The planets are scaled to the image of the sun. The text beside the sun says:
Hmm. would someone good at math work this out for me? (Using the Swedish model as the example.)
If you wanted your model to move, and the orbital periods of the objects were correct (for example, if Pluto was 300km from the center of the model), how fast would the Pluto-object have to move to complete one orbit every 248 years?
How fast would the Mercury object move? (distance from center = 2900 meters, orbit once every 89 days)
Hmmm. Methinks this would be an interesting geocaching project.
Shouldn’t it be somewhere in Florida? 
Lesseee… wiki says the circumference of a circle = 2r * pi.
Pluto: 300km * 2 * 3.141592653 = orbit circumference of 1884.955592153 km. Divide that by 248 years = 7.6006 km/year along its path, or 20.8 meters a day (which is 2.68 feet/hour).
Mercury: 2900m * 2 * 3.141592653 = orbit circumference of 18221.237 meters. Divide that by 89 days, and that comes to 204.73 meters/day (26.44 feet/hr).
Did I calculate that right? Wow. (Wiki verifies that Mercury moves 10 times as fast as Pluto does!)
If we’re going to spin/move these planets, somebody better calculate mass.
Does centrifugal force still exist? I think we now call it something else.
Anyway, these moving celestial bodies are going to try to go in a straight line.
If we’re making a working model (an orrery), we can’t have the sun in NYC, 'cause then someone will have to walk on the Atlantic to move Pluto, and He’s not available this week. 
So, either we cut the scale in half, and put the sun in the center of the US*, or move the whole thing to the middle of Eurasia somewhere. In any case, assuming mlees’ calculations to be correct, we will need to get someone to move Mercury 26 feet each hour (depending on how accurate we want the model to be in a minute-by-minute sense). I’m guessing that a clockwork mechanism is out of the question, but maybe not–can we put each one in a little remote-controlled car? Then we’d only have to charge the batteries once every couple of hours.
We also need a discussion about what to include in the model–is Pluto included? Major asteroids? Comets? Kuiper belt objects (out to approximately 55 AU)??? The Oort cloud???
All that said, I think it’s a GREAT idea! That’ll give people some idea how preposterously far away things are, even in our “local space.”
- Belle Fourche, a ranch town of 4,500 residents in western South Dakota, the geographic center of the USA, including Alaska & Hawai’i.
I used to do the Sagan Planet Walk in Ithaca, when I was in college. It’s pretty neat. The inner planets are all within one city block, and then you have to start walking. It’s not particularly large, though, with Pluto around 3/4 mile away from the Sun. (this was built before Pluto was demoted…the other dwarf planets were not there, at least the last time I was there.)
The obelisks are each 8 1/2’ tall, to represent the Sun’s diameter. It’d’ve been cool if they had built a geodesic sphere to represent the Sun itself. Maybe 1 or 2 people at a time could walk inside and see interesting facts about the Sun.
Better yet, make it 30 million degrees inside, so that people can experience what it’s like to touch — and then become — a plasma.
As I recall, the Smithsonian’s obelisk for the Sun has a brushed-metal, gold-colored sphere about six inches across to represent our star, which is nice and pretty certainly, but for reasons of cost no doubt is not to scale with the rest of the display.
Temperature’s all wrong too.
It’s still only the sun and nine (ha!) planets. There was some talk about setting a marker for Alpha Centauri; at the same scale it would have to somewhere in Hawaii.
There was some outfit that cast a series of small bronze plaques of the planets to scale, the idea being to mount them at scale distances on posts so you could take a solar system walk. The scale was the sun’s diameter at three feet, because that’s the size of those plastic spheres you see on cross country high tension lines. IIRC Pluto was to be about a mile and a half away.
Whenever I teach astronomy I use a hula-hoop (86.5 cm) as the sun, giving me a weird mixed-unit scale of 1 meter = 1 million miles. Mercury and Mars are peas, 37 and 140 meters from the sun; Venus and Earth are garbanzo beans, 67 and 93 meters away (the moon is a bb 24 cm from the Earth); Jupiter is a large orange, 450 meters away. Within our campus that’s as far as I can walk with the students and still see back to the sun; But I point out to them that, at this scale, pluto is another small pea about 2.3 miles away and the Alpha Centauri system could be represented by another hula hoop 25,000 miles (3 full earth diameters) away.
