For the kind of data Lara, Maureen, and Susan want to collect, STS-2 seismometers are the best in the world. Unfortunately, they’re not here yet.
The problem is that it’s inadvisable to ship the instruments until we have a good chance of getting them through customs in Lima. We’re trying to complete all possible paperwork that might be required for 60 seismometers to enter the country, but it’s not obvious what the requirements will be. At this point, we hope to have the machines by next Tuesday.
Dome shaped STS-2 Seismometers work by measuring electric current. Inside each one are three weights (or masses) which are held in place by a charge that runs through them. When the ground shakes, the outside of the instrument moves, but the current holds the masses in place. By measuring how much current is required, the seismometer records the size of the waves.
While they are in the ground, the masses hang down without touching the plates on either side of the dome. While they are in transit, the masses have to be locked to one side or the other. If they are left unlocked and allowed to swing, even picking one up is enough to break the delicate pivots holding the weights in place. Each pivot costs over $100, and if one breaks, there are only a handful of people in the world who know how to fix it. When the machines arrive, we’ll be able to test the whole group—then we can start to install them in the barrels we’ve prepared.
Lara’s priority is to install the seismometers that are on loan from PASSCAL first, because they have to go back in September 2012. Many of them are also going in areas with roads that will wash out in the rainy season, so the stations have to be assembled soon or the sites won’t be accessible until next spring.
Since we’ve been in Cusco, we’ve put one more barrel in, but apart from that, we’re mostly done until the seismometers get here. What’s left is to permit a few more sites on national park land, but it’s election day, so all the officials are busy.
With this in mind, Lara gives us a day off, and Jenny, Christine, Lara, and I jump at the chance to go to Machu Picchu. To get there, we take the train to the base of the mountain and then a bus to the ancient city. The trains are beautiful, with huge plate glass windows so passengers can see the mountains.
The tracks follow the Urubamba River up the Sacred Valley of the Inkas, where they built 100 temples in the shape of constellations. Our guide tells us that they hoped to match the Milky Way, creating harmony between the river in the sky and the river on the earth. Inkas were required to make a pilgrimage to Machu Picchu once in their lives, and carried offerings of stones from far away places.
Walking around the city ourselves, we come to the astrological observatory, which has a central sculpture depicting the compass points. Not only did the Inkas know true north, but they also added a lower point for magnetic north. At the winter solstice, the shadow of the stone makes a triangle on the ground. In the exact center of the triangle, they carved a circle, creating a symbol exactly like the Masonic eye on the dollar.
Lara wants to put a seismometer up here, and though they haven’t arrived yet, at least the delay allows us a second hitch—this stone the guide calls the hitching post of the sun.