Olbers’ paradox ‘Why is the sky dark at night?’

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2. Olbers’ paradox ‘Why is the sky dark at night?’ Eastbourne College Physics Department

3. Olbers’ paradox • ‘Why is the sky dark at night?’ • if the Universe is infinite and filled uniformly with stars, there must be a star in every direction you can look. So the sky should be as bright as the surface of a star. Eastbourne College Physics Department

4. Olbers’ paradox • ‘Why is the sky dark at night?’ • If the Universe is infinite and filled uniformly with stars, there must be a star in every direction you can look. So the sky should be as bright as the surface of a star. • But the sky is rather black at night. Most lines of sight do not seem to end on a star. Eastbourne College Physics Department

5. Olbers’ paradox • ‘Why is the sky dark at night?’ • If the Universe is infinite and filled uniformly with stars, there must be a star in every direction you can look. So the sky should be as bright as the surface of a star. • But the sky is rather black at night. Most lines of sight do not seem to end on a star. • In its simplest form, Olbers’ paradox arises because, if the Universe were infinite, static and uniformly filled with stars, the sky would be as bright as the surface of the stars, clearly in contradiction with our experience. At least one of these assumptions about the nature of our Universe has to be wrong…. • Probably the most general way of expressing the significance of this observation is that the Universe must, in some sense, be far from equilibrium, though the way in which it is in disequilibrium cannot be deduced from this very simple observation. The fact that the Universe is expanding and has a finite age are two contributions to the resolution of the paradox. Eastbourne College Physics Department

6. Astronomy is Astrophysics is Cosmology is Space Science is Astrology is Eastbourne College Physics Department

7. Astronomy is, broadly speaking, the observation of the motion and distribution of celestial objects. Astrophysics is the application of physics to astronomy. Cosmology is the study of the Universe as a whole, its origin, development and fate. Space Science is concerned with space exploration, including putting people in space. Astrology is an attempt to predict the future based on the positions of the stars and planets. Is this mumbo-jumbo, or should we respect personal or religious views? Eastbourne College Physics Department

8. Ursa Major The Planets in January http://www.schoolsobservatory.org.uk/news/month.php?year=2009&month=1 Eastbourne College Physics Department

9. Ursa Major The Planets in January http://www.schoolsobservatory.org.uk/news/month.php?year=2009&month=1 The pointer stars Eastbourne College Physics Department

10. Ursa Major Polaris, the North Star The Planets in January http://www.schoolsobservatory.org.uk/news/month.php?year=2009&month=1 The pointer stars Eastbourne College Physics Department

11. Ursa Major Polaris, the North Star Cassiopeia and the Andromena Nebula, M31 The pointer stars The Planets in January http://www.schoolsobservatory.org.uk/news/month.php?year=2009&month=1 Eastbourne College Physics Department

12. In 1925 Hubble showed that the Andromeda nebula was a collection of stars (i.e. a galaxy) outside and quite distinct from our own Milky Way galaxy. Eastbourne College Physics Department

13. In 1925 Hubble showed that the Andromeda nebula was a collection of stars (i.e. a galaxy) outside and quite distinct from our own Milky Way galaxy. • The Andromeda nebula, M31, is another galaxy like our own, the Milky Way, containing some 1011 stars. Eastbourne College Physics Department

14. In 1925 Hubble showed that the Andromeda nebula was a collection of stars (i.e. a galaxy) outside and quite distinct from our own Milky Way galaxy. • The Andromeda nebula, M31, is another galaxy like our own, the Milky Way, containing some 1011 stars. • The oldest light the unaided eye can see; the furthest back in time you can look for yourself. Eastbourne College Physics Department

15. In 1925 Hubble showed that the Andromeda nebula was a collection of stars (i.e. a galaxy) outside and quite distinct from our own Milky Way galaxy. • The Andromeda nebula, M31, is another galaxy like our own, the Milky Way, containing some 1011 stars. • The oldest light the unaided eye can see; the furthest back in time you can look for yourself. • It has taken 200 thousand years for that light o reach your eyes!!!!!! Eastbourne College Physics Department

16. Orion, The Hunter, constellation or a pattern of stars. They are not a group of stars and so only have this pattern when viewed from the earth Eastbourne College Physics Department

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18. On the western heel of Orion, the Hunter, rests brilliant Rigel. In classical mythology, Rigel marks the spot where Scorpio, the Scorpion stung Orion after a brief and fierce battle. Its Arabic name means the Foot. A heavy star of 17 solar masses, Rigel is likely to go out with a bang some day, or it might become a rare oxygen-neon white dwarf. Eastbourne College Physics Department

