Sky and Telescope - November 2018 - 70

A Scale Model
Solar System

p Robert Mass
poses with Saturn
on the Pere Marquette Rail Trail.
The Sun is visible
at the far end of
the trail.

This project is literally far out.
I LOVE BICYCLING TO PLUTO and

back. My wife and I do it several times
a month along the scale model solar
system in our hometown of Eugene,
Oregon. Now, thanks to Robert Mass,
people can do the same in Midland
County, Michigan.
Bob's scale model got its start nearly
38 years ago. He remembers: "I had
taken my young children, Kathy, Phil,
and Andy, to an open ﬁeld north of
town to see the great conjunction of
the planets in 1980. As the last rays of
the Sun disappeared, we and everybody
around the world could see the ﬁve
naked-eye planets form a very short arc
in the west." More recently, he has been
keeping track of Saturn and Jupiter's
relative position in anticipation of their
conjunction in 2020. That led his son
Phil to mention the Eugene model laid
out along 3.7 miles of river path, and
together they calculated that they could
do an even larger model along the Pere
Marquette Rail Trail, an old railway
right of way turned into a paved walking and bicycling path.
70

N OV E M B E R 2 018 * SK Y & TELESCOPE

Eugene's Sun is 4.5 feet in diameter,
for a 1:1 billion scale. Bob's is 7.5 feet
in diameter, for 1:600 million scale.
That puts his Pluto 5.6 miles (9 kilometers) away. There was a perfect stretch
of path for that between the towns
of Coleman and North Bradley. It's
arrow-straight, so you can see the entire
length of the solar system at once. With
a small telescope, you can even see the
Sun from Pluto. (And yes, since this is
a scale model, seeing Pluto from the
Earth is every bit as difﬁcult as spotting
the real thing.)

The section containing the Sun
through Mars is in a grassy park within
the city of Coleman. The straight section
of trail ends there, allowing Bob to place
the Sun off the trail but still directly in
line with the extended centerline.
All of the planets were placed within
their orbits' eccentric limits, but Bob
did have to adjust their positions a bit.
Mercury had to be placed close to perihelion to avoid putting it in the middle
of a cross street. Pluto's position at the
trail head in the Village of North Bradley 9 kilometers eastward places it well
outside Neptune's orbit, but as Bob says,
"It will be in perfect agreement with the
real Pluto's position in a few decades."
Each planet sculpture is mounted on
a three-feet-high by four-inch-square
stainless steel pedestal so each sphere
can be easily spotted. At each end of
the system are information signs with a
table of trail and solar system distances,
a photo of the conjunction of 1980,
Copernicus's heliocentric model of the
solar system, and a map of the trail.
Another volunteer, Henry Hellmann,
co-authored the design of the signs and
developed QR codes, which are afﬁxed to
the sculptures. These codes take smart
phone users directly to a NASA site for
detailed astronomical data.
The planets, rings, and stems were
made of stainless steel so should be
care-free for decades. The Sun was
fabricated of steel and painted at the
Gladwin Tank Factory (and Bob reports
that "It just cleared the utility wires on
its 26-mile trailer trip to Coleman.")
The gas giant planets are hollow spheres
purchased from Sharpe Products of
New Berlin, WI, but the smaller planets were made
in Bob's own
machine shop,
using a custom
sphere-turning
lathe attachment that he also
made himself.
t All the planets were
gathered for a group
photo next to the
Sun before their final
installation.

ROBERT M ASS: CH A RLES BONH A M, BONH A M PHOTOG R A PH Y;
SUN A ND PL A NE TS: BEN TIER NE Y

ASTRONOMER'S WORKBENCH by Jerry Oltion
Sky and Telescope - November 2018

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