Too early to as­sume aliens don’t ex­ist

The Weekend Australian - - WORLD -

If aliens are so likely, why have we never seen any? That is the Fermi Para­dox — named af­ter En­rico Fermi, a physi­cist who posed the ques­tion in 1950.

Fermi’s ar­gu­ment ran as fol­lows. The laws of na­ture sup­ported the emer­gence of in­tel­li­gent life on Earth. Those laws are the same through­out the uni­verse. The uni­verse con­tains zil­lions of stars and plan­ets. So even if life is un­likely to arise on any par­tic­u­lar as­tro­nom­i­cal body, the sheer abun­dance of cre­ation sug­gests the night sky should be full of alien civil­i­sa­tions.

Fermi won­dered why aliens had not vis­ited Earth. To­day, the para­dox is usu­ally cast in light of an in­abil­ity of ra­dio-tele­scope searches to de­tect the equiv­a­lent of ra­dio waves that leak from Earth into the cos­mos, and have done for the past cen­tury.

Think­ing up an­swers to this ap­par­ent con­tra­dic­tion has be­come some­thing of a sci­en­tific par­lour game. Per­haps life is re­ally very un­likely. Per­haps the pri­ests are right: hu­man be­ings were put on Earth by some cre­ator God for His own in­scrutable pur­poses, and the rest of the uni­verse is merely back­ground scenery. Per­haps there are plenty of aliens, but they have de­cided that dis­cre­tion is a safer bet than gre­gar­i­ous­ness.

Or per­haps ga­lac­tic so­ci­ety avoids com­mu­ni­cat­ing with Earth specif­i­cally. One chill­ing idea is that tech­no­log­i­cal civil­i­sa­tions de­stroy them­selves be­fore they can make their pres­ence known. They might blow them­selves up af­ter in­vent­ing nu­clear weapons, or cook them­selves to death by over-burn­ing fos­sil fu­els.

In a pa­per pub­lished last month on arXiv, an on­line repos­i­tory, a trio of astronomers at Penn­syl­va­nia State Univer­sity an­a­lysed the his­tory of alien­hunt­ing and come to a dif­fer­ent con­clu­sion. In ef­fect, they re­ject one of the para­dox’s main pil­lars. Astronomers have seen no sign of aliens, ar­gue Ja­son Wright and his col­leagues, be­cause they have not been look­ing hard enough.

Wright’s ar­gu­ment echoes that made by an­other as­tronomer, Jill Tarter, in 2010. Tarter reck­oned that decades of search­ing had amounted to the equiv­a­lent of dip­ping a drink­ing glass into Earth’s oceans at ran­dom to see whether it con­tained a fish. Wright and his col­leagues built on Tarter’s work to come up with a model that tries to es­ti­mate the amount of search­ing that alien­hunters have man­aged so far.

They con­sid­ered nine vari­ables, in­clud­ing how dis­tant any pu­ta­tive aliens were likely to be, the sen­si­tiv­ity of tele­scopes, how big a por­tion of the elec­tro­mag­netic spec­trum they were able to scan and the time spent do­ing so.

Once the num­bers had been crunched, the re­searchers reck­oned hu­man­ity had done slightly bet­ter than Tarter sug­gested. Rather than dip­ping a drink­ing glass into the ocean, they say, astronomers have dunked a bath­tub. The up­shot is that it is too early to as­sume no aliens ex­ist. Fermi’s ques­tion is, for now at least, not a true para­dox.

Newspapers in English

Newspapers from Australia

© PressReader. All rights reserved.