Posted by **KD** on Tuesday, September 13, 2011 at 5:07am.

Few question about astronomy:

1.how many centimetres is equivalent to a light-nanosecond

2. How long is an astronomical unit (AU) in light-minutes (1min, i.e., the distance that light travels in a vacuum in one minute)?

Please show the calculation if there is any

Thanks

- Astronomy -
**bobpursley**, Tuesday, September 13, 2011 at 5:28am
1. speedlight*time= distance

3E8m/s*1E2cm/m*1E-9sec=3E1 or 30 cm

2. speedlight*time=distance

3E8m/s*60sec= ?

- Astronomy -
**drwls**, Tuesday, September 13, 2011 at 7:01am
2. Sunlight reaches Earth in 8.3 minutes. The Earth-Sun distance is therefore 8.3 light-minutes.

One way to get the answer is to divide the Earth-Sun distance by the distance travelled by light in one minute, using the same units.

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