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  Wandering Through the Solar System

Ancient people were fascinated with the stars. Early on, they noticed that a few stars moved around among the others. They called these the wanderers, or πλανήτες (planites), in Greek. The word is from the Old Greek πλαναν (planan, to wander), which means to err in modern Greek.

On a visit to Washington in 2000, we saw a preview for a scale model of the solar system in the middle of the National Mall. Only the Sun and the inner planets were there, but everything was to scale (1:10-billion): the size of each object and the distance between them. It gave us a good lesson in why we call it space – there's an awful lot of space out there. On this scale, the Sun is 5½ inches in diameter, about the size of a grapefruit; Earth's diameter is 1/20 inch, one-quarter the size of a BB pellet. Mars is 75 feet from the Sun. So, the entire preview fit into a fairly compact area, even if the planets were a bit on the small side.

The model was completed the following year, called Voyage on the National Mall. The Sun is now in front of the National Air and Space Museum, with Pluto near the Smithsonian Castle, about 2000 feet away. Pluto was still considered a planet in 2001, so it's still part of the display.

It's a bit of trouble to visit Washington, so we've never seen the final installation there. It was heartening to learn that there's a better model, just an hour's drive from home. New Milford is a quiet town of 28,000 in northwestern Connecticut. Physically, it's the largest town in the state, which turns out to be quite useful for the purpose of this excursion – it needs a lot of breathing room. You can kick off your shoes and read in front of the library. If you're up for a deeper learning experience, you can make your way behind the high school, where you'll find the John J. McCarthy Observatory. Dedicated in 2000, the Observatory is the brainchild of Monty Robson, who wanted to do what he could to excite science students. It's affiliated with the high school, but was designed, built, and funded almost entirely by volunteers.

The Observatory has half a dozen good telescopes, and it has a tire that went to outer space and came back. Part of the shuttle Discovery's main landing gear, this tire spent ten days in space. It flew four million miles to the Hubble telescope and back before going to work for the 60 seconds needed for the shuttle to roll out on landing. After that one performance, the tire was retired. Our tax dollars at work.

The Kathleen Fischer Sundial was added in 2012 to honor a beloved science teacher. This is a feature of Galileo's Garden (2010), which showcases many varieties of perennial plants, some sculpture, benches for the visitor to relax and think, and a large model of the Sun. True to its namesake, the sundial's gnomon is a full-scale replica of Galileo's first telescope, angled exactly for the latitude at the site. The time band is calibrated for the longitudinal offset from Greenwich Mean Time, and for standard and daylight time. If the Sun shines and you're careful (and if you use the analemma on the Observatory's side door), you can tell time within ±5 seconds.

One of the stones in the garden (left) looks a bit like the Heelstone at Stonehenge (right), another important astronomical installation. It's no coincidence. A note on the Observatory web site points out that the red line is exactly west of the sundial. The real Sun will set behind this stone at the spring and fall equinoxes.

All of these things came after the Observatory's grand project. To commemorate the International Year of Astronomy in 2009, they built a scale model of the solar system, placing the Sun where the Garden and its features grew naturally around it. They chose a scale that kept the entire model within the boundaries of New Milford, 1:¾-billion. Pluto is 4.4 miles away from the human-sized Sun. The builders took minor liberties with scale so they could place all elements of the model at spots that are easily accessible to the public. This map is on an informational sign near each piece of the model, and you can download an excellent guide from the Observatory's web site. The guide has lat/long coordinates to program into your GPS. If you like, you could actually park your car within a dozen steps of any one of them. As it turns out, this is a mixed blessing.

Except for the Sun, each celestial model is mounted atop a narrow triangular pylon, near eye level for an average adult. There's an informational plaque next to it with a small brass plate on its stand. The plate is engraved with a symbol that a visitor can rub into a "passport" book as a memento of the visit. I didn't have a passport or rubbing wax, so I just took pictures of the models.

