Ra­dio sig­nals un­likely to be ex­tra­galatic aliens say­ing ‘hi’

China Daily (Hong Kong) - - COMMENT -

ul­tra-brief re­peat­ing en­ergy bursts from deep space for only the sec­ond time in his­tory, with some sug­gest­ing they could be ev­i­dence of ad­vanced alien life. Two re­searchers shared their views with China Daily writer Zhang Zhoux­i­ang:

ASTRONOMERS HAVE DE­TECTED

Shi Hao, a re­searcher of space tech­nol­ogy

Even if there is the pos­si­bil­ity an ex­trater­res­trial civ­i­liza­tion sent the fast ra­dio bursts (FRB), the dis­tance to us is be­yond the reach of any tech­nol­ogy we can im­age.

A lit­tle com­par­i­son will ex­plain how far away the ori­gin of the sig­nal is from us. The dis­tance from the Earth to the sur­face of the sun is called an As­tro­nom­i­cal Unit (AU), and it takes light from the sun about eight min­utes to reach the Earth.

Voy­ager 1, hu­man kind’s long­est trav­el­ling de­vice that started in 1977, is now 145 AU from the Earth after 42 years of trav­el­ling, yet that’s only 0.23 of one light-year.

It would take more than 17,000 years for Voy­ager 1 to travel one light-year, and the dis­tance to the ori­gin of the FRB is 1.5 bil­lion times that.

And tak­ing a large per­spec­tive, some sci­en­tists be­lieve the ra­dius of the uni­verse is 13.7 bil­lion light-years; The FRB sig­nal this time has trav­elled about one ninth of that to reach us.

Yu Jun, a se­nior ed­i­tor on space at pop-sci­ence web­site guokr.com

The sig­nal comes from 1.5 bil­lion light-years away, and the long dis­tance means a high

at­ten­u­a­tion rate. In other words, the burst at the ori­gin of the sig­nal must be ex­tremely pow­er­ful so that we can re­ceive it. There is no way to cal­cu­late the ex­act amount of en­ergy needed this time, but if we com­pare it to the sun: It is like burst­ing out the en­ergy ra­di­ated by the sun for dozens to tens of thou­sands of years within 0.01 sec­ond.

Since the dis­cov­ery of the first FRB in 2007, hu­mans have only ob­served about 60 of them. As a re­sult of in­suf­fi­cient ob­ser­va­tion data, there is no con­firmed the­ory on what phe­nom­e­non pro­duced them.

How­ever, con­sid­er­ing the ex­tremely high amount of en­ergy they need, the num­ber of “sus­pects” is lim­ited, too. Ac­cord­ing to ex­ist­ing the­o­ries, there are at least sev­eral pos­si­ble causes of FRBs, such as the merg­ing of black holes or neu­tron stars, hy­per­flares of mag­ne­tars, es­pe­cially en­er­getic su­per­nova, or the col­lapse of the mag­ne­to­spheres of Kerr–New­man black holes.

Strictly speak­ing, the pos­si­bil­ity of a su­per ex­trater­res­trial civ­i­liza­tion send­ing such a sig­nal can­not be ex­cluded, but the pos­si­bil­ity is re­ally low con­sid­er­ing the high amount of en­ergy needed. Be­sides, there is no ev­i­dence lead­ing specif­i­cally to this pos­si­bil­ity. So there is no need to ex­ag­ger­ate it.

LI MIN / CHINA DAILY

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