Expert: Philip Stahl - 9/21/2009

Question
How many light years would it take to get to venus(from earth)? venus to mercury? mercury to neptune? neptune to uranus?uranus to saturn? saturn to mars? mars to jupiter?
thanks heaps!

Answer
Hello,

Actually, the distances in the solar system are more suitably measured or noted in "light minutes"- not "light years", which is impractical. Bear in mind whether light minute or light year, the unit references a *distance*, not a time. Not a duration.

What I will do is give you the data you need, then work out a couple cases, and let you do the others! Good brain work!

We can do this on the basis of the distances in astronomical units (AU) from the Sun to the respective planets. (Note: 1 AU = 93 million miles or 150 million km). They are as follows:

Sun to:

Mercury   =   0.38

Venus  =  0.72

Earth = 1.0

Mars =  1.5

Jupiter = 5.2

Saturn =  9.5

Uranus  =  19.1

Neptune = 30.0


Now, for light to reach the Earth from the Sun (traversing a distance of 1.0 AU) requires

8 1/3 minutes

So, we may say the Earth is 8 1/3 "light minutes" from the Sun.

Now, you have the basis for a proportion, with every 1.0 AU yielding 8 1/3 light minutes.

Then, let us work it out for Uranus to Saturn:

Saturn is at 9.5 AU from Sun.  Uranus is at 19.1 AU.  Therefore, from Saturn to Neptune is:  (19.1 AU  -   9.5 AU)  =  9.6 AU

Now, since 1.0 AU requires 8 1/3 light minutes, then 9.6 will require:

(9.6) x (8 1/3)  =   9 3/5  x  8 1/3  =  48/5 x  25/3 = 16 x 5 = 80 light minutes

Now let's do the computation for Venus to Earth:

Again, Earth is at 1.0, and Venus is at 0.72 AU

Then:

(1.0 - 0.72) x 8 1/3  =   0.28  x  25/3  = 2  1/3   light minutes

As you can see, the same method can be used for all the distances you require, and the math is pretty basic.

Go for it!