Universe Today - Dr. Seth Shostak Answers Your = Questions About SETI

Dr. Seth Shostak Answers Your Questions About SETI

Thu, 27 Jan 2005 - You're really interested in = the=20 search for extraterrestrial intelligence. We put out the call, and = received dozens of questions for SETI researcher Seth Shostak. The = forum=20 team picked out their favorites, and passed them along to Dr. = Shostak.=20 Here are his answers. Thanks to everyone who participated: both = the=20 questioners and Dr. Shostak for taking the time to put together = his=20 answers. And a special thanks to Ola D. in the forum Community = Support=20 team for organizing this. See if your question was answered. =

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= Is there any other way a civilization = can be=20 detected other than by EM radiation (IR, UV, radiowave, microwave, = etc)=20 detection? What's the probability of finding an intelligent = lifeform in=20 our lifetime? - Alfchemist

Well, sure, there are = other=20 possibilities for finding cosmic company. You could look for = messages=20 being transmitted by particle beams (even neutrinos), and this has = been=20 suggested. But the problem is that these require harder-to-build=20 transmitters and receivers, and are also susceptible to absorption = by=20 interstellar gas. So they don't seem to offer much advantage. The = other=20 possibility is to find some evidence of "alien engineering" -- = maybe=20 sophisticated beings on other worlds have managed to rearrange the = stars=20 in their neighborhood, or build huge, starshine-collecting solar = panels=20 that we could somehow spot from afar. Some experiments have been = done to=20 locate such massive construction projects, but it's hard to know = how to=20 look or even what to look for.

I think it's likely that the = new=20 telescopes being built for SETI will trip across a signal by the = year=20 2025.

The SETI Project and SETI@home have processed = a bunch=20 of data. Other than the search for intelligent signals, have you = learned=20 anything new about the universe from all this information? -=20 corkft

In fact, not too much. This is rather = surprising,=20 because the history of astronomy suggests that whenever you build = a new=20 instrument, able to look at a previously unobserved bit of either = space or=20 the spectrum, you usually trip across some unexpected object or = other.=20 SETI projects have receivers with VERY narrow frequency channels. = But=20 there really doesn't seem to be any natural phenomena that lend = themselves=20 to being discovered with such equipment. In a sense this justifies = SETI's=20 assumption that any narrow-band signal would convincingly prove=20 intelligence!

What is the maximum distance at which = SETI=20 can detect signals which are not deliberately beamed at us, such = as normal=20 radio telecommunications traffic? And are there plans to increase = this=20 range? - Steve t

Our best SETI experiments to date = could=20 detect Earth-like "leakage" signals at no more than 1 light-year's = distance. So not too far. But keep in mind that (1) our = experiments do get=20 more sensitive with time, so this distance will increase, and (2) = we've=20 only had radio for a century. Aliens, who may have invented this=20 technology thousands or even millions of years ago, will = undoubtedly have=20 some transmitters and antenna systems capable of putting out = signals far=20 more powerful than what we manage with our erudite and always = entertaining=20 commercial television efforts!

To what degree does = our SETI=20 search make assumptions about the rate of information transfer? = What=20 transfer rates are we currently equipped to detect, and in what = modulation=20 modes? - wstevenbrown

We don't worry at all about=20 modulation, or schemes for encoding messages. That's something to = be=20 considered after you've found that their transmitter is on! At the = moment,=20 all SETI experiments simply look for narrow-band (typically 1 Hz = or=20 narrower) components to a signal... somewhat akin to the "carrier" = signal=20 for earthly transmissions, but not limited to those. We also look = for=20 slowly pulsing signals, too. But the point is that at least some = fraction=20 of the aliens' transmissions are assumed to put a lot of energy = into a=20 narrow bandwidth... making those signal components more easily=20 detectable.

Assuming Big Bang origins, how soon = would=20 sufficient astronomical metallicity have occurred to produce a = 0.8% or=20 better probability of the formation of CHON-based life supporting = planets?=20 Is there any way to evaluate how "typical" is the time required = for our=20 evolutionary path to technical competence? -=20 GOURDHEAD

Well this depends on where you are, as = the=20 metallicity varies across the Galaxy. I can't speak to "0.8% or = better=20 probability," as I don't know where this number comes from and = there's no=20 way to estimate it anyway. But put it this way: even in the oldest = globular cluster star systems in our Galaxy -- choked with stars = that were=20 born more than 10 billion years ago -- there's enough of the heavy = elements ("metals") to make earth-like worlds. I don't think there = was=20 much "dead time" between the formation of galaxies and the growth = of the=20 heavy element abundance to the point where life was=20 possible.

Do the recent conclusions that radio = signals from=20 advanced civilizations may be indistinguishable from the thermal = radiation=20 of their parent stars give you second thoughts on the likelihood = of=20 finding a positive signal? - Greg

Nope. It's true = that an=20 optimally encoded signal would look like (white) noise, and I'm = sure that=20 advanced societies will be very good at encoding. But there are = always=20 applications for which you need some narrow-band signals. For = example, you=20 might have a solar-system-wide GPS network for interplanetary = navigation.=20 Or big radar sets for tracking incoming, long-period comets. Not = to=20 mention a deliberate broadcast to galactic = brethren...!

How=20 will the new Allen Telescope Array (ATA) be incorporated into SETI = ? -=20 6EQUJ5

In the summer of 2005, there will be 32 = antennas=20 working at the ATA, and the SETI Institute will initiate a scan of = the=20 densest parts of the galactic plane. This is a straightforward = SETI=20 experiment that will scrutinize lots of stars, albeit stars that = are (on=20 average) thousands of light-years away. As the ATA gets built out = to 350=20 antennas, it will switch over to targeting individual, relatively = nearby=20 (less than 1,000 light-years) star systems. By 2025, it should be = able to=20 check out as many as a million such systems.

Should = an=20 alien signal be identified, what would be the protocol for = alerting the=20 people of Earth? Would the news be limited to a few,or would be = announced=20 for all to listen? - Duane

Well, there's no = secrecy in=20 SETI, and it's been our experience that whenever we pick up an=20 "interesting" signal, the media are on top of the story right = away. So you=20 can be sure you'll be reading about any signal long before the = SETI=20 researchers themselves have fully checked it out to convince = themselves=20 that it isn't interference or a software bug!

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