00:01
Okay, so the closest star to our sun is alpha centauri, and it is 4 .3 light years away.
00:10
So it would take light traveling at the speed of light 4 .3 years to get there.
00:17
Now it's important to remember that light year is still a unit of distance.
00:23
It is not a unit of time, and it is not a speed.
00:28
Okay? so we need to figure out how far 4 .3 light years is in meters.
00:35
Now you can look up a light year in a table, but in case you don't want to or you can't, we can always figure out how far a light year is by remembering the speed of light and going from there.
00:46
Okay, so light year is a unit of distance, which is just a speed multiplied by a time.
01:00
Okay, this is my favorite example.
01:03
If i travel at 10 meters per second for five seconds, so 10 meters per second is a speed, and if i do that for five seconds, i've traveled 50 meters.
01:14
That's a distance.
01:16
Similarly, i know that the speed of light, c, is three times 10 to the eighth meters per second.
01:27
And i can convert this into meters per second, year.
01:32
All right? so the speed of light in meters per year is three times 10 to the eighth times 60 seconds per minute times 60 minutes per hour times 24 hours in a day times 365 days in one year...