I like to take advantage of a coincidence in units to visualize interstellar distances.<p>1 mile is 63,360 inches.
1 light year is almost 63,250 Astronomical Units.<p>So if you scale everything down by a factor of 6 trillion, Terra would be an inch from Sol and Alpha Centauri would be 4 miles away. Voyager 1 would be 120 inches away, travelling at 3.5 inches per year.
Ten or fifteen years ago, they actually built a scale model of the Solar System up in up in northern Maine. As you drive north on Rt 1A, there's a particular rest stop with a shadowbox on the wall. Inside is a very small small sphere (size of a large marble). The label says "Pluto", with no further details. Keep driving until you get to Caribou or Limestone (I forget which) and you'll pass all the other planets. Some are inside (where there is a convenient building at the right distance), some are on purpose-built display poles by the roadside. When you get to the end, you can find the Sun painted on a wall -- or, at least, the very small arc of it that fits on a wall that size.<p>The planets are all carefully painted to look as accurate as possible and quite attractive. There's no explanation anywhere, you just have to be "in the know". It's an awesome treasure hunt to find them all.
Sweden has a large scale model of this with a 65cm Earth and a 110m sun, with a total length of over 500 miles: <a href="http://en.wikipedia.org/wiki/Sweden_Solar_System" rel="nofollow">http://en.wikipedia.org/wiki/Sweden_Solar_System</a>
Unfortunately the "Don't stand so close to me" picture has the wrong size of the Sun -- the width of the football field is around 50 meters, so the Sun in his scale (around 7 meter for Earth the size of a tennis ball) would span only one seventh of the shorter side of the seventh football field in the picture.
The earth, when shrunk down to the size of a billiard ball, is also smoother than a billiard ball: <a href="http://wiki.answers.com/Q/Is_earth_smoother_than_a_billiard_ball" rel="nofollow">http://wiki.answers.com/Q/Is_earth_smoother_than_a_billiard_...</a> :)
I was more expecting to see the absurd results of shrinking the Earth to the size of a tennis ball (as "what happens") instead of "what else do we have to do to keep scale?"<p>Not to say that the article wasn't interesting- it certainly was!
The "Deutsches Museum" in Munich, Germany has got a permanent outdoor exhibit exactly of this kind. Some pictures are here: <a href="http://www.deutsches-museum.de/ausstellungen/naturwissenschaft/astronomie/planetenweg/" rel="nofollow">http://www.deutsches-museum.de/ausstellungen/naturwissenscha...</a>
You have to walk more than 4 kilometers from the sun to the "edge" of our solar systems. It's a great thing to educate children or a school class.
Here are a couple of my takes on illustrating relative sizes:<p>1. <a href="http://davidjarvis.ca/dave/gallery/star-sizes/poster-04_sm.png" rel="nofollow">http://davidjarvis.ca/dave/gallery/star-sizes/poster-04_sm.p...</a><p>2. <a href="http://www.youtube.com/watch?v=wM0JMaM_tdQ" rel="nofollow">http://www.youtube.com/watch?v=wM0JMaM_tdQ</a><p>The first is a picture of the planets and stars. The second is a video fly-by of the solar system.
If you're also shrinking all the tennis balls on Earth, make sure you save their initial size and compare the Earth against that. Otherwise you end up with an infinite loop as size(Earth) > size(tennisBall) is always true.
I genuinely think that those who reject science (about space, evolution, etc) are largely unable to grasp these vast quantities. The idea of evolution over "millions of years" is unimaginable to them because they don't understand how 100 year lifespan of a human is nothing compared to a million years or a hundred million years.