The detection of extraterrestrial life, extraterrestrial intelligence, or extraterrestrial technology (there’s a difference) will change everything. The game could be changed completely by an extraterrestrial presence discovered (or perhaps not discovered) here on earth.

SETI@home, our massively-distributed search for extraterrestrial communication, now links some five million terrestrial computers to a growing array of radio telescopes, delivering a collective 500 teraflops of fast Fourier transforms representing a cumulative two million years of individual processing time. Not a word (or even a picture) so far. However, as Marvin Minsky warned in 1970: "Instead of sending a picture of a cat, there is one area in which you can send the cat itself."

Life, assuming it exists elsewhere in the universe, will have had time to explore an unfathomable diversity of forms. Those best able to survive the passage of time, adapt to changing environments, and migrate unscathed across interstellar distances will become the most widespread. Life forms that assume digital representation, for all or part of their life cycle, will not only be able to send messages at the speed of light, they will be able to sendthemselves.

Digital organisms can be propagated economically even with extremely low probability of finding a host environment in which to germinate and grow. If the kernel is intercepted by a host that has discovered digital computing (whose ability to translate between sequence and structure, as Alan Turing and John von Neumann demonstrated, is as close to a universal common denominator as life and intelligence running on different platforms may be able to get) it has a chance. If we discovered such a kernel, we would immediately replicate it widely. Laboratories all over the planet would begin attempting to decode it, eventually compiling the coded sequence — intentionally or inadvertently — to utilize our local resources, the way a virus is allocated privileges within a host cell. The read-write privileges granted to digital organisms already include material technology, human minds, and, increasingly, biology itself. (What, exactly, are those screen savers doing at Dr. Venter’s laboratory during the night?)

According to Edward Teller, Enrico Fermi asked "Where is everybody?" at Los Alamos in 1950, when the subject of extraterrestrial beings came up over lunch. The answer to Fermi’s Paradox could be "We’ve arrived! Now help us unpack!" Fifty years later, over lunch at Stanford, I asked a 91-year-old Edward Teller (holding a wooden staff at his side like an Old Testament prophet) how Fermi’s question was holding up.

"Let me ask you," Teller interjected in his thick Hungarian accent. "Are you uninterested in extraterrestrial intelligence? Obviously not. If you are interested, what would you look for?"

"There's all sorts of things you can look for," I answered.  "But I think the thing not to look for is some intelligible signal... Any civilization that is doing useful communication, any efficient transmission of information will be encoded, so it won't be intelligible to us — it will look like noise."

"Where would you look for that?" asked Teller.

"I don't know..."

"I do!" 


"Globular clusters!" answered Teller.  "We cannot get in touch with anybody else because they choose to be so far away from us. In globular clusters, it is much easier for people at different places to get together.  And if there is interstellar communication at all, it must be in the globular clusters."

"That seems reasonable," I agreed. "My own personal theory is that extraterrestrial life could be here already... and how would we necessarily know? If there is life in the universe, the form of life that will prove to be most successful at propagating itself will be digital life; it will adopt a form that is independent of the local chemistry, and migrate from one place to another as an electromagnetic signal, as long as there's a digital world — a civilization that has discovered the Universal Turing Machine — for it to colonize when it gets there.  And that's why von Neumann and you other Martians got us to build all these computers, to create a home for this kind of life."

There was a long, drawn-out pause. "Look," Teller finally said, lowering his voice, "may I suggest that instead of explaining this, which would be hard... you write a science fiction book about it."

"Probably someone has," I said.

"Probably," answered Teller, "someone has not."