I offered the warning back on Page 1, in the very first sentence: "You are reading an out-of-date book." Science marches on, exploring new territories and expanding older ones every week.
I knew this, but I didn't think I could do anything about it. Fortunately, I was wrong. Just about the time that Borderlands of Science was reaching the book stores, I was invited to begin a weekly science column for distribution to newspapers and other media (especially on-line outlets).
There was only one catch. The columns would have to be very short, "science bites" rather than science articles; six or seven hundred words, rather than the six or seven thousand that I am used to. I squirmed at the prospectwhat could I possibly say in six hundred words?but I couldn't deny the logic of the argument. The world speeds up, attention spans are down, so science bites won't catch the fish; all they can do is set the bait, so that an interested reader can follow up with longer articles or books. The good news was that I could write on any subject I liked. And the title of the newspaper column? What else but The Borderlands of Science.
Here, then, is a little bait, a couple of dozen of those brief articles. All were written after the main body of Borderlands of Science was complete. The Borderland has moved a little farther out. And if you want to see how it is still moving, go online to www.paradigm-tsa.com for more of the weekly columns.
A.1. The ship jumped over the moon. No matter what Star Trek and Babylon 5 may tell you, moving objects around in space is a tricky business. The Space Shuttle can sometimes do it, provided that it doesn't have to go after anything more than about 300 miles up. The in-space fix of the Hubble Space Telescope was a spectacular success. But if a satellite gets into trouble in a high orbit, thousands of miles from Earth, it's usually beyond saving.
That's the way it looked in December 1997 when the failure of a rocket booster sent a Hughes communications satellite into the wrong orbit. The spacecraft was supposed to sit at a fixed longitude, 22,300 miles above the Pacific Ocean. Instead it traced a looping, eccentric path, varying widely in its distance from the surface of the Earth.
Time to give up? It seemed tht way. From its changing position, the satellite could not deliver communications and television in Asia. And although the spacecraft had a small rocket of its own on board, there was not enough propellant to move it directly into the correct orbit. Insurers examined the situation and declared the satellite a total loss. In April 1998, they gave ownership back to Hughes, saying in effect, "Here's a piece of junk way out in space. It's all yours, do what you like with it."
Hughes engineers did, through a surprising and spectacular idea: Although the satellite's rocket was not big enough to force it directly into the right orbit, it could float the spacecraft out to the Moon. Once there, the lunar gravity field might be used to change the orbit of the satellite. In effect, the spacecraft would get a "free boost" from the Moon, stealing a tiny amount of Luna's vast orbital energy to modify the satellite's own speed and direction.
The first swing around the Moon was made in May 1998, after which the spacecraft came looping back in toward Earth. The orbit still wasn't right, so another small rocket firing and a second lunar swing-by was made three weeks later. This time the satellite returned close to its desired orbit. A final firing of the rocket engine in mid-June, 1998, did the trick. The spacecraft now sat in a 24-hour circular orbit, just as originally planned, going around the Earth at the same speed as the world turns on its axis.
It sits there now, drifting a few degrees north and south of the equator every day while remaining close to a constant longitude. Known as HGS-1, it is working perfectly and ready for use in global communications. More than that, HGS-1 serves as a tribute to human ingenuity. When a space mission in trouble had officially been declared dead, engineers down here on Earth "repaired" it without ever leaving their chairs. Perhaps even more impressive, to anyone who remembers the first disastrous attempts to launch an American satellite: this round-the-moon space shot didn't rate television coverage or a newspaper headline. We've come a long way in forty years.
A.2. Future cars. I'm a writer, so there's a chance my works will live on. But I agree with Woody Allen, I don't want to live forever through my works. I want to live forever by not dying.
That presents certain problems. If Iand youdon't die, we will certainly get older. Sixty years from now, without some spectacular medical advance, none of us will look or feel young. The retina of a 75-year-old has only 10 percent of the sensitivity of an 18-year-old. By age 75, we are at least a little deaf (particularly the men). The range of mobility of our neck and shoulders is down, and our reaction times are slower. However, if today's 70- and 80-year-olds are anything to go by, we'll insist on one thing: we want to drive our own cars. It's part of our independence, our ability to look after ourselves.
