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Beyond Contact: a Guide to SETI
Some readers may recall what Stephen Hawking said about his book, A Brief History of Time:
"Someone told me that each equation I included in the book would halve the sales. I therefore resolved not to have any equations at all. In the end, however, I did put in one famous equation, E=mc2. I hope that this will not scare off half my potential readers."
Hawking was facing the same challenge as Brian McConnell faces in this book. Both are trying to turn advanced knowledge of their field of endeavour (which requires heavy math, heavy astronomy, heavy physics, heavy programming, and so forth) into a work which can be comprehended by lesser beings. McConnell has taken a different path than Hawking - his book has plenty of advanced equations, diagrams, and concepts. McConnell does a reasonable (and often very good) job at trying to bring readers up to speed when he thinks he's going to go over their heads, but it is still not a book for the faint of heart or mathematically-challenged. There are enough equations in the book to bring its readership down to (.5)n -- oh, roughly zero, give or take.
In any case, it's a good book, but technical. You were warned.
The first couple of chapters cover the history of searching for extraterrestrial life, "are we alone?", the nature of intelligence, and similar areas. Drake's Equation is the famous set of fudge-factors that would tell us whether we were likely to find other life forms, if only we knew what the values of the variables were:
N = R * fs * fp * ne * fl * fi * fc * L
Fill in values for all of those and you'll be famous forever. But what it means, as our knowledge stands now, is that we have no clue at all whether there is likely to be life out there or not. Comforting, isn't it?
The next several chapters cover the technical aspects of communicating over interstellar distances. The electrical engineers in the audience will have a leg up here; everyone else has the opportunity to learn the basics of signal processing and the peculiarities specific to communication across galaxies. Pretty thorough and informative, without being overwhelming.
Finally, the latter half of the book covers the 64,000 lightyear question: what to say? How to communicate with an intelligence where you can't assume even the most basic things in common? Yes, yes, you've probably heard of the idea of starting with the periodic table or basic mathematics and working up. But that's sort of like a dot-com business plan:
- Establish Contact
- Send Periodic Chart
- ....
- Communicate!
McConnell fills in the "...." part, and it's obvious that a great amount of thought has been put into it. Pretty quickly McConnell is describing how to send entire self-executing programs (see Vernor Vinge's A Fire Upon the Deep).
This book is a bit of an oddity. If we're just talking about entertainment reading, it falls short - too technical. If I was grading it as a scientific work, again it would fall short - not technical enough. :) But as far as I know, this is the only work which tries to explain what SETI really is in terms that educated, reasonably bright laymen can understand, and as such, it does a fine job.
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crunching? Missile ranges? Nuclear calculation?
A few sys admins at The Swedish Radio
where fired some time ago because they had seti@home running on some machines.
The management said that didn't know what seti@home acutely did.....and of course that it was a security threat....
Just my 0.02
Probably the single greatest challenge facing SETI-like projects is not the daunting task of acquiring and analysing the vaast ammounts of data, but the criticisms levelled at it by many politicians and scientists.
To date, most books on bioastronomy in general and seti in particular have been rather daunting and require a good grasp of not just physics and biology, but even philosophical issues such as anthropomorphsim and technical matters such as DSP; a popular book on the subject, such as this one, could go a long way to raising public knowledge of the subject past the "looking through telescopes for aliens" level.
2. Let's be generous and say there is a one in a thousand shot of a star having planet capable of supporting life (right distance from the star so that it's between 250-350 K at the surface, enough atmospheric pressuse so that water can exist as a liquid, protected by massive outer planets against constant meteor bombardment, far above-average abundance of Oxygen, Sulphur, Nitrogen, and Phosphorous, etc, etc.) That puts the number of *potential* life supporting planets in the galaxy at 400 million.
