Astronomy in pop culture has usually focused on the biggest and the brightest the universe has to offer. Supernovae, black holes, massive asteroids hurtling toward earth - these are the subjects people find most exciting. And in an attempt to better understand this big universe we live in, three KU professors in the Department of Physics and Astronomy have turned their attention to something small but mighty: cosmic rays.
Professors Adrian Melott, Mikhail Medvedev and David Besson study subatomic cosmic particles, or cosmic rays. For Melott and Medvedev’s research, the important cosmic rays are high-energy particles produced by shock waves. For Besson, they are rare, ultra high-energy neutrinos that can travel through space and smash into Earth with the force of a large hailstone. Melott and Medvedev conduct their research from Lawrence. Besson conducts his from a research station at the South Pole. Though their methods of research are different, both cosmic ray studies have shed new light on some of science’s interesting mysteries.
Melott and Medvedev’s work with cosmic rays began a couple of years ago. They advanced a theory that offered cosmic radiation as an explanation for Earth’s previously unexplained cycle of plant and animal mass extinctions.
The other important finding for Melott and Medvedev’s theory is the fact that the sun not only revolves around the Milky Way Galaxy, but bobs up and down through the plane of the galaxy, dragging the Earth and everything else in our solar system along with it. The motion is much like a roller coaster riding along the valleys and peaks of its track. The time it takes for the sun to travel from a valley to a peak, it just so happens, is about 62 million years.
Melott and Medvedev’s theory synthesized the 62-million-year biodiversity cycle and
the motion of the sun through the galaxy. They proposed that, because of a cosmic-ray-producing shock wave generated by the motion of the Milky Way through space, the earth is bombarded with a higher-than-normal number of cosmic rays when it is at a peak.
“That means more radiation is hitting the ground,” Melott said. “It could lead to increased mutations, cancer, or possibly extinctions.”
The theory is the most plausible explanation for the Earth’s cycle of mass extinctions, Medvedev said. It also provides a harrowing glimpse into the potential future of the planet’s biodiversity when Earth reaches a peak again in 12 million years.
The increase in cosmic radiation could deplete the ozone layer and allow more ultra-violet radiation to reach the ground. It could increase cloud formation which could cool the global climate. It could also weaken the Earth’s organisms just enough to make an asteroid collision or volcanic eruption far more destructive than they otherwise would be.
“Suppose you have the flu and then you get shot,” Melott said. “If something big happens while organisms are already under stress, it could hurt a lot more.”
“Some species could get wiped out completely like dinosaurs did,” Medvedev said. “Species that have been on earth less than 45 million years are very vulnerable to cosmic ray fluctuations. Humans are only a million and a half years old. We may be wiped out in 10 million years. We don’t know.”
Alex Krejci, Olathe junior, is working with Melott to measure the amount of energy cosmic rays deposit in Earth’s atmosphere. Krejci, a physics and geophysics double-major, started his research in the spring. Brian Thomas of Washburn University will use his results to indicate the potential damage that increased cosmic radiation could inflict on the ozone layer.“There’s not anything humans can do to stop it,” Krejci said. “That’s what’s so interesting.”
The particles Melott and Medvedev study bombard the planet at a constant rate. But while they have found no shortage of cosmic rays to study, Besson has spent 10 years searching for just one ultra-rare, ultra-high-energy particle called a neutrino. The type of neutrino Besson is looking for is a subatomic particle whose energy is 100 million times greater than what researchers have ever been able to recreate in a lab. The particles are so high-energy they can pass unfazed through practically any solid medium, including planets.
Besson’s search for a neutrino is based at Antarctica’s Radio Ice Cherenkov Experiment, or RICE, where the almost-2-mile-thick ice cap is dense enough to give researchers the best chance of detecting a passing particle. RICE sensors monitor a 1.25 mile radius of the ice cap in search of the waves that would be given off by a neutrino’s collision with the ice. So far, they haven’t found detected much.
Besson said that, with the current size of the RICE experiment, a neutrino particle should be observed once every ten years. On Dec. 8, he will take his tenth research trip to Antarctica. In other words, for Besson, RICE is due.
Scientists think that super-high-energy particles such as neutrinos come from supermassive black holes at the center of some galaxies. These galaxies are called “active galactic nuclei”, or AGNs.
“The gravitational and magnetic field of the black holes causes particles to knock around,” Besson said. “There’s a huge energy transfer and an AGN pumps out a really high-energy particle every once in a while.”
Because of its ultra-high energy, a neutrino particle detected by RICE would travel virtually unimpeded from its AGN source to the RICE sensors. Besson said that would allow astronomers to follow a direct line from where the neutrino hits earth all the way back to the black hole it came from. It would be like looking through a new kind of telescope.
“We would be able to learn about black holes and measure how dense the universe is,” Besson said. “We would be able to view the universe in a new and different way.”
The scientific community will continue to test Melott and Medvedev's theory. Results from a telescope observing background radiation around the plane of the Milky Way will either strengthen their case or deal it a blow. Besson will spend two weeks in Antarctica this month continuing the search for an ever-elusive neutrino.
Comments (1)
Stories like this is why I am moving to Mars the first chance I get.
Posted by Sexton Hardcastle | December 5, 2007 10:30 PM
Posted on December 5, 2007 22:30