Let's put that together with another fact, and see where it takes us: People are living longer, and the US population is getting older. In 1810, there were only about 100,000 people over 65. By 1880 it was close to 2 million. By 1960, 16 million, and today it's over 30 million. In 2030 it will be near 60 million. And most of these aging peopleremember, that's you and mewill still want to drive their cars.
We will need help, and fortunately we will get it. Auto manufacturers who study ergonomicsthe way that people operate in particular situationsare already taking the first steps.
The driver doesn't see or hear too well? Fine. The car provides a "virtual reality" setting. Actual light levels outside the car will be changed, so that what the driver sees compensates for loss of visual sensitivity. The driver will receive an enlarged field of view without having to turn very far, so as to compensate for decreased head and neck mobility. The speed of reaction of the driver will be improved using servo-mechanisms, just as today the strength of a driver is augmented by power steering.
These are all, relatively speaking, easy. They can be done today. Most older drivers already wear glasses. We simply replace them with goggles that present virtual reality views of the surroundings. The driver should hardly notice, except to remark how much clearer everything seems.
At the same time, the car will do more things for itself: monitoring engine temperatures, stresses, loads, and driving conditions. Rather than presenting this information in the "old-fashioned" way, through dials and gauges, the car's computer will report only when something is outside the normal range.
More complex, and farther out in time, comes the involvement of the car's control systems in real-time decision making. Here, the automobile not only senses variables from the environment, it also interprets the inputs, draws conclusions, and recommends actions (ACCIDENT FOUR MILES AHEAD; SUGGEST YOU LEAVE FREEWAY AND TAKE ALTERNATE ROUTE. SHALL I MAKE ADJUSTMENT AND ESTIMATE NEW ARRIVAL TIME?). Or, in emergency, the car's computer will initiate action without discussion. A human cannot react in less than a tenth of a second. A computer can react in a millisecond. The difference, at 60 miles an hour, is about 10 feetenough to matter.
These changes to the automobile are more than probabilities; I regard them as future certainties. My job, and yours, is to be around long enough to enjoy them.
A.3. Making Mars. A hundred years ago, Mars was in the news. H.G. Wells had just published his novel, The War of the Worlds, and everyone seemed convinced that there must be life on the planet. Astronomers even thought they had seen through their telescopes great irrigation "canals," showing how water was moved from pole to pole.
Today, Mars is a hot topic again. Some scientists believe they have found evidence of ancient Mars life in meteorites flung from there to Earth. Others say, forget the ancient past. Mars is the place for life in the futurehuman life. Let's go there, explore, set up colonies, and one day transform Mars so that it is right for people. Mars has as much land area as Earth; it could be a second home for humanity.
Sounds great. NASA ranks Mars high on the list of its priorities. Can we make another planet where humans can live, work, raise families, and have fun? How easy is it to change Mars so it is more like our own planet?
In a phrase, it's mighty tough. Mars has plenty of land. What it does not have are three things we all take for granted: air, water, and heat. Making Mars more like Earth"terraforming" the planetrequires that we provide all three.
Heat should be the easy one. We can load the thin atmosphere of Mars with CFC's, "greenhouse gases" currently in disfavor on Earth because they contribute to global warming. As the temperature rises, solid carbon dioxide held in the Mars polar ice caps will be released into the air, trapping more sunlight and adding to the warming process. The Mars atmosphere, currently only about one percent as dense as ours, will thicken. At the same time, the temperature will rise enough for water, held below the surface as permafrost, to turn to liquid as it is brought to the surface. Recent estimates suggest enough water on Mars to provide an ocean three hundred feet deep over the whole surface.
When the warming process is complete Mars will have heat, water, and air. Unfortunately, that air will be mostly carbon dioxide. Humans and animals can't breathe thatbut growing plants rely on it, taking it in and giving out oxygen. The key to making breathable air on Mars is through the import of Earth plant life, genetically engineered to match Mars conditions.
