The Earth and Beyond

1. The Earth and Beyond

2. Contents • The Solar System • Stars • Solar Systems, Galaxies & the Universe • Comets • Life Cycle of Stars • Red-Shift • History of the Universe • Future of the Universe • SETI

3. The Solar System My Very Efficient Mind Just Stores Up Nine Planets

4. Stars • Stars are burning balls of gas e.g. our Sun • Stars give out light • This light reflects off planets so we can see them • Planets are much smaller than stars … but they seem much bigger as they are much closer • The 9 planets orbit the sun, Earth orbits the Sun once a year

5. Stars • Stars are burning balls of gas e.g. our Sun • Stars give out light • This light reflects off planets so we can see them • Planets are much smaller than stars … but they seem much bigger as they are much closer • The 9 planets orbit the sun, Earth orbits the Sun once a year

6. Solar Systems, Galaxies & the Universe Our Sun is one of millions of stars that orbit the centre of the Universe The Milky Way is one of more than a billion galaxies in the Universe The Universe is expanding

7. Comets • Comets appear every few years • Comets have highly elliptical orbits around the Sun • Comets are visible when they are close to the Sun • A comet’s orbit is fastest near the Sun due to the Sun’s gravity. It slows as it moves further away from the Sun Tail is pushed away from sun by solar pressure Tail is made of ice and rock

8. Life Cycle of Stars cools and contracts Layers of dust & gas are ejected clouds of dust & gas HHe heat & light ejectedstar H runs outswells red = cooler dense core = neutron star explode supernova or black hole (crushes atoms!)

9. Red-Shift • Light from distant galaxiesis shifted towards the red end of the spectrum • Frequencies become lower as they move away (like the Doppler Effect for sound) • Further away = greater red-shift • Universe is expanding • Also evidence from microwave radiation (background radiation) that Universe is cooling

10. History of the Universe • 1. Steady State Theory • Universe has always existed… • and Universe will always exist • No convincing evidence • Not much support for the Steady State Theory

11. History of the Universe • 2. Big Bang Theory • Universe was compressed and exploded – Big Bang • Occurred 15 billion years ago • Estimated by current rate of expansion • Expansion is slowing due to gravity

12. Future of the Universe According to the Big Bang Theory… • 1. Expand Forever • If too little mass for gravity to stop expansion… • Universe will expand and spread out into eternity • 2. Big Crunch • If enough mass to stop expansion, universe will contract • Big Crunch! • Big Crunch would produce another Big Bang… and so on!

13. SETI Scientists search for extra terrestrial intelligence • Radio Signals • SETI looks for radio wavelength signals being sent to Earth • These signals can only be sent by a transmitter • SETI has been running for 40 years… not found anything • Now searching for laser signals too! • Robots Collect Photos and Samples • Spacecraft are sent to planets to look for microorganisms • Collect samples and take photos • Scientists analyse samples and look for fossils etc.

14. Summary • Solar system – 9 planets & 1 star • Stars emit light, planets reflect this light • Solar systems are in galaxies which are in the Universe • Comets (rock and ice) have long elliptical orbits around Sun • Life cycle of stars – differs for massive & small stars • Red-shift – evidence for fast expansion of galaxies • History of the Universe – Big Bang or Steady State • Future of the Universe – Big Crunch or Eternal Expansion • SETI – Radio signals, laser signals, collect photos & samples