Took pictures of the remaining models, I should say. Sadly, this beautiful installation has been the target of vandals from Day One. All of the larger pieces have been stolen or broken. The Observatory has replaced the original bronze castings with wooden replacements, but even some of these are missing. What a waste.

But let's take a ride – it's still worth the trip. This is what you could see in January 2017. The Sun and inner planets are all near the Observatory, on the grounds of the New Milford High School, and have not been disturbed.

With one Greek exception, all of the planets have names from Roman mythology.


As already noted, the scale was chosen to keep all the planets in town. Conveniently, this produces a six-foot Sun, the centerpiece for the Galileo Garden and Sundial. Galileo would be pleased to know this Sun has not moved. But neither have most of the other "wanderers." The sunspots have faded a bit since 2009, but they're still visible, even on this cloudy day. The sign explains more about the sunspots and the structure of the Sun, which isn't reproduced on the model.

The sundial's one-ton polished granite base is visible in the background. Like the sun's own base, it was donated by Goodrich Aerospace Systems in Danbury, where it was formerly used as a reference plane for making telescope mirrors.

Mercury – Messenger of the Gods

We see immediately why the models are mounted on pylons. At ¾-billion scale, Mercury is only ¼ inch in diameter. The 36 million "miles" from the Sun take only a few seconds to walk. An easy walking pace scales to over 400,000 miles per second, or about 2½ times the speed of light. This could turn into quite a workout.

Like the planet itself, the Mercury model doesn't have many distinctive features. It's the small sphere at the very top.

Venus – Goddess of Love

Venus is 0.63 inch in diameter, with a color that is more reminiscent of Mars. That's what happens when you make a planet out of bronze.

Like Mercury, Venus can only be seen in twilight, near dawn or dusk. That's because these planets are closer to the Sun than we are. In the middle of the day, the Sun's light overpowers the planets, and at night we're facing the wrong direction.

Venus rotates in the opposite direction from Earth, so if you went to live there you'd have to get used to the Sun rising in the West. I think Velikovsky explained this backspin as the result of Venus's "collision" with Earth – like pool balls – about 4000 years ago. The Observatory signs are silent on this point.


Earth is about the same size as our sister Venus, 0.66 inch. Although the contours aren't exact continents (they're close!), the sculptor has done a masterful job of showing the nature of the blue ball we live on. Because the ancients were already here, they had no reason to name our planet for a deity. Our name is from Saxon eorthe, which – like Dutch aarde or German Erde – means, simply, land.

If the model could include our Moon, it would be a piece of green cheese 0.18 inch in diameter, with an orbit 39.8 inches across. The entire scope of human travel to date, within the distance a child could embrace.

Mars – God of War

Bronze is the ideal material for the Red Planet, scaled to 0.35-inch diameter. Looking back to the start point, one can see the Sun and other inner planets, but this part of the model is mostly in a parking lot behind the high school. There are cars and a couple of dumpsters in the way. This reminds me of all the space junk out there, but it doesn't make a very good photograph.

The sign tells us that Mars has a thin atmosphere, mostly carbon dioxide. Some folks think we're making too much of this stuff on Earth. Maybe we could ship some to our neighbor.

Once we pass Mars, it gets awkward to talk about mileage. Too many zeroes. It's easier to express distance in Astronomical Units, where one AU is the Earth's distance from our Sun: 93 million miles. For example, Mars is 141,634,848 miles from the Sun, on average. In casual conversation, it's much easier to call that 1½ AU. On the model's scale, 1 AU is about 645 feet.

Asteroids are 2.3-3.3 AU out. They wouldn't fit on the high school grounds, but they should be visible from here. However, even the biggest ones would be dust-sized at the scale of this solar system. Use your imagination as you look northward on a windy day.

Jupiter is 5.2 AU out, well beyond the high school property. Time to get back into the car.

