In my last column I revealed my sorry record as a fortuneteller of scientific events. Today, undaunted, I will try my hand again at the risky business of prediction. Here are five things that I expect to see in three decades or less.

First, we will see the widespread use of nanotubes. These are minute tubes made of pure carbon and direct descendants of "buckyballs" (fullerenes). Nanotubes will form logic gates and transistors in the next generation of computers; they will offer super-strength building materials, able to bear enormous tensile stresses; and you will find them wherever you now find Kevlar, in bulletproof vests and shields. They will, however, be much stronger and thinner than today's products. I look for these in 20 years or less. I would love to think that nanotubes also would make possible the construction of a space elevator, a beautiful way of going into space, which I discussed a long time ago. Unfortunately, the space elevator lies well beyond my 30-year limit.

Second, our bodies already are filled with symbiotic organisms, most of them in our digestive tracts. They have been there for millions of years and we remain quite unaware of them unless we travel to foreign parts, when they sometimes show their objection to unfamiliar food and water in unpleasant and unmistakable ways. The use of other symbiotes for other purposes is going to become increasingly common. Our insides will some day crawl with minute organisms, doing everything from stripping away arterial plaque to removing from within the brain beta amyloids (increasingly suspected as a cause of Alzheimer's disease). All this will happen within 30 years, or as soon as we get over our discomfort at sharing our bodies with other inhabitants.

Third, super telescopes will be developed, with an effective "lens size" equal to the diameter of the Earth's orbit around the Sun. Radio telescopes lead the way here, employing a technique known as interferometry to give high-resolution radio images. The same technique can be used at optical wavelengths, and small prototype sets of telescopes employing the technique already exist. Extending this, by the use of a large number of small spaceborne telescopes with precisely coordinated targets, we will achieve most of the results possible from a single huge telescope. What would such a giant telescope mean to science? That's harder to predict. Although it would not provide conventional images, such an instrument would allow us to discern continents on Earth-sized planets in the Andromeda galaxy, two million light years away.

Fourth, we will achieve within 30 years the long-awaited synthesis of quantum theory and general relativity - what John Wheeler referred to as "the fiery marriage." We have known for over half a century that the two theories cannot both be right in their present forms. Stephen Hawking's discovery that black holes can radiate energy derived from a rather patchy melding of elements of the two fields. Maybe I am being optimistic in my time frame. It could be that new mathematics will be required before the synthesis can take place. That mathematics, however, might derive directly from my next item.

Fifth, in less than 30 years superstring theory will change its status, from being a somewhat haphazard collection of conjectures, analogies, simplified models, and partial results, to being a real and integrated theory. If so, we will achieve a new understanding of the universe at the smallest and largest scales. Today our understanding is hazy at both ends.

So much for a handful of what could be optimistic predictions. To compensate for them, I will now play the pessimist and offer five things I do not expect to see in the next 30 years - and probably not in the next 200. Here is where I expect to get into trouble with readers. I know from previous letters that some people believe that we already have seen evidence of much of what follows.

First, I do not think we will find that one human brain can send information to another, except through speech, gestures, body language, and pheromones. In other words, we will find no evidence for telepathy. In the same way, we will find no acceptable proof that humans can influence objects at a distance using purely mental powers - no telekinesis, no "spoon bending," no "firestarter" powers. I hold these opinions not because I wish it were so, or because such things can be proven impossible on physical grounds (although physics offers less and less wriggle room to permit the existence of such phenomena), but because a century of hard work has revealed ample evidence of charlatanism, trickery, and wishful thinking, but little else.

Second, I do not believe we will be visited by beings from other worlds; nor do I believe that we will discover evidence of intelligence anywhere in the universe except on our own planet (and sometimes you have to wonder about that).

Third, I do not believe that we will develop a means for teleportation of humans or objects. If you calculate the amount of information needed to transmit a complete copy of me or you to another location (such transmission presumably to be followed by our reconstruction) you come up with the daunting number of a ten billion trillion trillion bits. Using the fastest data transfer method we know, you are facing electronic transfer times of a billion years. They can beam you up if you like. Me, I'd rather walk.

Fourth, I do not believe that in the next half century we will have a colony of humans living on Mars or any other planet of the solar system. You have no idea how much this thought distresses me. All my life I have been fascinated by space travel and space exploration. Thirty years ago I would have bet money on a Mars colony by 2020. But in today's world I see no chance of the combined worldwide effort that such colonies imply.

Fifth, despite the popularity of the idea in fiction, I do not think that we will, in the next century or two, find any way of downloading a human consciousness into a computer. On the other hand, I believe that in half a century or less we should be able to make a computer program, able to exist in many copies, that everyone will swear is just like me, including all my crankiness, irrationality, and personal foibles.

Whether anyone will choose to do so is another matter.

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