The development of astronomy following the invention of the telescope was rapid. Early astronomers seem to have assumed that the planets they now realised were other worlds would be very similar to the earth. To populate them with human beings (or, at least, human-like beings) was a natural assumption. As early as 1698, the astronomer Huygens discussed the features a planet requires to allow it to support life and even speculated about extraterrestrial intelligence in his book Cosmotheros.
During the opposition of 1877, Professor Giovanni V Schiaparelli (1835-1910, director of the Brera Observatory in Milan from 1862 to 1900) discovered a network of narrow dark lines running between the larger dark areas on Mars, which he named canali, ‘channels’. Two years later, he noted that some of the canali appeared as double lines, a feature he attributed to vegetation growth due to meltwater from the polar caps flowing along canali. Although Schiaparelli nowhere expressed a belief that his canali might be of artificial origin, the word was seized upon by certain English-speaking astronomers, who mistranslated it as ‘canals’ and suggested that Mars was criss-crossed with a network of irrigation channels. Most notable of these was Percival Lovell, the millionaire philanthropist and amateur astronomer, eventual co-discoverer of Pluto. However, from the outset, both the explanation and existence of Schiaparelli’s canali were beset with controversy. Many astronomers could not see the features, even under favourable conditions; others thought that they might be cracks in the planetary surface, even cracks in a Mars-wide ice sheet. No convincing photographs of canali were ever obtained. As larger telescopes became available during the first half of the twentieth century, further searches for canali failed to reveal them and it became clear that the original observations had been mistaken. It is still unclear what Schiaparelli and other astronomers had observed, although one possibility is that groups of unrelated features on the surface of the planet, at the very limits of visibility through telescopes of the day, were being joined through optical illusions into straight lines.
By the late 1950s, other suggestions were being made about the best way to identify intelligent life on other planets. Most astronomers had concluded that it was unlikely that intelligent life would be found anywhere in the solar system, so techniques were proposed for locating such life elsewhere in our galaxy. In 1959, Giuseppi Cocconi and Philip Morrison of Cornell University published an article in Nature pointing out the potential for using microwave radio to communicate between the stars. At the same time, Frank Drake had reached a similar conclusion, and in 1960, he conducted the first search for signals from outside the solar system. His Project OZMA failed to detect any signals of extraterrestrial origin, but he drew attention to the possibilities of searching for extraterrestrial life in this way.
In the 1960s, the search was led by astronomers from the then Soviet Union, observing large areas of sky, in the assumption that a few very advanced civilisations would be able to radiate enormous amounts of transmitter power. NASA became interested in the search during the early 1970s and a team of consultants drew up Project Cyclops, the foundation on which much of the later work has been based. During the 1970s, many radio astronomers began searches, using existing radio telescopes, and this has continued up to the present day. Important players in the search today include the Planetary Society’s Project META, the University of California at Berkeley’s SERENDIP Project and a long-standing observing programme at Ohio State University.
By the late 1970s, SETI [i] programmes had been established by NASA at the Ames Research Center and at the Jet Propulsion Laboratory (JPL) in Pasadena. A targeted search was proposed of a thousand sun-like stars that were thought likely to have terrestrial type planets capable of producing civilisations. In 1988, after a decade of study and preliminary design, NASA adopted this strategy and funded the programme. Observations began in October 1992, but within a year, Congress had stopped the funding.
The SETI Institute, established with private funding in 1993, now aims to continue the abandoned programme with funding from the private sector. Project Phoenix—as it is known—continues the targeted search using large radio telescopes. It began observations in February 1995, using the Parkes radio telescope in Australia. From September 1996 to April 1998, the 140 Foot radio telescope at the National Radio Astronomy Observatory in Green Bank, West Virginia, was also used. Observations are currently being made during two three-week sessions each year using the 1000-foot radio telescope at Arecibo, in Puerto Rico. The project examines signals on a single frequency between 1,000 and 3,000 MHz, considered characteristic of an intelligent transmission. The spectrum is broken into narrow 1 Hz-wide channels, which means that two billion channels are examined from each target star.
As home computers
became more powerful during the later 1990s, the
SETI Institute and Project SERENDIP developed a gigantic distributed computing
program (known as SETI@home) to perform the calculations on data sent via the
Internet and to return them to the project after completion. It is
thought that millions of individuals worldwide now participate in and contribute
to the programme. By mid-1999, Phoenix had examined about 500 stars, but no
clearly extraterrestrial signals have so far been identified. In
the context of scientific research, SETI has been a very small scale and poorly
funded programme in view of the potential impact of the discovery of
extraterrestrial civilisation.
The search for extraterrestrial life during the second half of the twentieth century was also heavily influenced by the growth of the UFO phenomenon from the late 1940s onwards. While mainstream science continues to dismiss UFOs and anything that might be associated with them by Ufologists, they have continued to fascinate the public. Opinion polls consistently show that a majority of the public in the western world believes that UFOs are structured craft from other worlds. Discussion of supposed extraterrestrial monuments and artefacts cannot ignore this.
[i] Search for ExtraTerrestrial Intelligence.