Jupiter – King of the Gods


Here is where disappointment first greets the visitor. Where Jupiter's 7.4-inch orb once sat, there is now only an empty pylon. A note on the Observatory web site says that the model has been "removed due to local vandalism."

Fortunately, there are some photos available from shortly after the models were installed. Cropped and enhanced for clarity, they're shown here with the caption 2009. That way, you can see the bronze sculptures that we're missing today. There are also some brilliant shots on the Observatory web site.

The next planet is the only model in the series on private property. Frank Harden lived on 48 acres by the Still River (tributary to the Housatonic) from 1941 until he died in 1965. His will endowed a trust that maintains the park for public use. It's a tranquil year-round retreat from any stress you could imagine. Mr. Harden's house is now a small museum, including an art collection.

One of the park's popular features is the Sri Chinmoy Peace Mile, a measured path that invites visitors to run, walk the dog, meditate, whatever seems like the right thing to do at the time. The sixth planet is next to this path that was inspired by the great spiritual and fitness guru.

Saturn – God of Agriculture


Well, it was there, for a couple of years. The beautiful bronze model (right) was stolen from its mount in August 2011. Like the others, it's been replaced by a replica made from less valuable materials, to the same scale – 6.3-inch diameter planet, with proportional rings. It's attractive, but I would have preferred to see the original. As with the other missing models, the Observatory would be delighted if somebody returned the original Saturn. No questions asked.

New Horizons Space Probe


In 2009, the New Horizons Space Probe was between the orbits of Saturn and Uranus, so that's where the model was placed.

The probe was too complicated to be reproduced as a casting, and would be ridiculously small at the standard scale of the model solar system. So Donald Ross, a charter member of the Observatory, built a model in the machine shop. Alas, this model also became a target. It disappeared after about a year, to turn up broken in a Newtown front yard. There was too much damage to repair the original, so a two-dimensional bronze piece replaced it – for a while. That one also was stolen.

To add insult to injury, in Spring 2015 New Milford closed the Pettibone School, where the model stood. If you visit there now, you'll find a boarded-up schoolhouse with two concrete foundations out front where the model's pylon and sign used to be. Mr. Ross has machined a new bronze model, but its fate is unknown. Most likely, it will be an object to be admired privately by future generations of the Ross family.

The New Horizons probe was an important inclusion here because of its mission to explore distant objects in the solar system. Specific goals are Pluto and its five moons, especially Charon; and Kuiper Belt objects. It passed near Jupiter in 2007 to get a boost from the giant's gravity, getting some good pictures in the process. Its path has been re-programmed en route to accomplish tasks that couldn't be anticipated during pre-launch planning. For example, the next major objective is 2014 MU69, for now known as Ultima Thule. This Kuiper Belt object wasn't discovered until eight years after the probe was launched. The photo pass is scheduled for New Years Day, 2019. Don't miss it.


Update, January 2019:
The probe passed within 2200 miles of 2014 MU69, collecting seven gigabytes of data on the way by. Low-resolution pictures were available in a day or two, but it will take more than a year and a half to get all the data back — roughly comparable to using a 1200-baud modem, but not bad for a 15-watt transmitter several billion miles away.

To come that close, starting from Earth, needs about the same accuracy as hitting a U.S. dime from over twenty miles. Or a Euro coin from 46 km.

Ultima Thule is a contact binary about 9 ×22 miles overall. A contact binary is a single object that used to be two, dancing around each other in orbits that slowly shrank until the objects fused.

November 2019:
This object was officially given the name Arrokoth.

On the way from the Lost New Horizons probe to the next planet, my GPS led me astray. Maybe it's time to update the database. The GPS advised me to follow a road that might have been there two years ago, but in 2017 it only leads to the parking lot of a car-parts store. After a short backtrack, I followed the instructions on the Observatory's guide, which led me exactly where I wanted to be.

