Waiting for Contact: The Search for Extraterrestrial Intelligence
By Lawrence Squeri, University Press of Florida, 248 pages, $27
Welcome to the Universe: An Astrophysical Tour
By by Neil deGrasse Tyson, Princeton University Press, 472 pages, $40
All These Worlds Are Yours: The Scientific Search for Alien Life
By Jon Willis, Yale University Press, 232 pages, $30
Placing Outer Space: An Earthly Ethnography of Other Worlds
By Lisa Messeri, Duke University Press Books, 248 pages, $24
In October of 1995 two Swiss astronomers announced a major discovery: they had detected, about 50 light-years from Earth, a planet orbiting a Sun-like star. Scientists had long imagined there were such planets outside our solar system, but never before had one been confirmed. This extrasolar planet, or “exoplanet”, appeared to be a Jupiter-like ball of gas and liquid with a blistering atmospheric temperature of 927°C. In the two decades since, astronomers have detected more than 3,000 exoplanets. No one has yet found a replica of Earth, although Proxima b, an Earth-size planet in a temperate orbit a mere 4.2 light-years away, whose discovery was announced in August, sounds as if it could be a decent place to live.
The discovery of exoplanets has been a source of special excitement to the scientists of the so-called SETI movement — the search for extraterrestrial intelligence. As the historian Lawrence Squeri notes in his engaging chronicle “Waiting for Contact: The Search for Extraterrestrial Intelligence”, the movement, which began in earnest in the 1960s, would have been “pointless” had there not turned out to be planets beyond our solar system.
Where else would alien civilisations reside? Just as significant to SETI enthusiasts has been the very high percentage of stars that, when scrutinised, have revealed themselves to host a planet. The percentage is high enough that we can basically assume each of the 400 billion stars in our galaxy has a planetary companion. That’s a lot of potential places for alien life to arise, evolve and — ideally using electromagnetic signals at a frequency we’re monitoring — drop us a line.
SETI’s principal methodology was first outlined by two physicists in the journal “Nature” in 1959. They proposed that the radio telescope, a new technology used to “see” objects in space thanks to the radio waves they emit, could also be used to send and receive interstellar messages with aliens at the speed of light. The next year, at an observatory in West Virginia, an astronomer named Frank Drake conducted the first such search for alien broadcasts, aiming a radio telescope at two stars about 10.5 and 12 light-years away.
It was a crapshoot, and it was unsuccessful: aliens had not, in fact, been sending us messages from those stars — at least not at the frequency Drake guessed aliens would use. The next step for the movement, as Squeri writes, was to demonstrate this was “a cutting-edge experiment rather than a lost weekend for reputable scientists who had read too much science fiction”.
The second American SETI search didn’t take place until 1971, more than a decade later. (Securing time with a radio telescope is a competitive affair.) In the interim, and indeed throughout the movement’s history, SETI scientists spent much of their time justifying and promoting their project. In this capacity, Squeri argues, SETI amounted to more than just a scientific enterprise; it was a kind of “offbeat political movement”, a Utopian ideology and perhaps surrogate religion — with aliens serving as our more enlightened counterparts.
SETI arose amid widespread fears that nuclear weapons and population growth had made the human race a threat to itself. Many of the movement’s founders were political progressives who believed that any alien civilisation advanced enough to contact us would have survived as long as it did because it had solved such problems, presumably by mastering a system of world government. Drake, who later observed that many SETI supporters such as himself were exposed in their youth to “fundamentalist religion”, entertained hopes that alien wisdom would help humans end war and cure cancer.
Drake’s other legacy to the movement was an equation he devised in 1961 for estimating the number of alien civilisations in our galaxy capable of communicating with us. The astrophysicist Neil deGrasse Tyson, in “Welcome to the Universe: An Astrophysical Tour”, revisits the Drake equation using contemporary data. The equation holds that the number of communicating alien civilisations is a function of seven variables, starting with the rate at which new stars are born in our galaxy, the fraction of these stars that host planets and the number of planets per star that are habitable.
In 1961, scientists could fill in only one variable; the other six were sheer guesswork. With our advanced understanding of the cosmos, Tyson — whose book is written with the astrophysicists Michael A. Strauss and J. Richard Gott — is able to work out, in some technical detail, a more sophisticated estimate. The verdict? According to his calculations, we might expect to find as many as 100 alien civilisations in our galaxy communicating with radio waves right now. “So,” he concludes, “we have a chance.”
In “All These Worlds Are Yours: The Scientific Search for Alien Life”, a lively introduction to the field of astrobiology, the astronomer Jon Willis concurs that exoplanets are an exciting development. But because our first contact with alien life, he suspects, “is likely to be a meeting of microbes rather than a meeting of minds”, he is more optimistic about finding a simple organism elsewhere in our own solar system. Perhaps it will be an “extremophile” bacterium of the sort scientists have recently found on Earth living in conditions previously assumed to be fatal (such as volcanic hot springs and subzero temperatures).
Three of Willis’s top contenders for habitats are Mars, Jupiter’s moon Europa and Saturn’s moon Titan. But if forced to choose a single project for both feasibility and promise, he would send a spacecraft on a flyby mission to Saturn’s ice moon, Enceladus. The craft would collect (and bring back to Earth) icy particles and gases from Enceladus’s subsurface liquid ocean, whose chilly waters are regularly spouted into space via geysers. Maybe we’d find something alive in that stuff.
Do planetary scientists, with their arcane interests and occasional searches for alien life, strike you as an exotic tribe? Do they seem to require decoding by an anthropologist who conducted fieldwork amid them? If so, you might consult Lisa Messeri’s study “Placing Outer Space: An Earthly Ethnography of Other Worlds”. Messeri, an anthropologist whose undergraduate degree is in aeronautical and astronautical engineering, spent 15 months working with — and closely observing the customs of — several groups of planetary scientists, including astronomers at a Chilean observatory, Nasa researchers creating 3D maps of Mars and exoplanet scientists at MIT. What she was trying to understand was their “pursuit of planetary place”. By this phrase she means to identify a rarely considered aspect of their professional practice: how these scientists, whose objects of study exist at distances and scales and time-frames that can defy human grasp, nonetheless manage to conceive of these uncanny things more intimately as “places” or “worlds”, thus allowing the scientists to better engage with them.
Exoplanet scientists offer the best example of what Messeri is talking about. Exoplanets are not visible from Earth, even with the assistance of the most powerful telescopes; instead, they are inferred from subtle changes in the light from the stars they orbit. A slight dimming in the light, a slight wobble in the light — it is from such fine measurements that astronomers determine an exoplanet’s existence, the radius of its orbit, its mass and its density. From its density, they extrapolate what it is made of.
In practice, this means exoplanet scientists pass their days looking not at planets but at data: light curves and radial velocity graphs and theoretical models. To become an exoplanet scientist, Messeri shows (in part by undergoing some training herself), is to learn to see and convey these abstractions as something more relatable — as “super-Earths” or “mini-Neptunes” or such. “To excite the community about a particular visualisation,” as Messeri nicely puts it, “is to convince them that the image contains a world.” And to really excite the community, presumably, is to convince them that a world contains little green men.
–New York Times News Service
