Let's work out how far a light year is. The speed of light = 300,000,000 m/s (3·00 × 10^{8} m/s). Length of Earth year = 365 days = 365 × 24 hours = 365 × 24 × 60 minutes = 365 × 24 × 60 × 60 seconds = 3·15 × 10^{7} seconds Now speed = distance / time ... so ... distance = speed × time So: 1 light year = 3·00 × 10^{8} × 3·15 × 10^{7} 1 light year = 9·46 × 10^{15} m That's nearly 9 1/2 million, million kilometres! Phew!!