Uranus – Greek God of the Heavens


Sadly, what I found there was just a ¼-20 screw with some Loctite stains. It should have been a 2.64-inch green ball representing the planet Uranus. The info sign is still there, however. It settles an age-old debate: the planet is named for the Greek god of the sky, Ούρανός (Ouranos). Accordingly, English speakers should pronounce the name "urine-us," not "your anus." The sign uses different spelling, but that's the general message. Somehow, I think Ούρανός would not be flattered, either way.

Uranus is the first planet that was unknown to the ancients. Invisible to the unaided eye, it had to await the telescope and William Herschel's patient surveys.

This was the first model to be stolen, five days after is was installed. To the Observatory volunteers' great relief, it was soon found, undamaged, in a local front yard. It was re-mounted, but obviously to no long-term avail.

Neptune – God of the Sea


The sculpture Boy and Girl Reading on a Tree Branch is on one side of the town library; the 2½-inch Neptune model is on the other. This model is also a replacement. The original metal Neptune was stolen a few weeks before the solar system was unveiled in 2009. So far, the substitute has been safe from pilfering.

The planet was named for the sea god because of its intense blue color. It's the first planet that was predicted before it was seen, a milestone for mathematics in astronomy.

Pluto – God of the Underworld

Pluto's model is too small to be attractive to vandals: only 1/8 inch across. The model almost gets lost in its support structure. The planet is the tiny sphere on top of the bullet on top of the small cone on top of the larger cone with a dime leaning on it, on top of the pylon.

Pluto was the only planet discovered in the 20th century. Measured irregularities in the orbits of Uranus and Neptune had long implied there was something else Out There. In 1930, Clyde Tombaugh confirmed the existence of an object in about the right place, from photographic observations he took with a blink comparator and a telescope in Arizona. Six years later, he earned a bachelor's degree in astronomy.

The name Pluto was submitted by an eleven-year-old girl in England, Venetia Burney. It prevailed over other submissions because the god Pluto could make himself invisible, which certainly fit the description of the new planet. It didn't hurt that one of the astronomers whose math predicted Pluto's orbit was Percival Lowell, whose initials begin the name PLuto. Many years later, some errors were discovered in Lowell's work, so Tombaugh's discovery turns out to have been a lucky coincidence.

Clyde Tombaugh discovered many other celestial bodies before and after he got his college degrees. His contribution to modern astronomy cannot be understated: some of his cremains were sent into space aboard the New Horizons Space Probe. Fortunately, they are well out of reach for New Milford's marauders.

This striking photo of Pluto was taken from the New Horizons probe, offering crisp resolution that could not be attained from Earth today, and definitely not with Tombaugh's 1930 optics. If the Moon has a face, then Pluto has heart.

Walt Disney's famous dog did appear in a movie in 1930, when Tombaugh made his discovery. But the dog's original name was Rover. He wasn't called Pluto until Disney Studios released Moose Hunt in 1931, so we know the planet's name came first. What we don't know, is why Disney renamed the dog.

In January 2005, astronomer Mike Brown confirmed the discovery of the object 2003 UB313, which appeared to be in contention for recognition as the tenth planet. Its orbit was outside of Pluto's, and it was bigger. Informally, researchers called it Xena, a name that caught on quickly with the public for "Planet X." If Pluto is a planet, then surely this newcomer must also be one. The discovery started a firestorm in the international astronomical community, which ultimately led to the demotion of Pluto. It was a bittersweet conclusion for Dr. Brown, but either Pluto and Xena are both planets, or neither is one. So Mike Brown hadn't discovered a planet after all.

Before the debate was finished, the International Astronomical Union came up with the first re-definition of the word planet in human history. To be called a planet, an object must

It was the third point that caused the most trouble, especially as Pluto's orbit is sometimes inside Neptune's. (Is Neptune also not a planet?) The rule was muddied a bit by something about relative mass of objects that travel through the same part of space, but the IAU eventually came to agree about how to classify these things. Pluto and Xena were both declared to be "dwarf planets," and the IAU set about the process of finding an official name for Xena. After more debate, they eventually settled on Eris — appropriately, the Greek goddess of discord who started the Trojan War. But that's another story.

