Rates and Potential Effects On Life On Earth
All the bursts astronomers have recorded so far have come from distant galaxies and have been harmless to Earth, but if one occurred within our galaxy and were aimed straight at us, the effects could be devastating. Currently orbiting satellites detect an average of about one gamma-ray burst per day. The closest known GRB so far was GRB 031203.
Measuring the exact rate is difficult, but for a galaxy of approximately the same size as the Milky Way, the expected rate (for long GRBs) is about one burst every 100,000 to 1,000,000 years . Only a small percentage of these would be beamed towards Earth. Estimates of rates of short GRBs are even more uncertain because of the unknown degree of collimation, but are probably comparable.
Gamma-ray bursts are thought to emerge mainly from the poles of a collapsing star. This creates two oppositely-shining beams of radiation shaped like narrow cones. Planets not lying in these cones would be comparatively safe; the chief worry is for those that do.
Depending on distance, a gamma flash and its ultraviolet radiation could damage even the most radiation resistant organism known, the bacterium Deinococcus radiodurans. These bacteria can endure 2,000 times more radiation than humans. Life surviving an initial onslaught would have to contend with a potentially lethal aftereffect, depletion of the atmosphere's protective ozone layer by the burst.
Read more about this topic: Gamma-ray Burst
Famous quotes containing the words rates, potential, effects, life and/or earth:
“[The] elderly and timid single gentleman in Paris ... never drove down the Champs Elysees without expecting an accident, and commonly witnessing one; or found himself in the neighborhood of an official without calculating the chances of a bomb. So long as the rates of progress held good, these bombs would double in force and number every ten years.”
—Henry Brooks Adams (1838–1918)
“The planet on which we live is poorly organized, many areas are overpopulated, others are reserved for a few, technology’s potential is only in part realized, and most people are starving.”
—Friedrich Dürrenmatt (1921–1990)
“The hippie is the scion of surplus value. The dropout can only claim sanctity in a society which offers something to be dropped out of—career, ambition, conspicuous consumption. The effects of hippie sanctimony can only be felt in the context of others who plunder his lifestyle for what they find good or profitable, a process known as rip-off by the hippie, who will not see how savagely he has pillaged intricate and demanding civilizations for his own parodic lifestyle.”
—Germaine Greer (b. 1939)
“They say the seeds of what we will do are in all of us, but it always seemed to me that in those who make jokes in life the seeds are covered with better soil and with a higher grade of manure.”
—Ernest Hemingway (1899–1961)
“made of earth and sea
His overcoat for ever,
And wears the turning globe.”
—A.E. (Alfred Edward)