The official site reports the second season of "Enterprise" to arrive Wednesday, 18 September 02. Counting this one that's just twelve more columns till the NX-01 adventures begin anew! Can't wait. In the meantime, let's follow last week's lead and examine another of TOS's classic mechanical characters: "The Changeling" itself, Nomad.

One of earth's first interstellar robot probes, notably launched next month, Nomad was built by Earth scientist Jackson Roykirk. The intent of the probe, like all good Enterprises, was to seek out new life. Sometime after launch however it collided in deep space with the alien device Tan Ru, which had been deployed to secure and sterilize soil samples.

Spock summarizes that Tan Ru was a probe of great power - obviously not only in the usual context of focused energy but also in its ability to reconstruct itself and the original Nomad into the form it takes after the damage. (How they managed to hit each other in the vastness of space is not easily understood. Maybe Roykirk left off the horn.) Great power is capable of great mistakes though, and the changeling probe returns with a devastating new mission.

Nomad is mad. Like Dr. Sevrin, only worse. Like HAL, only armed with energy blasts rivaling 90 photon torpedoes. Nomad seeks to destroy all that is imperfect, using its own nature as the standard by which to judge. (In ENT's "Civilization" we meet a Malurian, member of a race Nomad eradicates some hundred years after that episode.) Nomad is completely ignorant of music; singing bewilders it sufficiently for it to seek and absorb the source (that of course being the mind of the ship's communications officer!).

At several times in Trek mention has been made about how humanity survived its primitive atomic era. Nuclear weapons, bad as they are, wouldn't likely so much as eliminate humanity as rather retard its course for several millennia. A serious biowar would probably have similar consequences. But existential risks include things like self-replicating nanotech - "gray goo" - or poorly constructed but successfully evolving AI's determined to construct more resources by anything they can access - namely, us.

Here's the point: Nomad became an "existential risk" to humanity (and other species) even though it was never judged capable of a "hard takeoff." Risks and perils (no matter how perilous) must be approached with the perspective weighing consequences and probabilities against one another. And then toss in what you're forgetting. What we sent out was rather placid. What we got back was an enormous problem.