This all happened before The International Year of Astronomy, but the McCarthy volunteers decided to make Pluto a planet in their installation. Everything else, including Eris, got collective representation in the next part of New Milford's solar system.

Kuiper Belt / Oort Cloud

At this point, the scale of the model solar system starts to fail us. Beyond Neptune's orbit lies the Kuiper Belt, thousands of small objects in orbit from 30 to 50 AU. Pluto and Eris are now classified as Kuiper Belt objects, as are the more recently discovered Haumea and Makemake. The last two are named for Pacific Island deities, breaking the European monopoly on the heavens.

The Kuiper Belt still fits within town lines (4-6 miles), but the Oort Cloud certainly does not. This is yet another group of objects associated with our Sun, roughly 50 to 100 thousand AU away. That would require a station somewhere between 6000 and 12,000 miles from New Milford's high school. At this point even the Astronomical Unit starts looking small, and we speak of distances in terms of how far light travels in one year. A light-year is 63,000 AU, which would require almost 8000 miles on our scale. If the Observatory had stuck to that standard, we'd have to travel to the Taj Mahal to find the next pylon, on a Great Circle route crossing Iceland and Kazakhstan.

Let's just say that the Oort Cloud is between one and two light-years out, or halfway to the nearest star. Our Sun has quite an attraction for space objects, doesn't it?

The McCarthy volunteers chose the twin-tailed Hale-Bopp Comet to represent all of these things, locating it just over 50 scaled AU from the high school. Short-period comets like Halley (less than 200 years) belong to the Kuiper Belt; long-period comets like Hale-Bopp are Oort Cloud objects. The Oort Cloud is believed to have a trillion comets.

Gateway to the Galaxy


The outermost stop is not the Taj Mahal, but it might as well be. The pylon that once supported our galaxy is also empty. The thief didn't take the sign, though, so the visitor can still read some facts about the Milky Way.

We can read that our solar system is 26,000 light years from the center of things, where there is a black hole in line beyond our view of Sagittarius. We move slowly around this center, revolving once every 220 million years or so. If we don't do something about it in the next three billion years, we're going to collide with the Andromeda Galaxy. One wonders how theories and viewpoints will change between now and then.

Planet Nine

In his delightful book How I Killed Pluto, and Why It Had It Coming, Mike Brown describes first his elation at the thought of discovering a new planet, then his mixed emotions as the International Astronomical Union decided that Xena/Eris wasn't a planet, and neither was Pluto. Now imagine his feelings when his observations predicted a new object that met all three of the modern criteria for a planet. Disturbances in the orbits of other planets in our solar system are consistent with the existence of an object ten times the size of Earth, in an orbit about 700 AU away – over 20 times the distance of Neptune.

If this thing is really out there, its orbit takes 10-20,000 years, so we may have to wait a while for solid confirmation. If that verification comes, the McCarthy volunteers might want to look for a site some 85 miles away for another station in their model. Preferably where looters won't find it attractive.

Other Models

If you'd like to visit a scale solar system, you don't have to come to Connecticut. There are several of them around the world, at least fifty in North America. Some of the installations are truly noteworthy. The one featured in this article, in New Milford, would be near the top of the list if it had not been pillaged so badly. The craftsmanship there is meticulous. Here are some of the other standouts:

photo by

Sagan Planet Walk, Ithaca, New York. This is probably the most elegant installation, dedicated to the memory of the famed Cornell professor Carl Sagan. The markers are six-foot stone obelisks using a 1:5-billion scale, putting Pluto just ¾ mile from the Sun. The artists were ingenious in dealing with the enormous disparity between the sizes of the planets and the distance between them. The first marker has an 11-inch hole to represent the Sun's diameter. All of the others repeat this hole, with scale models of the planets inside as you can see here. This one is Jupiter, about one-tenth the diameter of the Sun. Your eyes will be tested to find the tiny models for Mercury and Pluto, each less than a millimeter across. Between Mars and Jupiter is a newer obelisk for the asteroid belt, featuring a real meteorite for visitors to touch. It's the only unguarded meteorite in the world on public display.

