Science trouble...physics i think?

Question

i dont understand how to answer this question..can anyone help?

Light form the sun reaches the earth in 8.3 minutes. The speed of light is 3.00 x 10^8 m/s. In kilometers, how far is the earth from the sun?

thanks! :)

Answer 1

Because the earth's orbit is elliptical, the distance is never constant, actually. This web site explains the whole thing (including the formula):

http://www.newton.dep.anl.gov/askasci/ast99/ast99431.htm

Answer 2

It's not a physics question, it isn't even really a science question -- it's a math question. Let's see if I can show you how to break it down.

The first thing to do is to ask if you understand what "m/s" means. No? It means "meters per second," and it's an indication of speed -- like miles per hour, it's how far something goes in a given length of time. 3 x 10^8 is 300,000,000, so light goes three hundred million meters per second.

With me so far? Okay... so the other fact we're given is that it takes light 8.3 minutes to get to the Earth from the Sun. So now you have to figure out how to use these two facts -- the speed of light and the time it takes light to get to the Earth -- to figure out how FAR the Earth is from the Sun.

How would you do that? Well, first, you're talking minutes in one figure (8.3 minutes) and seconds (3 x 10^8 meters/second) in the other. We need them to be in the same measurement for this to work out. So you can either convert the time to seconds or the speed to meters/minute. It'll be easier, I think, if we convert the minutes to seconds, so let's do that: 8.3 minutes times 60 seconds per minute is 498 seconds.

Now let's move you another step closer to your answer, which has to be in kilometers. That's 1,000 (10^3) meters, so the speed of light in kilometers would be 3 x 10^5 (8 minus 3 equals 5), or 300,000 km/sec.

So in each one of those 498 seconds, the Sun's light is traveling 300,000 km. So how far does the light travel in 498 seconds? Solve that and you've solved your problem.

(And if you've ever wondered about the difference between mathematics and arithmetic... mathematics is what we've been doing so far -- figuring out how to analyze a problem, break it into small pieces that all work together, and craft a solution. Arithmetic is actually calculating the answer.)