How we’ll talk to alien life

The SETI In­sti­tute's Seth Shostak re­veals all

All About Space - - Contents -

The Search for Ex­trater­res­trial Intelligence (SETI) is one of the most ex­cit­ing

top­ics in all of as­tron­omy, but what are the dif­fer­ent ways we might re­ceive mes­sages from ET – and what lan­guage could we use to strike up a

con­ver­sa­tion? We caught up with lead­ing SETI re­searcher Seth Shostak

Can you tell us a lit­tle about your back­ground and how you first got in­volved in the SETI field?

I’m the se­nior astronomer and also an In­sti­tute fel­low here at the SETI In­sti­tute. I’ve been here for about 24 years, so it’s the long­est job I’ve ever had. I got here kind of ac­ci­den­tally – I stud­ied ra­dio as­tron­omy and spent quite a bit of time study­ing gal­ax­ies with ra­dio tele­scopes, in­clud­ing 13 years in Hol­land. I wasn’t do­ing SETI at the time, but I was cer­tainly in­ter­ested in it, as it’s the same tech­nol­ogy that we were us­ing to study gal­ax­ies; it’s just ra­dio as­tron­omy but with a slightly dif­fer­ent kind of re­ceiver and ob­vi­ously a dif­fer­ent goal.

Af­ter I moved back to the US in 1988 to work with one of my broth­ers on a soft­ware startup that un­for­tu­nately failed, I was with­out a job for about a year. Thank­fully, some peo­ple here at the SETI In­sti­tute, which hap­pens to be lo­cated in the same town where I was liv­ing [Moun­tain View, Cal­i­for­nia], heard that I was here, and they sim­ply rang me up and asked if I wanted a job. That was at the time when there was some NASA fund­ing for SETI, so there was more money around!

When most peo­ple think of SETI they think of big ra­dio dishes point­ing to­wards the sky, and as you say, your own back­ground is in ra­dio as­tron­omy. Is that the only re­al­is­tic way that we might re­ceive sig­nals from ex­trater­res­tri­als?

Ra­dio’s cer­tainly not the only game in town, but I think what’s ac­tu­ally be­ing done in SETI is al­ways rather re­stricted by money and re­sources. You have to make some­thing of a bet and de­cide what it is you’re go­ing to do given what­ever money you have. So far that’s largely been ra­dio SETI, but there’s no doubt there are other ways to look for things.

For in­stance, both the Univer­sity of Cal­i­for­nia at Berke­ley and we here at the SETI In­sti­tute are build­ing equip­ment that will look for laser flashes. There’s been some work in that field for 20 or 30 years, but not much has been done – no one’s sys­tem­at­i­cally searched the sky for flash­ing laser bea­cons. For ex­am­ple, if tonight some spot­light went off in the Orion con­stel­la­tion for a mi­crosec­ond – a green flash or some­thing like that – it prob­a­bly wouldn’t be seen. Those sorts of sig­nals could be hap­pen­ing all over the place all the time, but we wouldn’t know. So it’s a ripe area for in­ves­ti­ga­tion and it’s time we started look­ing.

But I guess 90 per cent of the effort is still go­ing to ra­dio SETI. The ad­van­tage of ra­dio, of course, is that you can broad­cast it. If you have a big laser then you have to de­cide ex­actly where you’re go­ing to point it, but with ra­dio, you can send it across a broader swath of the sky. Of course if aliens were be­ing thrifty, they could also tar­get the ra­dio trans­mis­sions, which is to say aim them in a tighter beam. But per­haps if lasers had been in­vented be­fore ra­dio, then maybe 90 per cent of to­day’s effort would be ded­i­cated to op­ti­cal SETI – there’s def­i­nitely a his­tor­i­cal com­po­nent there.

There seems to have been a surge of in­ter­est in the pos­si­bil­ity of de­tect­ing artificial struc­tures built by alien civil­i­sa­tions. What do you think are the pos­si­bil­i­ties for that kind of dis­cov­ery, and how would it com­pare to de­lib­er­ate sig­nals?

Arte­facts have ad­van­tages and dis­ad­van­tages – the ad­van­tage is that if you build some­thing big, you don’t have to aim it at any­body; you don’t have to de­lib­er­ately get the at­ten­tion of some­body else, they might just trip across it. We might be able to find some­thing even though a dis­tant civil­i­sa­tion had no in­ten­tion of get­ting dis­cov­ered. Arte­facts are also long-lasting – if you’re send­ing a sig­nal you have to hope that some­one’s look­ing in the right di­rec­tion at the right time.

The dis­ad­van­tage is that an arte­fact prob­a­bly isn’t go­ing to be very use­ful for sig­nalling. Of course if you’re talk­ing about aliens with the tech­nol­ogy to build a Dyson sphere, then they’d have the abil­ity to send sig­nals, but that de­pends on their in­ten­tions.

As far as send­ing ac­tual bits of in­for­ma­tion, then you’d prob­a­bly rely on op­ti­cal or ra­dio sig­nals. Op­ti­cal sig­nals such as laser beams could send more bits per sec­ond than ra­dio, but they have their own prob­lems – they might be ab­sorbed or scat­tered by the in­ter­stel­lar medium, de­pend­ing on what the wave­length is.

Are there any other hy­po­thet­i­cal ways of send­ing ac­tual mes­sages that don’t rely on light or ra­dio?

Some peo­ple have sug­gested neu­tri­nos as a way of com­mu­ni­cat­ing. I’ve never been very keen on the idea – they’re very ex­pen­sive to pro­duce in terms of en­ergy, and so far as we know they’re very hard to de­tect. Hav­ing said that, maybe they’re only hard to de­tect for us, and the big ad­van­tage is that neu­tri­nos go ev­ery­where – they pass straight through the Earth.

In terms of how much data you could send, there was a pa­per a good few years ago that pointed out, if your goal is to send the max­i­mum number of bits per sec­ond, then the best way of do­ing that is to load up a bunch of thumb drives, put them in a rocket and send them some­where. It would ob­vi­ously take a long time and you have to know where the rocket’s go­ing, but you could ar­gue that some of that also ap­plies to other SETI meth­ods…

Peo­ple write me all the time talk­ing about grav­i­ta­tional waves, but I’m not sure. Grav­i­ta­tional waves are very hard to pro­duce and hard to de­tect and I can’t see any real ad­van­tage over neu­tri­nos. You can’t en­code a lot of bits of in­for­ma­tion by col­lid­ing a pair of neu­tron stars to­gether!

When we’re talk­ing about send­ing mes­sages, we nat­u­rally fall into ter­mi­nol­ogy that we use when talk­ing about sig­nals on Earth – do those terms re­ally make sense when talk­ing about com­mu­ni­cat­ing with alien civil­i­sa­tions?

Well some peo­ple would say that talk­ing about bi­nary and bits as an en­cod­ing scheme is maybe too an­thro­pocen­tric, but I don’t think so. With

The Allen Tele­scope Ar­ray (ATA) con­ducts a si­mul­ta­ne­ous search for ex­trater­res­trial intelligence (SETI)

The SETI In­sti­tute and the Univer­sity of Cal­i­for­nia at Berke­ley are de­vel­op­ing Op­ti­cal SETI – a search for laser pulses from dis­tant aliens

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