In 2012, the Sagan Planet Walk added a station at the correct scale (distance and diameter) to represent Alpha Centauri, nearest star to our own. It's in Hilo, Hawaii, over 5000 miles from the Sun in Ithaca, making this officially the largest model solar system in the world.

Maine Solar System, Aroostook County. This one is enormous, spanning 40 miles from Presque Isle to Houlton. The Sun is so big at this scale, that the artists only represent part of its outline. It's a big wooden curve inside a large building at the University in Presque Isle. Pluto is a one-inch ball in the Houlton Information Center. The other planets (and some of their moons) are on roadside pylons. Uranus and Neptune are specially mounted to show their extreme rotation axes.

Pluto Walk, Flagstaff, Arizona. Here is where Clyde Tombaugh discovered Pluto. They've dealt with the scaling problem by making the planets twenty times larger than the distances between their orbits. So the visitor can see the planets, and the scale of the model is an easy stroll.

Anderson Family Solar System, Lehi, Utah. Here the planets are at 300 times the scale of their orbital distance. The Sun is a semicircular arch, 25 feet in diameter. Walk beneath it to stroll about 100 yards along a garden path to Pluto.

Several more of these models are in the table here. For a more complete list that includes the rest of the world, see this Wikipedia entry, or the Pillow Astronaut's extensive list. The list is alphabetical by state or province.

There's a little mark () before most of the site names. If you click it, a small window will pop up with map coordinates for that model. You can copy these numbers and paste them into a map site or GPS application, suitable for driving directions to that model. If that explanation seems fuzzy, there are more complete instructions at this link.

If a scale factor looks odd, hover on it. It was probably chosen for a reason.

The distance in the last column is from the Sun to Pluto; hover on it to see metric measure. An asterisk (*) means the distance is from the Sun to Neptune.

The Voyage Project was launched in the hopes of building 100 scale models of our solar system. Only a handful have even been started. The four completed models in the United States are marked with a dagger (†) in the list. If you have 2000 feet to spare (1500 feet if you leave out Pluto), maybe you'd like to build one too.

