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Scales of the Universe

Scales of the Universe. (and a little refresher) www.astro.umass.edu/~mauro/astro100. Goals. to refresh and use scientific notations to remember how to convert units! to see the levels of structure in the Universe to comprehend the vastness of scales in the Universe. Amherst:

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Scales of the Universe

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  1. Scales of the Universe (and a little refresher) www.astro.umass.edu/~mauro/astro100

  2. Goals • to refresh and use scientific notations • to remember how to convert units! • to see the levels of structure in the Universe • to comprehend the vastness of scales in the Universe

  3. Amherst: UMass is about 1.5 miles from the center; Antonio’s pizza is about 1 pound a slice The town was founded about 200 years ago The Universe: The nearest star is 4 light years away; The mass of a massive black hole is about 108 solar mass (1 solar mass is about 2*1030 Kg) The age of the Universe is about 14 billion years In order to describe and understand what you see, you need numbers and units The scales we meet in exploring the Universe are very big, we must learn how to deal with them

  4. How to say big numbers Billion Giga (G) 109 Million Mega (M) 106 Thousand Kilo (K) 103 ... thousandth milli (m) 10-3 millionth micro (m) 10-6 billionth nano (n) 10-9

  5. Units Conversion First of all – Units are good things! You can say the distance to Boston in miles (or km) instead of inches (or cm)! Translating to useful units is a very handy skill. The key to changing units is remembering to replacea unit by something equivalent

  6. Converting Units How many quarters are there in 1000 dollars? 1000 dollars= 1000x 1 dollar = 1000x 4 quarters = 4000 quarters Question: How many cm are there in 3 km? 3 km = 3x 1km = 3x 1000 m= 3000 m = 3000x 1m = 3000x 100 cm = 300000cm

  7. Light-time=Light traveling time=distance Car-traveling time as distance: Boston is about 1.5 hours away(assuming the speed of a car is 60 mph) The speed of light: c = 3x105 km/s. Destination Distance (km) Light Travel time London 6,000 0.02 s Moon 385,000 1.3 s Sun 1.5 x 108 500 s (8.3 min) Jupiter 7.8 x 108 43 min Nearest Star 4 x 1013 4.3 years Most Distant Galaxy 1.4 x 1023 14 billion years Whenever you see "light-(time)", that means we are talking about distance, not time.

  8. Examples 1 yr = 3.15 x 107 s (Earth revolves around the Sun once) 1 ly = (3 x 105 km/s) x 3.15 x 107 s = 9.45 x 1012 km =10 thousand billion km!

  9. Now… on to scales in the Cosmos...

  10. 52 feet across

  11. 1 mile across

  12. 160 kilometers across 1 mile = 1.61 kilometers Infrared photo

  13. 12,756 km

  14. 1,600,000 km =1.6 x 106 km Moon

  15. 1.6x108 km =1.6x1011m 1AU = 1.5x1011 m AU is a distance unit

  16. 1.6 x 1010 km, or a trillion (1012) times wider than the first picture! 32 AU

  17. 100 AU

  18. 10,000 AU Stars are so far apart from each other! If the Sun is a golf ball in NYC, the nearest star is a golf ball in Chicago!!!

  19. 106 AU = 17 ly 1 ly =63,000 AU = 1013 km

  20. 1700 ly

  21. 170,000 ly

  22. 1.7 x 107 ly The local group of galaxies

  23. 1.7 x 109 ly

  24. Basic classes of objects: Planets: Earth as one Stars Sun as one Galaxies Milky Way as one Their sizes Earth: 104 km poppy seed Sun: 106 km grape fruit Milky Way 1018 km Earth-Sun distance Universe 1023 km 100,000 Earth-Sun distance

  25. A Sense of Space • The Sun would hold 1.3 million Earths. • i.e. the radius of the Sun is about 100 times • that of the Earth. • 2. There are ~100 billion "Suns" in a galaxy like our own Milky Way Galaxy. • 3.Astronomers can see billions of galaxies.

  26. Your local address:

  27. So…How Big is the Observable Universe anyway? …about 14 billion-billion-billion centimeters in diameter or 14,000,000,000,000,000,000,000,000,000 cm or 1.4x1028 cm or 14 billion ly or 6000 Mpc

  28. Summary of concepts • Various units and their conversion • Order of magnitude • Power of 10, exponent • Scientific notation • The speed of light • Various scales of the Universe • Our place in the Universe, both in space and time

  29. Assigned Reading for Next Class • Chapter 2, “The Sky”, complete (p.12 to p.33)

  30. What is our address in the Universe? UMass, Amherst, Massachusetts U.S.A., Earth, Solar System Milky Way Galaxy, Local Group, Local Supercluster Our Universe

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