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How Far is a Light Year?

How Far is a Light Year?. Claire Hodgin – Science Instructional Coach University of Texas – University Charter Schools Armosky and Hodgin  University of Texas at Austin, 2009. Engage. Powers of Ten About the Relative Size of Things in the Universe

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How Far is a Light Year?

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  1. How Far is a Light Year? Claire Hodgin – Science Instructional Coach University of Texas – University Charter Schools Armosky and Hodgin  University of Texas at Austin, 2009

  2. Engage Powers of Ten About the Relative Size of Things in the Universe What was the smallest to the largest distance on the video? 1040 10,000,000,000,000,000,000,000,000,000,000,000,000,000 m

  3. Explore If we could shrink the Sun to the size of this balloon, how big would the Earth be? messagesfromearth.wordpress.com

  4. Our Solar System kiroastro.com

  5. What is one way to measure a planet or star? By the Diameter of the sphere…

  6. Diameter of a planet… Diameter of a sphere The distance from one edge to the opposite edge

  7. It would take 108 Earths laid side-by-side to go across the Sun’s diameter messagesfromearth.wordpress.com findfreeclipart.com

  8. Finding the Earth/Sun Diameter Ratio The Earth’s diameter is 12,756,000 meters or ~ 1.3 X 107 m The Sun’s diameter is 1,400,000,000 meters or ~ 1.4 X 109 m The ratio of the Earth : Sun diameter is 1.3 X 107 m : 1.4 X 109 m Simplify the ratio... 1.3 X 107 m : 1 m 1.4 X 109 m : 108 m Earth to Sun Diameter ratio is 1 : 108

  9. Actual Distance from the Sun to the Earth

  10. If we use the same scale as we used for the SIZE of Sun and Earth… How far apart would the Sun and Earth be in our model? Cross multiply and x = 4.8 x 101 m (48 m) or ~ 50 m

  11. Distance from the Sun to the Earth in our model

  12. Let’s take a field trip • To build a model to scale the Sun will be a 450 mm balloon the Earth will be a 4 mm lentil and they will be 50 meters apart

  13. Explain The Milky Way Galaxy is about 100,000 light years across Powersof10.com

  14. One light-year is the DISTANCE that light travels in one year If we are going to find out HOW FAR is a Light Year, we need to know two things… • The speed of light, measured in meters per second and • The number of seconds in a year

  15. What is the fastest speed in the universe? The Speed of Light What is the speed of light? (abbreviated “c”) 300,000,000 meters per second or 3 X 108 m/s (remember the line in Powers of Ten?)

  16. How Many Seconds in a Year? 60 seconds per minute X 60 minutes per hour X 24 hours per day X 365.25 days per year = the number ofseconds per year

  17. On the Graphing Calculator… • Turn on and press “Mode” • At the top row are the words: Normal Sci Eng And the “Normal” is highlighted in black • Arrow right to “Sci” until it is highlighted, and press “Enter” • Quit (2nd Mode), and now all of your calculations are in Scientific Notation (Powers of Ten)

  18. In science we call this “Dimensional Analysis,” in math “Unit Conversion” = Let’s try this on the graphing calculator

  19. So How Far is a Light Year? Multiply the Speed of light (m/s) by the number of seconds per year (s/yr) = number of m/yr 3 x 108 m/s X 3.2 x 107 s/yr = “3 2nd LOG 8 ) X 3.2 2nd LOG 7 ) Enter” 9.5 x 1015 m/yr Or 9,500,000,000,000,000 meters That’s Nine Quadrillion, Five Hundred Trillion Meters

  20. How long does it take light to get from the Sun to the Earth? 8 minutes It takes 16 minutes to go there and back

  21. If we use the same scale as we used for the SIZE and DISTANCE of Sun and Earth… How long would a light year be in the model? Cross multiply and x = 3.1 x 106 m

  22. 3.1 x 106 meters That’s 3.1 x 103 kilometers! That’s 3 times wider than Texas! That’s too much tape!

  23. Let’s change the scaleof our model. What is the new scale factor so that 1 light year fits insidea 50 meter paper strip? Cross multiply and x = 7.4 x 10-6 m

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