Not a Dry Heat by David A. Rosenthal Imagine: adventure among the ruins of a vanished civilization, hacking your way through a steaming jungle in search of a pyramid lost for 1,000 years, or experiencing the thrill of genuine discovery: If you've relegated these notions to movies and fantasy, you haven't been keeping up. Despite the Internet, paved roads to nearly everywhere, and helicopters to everywhere else, there are lots of places and interesting adventures still waiting to be experienced. That is, if you really want to find them. As a desert denizen, this adventure embodied my worst nightmare: humid heat and lots of it. I traveled to the jungles of Mexico's Yucatán Peninsula--home of the ancient Maya civilization--to make some scientific measurements, then track down that abovementioned pyramid. These were two important tasks that will enable archaeologists to witness a rare and never- before-recorded astronomical event. The BAD news was that, in the heat and constant 80%+ humidity, a ten- minute walk drenches you in never-to-evaporate sweat. More than 500 years before Kepler fooled with his first equation, the Maya had long since perfected their understanding of the planet Venus' orbit. Not only that, they'd produced a 365-day calendar and were well aware that Venus' sweeps out a grand cycle: a repeating set of five appearance patterns in the sky in very nearly precisely eight Earth years. The Maya of the ancient city of Uxmal were so concerned with this brilliant planet and its pathways through the heavens, they built a temple facing the very spot on the southeastern horizon where, only once every eight years, Venus rises to begin a new grand cycle. And as a marker, several miles to the southeast, they built a pyramid in a place called Cehtzuc. The next grand cycle of Venus would begin in January 1997 when, as seen by an observer standing in the central doorway of the Uxmal temple, the planet would appear directly above that pyramid. But though scientists have known about this event for at least twenty years, no one has ever photographed it or made sufficiently precise on-site measurements to determine the optimum time to view it. Astronomical software predictions are only so good; to pin down the precise situation, you have to look for yourself. This is where I came in. With the help of several Maya scholars at universities here in the U. S., the Mexican government granted me clearance during September 1996 to use a surveying tranist at Uxmal--now a totally developed archaeological park--to make my measurements. The first part was easy: set up my transit at the doorway of the temple at 3:30 AM and wait for Venus to rise. Then, noting the precise time, make an azimuth measurement of where it rose, then make several more as it moves higher. This procedure would enable me to add an empirical correction to my computer's predictions. The only problem was the calm, clear sky that allowed the predawn temperature to plummet through the 80+ degree dewpoint and soak everything--transit, glasses, writing tablet--with water. Wet, wet, wet; as if sweating wasn't bad enough. Sleepy, but with data in hand, I descended from the well-groomed, Disney World-like, don't-touch-this, don't-climb-on-that ruins, shepherded by a watchful, but also sleepy, watchman. Step two was getting to the pyramid and measuring the azimuth back to the temple. From Uxmal, the pyramid at Cehtzuc, abandoned for nearly 1,000 years and totally overgrown, is barely visible as a bump on the horizon. Only one person was really familiar with Cehtzuc and how to get there. He's a local Mayan and sometime shaman named Manuel Ay. We left at 6 AM, before sunrise and an excellent time to start a cross-country trek since temperatures in the jungle are lowest then. We drove as far along the trail as we could, then grabbed our gear and began walking. About a mile later, Manuel turned into the bush and the hacking began. Machetes flailing, we crept along, zigzagging, always seeking the path of least resistance. Thought processes reduced to a simple stream of consciousness. Despite temperatures only in the high 70s, the 100% humidity had us both soaked in sweat in about a minute. I now realize my canteen is WAY too small. An hour passes, then more time. You measure progress by the length of your next step. I have my handheld GPS unit but it's useless under all the foliage. It's compass only now. The sun is up and you can hear the wind in the treetops--up there and out of reach. The heat builds and you can feel it. Manuel points out a huge tarantula, then a place where a deer had passed the night. No trash or signs of people out here. Finally, we begin encountering scattered plinths, all just piles of rock now. Suddenly, a bunch of stones blocks my path. Wearily, I raise my eyes just enough to try and see a way around that will expend the least possible energy. But the pile goes up and up. It's the pyramid and I've literally bumped into it. Manuel and I heft our gear onto our backs and begin to climb. Carefully, we make our way higher, finally into the trees. All at once, we're on top; we can now see the treetops from just above--a fascinating perspective. The morning cool had produced a dense fog that covered the jungle and we try to see where we are--to see ANYthing. Just at the limit of visibility, something gradually begins taking shape. Soaked in sweat and miserable, we both strain to identify it. All at once, we realize it's the ancient city looking right back at us! Through mist and trees, we shared the same sudden and powerful vista early 19th Century explorers must have experienced. I begin setting up the transit and Manuel works on clearing brush for our sightline. He hacks into a dead henequen plant (like a yucca) and it explodes with yellow-jackets whose hive we've disturbed in its trunk. We dive into the bushes; not many places to hide up here. He says we're lucky since they're not too aggressive when it's cool. I wait for the sun to burn off the fog so I can calibrate the transit. Manuel goes back down to strip some bark from a type of tree that only grows this far out; boiling it makes an ancient remedy for kidney stones. He bundles some up to take home. Measurements taken, pictures shot, GPS reading recorded, we head back. Hours later, I'm taking a long shower. According to Manuel, I'm only the eighth person in history to have been there. The data were good, the measurements more than adequate to predict the Venus rise window. All that mattered at that point was the sky being clear on the days in January.
David Rosenthal is a physicist and electronics engineer. He's also a reserve military pilot, flying the UH-60 Blackhawk in the California National Guard.
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