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:
“Good government cannot be found on the bargain-counter. We have seen samples of bargain-counter government in the past when low tax rates were secured by increasing the bonded debt for current expenses or refusing to keep our institutions up to the standard in repairs, extensions, equipment, and accommodations. I refuse, and the Republican Party refuses, to endorse that method of sham and shoddy economy.”
—Calvin Coolidge (1872–1933)
“The real community of man ... is the community of those who seek the truth, of the potential knowers.”
—Allan Bloom (1930–1992)
“Virtues are not emotions. Emotions are movements of appetite, virtues dispositions of appetite towards movement. Moreover emotions can be good or bad, reasonable or unreasonable; whereas virtues dispose us only to good. Emotions arise in the appetite and are brought into conformity with reason; virtues are effects of reason achieving themselves in reasonable movements of the appetites. Balanced emotions are virtue’s effect, not its substance.”
—Thomas Aquinas (c. 1225–1274)
“I feel a sincere wish indeed to see our government brought back to it’s republican principles, to see that kind of government firmly fixed, to which my whole life has been devoted. I hope we shall now see it so established, as that when I retire, it may be under full security that we are to continue free and happy.”
—Thomas Jefferson (1743–1826)
“This whole earth which we inhabit is but a point in space.”
—Henry David Thoreau (1817–1862)