Our Place in the Cosmos Our Place in the Cosmos Course Aims and and To explain primarily at a descriptive Introduction to Introduction to level the contents, dimensions and history of the Universe, and our place Astrophysics Astrophysics within it. This will include a survey of the basic astronomical tools, and will seek to explain the way in which some Jon Loveday basic physical laws can be applied in Astronomy Centre order to understand the observed Department of Physics & phenomena. Astronomy Class organisation Assessment � Lectures � Our Place in the � Introduction to Cosmos Astrophysics � Monday 9am Arts A5 � 15 minute � 4 x problem sheets � Friday 9am Pev1 1A6 presentation (weeks (10% each) � Workshops Friday 10am 5-10; 20%) � In-class quiz (week 9; � Our Place in the Cosmos: Pev1-2A2 � In-class quiz (week 40%) � Informal discussion, quizzes, student 10; 20%) � Briefing paper (week presentations � 2000-word essay 9; 20%) � Intro to Astrophysics: Arundel 1B (week 10; 60%) � Mathematical background, problem sheets � Taken by Peter Thomas Lecturer Web Resources � Jon Loveday � Sussex Direct has links to the official course document (click on the course � Pev2 5A5 x 7719 code: F3095 or F3156) � J.Loveday@sussex.ac.uk � Study Direct includes copies of these � Office hour: Tuesday 1.30-2.30 slides and other useful resources
Course textbooks Student Feedback � Please feel free to stop me and ask for � 21st Century Astronomy by Hester et al. clarification at any time during classes if is very good, though expensive at £42 anything I have said is unclear � Introductory Astronomy by Holliday is � Feedback on any aspect of the course is cheaper welcome during the Friday seminar � Other useful books you should find in the � Formal feedback will be requested via library include: the Study Direct website during weeks � Universe Freedman & Kaufmann 8-9. Please note that feedback provided in this way is completely anonymous � In Quest of the Universe Kuhn & Koupelis Why Astrology is not a What is Astronomy? Science � Literally means “naming the stars” � The constellations are only imaginary, � The earliest astronomers simply tracked the not physical associations of stars motions of the heavenly bodies � Constellations have shifted relative to � Modern astronomers use observations to help our calendar due to precession of understand the Universe and our place within equinoxes since founding of astrology it via scientific reasoning � Rigorous tests of astrological � Astrology is not astronomy, but a pseudo- “predictions” have shown they do not science work The Scientific Method � Guided by observations, posit a theory that explains them � A good theory makes testable predictions about future observations, and thus is falsifiable � Scientific theories can never be definitively proved, they can only be ruled out by contrary observations � A theory that stands the test of time becomes generally accepted and possibly modified
Why Study Astronomy? Course Outline � Brief tour - scales in the Universe � Early astronomers used positions of the stars to track the seasons and later as a vital � Historical overview navigational aid � Earth, Moon and Sun � Help understand phenomena such as tides and � Orbits and Gravity eclipses � Solar System � Understand and appreciate even more the � Stars beauty of the night sky � Galaxies � Learn about the origin and fate of the � The Milky Way Universe � The Universe A brief tour
Solar System Sun Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto Milky Way Milky Way as Viewed from Earth NGC 891
Milky Way in the near-IR NGC 4414 Virgo Galaxy Cluster A cluster of galaxies Infrared Universe The Deep Universe CMB Temperature Map Hubble Ultra-Deep Field
Distances as light travel times - not to scale! Scales in the Universe � Astronomical distances are commonly given in terms of light travel time, ie. distance light will travel in that time at its speed of 300,000 km/s Earliest depictions of the skies are found in the Prehistoric astronomy Cave paintings in Lascaux, SW France (c15,000 BC) � Since prehistoric times, man has observed the changing phases of the moon during the lunar month, and the changing passage of the Sun during the year � One can understand how, as well as indicating the change of the seasons, man might well have thought of the stars as causing the change � Hence religious significance of the heavenly bodies, and birth of astrology Dots below horses thought to represent changing phases of the Moon The Great Bull: An Ice Age Star Map? Prehistoric astronomy � Observations of the changing passage of the Sun and the star patterns in the night sky Pleiades enabled tracking of the seasons, and hence the best times to plant and harvest crops � Observations of the Moon’s phase allowed Hyades fishermen to predict the tides � Observatories were built to track the positions of the heavenly bodies, most famously Orion Stonehenge, 3000-1500 BC
Stonehenge � An early astronomical calculator? � On summer solstice, Sun rises exactly above the Heelstone � In Stonehenge Decoded (1965), Gerald Hawkins claimed large number of alignments with Lunar and Solar phenomena, and hence that eclipses could be predicted � These claims are still controversial El Castillo, Chichen Itza The Planets (Mayan, c1000 AD) � It must have been noticed very early that some bodies moved faster in the night sky than the surrounding stars. � The word "planet" comes from the Greek word "planetes," which means "nomad” or “wanderer”. � To the Babylonians and Sumerians before them, the planets were "stray sheep”. At sunset close to the spring and autumn equinoxes, shadows give the effect of a snake slithering down the stairway. Thales (624 - 545 BC) The Ancient Greeks Realised that celestial objects were at different distances, that the Earth By far the most famous early astronomers are the ancient was spherical, and that the light of Greeks. Between about 500BC and 100BC, they built a the moon was reflected sunlight . picture of the Universe which dominated for over 1000 years. Pythagoras (582 - 500 BC) Produced the first geocentric model of the Universe, with everything making perfectly circular orbits around the Earth.
Geocentric Model
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