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  • Listen.

  • Do you hear anything? Me neither.

  • It's pretty deserted out here.

  • For the past 50 years, astronomers have been using radio dishes

  • to eavesdrop on the cosmos.

  • They are listening for signals from alien civilizations.

  • But so far, it's been pretty silent.

  • That begs the question: Are we alone in a cosmic desert?

  • In 1961, astronomer Frank Drake,

  • came up with a way to approach the question mathematically.

  • He created an equation that estimates how many alien cultures inhabit our galaxy.

  • The equation depends on a bunch of factors.

  • First, the number of new stars born each year,

  • times the fraction of stars with planets,

  • times the number of planets that could potentially support life

  • in each planetary system,

  • times the fraction of life-supporting planets where life actually takes hold,

  • times the percentage of planets with life forms that develop intelligence,

  • times the fraction of intelligent species that develop the ability

  • to broadcast signals across interstellar space,

  • times how long those civilizations are likely to survive,

  • or at least how long they'll broadcast their signals into space.

  • Multiply all those together and you get "N",

  • the number of detectable civilizations in the galaxy.

  • It's a long equation and astronomers only have estimates for some of the factors;

  • the ones we can observe from Earth,

  • like how many stars are born each year.

  • On the other hand, we don't know much about how life develops on other worlds.

  • Many experts think that alien microbes and slime molds may be common.

  • But little green men? Not so much.

  • Perhaps the biggest question is the value of "L" in the Drake equation.

  • How long will a given civilization last before dying out or self-destructing?

  • "L" could be hundreds of years

  • or it could be billions.

  • Humankind has only used technology; like radio broadcasts for a century or so

  • and in that short time, we've already had a few close shaves.

  • So the lifetime of a given civilization could be rather short.

  • If that's the case, we may be alone in the cosmic desert after all.

  • For Scientific American's Instant Egghead, I'm John Matson.

Listen.

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我們在宇宙中是孤獨的嗎?- 即時蛋頭#27 (Are We Alone in the Universe? - Instant Egghead #27)

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    rcnwxiqtnqj 發佈於 2021 年 01 月 14 日
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