Expert: Jayendra Upadhye - 9/1/2004

Question
How long does it take light to travel from the Sun to the Earth. (In math terms)How do I find out the answer?

Answer
Hi,
You could have a straightforward answer using google search engine thus:-
type without enclosing quotes, the string
"define:astronomical unit"
in the google search pane and find mean distance of earth from the sun in km.
[= 149,597,870 km; the average distance from the Earth to the Sun].
Now speed of light C =
Distance to sun from earth / time taken to do so.

Using "maths" and knowing C to be a universal constant = 300000 km/sec, we get by re-arranging the terms,

time taken taken to reach earth = Distance to sun from earth / speed of light C.

or
time taken taken to reach earth = 149,597,870 km / 300,000 km/sec

or Time = 498.65957 seconds.
or time = 8.311 minutes = 8 minutes, 18.7 seconds!

In maths terms as applied in physics, you may see how the dimesioning coems correct. ie km / [km/sec] = [km/km]*[secs]
which leaves with a quantity dimensioned in seconds only, which is correct dimension for time. [by dimension, we mean "units"].
Hope this is what you wanted.
Jayen