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The distance that light travels in one year is called a light year. A light year is 9,56 * 1012km.

a. Show with a calculation that the speed of light is around 3,0 * 108 meters per second.

b. The star Pollux is 3,3 * 1014 km away from us. How many light years is the distance between Pollux and Earth?

c. The light of the star Sirius takes 8 years and 282 days to reach us. How many kilometers is the distance between Sirius and Earth.

 Jun 6, 2019
 #1
avatar+103915 
+1

a.

Number of meters in a light year  =  9.56 * 10^12 * 1000  =  9.56 * 10^15  m

Number of secons in a year  =   3600 * 24 * 365  = 31536000 sec  = 3.1536 * 10^7 sec

 

So .....    9.56 * 10^15

              ___________  ≈  3.03 * 10^8  m / s  ≈   3 * 10^8 m / s

              3.1536 * 10^7

 

b.   3.3 * 10^14

      __________   ≈  34.5 light years  

      9.56 * 10^12

 

c.   Distance  =   [ 8 + 282/365 ] * [9.56 * 10 ^12 ]    ≈  83866082191780.8  km

 

 

cool cool cool

 Jun 6, 2019
 #2
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+1

Thank you so much! :D

Guest Jun 6, 2019
 #3
avatar+39 
+1

Wow CPhill, I had no idea how to solve this... Congrats!

 #4
avatar+103915 
+1

THX  ....!!!

 

cool cool cool

CPhill  Jun 6, 2019

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