Lightyears14­15JM.notebook
January 29, 2015
Measuring Distance in Space
Big (and Small) Numbers can be tricky
Let's make them easier
The distance it takes light to travel in one year.
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What is a light year (LY)?
Speed of light ( 300,000 km /s) and Number of seconds in a year.
• Examples 10000, 100000, 1000000, 10000000, 100000000, 100000000… • We will often use powers of 10 for large and small numbers
Light travels
300,000 km
• Count the zeros.........1,000,000 = 10x10x10x10x10x10 = 106 • How would you express 150,000,000,000 meters using exponents?
1 second
60 seconds
60 minutes
24 hours
1 minute
1 hour
1 day
365 days
1 year
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What do we need to know in order to calculate a light year?
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To measure large distances in space.
9.5 x 1012
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How far is a light year?
What are light years used for?
9,460,800,000,000 km in one yr
Why do we use light years?
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It is easier to record and use 1 ly instead of 9,460,800,000,000 km per year
Light year facts...
Star Name
Distance What year will it be if How long ago did light this star burned out come from this star?
tonight? Sirius 9 ly
2006
2024
Vega
27 ly
1988
2042
Spica 275 ly
1740
2290
Rigel 900 ly
1115 2915
Dineb 1600 ly 415
3615
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The nearest star Alpha Centauri 4.3 lyr
5min
Also, when it burns out, earth won't know until 2373!
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That means that the light we see shining from it today is from 1653!
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The North Star is 360 light years away
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The nearest galaxy to earth is 2.9 million light years away (Andromeda)
link
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Attachments
starlife.jpg
Beyond the Milky Way and Back in Time.asf