Today, we watch as conspiracy theories realign themselves. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

These are fascinating times. While the media provide an ample supply of conspiratorial interpretations of the natural world, levelheaded people try to separate the few real cover-ups from a sea of contenders. July 1997 has provided a lot of information that'll force us to alter our thinking about such mischief.

For example: The Air Force recently revealed that the aliens whom people saw near Roswell, New Mexico, fifty years ago were actually dummies used in an experiment. That won't satisfy people committed to a conspiracy theory. But it makes a far more plausible picture than Air Force personnel doing lab tests on extra-terrestrials.

And that plays against the backdrop of a small Mars lander beaming back evidence consistent with the suspicion that Mars once sustained life -- and might still do so. By July's end, our questions about alien life won't be erased, but they will be changed.

Back here on Earth, the National Cancer Institute and the University of Minnesota have just released a new report on the non-effects of low-frequency electromagnetic fields. For years we've heard claims that fields generated by power lines (both in and outside our homes) are causing childhood leukemia. No compelling evidence has supported the idea, yet it has lingered. Now a five-million-dollar study convincingly shows no connection.

I'll be curious to see how cover-up accusations shift in the wake of this new evidence. A few people will choose not to be convinced. And many, on both sides of the issue, will see the study as wasted money. But the conspiracy claims are going to shift in its wake.

Then there's the enigma of the Neanderthals -- those heavy-browed, intelligent, and communal toolmakers. A group of scientists in Munich has just isolated Neanderthal DNA. It's different enough from ours to suggest that Neanderthals split off from our common ancestor a half-million years ago -- long before our subspecies appeared. For biblical literalists, that enforces the idea that modern humans were a separate creation. Racists are bothered by the way it vectors all human evolution back into Africa.

And so the data pour in this summer. Conspiracies and cover-ups occur just often enough to leave us all suspicious on some level. The government really did let Black patients die untreated in the Tuskegee syphilis experiments. Big tobacco really has set out to addict our children.

But this new bumper crop of information is reshuffling the deck. With each new piece of hard data, we have to spin new yarns and seek out new fears. We have to rewrite our fringe beliefs and our superstitions. And, make no mistake, we all have superstitions. It's worth the trouble to look coolly and analytically at cover-up theories. We need to find that subtle point where our own thinking takes leave of empirical reality.

I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.

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Kahn, P., and Gibbons, A., DNA from an Extinct Human. Science, Vol. 277, 11 July, 1997, pp. 176-178.

Kerr, R. A., Pathfinder Strikes a Rocky Bonanza. Science, Vol. 277, 11 July, 1997, pp. 173-174.

Taubes, G., Magnetic Field-Cancer Link: Will It Rest in Peace. Science, Vol. 277, 4 July, 1997, p. 2.

Much of this episode arises out of conversations about his Web home page with local junior-high-school student Shamsundar Dileep.