foundations

# foundations - Announcements Homework is due next Tuesday...

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8/25/11 1 Announcements Homework is due next Tuesday (8/30/11) Read Chapter 1 before next Tuesday For help with Mastering Astronomy account or iClicker setup see Cathy Webster (room 115 of Physics and Astronomy) My office hours are on Mondays 9-11am, please stop by Physics and Astronomy Room 180 Mondays 9-11am or by appointment you are here Foundations of Astronomy The Metric System (used by scientists and foreigners) Mass 1 kilogram (kg) = 1000 grams (g) 28 g = 1 ounce If your mass is 220 lbs , it's also 100 kg . We tend to use mass and weight interchangeably, but weight depends on gravity. Distance 1 meter (m) = 100 centimeters (cm) = 39.4 inches (slightly longer than a yard - your professor is 1.8 m in height) 1 cm = 0.39 inches Volume 1 cubic centimeter or 1 cm 3 = 0.06 cubic inches (about the size of a sugar cube) Density Density = Mass (g / cm 3 ) Volume Densities of Substances Balsa Wood 0.13 g / cm 3 Oak 0.7 Gasoline 0.7 Plastic 0.9-1.1 Water 1.0 Average Rock 2.4 Glass 2.6 Iron 7.9 Lead 11.3 Gold 19.3 Osmium 22.5 Sink or Float Game Temperature The Celsius Scale: T( o C ) = 5/9 [ T( o F) - 32 o F ] so 32 o F = 0 o C 212 o F = 100 o C 68 o F = 20 o C The Kelvin Scale: T(K) = T( o C) + 273 o C “Absolute zero” 0 K = -273 o C

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8/25/11 2 Angular Measure 90 o 20 o 360 o , or 360 degrees, in a circle . 1 o = 60’ or arcminute s 1’ = 60” or arcseconds 1” = 1000 mas or milli-arcseconds THE QUEST FOR RESOLUTION Resolution = Observing wavelength / Telescope diameter Angular Resolution Optical (5000A) Diameter Instrument Radio (4cm) Diameter Instrument 1 2mm Eye 140m GBT+ 1 10cm Amateur Telescope 8km VLA-B 0. 05 2m HST 160km MERLIN 0. 001 100m Interferometer 8200km VLBI Jupiter and Io as seen from Earth 1 arcmin 1 arcsec 0.05 arcsec 0.001 arcsec Simulated with Galileo photo Atmosphere gives 1" limit without corrections which are easiest in radio Scientific Notation (A shorthand way of writing very large and small numbers, which occur often in astronomy). We use powers, or exponents, of 10: 100 = 10 2 (= 10 x 10) 1000 = 10 3 (= 10 x 10 x 10) 1,000,000 = 10 6 10 = 10 1 1 = 10 0 0.1 = 10 -1 0.0001 = 10 -4 0.007 = 7 x 10 -3 4000 x 0.002 = (4 x 10 3 ) x (2 x 10 -3 ) = 8 x 10 0 = 8 Add the exponents In astronomy, we deal with: 1. Vast distances - Radius of Earth = 6400 km = 6.4 x 10
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