Now for the catch. If we started today, how long would it take to transform Mars to a place where humans could survive on the surface? In the best of circumstances, assuming we use the best technology available today and make this a high-priority project, the job will take four or five thousand years.
That's as much time as has elapsed since the building of the Egyptian pyramids. The technology available to our far descendants is likely to be as alien and incomprehensible to us as computers and genetic engineering and space travel would have been to the ancient Egyptians. Maybe we ought to wait a while longer before we start changing Mars.
A.4. Close cousins: How near are we to the great apes? A visit to the monkey house at the zoo is a sobering experience. We stare in through the bars. Looking right back at us with wise, knowing eyes is someone roughly our shape and size, standing like us on two feet, perhaps pointing at us with fingers much like our own and apparently laughing at us. He bears an uncanny resemblance to old Uncle Fred. Maybe we should look twice to make sure who is on the right side of the bars.
It is easy to believe that of all the creatures in the animal kingdom, the chimps, gorillas, and orangutans are nearer to humans than any other. The question is, how close?
A generation ago, we could offer only limited answers. We were different species, because inter-breeding was impossible. As for other similarities and differences, they had to be based on the comparison of muscle and bone structure and general anatomy.
Now we have new tools for the comparison of species. The complete genetic code that defines a gorilla is contained in its DNA, a gigantic long molecule organized into a number of long strands called chromosomes. Moreover, every cell of a gorilla (or a human) contains the DNA needed to describe the complete animal. Given a single cell from a chimp and a cell from a human, we can take the DNA strands and do a point-by-point comparison: the structure is the same here, different there. The extent to which the two DNA samples are the same is a good measure of the closeness of the two species.
This analysis has been performed, and the results are breathtaking. Humans and chimps share more than ninety-eight percent of their DNA. Each of us is, in an explicit and meaningful way, less than two percent away from being a chimp.
The same exercise, carried out with DNA from orangutans, shows that humans are rather less closely related to them. As we consider other animals, everything from a cheetah to a duck to a wasp, we find that our intuitive ideas are confirmed. The differences between our DNA and those of other creatures steadily increases, as the species become more obviously "different" from us in form and function. DNA analysis tells us that we are more like every other mammal than we are like any bird, and we are more like every bird than we are like any insect.
We can use this and other information to estimate how long ago different species diverged from each other. Humans and chimps have a common ancestor which lived roughly five million years ago. Humans and gorillas diverged at much the same time, as did chimps and gorillas from each other. We and the orangutans parted ancestral company farther in the past, about twelve to fifteen million years ago.
Five million years may sound like a long time, but there has been life on Earth for more than three and a half billion years. We and the great apes separated very recently on the biological time scale, and we really are close cousins. It should be no surprise that we feel an odd sense of family recognition when we meet them.
A.5. Breathing space. How many can Earth hold? Stuck in rush hour traffic on a hot day, you sometimes wonder: Where did all these people come from? You may also mutter to yourself, Hey, it wasn't like this when I was a kid.
If you do say that, you'll be right. It wasn't. There are more people in the world today than ever before. Next year there will be more yet.
Here are some sobering numbers: At the time of the birth of Christ, the world population was around two hundred million. By 1800 that number had climbed to one billion. Two billion was reached about 1930; three billion in 1960; four billion in 1975; five billion in 1988. By 2000 the population topped six billion.
Not only more and more, but faster and faster. People are living longer and the old equalizers, famine and plague, seem largely under control. War remains, but the two great conflicts of the twentieth century did little to slow the growth in population. It took a hundred and thirty years to add the second billion, only twelve years to add the sixth. With any simple-minded projection for the next century apparently zooming to infinity, we have to ask, how long can this go on? Also, where will all the new people fit? Not, we hope, on the commuter routes that we use.
A glance at a population map at first seems reassuring. Most of the world still looks empty. A second glance, and you realize why. Of the Earth's total land area, one fifth is too cold to grow crops, another fifth is too dry, a fifth is too high, and another seventh has infertile soils. Only about a quarter of the land is good for farming. Empty areas of the planet are empty for good reason.
