According to the eminent physicist Stephen Hawking, instead of trying to find and communicate with life in the cosmos, humans would be better off doing everything they can to avoid contact. "If aliens visit us, the outcome would be much as when Columbus landed in America, which didn't turn out well for the Native Americans," Hawking has said in a forthcoming documentary made for the Discovery Channel.
Hawking believes that, based on the sheer number of planets that scientists know must exist, we are not the only life-form in the universe. There are, after all, billions and billions of stars in our galaxy alone, with, it is reasonable to expect, an even greater number of planets orbiting them. And it is not unreasonable to expect some of that alien life to be intelligent, and capable of interstellar communication.
Seth Shostak, a senior astronomer at the SETI Institute in California, the world's leading organization searching for telltale alien signals, is not so sure. "This is an unwarranted fear," Shostak says. "If their interest in our planet is for something valuable that our planet has to offer, there's no particular reason to worry about them now. If they're interested in resources, they have ways of finding rocky planets that don't depend on whether we broadcast or not. They could have found us a billion years ago."
There are a multitude of reasons a visiting civilization would refrain from "landing on the White House lawn," foremost among them the potentially debilitating effect open contact might wreak on terrestrials. History shows that relatively advanced sea-faring cultures topple less developed cultures, in part by collapsing defining assumptions and rendering cultural self-hood obsolete. If we're of any research value to a visiting civilization then interfering at the macro-sociological level might threaten to destroy thousands of years of patient work.
One idea to account for this behavior is that the UFO intelligence somehow hinges on our belief in it (a notion that assumes an esoteric origin instead of the more common "nuts and bolts" extraterrestrial hypothesis). In this scenario, the UFOs are engaged in an elaborate act of psychic propaganda, preparing our collective unconscious for the idea of "others," ET or otherwise. It's well worth remembering that humanity's interaction with apparent visitors is hardly limited to alleged space travelers in the 20th century; Jacques Vallee's classic Passport to Magonia offers strong support to the (admittedly slippery) prospect that the UFO intelligence was functioning under the guise of faerie lore in Europe centuries before the idea of spaceflight became fashionable.
It's possible that UFOs would like to initiate something like formal contact but are restrained from doing so by the physics of perception, as Whitley Strieber has suggested. So the pageant in our skies might be an ongoing indoctrination, an attempt to become more substantial (in our universe, at least) so that a more meaningful dialogue can be reached at some indeterminate point in the future. One way of achieving this might be to cultivate a milieu of incipience, in which nonhuman contact (or disclosure) seems inevitable.