About 25 million years ago, Earth parted in the southeast corner of Siberia. Since then, countless rivers have converged on the gaping continental rift, creating the vast body of water known as Lake Baikal. Surrounded by mountains, this 400-mile-long inland sea has remained isolated from other lakes and oceans, leading to the evolution of unusual flora and fauna, more than three-quarters of which are found nowhere else on the planet. Russians regard it as their own Galápagos. The lake contains 20 percent of the world’s unfrozen freshwater—or just a little less during the severe Siberian winter when, despite its enormous size and depth, Baikal freezes over.
On one such winter’s day, I found myself on the lake near the town of Listvyanka, which is nestled in a crook of the shoreline. I was in an old van that was trying to head west, not along a coastal road—for there was none—but over the ice. The path, however, was blocked by a ridge. It looked like a tectonic fault: Two sections of the lake’s solid surface had slammed together and splintered, throwing up jagged chunks of ice. The driver, a Russian with a weather-beaten face, peered from underneath his peaked cap, looking for a break in the ridge. When he spied a few feet of smooth ice, he got out and prodded it with a metal rod, only to shake his head as it crumbled: not thick enough to support the van. We kept driving south, farther and farther from shore, in what I was convinced was the wrong direction. The van shuddered and lurched, its tires crunching on patches of fresh snow and occasionally slithering on ice. The ridge continued as far as the eye could see. Suddenly we stopped. In front of us was a dangerous-looking expanse littered with enormous pieces of ice that rose from the lake’s frozen surface like giant shards of broken glass.
The driver seemed to be contemplating going around them to look for thick ice that would let us reach our destination, an underwater observatory operating in one of the deepest parts of the lake. But if he did that, we’d get even farther from the shore, and it would take just one punctured tire to strand us. The sun was little more than an hour from setting, and the temperature was falling. I couldn’t ask the driver if he had a radio or a phone to call for help, since he did not speak a word of English and the only Russian phrase I knew was do svidaniya. The last thing I wanted to say to him at this point was “Good-bye.”
Thankfully, he decided to turn around. We drove along until we came upon vehicle tracks that went over some ice covering the ridge. The driver swung the van westward and cleared the ridge, and soon we were racing across the lake at a speed that turned every frozen lump into a speed bump. The van’s front rose and fell sickeningly, rattling the tools strewn around on the front seat. I worried that the ice would give way and we would plunge into the frigid waters below. But it remained solid, and the van, despite its appearance, was in fine mechanical fettle, its shock absorbers holding firm. In the distance I spied a dark spot on the otherwise white expanse. As we approached, the spot grew to its full size, revealing itself as a three-foot-high Christmas tree. We still had 20 miles to cover, and the sun would soon disappear below the icy horizon. But now that we had found the Christmas tree, I knew we were fine.
I had first seen the tree two days earlier, with Nikolai (Kolja) Budnev, a physicist from Irkutsk State University, and Bertram Heinze, a German geologist. We were headed to the site of the Lake Baikal neutrino observatory, which lay deep beneath the ice. We had just driven onto the lake from the shore near Listvyanka when Heinze asked, “When does the ice start breaking?”
“Sometime in early March,” Budnev answered. My heart skipped a beat. It was already late March, and we were on the ice in an old, olive-green military jeep. “Sorry, sometime in early April,” Budnev corrected himself. Phew.
For more than two decades now, Russian and German physicists have camped on the frozen surface of Lake Baikal from February to April, installing and maintaining instruments to search for the elusive subatomic particles called neutrinos. Artificial eyes deep below the surface of the lake look for dim flashes of blue light caused by a rare collision between a neutrino and a molecule of water. I was told that human eyes would be able to see these flashes too—if our eyes were the size of watermelons. Indeed, each artificial eye is more than a foot in diameter, and the Baikal neutrino telescope, the first instrument of its kind in the world, has 228 eyes patiently watching for these messengers from outer space.
The telescope, which is located a few miles offshore, operates underwater all year round. Cables run from it to a shore station where data are collected and analyzed. It is a project on a shoestring budget. Without the luxury of expensive ships and remote-controlled submersibles, scientists wait for the winter ice to provide a stable platform for their cranes and winches. Each year they set up an ice camp, haul the telescope up from a depth of 0.7 mile, carry out routine maintenance, and lower it back into the water. And each year they race against time to complete their work before the sprigs of spring begin to brush away the Siberian winter and the lake’s frozen surface starts to crack.
What is it about the neutrino that makes scientists brave such conditions? Neutrinos—some of them dating back to right after the Big Bang—go through matter, traveling unscathed from the time they are created and carrying information in a way no other particle can. The universe is opaque to ultraenergetic photons, or gamma rays, which are absorbed by the matter and radiation that lie between their source and Earth. But neutrinos, produced by the same astrophysical processes that generate high-energy photons, barely interact with anything along the way. For instance, neutrinos stream out from the center of the sun as soon as they are produced, whereas a photon needs thousands of years to work its way out from the core to the sun’s brilliant surface.
Neutrinos therefore represent a unique window into an otherwise invisible universe, even offering clues about the missing mass called dark matter, whose presence can be inferred only by its gravitational influence on stars and galaxies. Theory suggests that over time the gravity wells created by Earth, the sun, and the Milky Way would have sucked in an enormous number of dark-matter particles. Wherever they gather in great concentrations, these particles should collide with one another, spewing out (among other things) neutrinos. It is as if a giant particle accelerator at our galaxy’s center were smashing dark-matter particles together, generating neutrinos and beaming them outward, some toward us...
Source: http://discovermagazine.com/2010/mar/15-ice-fishing-for-neutrinos-from-middle-of-galaxy
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