3. Let's be very, very generous and estimate that life actually *does* form on one in every thousand potential life-supporting planets. Most molecular biologists will tell you that even the most basic life is so complex that the odds of it forming from inanimate matter are staggeringly small, and we should count ourselves lucky that it managed to happen once in the entire history of the Universe. But we'll be liberal and say one in a thousand. That puts the number of planets in the galaxy with any sort of life at 400 thousand.
4. There is no reason to assume that just because life exists, it will become intelligent and start using EM communications that we can receive. I don't know how you could put odds on something like that. Let's just go nuts and say that ALL planets with life eventually give rise to intelligent life. So 400 thousand planets out there in our own galaxy will have intelligent life at some point in their history.
5. Now, here's the depressing part. Our planet has been around for 4 billion years. We've been using EM waves to communicate for roughly 100 years. So, in the whole history of our planet, civilization has only been detectable for 0.0000025 *percent* of the time. Let's say your typical advanced civilization (using radio waves) can last 1000 years before nuking itself into oblivion, and your typical planet exists for 5 billion years. That would mean that out of the 400 thousand planets with life, chances are only 0.00002 percent of them, or 0.08 total, are broadcasting at the same time we are receiving.
Thus, even with the most wildly optimistic estimates, there is only an 8% chance that there is even one civilization out there that we can listen to, in the entire galaxy. Forget about there being one within 100, or even 1000 light years.
Of course, you could simply throw those numbers out, and believe in a God who likes to put intelligent life on planets all over the place. But that wouldn't be very scientific.
dinner: it's what's for beer
I confess to not having read the book, but I've never seen any decimal used in proposed SETI communications (nor, I suspect, have you).
Most "number" transmissions I have seen have been unary (in other words, three pulses equals three). I know binary was used on the plaque in (ummm) Voyager, was it? but that wasn't a serious attempt to communicate with other species.
Mathematicians aren't stupid, and I promise you that they know perfectly well that aliens aren't likely to use base 10.
ZFS: because love is never having to say fsck
If you happen to be talking with someone via radio who has never seen a clock, try to explain to him what "clockwise" works. Maybe you would turn to the rising and falling of the sun and moon as a reference point, but if this person has never been outside or lives in a different solar system? Where is the common reference point?
How we know is more important than what we know.
While I tend to agree with this -- I believe humans are likely alone in the galaxy -- it does rely on some very specious assumptions.
Other species may have no interest in space travel. They may well be shocked that at this point in our technological development, we *still* haven't developed the Microstatic Dweebelizer, while we would be shocked at how primitive their transportation technology is.
Other species may have no interest in colonization. Wanting to spread your seed among the stars may be a purely human affair.
Other species may not be as suitable for space travel as we are (not that we're particular suitable). If they are less able to survive a wide range of conditions, for instance if slight (to us) temperature variations are fatal to them, space travel might not appeal to them very much. Further, if they could only live within a narrow range of conditions then other planets wouldn't be particularly appealing. Maybe humans are particularly able to adapt to the physical and psychological rigors of space travel.
Again, while I do tend to agree with Fermi and assume that we are the only intelligent life in the galaxy, there are a lot of unknowns about the way an extraterrestrial species would behave. We're *probably* an 'average' species, in the sense of intelligence, capabilities, and so forth, simply because being in the middle is a lot more likely than being one of the extremes, but for all we know we're exceptional in every way (for better or worse). Maybe we're the only species that wants to conquer space, or maybe we're the only species that has gotten this far and not even tried yet.
ZFS: because love is never having to say fsck
This is true, but that doesn't make our logic arbitrary. In fact our logic is based on a type of "natural logic", according to which the whole universe is organised. That the why our mathematics (which is derived from "our" logic) is so damn good at describing the universe. The reason our logic coincides (or at least closely approximates) this universal logic is just evolution: those of our potential ancestors who had a better grasp of logic had a survival advantage. So there was (still is, see the Darwin awards) a selection pressure in favour of those who understood this natural logic.
"...Look on my works, ye mighty, and despair!"