for K3 Movie Cosmology 1 Our Solar System Kepler’s Laws (1609) Answer the following questions based on Kepler’s laws: 1 a) Compare planetary ellipses to circles. In what way are they different? b) Use your worksheet ‘Structure and size of the universe’ to find out which planet is furthest off the circle and which one is closest to a circle. What about ‘Mars’- Kepler’s favourite…? c) Draw an ellipse with its two focal points and the two radii. Cosmology 1 Our Solar System Kepler’s Laws (1609) Answer the following questions based on Kepler’s laws: 2 a) Use Kepler’s second law of equal areas describe the planets speed when its orbit is furthest from the sun and when its closest to the sun. b) Does the force that keeps the planet on its path change? Explain. 3 How does the period of rotation of a planet change if the average distance to the sun a) doubles or b) triples. The Big Bang Theory - Our Expanding Universe Cosmology is the search for origins. It seems as if everyone wants to know how the Universe began. The Big Bang theory is the result of several important observations. In 1927, Edwin Hubble first observed that light from distant galaxies is red shifted and that galaxies are moving farther and farther away from us. Second, he determined that the farther away a galaxy is from us, the faster it is receding from us. Hubble’s Law What does this graph tell us? Note how there is a clear proportionality between distance and recessional velocity. This proportionality is known as the Hubble Law. The slope of this line, with dimensions of velocity over distance, is called the Hubble Constant (H). Recessional Velocity The graph shows that the recessional velocity (the speed a galaxy is moving away from us) is proportional to the distance from us. i.e. stars further away from us are moving away from us faster than stars closer to us! What is the inference from Hubble’s Law Almost all Galaxies are red shifted and are thus moving away from us (The Milky Way) The most Distant galaxies exhibit the most red-shift, thus the most distant galaxies are moving away from us fastest. The Hubble Constant Let us look more closely at the slope of the Hubble Law Graph. Slope = Velocity/Distance (Hubble Constant) The inverse of the Hubble Constant then has the dimension of time, and can be taken as an estimate of the age of the Universe! The Hubble Constant has been found to be between 50 and 100 km/s per kiloparsec. The Universe has thus been expanding for 8 to 15 billion years The Future of the Universe? Don’t Worry - if there is to be a Big Crunch it won’t be for a very, very long time! The gravitational attraction will eventually overcome the expansion. The Universe will stop expanding and then collapse to an eventual big crunch This is called a closed universe. Alternatively the expansion slows to zero ‘at infinity’. This is called a flat universe. If there is not enough mass for its gravitation effect to overcome the expansion, the Universe will continue to expand forever. This is called an open universe. A closed universe might rebound forever – a big bang eventually resulting in a big crunch which rebounds into a big bang and so on. The whole Universe may be a gigantic oscillator!