I see that SETI@home is concerned about being able to continue its matching funds program from the University of California and is actively soliciting donations. It’s a terrific project, of course, and the numbers are staggering: with early expectations of raising 100,000 participants, SETI@home wound up with 5.4 million volunteers who donated 2.4 million years of processing time. A new data recorder at Arecibo and juiced up operating software make the program more potent than ever, and certainly worthy of support.

Also on the SETI front is the Planetary Society’s dedication of the first telescope exclusively devoted to optical SETI (OSETI). The Harvard-based observatory includes a 72-inch primary mirror that is larger than any U.S. optical telescope east of the Mississippi. Performing one trillion measurements per second and expanding existing optical searches by 100,000-fold, the new installation will search for laser signals that can far outshine the light of a nearby star even with today’s technology.

Here’s more on just how visible such signals might be (via the Princeton Optical SETI project:

Light coming from a star alone filtered to one part in 10,000 amounts to 4 Joules of energy every nanosecond. Therefore, a laser signal coming from near the star must exceed 4 Joules within a nanosecond in order for it to outshine the star. Modern lasers designed for nuclear fusion can exceed this power requirement by some 300,000 times… Even if the exact frequency of transmission is unknown, such a laser would still outshine the sender’s star by 30 times during the nanosecond pulse without any filtering.

All this is exciting stuff, even for those of us whose deep suspicion is that while life is abundant — perhaps ubiquitous — in the universe, technological civilizations are vanishingly rare. For let’s face it, everything we can surmise about extraterrestrial civilizations is based on our own assumptions as a species. We have no idea whether an advanced civilization would attempt to contact other less developed cultures, or for what reason, but we will never be sure that a bright beacon isn’t pumping terabytes of galactic know-how to us every second unless we look.

Optical SETI is particularly intriguing because a laser signal’s high frequencies can carry vast amounts of information. But the history of the concept was low-bandwidth indeed. The first optical SETI proposal I am aware of came from the German mathematician Karl Gauss (1777–1855), who proposed using a system of light and mirrors to send a signal to the Moon (not Mars, as I misstated in my book). Gauss seems to have influenced Joseph von Littrow (1781–1840), director of the Vienna Observatory, who attributed his suggestion of filling ditches with kerosene and lighting them as a celestial beacon to a ‘German geometer’ (I owe this information to Brett Holman at the University of Melbourne, in what turned out to be a very helpful e-mail).

In more recent times, the classic 1959 paper by Giuseppe Cocconi and Philip Morrison discussed using masers for communication, operating with microwaves rather than visible light. It was Charles Townes’ ongoing work on the laser that suggested to him that the optical spectrum be used for the SETI hunt. The variety of OSETI attempts that have followed rely on the key advantages of laser communications, not only the high bandwidth but the fact that interference from natural sources is more of a problem with microwaves than visible frequencies. And as far as we know, nanosecond pulses of light do not occur in nature, making their creation a probable technological event.

The Morrison and Cocconi paper is “Searching for Interstellar Communications” (Nature 184, no. 4690 (September 19, 1959): 844–46. For those of us who collect key scientific papers, this one is still a thing of beauty. Charles Townes’ paper on using visible light was written with R.N. Schwartz; it’s “Interstellar and Interplanetary Communication by Optical Masers,” Nature, 190, no. 4772 (April 15, 1961): 205–208.