Alabama Huntsville Solar System Walk 1:27 B 713 ft
Alaska Anchorage Light Speed Planet Walk 1:350 M 10.3 mi
Arizona Flagstaff Pluto Walk 1:63 B 350 ft
Arizona Gilbert Riparian Preserve Trail 1:9 B 2130 ft
Arizona Phoenix Scale Model Solar System 1:15 B 1291 ft
Arkansas Mountain Home Baxter County Orrery 1:1 B 3.7 mi
B.C. Fort St. John Walk the Solar System 1:682 M 5.4 mi
California Carlsbad Solar System Walk 1:5280 M 3670 ft
California Kenwood Robert Ferguson Observatory 1:2 B 2.3 mi
California Ladera Ranch Planet Walk no scale
Colorado Broomfield Our Solar System 1:78 B 250 ft
Colorado Boulder Fiske Planetarium 1:10 B 1970 ft
Connecticut New Milford McCarthy Observatory 1:761 M 4.4 mi
Delaware Newark Planet Walk 1:2.8 B 1.3 mi
D.C. Washington † Voyage on the National Mall 1:10 B 1970 ft
Florida Gainesville Solar Walk 1:4 B 0.9 mi
Georgia Gainesville Solar System Walking Tour 1:2 B 1.8 mi
Idaho Boise Planet Walk 1:2.2 B 1.5 mi
Illinois Elmhurst Elmhurst Solar System 1:3 B 1.2 mi
Illinois Peoria Lakeview Museum 1:125 M 29 mi
Indiana Cumberland Solar System Model 1:1 B 3.8 mi
Kentucky Berea Planetary Plate Project 1:37.6 B 515 ft
Maine Presque Isle Maine Solar System 1:93 M 40 mi
Maryland Glen Burnie Baltimore Annapolis Trail Park 1:800 M 4.6 mi
Mass. Boston Community Solar System Trail 1:400 M 9.5 mi
Michigan Escanaba Walk of the Planets 1:4.6 B 13.5 mi
Michigan Grand Rapids Foster Planet Walk 1:12 B 1600 ft
Michigan Lansing Planet Walk 1:2.74 B 1.3 mi
Missouri Kansas City † Voyage in Kansas City 1:10 B 1970 ft
Missouri St. Louis Delmar Loop Planet Walk 1:5 B 2850 ft *
New Jersey High Bridge Solar System Walk 1:7 B ½ mi
New Jersey Ringwood N.J. State Botanical Garden 1:10 B 3040 ft
New Mexico Silver City Sidewalk Solar System 1:3 B 1.2 mi
New Mexico Sunspot Solar System Model 1:250 M 14.6 mi
New York Ithaca Sagan Planet Walk 1:5 B 3940 ft
Ohio Cleveland Solar Walk 1:5280 M 3940 ft
Ohio Wooster Wooster Planet Walk 1:5 B 3940 ft
Oregon Eugene Scale Model Solar System 1:1 B 3.6 mi
Oregon McMinnville Solar System Walkway 1:41 B 360 ft *
Pennsylvania Allentown Andrews Planet Walk 1:5280 M 3676 ft
Quebec La Malbaie Strolling at the Speed of Light 1:1.5 B 1.9 mi *
South Dakota Sioux Falls Sertoma Park Solar System 1:30 M mixed
Tennessee Kingsport Bays Mountain Park unknown unknown
Texas Corpus Christi † Voyage in Corpus Christi 1:10 B 1970 ft
Texas Houston † Voyage in Houston 1:10 B 1970 ft
Utah Lehi Anderson Family Solar System 1:55 B 355 ft
Utah Logan Logan River Planet Walk 1:2.8 B 1 mi *
Utah Moab Family Solar System 1:400 M 9.5 mi
Vermont Norwich Montshire Museum of Science 1:2.2 B 1.7 mi
Washington Longview Solar Walk 1:2.2 B 1.7 mi
Wisconsin Madison Madison Planet Stroll 1:4 B 4850 ft
Wisconsin Madison Planet Trek Dane County 1:200 M 23.8 mi

These models do show the difficulty of expressing the scale of objects in space, even in a tiny part of the universe like our solar system. You can get a feel for this by visiting a web site that scales the solar system so the Moon is one pixel in diameter. The author invites you to start at the Sun and scroll to Pluto (almost two million pixels). On that scale the Sun is 400 pixels across and everything else is just about invisible. There must be a better way to show this thing on a human-readable scale.

We might take a hint from what some of the large scale models have done: use one scale for the size of the planets, and another for the distance between them. To reduce our solar system (and include Pluto), here's what it looks like if the planets are shown on a scale about 3000 times as large as the size of their orbits. Since the Moon isn't in this picture, the planet scale is set so that Pluto is one pixel across. If the distances were set to the same scale as the planets, Pluto's pixel would be 2123 feet from the Sun, with a typical screen resolution of 72 pixels per inch. You'd need a very big monitor to find that pixel.

If you zoom in here as far as your browser will go, you can see Pluto's pixel. There's a circle around it in the diagram to help you find it. Like all of the models we've seen, the inner planets are clustered right on top of the Sun (big yellow circle). Jupiter and Saturn are about one-tenth the Sun's diameter, and things get small very quickly after that.

Here's how it might look if we took a cue from audiophiles, and put everything on a logarithmic scale. What irony: now the Sun is the outlier! In this diagram, orbits and diameters are all on the same scale, but the logarithm business really compresses things, doesn't it?