That can change, and is already changing. Sunlight is available everywhere, regardless of how high or cold the land. Plants are remarkably efficient factories for converting sunlight, water, and carbon dioxide into food. By genetic engineering, we are producing new crop varieties with shorter growing seasons and more tolerance of cold, drought and high salinity. In the future, it seems certain that areas of the globe now empty will be able to fill with high-yield food crops, and then with people.
According to projections, they will have to. Population estimates for the year 2050 range from eight to twelve billion, for 2100 from ten to fifteen billion. Even these numbers are nowhere near the limit. Provided that we can produce the food (and distribute it), the Earth can easily support as many as twenty billion peoplealmost four times as many as we have today.
The question you may ask, sitting in your car on a freeway that has become one giant parking lot, is a different one. Sure, if we struggle and squeeze, maybe we can handle four times the present population. But do we want to? How many people is enough?
A.6. The inside view. Last week I had to go for a CAT scan of my abdomen. It was nothing special, more a loss of dignity than anything else. But it was still an indignity, still uncomfortable, still invasive (I had to swallow a barium milk shake that tasted like glue). Most people hate the standard medical routines. We don't like lying semi-naked on a slab, or having blood taken, or the prospect of the insertion of mechanical devices into veins, sinuses, bronchial tubes, urethras, and other personal apertures.
How might we improve all this? Before we get to that, let's recall the pastand things far worse than anything that will happen to me next week.
Until a hundred years ago a doctor had few tools to examine a patient's interior. A stethoscope to listen to body processes, a thermometer to measure body temperature, a spatula to examine tongue and throat, and that was about it. The rest of the diagnosis relied on palpation (feeling you), tapping, external symptoms such as ulcers and rashes, and the appearance of various waste products. If all those failed, the dreaded next step could be "exploratory surgery," with or without anesthetics.
And then, as though by magic, in the last decade of the nineteenth century a device came along that could actually see inside a human body. True, the X-ray was better at viewing bones and hard tissue than organs and soft tissue, but it was an enormous step forward.
The X-ray was the first "modern" tool of diagnosis. Since then we have developed a variety of other methods for taking an inside look: the CAT scan, the MRI, and ultrasonic imaging. They permit three-dimensional images of both hard and soft tissues. Used in combination with the injection of special materials, they allow the operation of particular organs or the flow of substances through the body to be studied as they happen. The radioactive tracers used for this purpose are one undeniably positive fall-out of the nuclear age.
Hand in hand with the images goes chemical diagnosis. Today, blood samples can provide a doctor with information about everything from liver function to diabetes to urinary infection to rheumatoid arthritis to AIDS to the presence of the particular bacterium (Helicobacter pylori) responsible for most stomach ulcers. Any tiny skin sample is sufficient to permit a DNA analysis, which can in turn warn of the presence of certain hereditary diseases and tendencies.
We have come a long way in a hundred years. What about the next hundred?
Completely non-invasive diagnosis, with superior imaging tools and with chemical tests that can operate without drawing blood, will become available in the next generation. The chemical tests will use saliva and urine samples, or work through the skin without puncturing it. For the digestive system, we may swallow a pill-sized object, which will quietly and unobtrusively observe and report on the whole alimentary canal as it passes along it.
No more upper GI exams, no more sigmoidoscopies. Our grandchildren will regard today's invasions (drawing blood, taking bone marrow samples, or inserting objects into the body) the way we think of operations without anesthetics: part of the bad old days of the barbarous past.
Or even the uncomfortable indignity of last week.
A.7. Attack of the killer topatoes. Genetically modified vegetables are in the news. Should you eat these "genemods" (GMs, in England) or should you avoid them at all costs?
Let's back up a bit. Your wife may not like it when you say that her brother is a louse. You explain to her, that's not really an insult. At the most basic level, down where it matters, a louse is not that different from a human being.