The Zurich Planetenweg is a great hike. It begins by the train station at Uetliberg, a low hill on the ridge that defines the western edge of the city. The sun is a yellow globe on a lamppost 1.4 meters in diameter. The scale is 1:1,000,000,000 and the planets are cast in brass and set in resin on stone monuments along the trail. The hike to Pluto’s aphelion is just over 6 km along the ridge, with gorgeous views of the city and the Zurichzee. At this point you can take a cable car down to the train station in Felsenegg.
You’re right, I think the cursive on distance threw me off, leading me to think the whole thing was only to scale distance wise. Thanks for the correction!
BTW, has anybody so far found a planet besides Pluto? I only found Saturn, so far…
[Danged hampsters…]
For amusement, I figured distances such that a normal highway driving speed would be the speed of light^. Here’s what I got…
Conversion factor: 1 map km = 10,792,512 real km.
Speed of Light=100.00 km/hr (62 MPH) It’s not just a good idea, it’s the LAW!
Sol diameter=129.72 m*
Mercury diameter=0.45 m distance=5.36 km
Venus diameter=1.12 m distance=10.03 km
Earth diameter=1.18 m distance=13.86 km (3’ 10" diameter, 8.6 miles from Sol)
–Luna diameter=0.32 m distance=0.04 km (12.5" diameter, 130 feet from Earth)
Mars diameter=0.63 m distance=21.12 km
Asteroids
–Vesta diameter=0.10 m distance=32.73 km
–Ceres diameter=0.09 m distance=38.43 km
–Pallas diameter=0.10 m distance=38.43 km
–Hygiea diameter=0.07 m distance=43.49 km
Jupiter diameter=13.23 m distance=72.11 km
–Ganymede diameter=0.49 m distance=0.10 km
–Callisto diameter=0.45 m distance=0.17 km
–Io diameter=0.34 m distance=0.04 km
–Europa diameter=0.29 m distance=0.06 km
Saturn diameter=11.12 m distance=132.22 km
–Titan diameter=0.48 m distance=0.11 km
–rings+ ID diameter=11.25 m rings OD diameter=21.82 m
Uranus diameter=4.74 m distance=266.02 km
Neptune diameter=4.60 m distance=416.69 km
KuiperBelt ID=463.28 km KuiperBelt OD=849.35 km
Pluto diameter=0.21 m distance=547.88 km
Eris diameter=0.24 m distance=937.69 km
AlphaCentauri diameter=79.07 m distance=3,826,468 km
- Hey, that’s a big bleepin’ ball! The Unisphere is only 42 meters! We could put it half-way in the ground, and then it would be ONLY 65 m. high.
- Rings 6,630 km to 120,700 km above the surface, 20 meters thick, so id=121,434 od=235,504
^ If you don’t consider distances by how long it takes to drive there…well…that’s just un-American!
Thank you for that, NCUN.
You have rekindled my faith humankind.
If you were to make a scale model with all the proportional masses, stick it in deep outer space and set things in motion, would you have a working model based on the gravity of the system? I suspect that the orbital speeds would be off, but could you film it with time lapse to get the same thing, or would the planetary orbits be proportionally off from each other?
Check out the page source - like Pluto, all the other planets are tagged with link anchors in the HTML. Using the provided link for Pluto, just replace #pluto with #mercury, #jupiter, etc.
Glad to be of service. I wrote a program to do the conversion, of course, so if you have a favorite conversion factor, just let me know.
If it could be done, that’d be so cool and easy there’d be scale models performing like that all over the place. But there aren’t any.
Here’s why it can’t be done. When you reduce all the lengths by a fraction, all the bodies’ volumes are reduced by the cube of that fraction, and therefore so are the masses. For example, in just a 1/2 scale model, the masses would decrease by 1/8. For this to work, you’d at least have to increase the density a lot. And you can see that’s a problem.