Celestial distances are so enormous that nobody can be faulted for regarding astronomy as the study of things far, far away and long, long ago. Until the era of Galileo and Newton, people generally regarded the heavens and Earth as two separate entities. The recognition that we are intertwined with the rest of the universe is quite modern—and scientists are still learning how tightly life down here is linked with events going on up there.
WHAT’S UP IN THE NOVEMBER SKY?
The main event is a tight pairing of the two brightest planets, Jupiter and Venus. At their closest, they are just over half a degree apart.
Jupiter and Venus draw together in the eastern sky, prominent at dawn.
The thin, waning crescent moon passes close by Jupiter and Venus.
A new moon means dark skies—a good time to look for the Milky Way’s center in the southwest at nightfall.
The Andromeda galaxy lies high up at 9 p.m., visible as a faint, fuzzy oval of light.
Mars returns to view, emerging from the sun’s glare in the predawn east.
Saturn climbs back into the evening sky, rising at 8 p.m. by November’s end.
This theme of connectedness got a dramatic boost in 1980, when physicist Luis Alvarez and his geologist son, Walter, convincingly argued that the sudden extinction of the dinosaurs some 65 million years ago was caused by the impact of an asteroid. Just a few years later, exobiologists began taking seriously what had previously been a fringe theory—that amino acids, the chemical precursors of biological proteins, probably hitched rides here aboard the comets that rained down on Earth prior to 3.9 billion years ago. Not only are amino acids common in comets, researchers found, but simple amino acids, such as glycine, exist even in interstellar clouds. These findings undermined the millennia-old assumption that life on Earth arose totally independently from the rest of the cosmos.
Our appreciation of the importance of these connections keeps growing. Earlier this year, geochemist Luann Becker of the University of California at Santa Barbara and her colleagues identified an enormous crater off the coast of Australia. This scar may be the site of an asteroid strike that killed off more than 90 percent of all species on Earth 250 million years ago.
Impacts are not a horror of the past. Sooner or later, another asteroid will collide with Earth; a 100-foot-wide rock missed by just 27,000 miles last March. Over the past couple of years, two homes in the United States have been hit by small meteors. On March 26, 2003, 13-year-old Robert Garza screamed in terror as a five-pound space rock rolled to a stop next to his bed in a Chicago suburb. At an even finer level, specks of meteoritic dust fall into the atmosphere constantly, adding at least 40,000 tons of mass each year. (Some of the dust on your furniture comes from outer space.)
On the subatomic scale, Earth experiences additional extraterrestrial bombardment. Cosmic rays—energetic particles generated by distant supernovas and other violent deep-space processes—strike and break apart atoms of air 35 miles overhead. The detritus from these interactions include muons, unstable particles that are related to electrons but are roughly 200 times heavier. Unfortunately, muons have the right mass and electrical charge to damage organic molecules in our bodies, including DNA—and they are responsible for some of the “spontaneous” cancers that have always plagued the human race. Roughly 240 muons shoot through our bodies every second.
The sun also contributes to the subatomic barrage. Some of the consequences are familiar: Ultraviolet rays can cause sunburn and skin cancer. Solar flares unleash storms of charged particles that get tangled in Earth’s magnetic field and, in extreme cases, disable satellites and overload power lines. Less obvious is the torrent of neutrinos gushing from the sun’s core. Thankfully, these ghostly particles rarely interact with atoms—in fact, it would take a lead wall half a light-year thick to stop the average neutrino. At night, neutrinos enter our feet and exit our heads, having first zipped through the entire Earth in 1/25 of a second. By day, the same number enter our heads and exit our feet before heading through the planet and back out into space.
Stranger still is the neutralino, a hypothetical massive cousin of the neutrino. According to a popular physics model, these particles are so common that combined they greatly outweigh all the stars in the universe. If they truly are that abundant, some 100,000 neutralinos must pass through each pinkie-nail-size portion of our bodies every second. These particles meddle with atoms so little that they are both harmless to us and exceedingly difficult to detect. But collectively they would provide the crucial gravitational pull that keeps our galaxy from flying apart.
|The number of dark spots on the sun seems to affect climate on Earth. Normally, the number of sunspots rises and falls during an 11-year cycle, but the process mysteriously stopped from 1645 to 1715—a period of bitter cold in Europe. That could happen again, but no one can predict when.|
Long ago and far away? Think again. The universe is right here, right now.