How so? Your brother-in-law and the louse are made up of cells. So are you. In the middle of almost every cell is a smaller piece called the cell nucleus. Inside that, even smaller, are long strings of material called chromosomes. It's your chromosomes that decide what you are like, while the louse's decide what it is like.
When you examine a human or a louse chromosome in detail they look remarkably similar. And it's not just the louse and your brother-in-law. It's everything you can think of, from snails to snakes to Susan Sarandon. All our chromosomes are made of the same basic stuff; and that stuff is what makes each of us, physically, what we are.
This suggests a neat idea. Suppose we have a variety of tomato that is very tasty and productive, but suffers from tomato wilt. We also have a wilt-resistant type of potato. The immunity is carried in a particular part of a potato chromosome (let's call it a "gene"). If we could snip just that gene out, and insert it into the tomato chromosome, we might be able to create a new somethingcall it a "topato"that produces great tomatoes and doesn't suffer from wilt.
We are not quite that smart yet, although with some foods we are well on the way. Do you believe you have never eaten genetically modified foods? Then take a look at the boxes and containers in your kitchen. See if they contain soy (most of them do). Today nearly half of the US soybean crop is a genetically engineered variety. Crops with genetic modification can have a higher yield, or an extra vitamin, or greater tolerance for weedkillers, bacteria, or salty soil. The variations are endless, and the topato I'm describing is a real possibility.
Should we worry about all this? I think we should be careful. We are making things that never existed in Nature. Maybe a "Frankenstein tomato" could have new properties that never occurred to us when we were making it.
On the other hand, plant and animal breeders have been playing this game, through cross-breeding, for thousands of years. There was no such thing as a nectarine or a loganberry before a human developed them, but we eat them quite happily. Even if we hadn't made such things, nature has a way of trying so many different combinations that they might occur naturally in time.
My only concern is that we may be, as usual, in a bit too much of a hurry. We are duplicating in a few years a process that in nature would normally take millions; and we, unlike nature, have to explain our mistakes.
A.8. Twinkle, twinkle? "It's not the things we don't know that causes the trouble, it's the things we know that ain't so." I love that quote and I wish I'd said it first, but Artemus Ward beat me to it by about a hundred and fifty years.
Less than fifty years ago, one thing every astronomer "knew" was that there was a limit to what a telescope could see when looking out into space. If you made a telescope's main lens or mirror bigger and bigger, it would collect more and more light but the degree of detail of what you saw would not increase. The limiting mirror or lens size is quite small, about ten inches, and beyond that you will get a brighter but not a sharper image.
The problem is nothing to do with the telescope's design or manufacture. The spoiler is the Earth's atmosphere, which is in constant small-scale turbulence. The moving air distorts the path of the light rays traveling through it, so that instead of appearing as a steady, sharp image, the target seems to be in small, random motion. The nursery rhyme has it right. When the target looks small, like a star, it will twinkle; when it is larger and more diffuse, like a planet or galaxy, fine detail will be blurred.
Twenty years ago that was the end of the story. If you wanted highly detailed images of objects in space, you had to place your telescope outside the Earth's atmosphere. That idea led to the orbiting Hubble Space Telescope, whose wonderful images have appeared on every TV channel and in every magazine. The Hubble pictures are far more detailed than any obtained by a telescope down here on Earth, even though the size of the Hubble's mirror, at 94 inches, is much smaller than the 200-inch mirror at Mount Palomar. The only road to detailed images of astronomical objects was surely the high road, through telescopes placed in orbit.
This "fact" turned out to be one of the things we know that ain't so. About fifteen years ago, a small group of scientists working on a quite different problem for the Strategic Defense Initiative ("Star Wars" to most people) came up with the idea of aiming a laser beam upward and measuring the way that its path was distorted in the atmosphere. Knowing what happened to the laser beam, the focus of the observing telescope mirror could be continuously (and rapidly) changed, so as to compensate for the changes in light path. The procedure, known as "adaptive optics," was tried. It worked, spectacularly well. Today, ground-based telescopes are obtaining images of a crispness and clarity that a generation ago would have been considered impossible.
