Waves and Light cont.

Q. What is the speed of light in miles/hour?



Q. The Sun is 93,000,000 miles away. How long does it take for the light that leaves the Sun to reach the Earth?


Q. What is a Light Year?

First, this is a unit of DISTANCE (not time). It is the distance light travels (in a vacuum) in 1 year.

Light travels:



Lookback Times: The Galaxy disk has a diameter of around 50,000 LY, the nearest big galaxy (Andromeda) is 2 million light years distance. We see Andromeda as it looked 2 million years ago.

The most distance objects we have observed in astronomy have ``look-back'' times of > 8 billion years. The finite speed of light is very handy in that it allows us to look back in time...

Michael Bolte
Wed Jan 14 23:06:17 PST 1998