Light Years

Let's work out how far a light year is.

The speed of light = 300,000,000 m/s (3·00 × 10⁸ m/s).

Length of Earth year = 365 days = 365 × 24 hours = 365 × 24 × 60 minutes = 365 × 24 × 60 × 60 seconds = 3·15 × 10⁷ seconds

Now speed = distance / time ... so ... distance = speed × time

So: 1 light year = 3·00 × 10⁸ × 3·15 × 10⁷

1 light year = 9·46 × 10¹⁵ m

That's nearly 9 1/2 million, million kilometres! Phew!!