I went for a leisurely hike a couple weeks ago, and stumbled onto rocket science.
Sachem Head is a pretty well-known Greenfield hike, whether you’re coming up the steep side from the Highland Park parking lot, or taking the long, gradual climb up the ridge from the Poet’s Seat gate.
It’s got great views to the south and west, and when the leaves thin out, you can see the Deerfield Railyard to the east. Looking north yields a nice view of the ridge’s rock face, especially when it’s bathed in the golden-hour light of the setting sun. But one of the more interesting sights at Sachem’s is right underfoot.
I was out with friends years ago when I first noticed the tarnished bronze marker just north of the wooden platform. I licked my thumb and rubbed it against the disc to make the engraving a little clearer. This confirmed that what I’d seen was no misread.
“SATAN 2” is the most prominent phrase on the marker, which also reads, “Mass. Dept. of Public Works Triangulation Station,” and is marked 1937.
An afternoon hike earlier this month with my friends Kelly and Chelsea inspired me to take a closer look at this odd relic.
“Does anyone have a compass on their phone?” asked Chelsea, crouched to look at something down by her feet.
She’d found a bronze marker I’d missed on my hikes here. It had an arrow on it, and she wanted to see if it pointed true north.
I don’t trust my phone’s compass, since the little arrow on Google maps always tells me I’m driving sideways. So, I looked at the sun and figured the marker’s arrow is close enough to north. Then I showed them the other marker. While they stood at that one, I ran back to the one Chelsea had found, knelt down, lined my eye up with the arrow, and found that I was looking straight toward the two of them.
Walking around the immediate area, we saw another marker to the east, and another farther north. Both of these also bore arrows pointing toward the “Satan 2” marker, which also had the words “triangulation station” on it. But the three arrow markers read “US Coast and Geodetic Survey.”
When I got home, I looked them up, and found that they’re much more common than I’d expected.
Markers like this are all over the planet. A quick search on the National Geodetic Survey website revealed three other major markers in Greenfield, along with several others, each with different designations. There’s one on the top of Poets Seat Tower, one off of Meridian Street, and even one on the roof of the jail, as well as lesser ones along Interstate 91 and Routes 5 and 10 and a few lined up with the runway at the Turners Falls Airport. But the legend on the map I’d found did little to explain anything to the untrained.
I went to do some quick research, figuring it couldn’t be too complicated. I was wrong. The simplest explanation I could find was a primer on geodesy put together for the Department of Defense in 1977.
These markers are used for geodetic surveying, which is used for map-making, GPS reference points, and even studies on the motion of the Earth’s crust. It also determines the gravity of different parts of the planet. Those gravitational irregularities can change the orbits of satellites, as well as the trajectory of missiles or spacecraft.
And that’s where the rocket science comes in to correct the course of these vessels.
Geodesy also tells us which way is down. At the planet’s surface, gravity doesn’t necessarily pull things straight toward the center of the Earth. It pulls them toward the center of mass, which is affected by hills, valleys, and the very makeup of the ground.
So, while my little hike led me to a weighty subject, I did learn some interesting tidbits, like the Earth being shaped like a lumpy potato, and the fact that it takes a bit of math to actually figure out which way is up.
A closeup of the geodetic surveying marker at the point named “Satan 2” on Sachem Head in Greenfield.