(Using a one-click website to make a customized guide for planet-distances on your wall.)
Do you want to make a simple scale model of the solar system with your kids? If the children's books and science-placemats in your house are like those in ours, you probably noticed that the scale of orbital diameters (and planetary diameters) are way off. I suppose that's an artistic necessity.
Ever come home to find that your budding scientist has taped little planet-cutouts to the wall, along a hallway?
Wouldn't it be neat to have kinda'-correct spacings away from the Sun? WolframAlpha to the rescue! Here's how:
1. Find a decent tape measure in cm (or mm), and a long stretch of walls or hallway. Say it's 3000 mm (3 m) long.
2. The sun will be at 0 mm, and Neptune will be at 3000 mm. (Don't even get me started on Pluto. Poor Pluto.)
3. Click here on this URL and wait several seconds:
5. As you can see, it lists the distances to each planet from the sun. In this case Earth is at 10 mm from the Sun. Yes, the planets seem pretty squooshed together at the beginning, don't they?
6. What about Uranus? (For some reason the pattern breaks down when I add Uranus.) Here's the input for your scale, and Uranus:
How do I scale this up or down?
Easy! Just change the "3000" to the length of your wall.
Why isn't Pluto here, and why is Neptune missing?
I actually had problems with WolframAlpha accepting a long list of planets. Neptune's at the end, of course. And... Pluto. Poor, poor Pluto.
Why did you use the semimajor axis instead of the current distance to the Sun?
Lack of sleep, I guess.
ps It will also draw pictures and show you star charts! Check this out - what does Saturn look like right now, and where is it, from your ZIP code?:
pps Or this, the whole solar system from "above:" (hint: let it think a while)