Scientific Notation and the Structure of the Universe

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Scientific Notation and the Structure of the
Universe

• Paul J. Thomas
• Department of Physics and Astronomy
• UW-Eau Claire

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Scientific Notation

• A way of representing numbers that are very large
  or very small
• Distance from the Earth to the Sun
• 150,000,000,000 m 1.5 1011 m
• Diameter of an atom
• 0.0000000001 m 1.0 10-10 m 0.1 nm
• Calculation example
• (2 103) (3 105) 6 108

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Calculator Use

• Note! To enter a number like 1.5 1011, press
  1.5 EE 11, NOT 1.5 10 EE 11.
• If units are part of the answer, you must have
  them in the answer.
• Example how long will it take to go 200 mi at 60
  mi/h?
• v d/t, so t d/v
• t d/v 200 mi/(60 mi/h) 3.3 h

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Units

• Well use the metric system
• length m
• mass kg
• time s
• temperature C (well also use K)

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Other Units

• Astronomical Unit
• (mean distance from Earth to Sun)
• 1 AU 1.496 1011 m
• Light Year
• NOT a unit of time
• (distance traveled by light in one year)
• 1 ly 9.46 1015 m
• Speed of light 299,792,458 m/s
  3.0 108 m/s (approx)

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Scale of the Universe 1
Diameter of Earth 12,756 km
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Scale of the Universe 2
Distance from Earth to Moon 384,400 km
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Scale of the Universe 3
Distance from Sun to Pluto (average) 39.54 AU
5.916 109 km
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The Sagan planet walk, Ithaca NY
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Scale of the Universe 4
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Scale of the Universe 5
Diameter of Milky Way galaxy (approx) 100,000
ly 1021 m
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Scale of the Universe 6
Distance to the Great Galaxy in Andromeda 2.5
million ly
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Scale of the Universe 7
Typical galaxy in Hubble Ultra Deep Field Image
13 billion light years