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20. Betelgeuse is an M1 red supergiant, 650 times the diameter and about 15 times the mass of the Sun. If Betelgeuse were to replace the Sun, planets out to the orbit of Mars would be engulfed! Betelgeuse (pronounced beetle juice by most astronomers) derives its name from an Arabic phrase meaning "the armpit of the central one." Eastbourne College Physics Department

21. Betelgeuse is an M1 red supergiant, 650 times the diameter and about 15 times the mass of the Sun. If Betelgeuse were to replace the Sun, planets out to the orbit of Mars would be engulfed! Betelgeuse (pronounced beetle juice by most astronomers) derives its name from an Arabic phrase meaning "the armpit of the central one." Eastbourne College Physics Department

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23. The Ultra Deep Field observations began Sept. 24, 2003 and continued through Jan. 16, 2004. The telescope's ACS camera, the size of a phone booth, captured ancient photons of light that began traversing the universe even before Earth existed and when the cosmos was between 1 and 2 billion years old. Photons of light from the very faintest objects arrived at a trickle of one photon per minute, compared with millions of photons per minute from nearer galaxies. Eastbourne College Physics Department

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25. Discussion: The hot big bang Imagine running a film of the Universe ‘backwards’ – all matter and energy were originally in a very, very dense state. All exploded outwards = the Big Bang (Fred Hoyle coined this name, intending it to be derisive). What happened before the Big Bang?  Space-time was created at the Big Bang; so many cosmologists argue that the question has no physical meaning. At the present time (2005) the overwhelming weight of evidence favours the Hot Big Bang theory. There are 3 independent pieces of evidence: Time Eastbourne College Physics Department

26. the observed expansion of the Universe • the Cosmic Microwave Background (CMB) radiation • the cosmic relative abundance of the light elements (created by the Big Bang, rather than subsequently in stars or supernovae). Eastbourne College Physics Department

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29. This diagram shows how we come to estimates of the age of the Universe. Eastbourne College Physics Department

30. the observed expansion of the Universe • the Cosmic Microwave Background (CMB) radiation • the cosmic relative abundance of the light elements (created by the Big Bang, rather than subsequently in stars or supernovae). Eastbourne College Physics Department

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33. the observed expansion of the Universe • the Cosmic Microwave Background (CMB) radiation • the cosmic relative abundance of the light elements (created by the Big Bang, rather than subsequently in stars or supernovae). Eastbourne College Physics Department

34. The Keyhole or Carin Nebula Eastbourne College Physics Department

35. Gas Pillars in the Eagle Nebula (M16): Pillars of Creation in a Star-Forming Region Eastbourne College Physics Department

36. http://videos.howstuffworks.com/hsw/21363-savage-sun-the-birth-of-stars-video.htmhttp://videos.howstuffworks.com/hsw/21363-savage-sun-the-birth-of-stars-video.htm The Birth of Stars Eastbourne College Physics Department

37. http://uk.youtube.com/watch?v=1IKjgmIDeBU How big are the planets and stars?????? Eastbourne College Physics Department

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39. A violent and chaotic-looking mass of gas and dust is seen in this Hubble Space Telescope image of a nearby supernova remnant. Denoted N 63A, the object is the remains of a massive star that exploded, spewing its gaseous layers out into an already turbulent region. Eastbourne College Physics Department

40. This image of Centaurus A shows a spectacular new view of a supermassive black hole's power. Jets and lobes powered by the central black hole in this nearby galaxy are shown by submillimeter data (colored orange) from the Atacama Pathfinder Experiment (APEX) telescope in Chile and X-ray data (colored blue) from the Chandra X-ray Observatory. Eastbourne College Physics Department

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42. Critical density Observation has yet to pin down the actual density with sufficient precision to decide if our Universe has a density larger or smaller than the predicted critical density.  (The critical density is the demarcation between an open and closed Universe) Discussion: Missing mass and dark energy According to the standard cosmological model, the Universe consists of three categories of mass/energy. Dark matter (25%), dark energy (70%) and a smattering of normal matter (5%). Dark matter was invented to account for the observed rotational shape of galaxies. Dark energy has been invented more recently to account for the latest red shift data. (As of 2005) at the highest red shifts the Universe seems to be accelerating! Eastbourne College Physics Department

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