What else do we "know" that can't be done with ground-based telescopes today? Well, the Earth's atmosphere completely absorbs light of certain wavelengths. If we want to learn what is happening in space at those wavelengths, we still need orbiting telescopes. I certainly believe that is true. On the other hand, it may be just one more thing I know that ain't so.
A.9. Are you a cyborg? At the turn of the millennium, I get asked one question over and over: What's going to happen to us? How will we change, as humans, when science and technology advance over the years and the centuries?
The only honest answer is, I don't know; but I am willing to stick my neck out and make a prediction in one specific area: we will all become, more and more, cyborgs.
A cyborg is a human being, changed to improve or restore body functions by the addition or replacement of man-made parts. Almost everyone reading this is already a cyborg in one or more ways. Are you wearing eyeglasses or contact lenses? Do you have dental fillings, or a crown on a tooth? Are you perhaps wearing a hearing aid, or a pacemaker, or is one of your knee, hip, or shoulder joints artificial? Has part of a vein or artery been replaced by a plastic tube?
If your answer to any of these questions is yes, then you are part cyborg. Admittedly, these are cyborg additions at the most primitive level, but we already have the technology to make much more versatile and radical changes to ourselves.
Let's consider a few of the easy ones. First, we can make an artificial eye lens containing miniature motors, sensors, and a tiny computer. The lens will adapt, just like a human eye lens, to changes in light levels and in the distance of the object being viewed. Near-sightedness, far-sightedness and astigmatism will become history. As the human retina ages, or light levels become low, the lens can also boost the contrast of scenes to compensate. Everyone will have eyes like a hawk, able to see with great clarity, and eyes like a cat, able to see well in near-dark. Last night, driving an unfamiliar winding road through heavy snow, I would have given a lot for a pair of these future eye lenses.
At first, of course, such things will cost a lot; millions of dollars for the prototypes. But, like hand calculators or cameras, once they are in mass production prices will fall dramatically. The main cost will be the one-time installation charge.
Suppose that your eyes are excellent, and you have no need for cyborg eyes. What about your hearing? Today's hearing aids, despite the claims made for them, are rotten. They don't give directional hearing, and they can't separate what you want to hear from background noise. The next generation of hearing aids will also contain tiny computers. They will be invisibly small, provide full stereo directional hearing, and boost selected sound frequencies as necessary. They too will be expensive at first, but manufacturing costs will drop until they are cheap enough to throw away rather than repair.
Your ears and eyes are in fine working shape, you say, so you don't need cyborg help? Very well. Here are a few other third millennium optional additions. You choose any items that appeal to you.
Peristalsis control, to provide perfectly regular bowel habits. A sleep regulator, which can be set to make you fall asleep or awake according to your own preferred schedule. A general metabolic rate regulator, boosting or lowering body activity levels to match the situation (or the level of a partner; we probably all know couples who wage constant war over setting the thermostat). A blood flow controller, solving any possible problems of male impotence. A vocal cord monitor, which adjusts your rough shot at a note so you sing exactly in tune. Built-in computer chips, to provide instant answers to arithmetic and logical questions of all kinds.
If this list worries you, and you say, isn't there a danger that devices like this will sometimes be abused or misused? I reply, can you think of any piece of technology that sometimes isn't?
A.10. "You've got a virus." Sometimes I think that viruses were created mainly to benefit the medical profession.
You're not feeling well, and you go to see your doctor. After an examination and a test or two, she says, "You're sick all right. You have an infection. But it isn't a bacterial infection, it's a viral infection. So there's no point in giving you antibiotics. Just go home and take it easy until you feel better." Meaning, "We're not quite sure what's wrong with you, but we do know we can't give you anything to cure it."
Are viruses and bacteria really so different? On the face of it, they have a lot in common. They exist in large numbers everywhere, some forms serve as the agents for disease, and they are too small to be seen without a microscope. On closer inspection, however, viruses are much more mysterious objects than bacteria.
First, although both are tiny, viruses are orders of magnitude smaller. The largest known bacterium is relatively huge, a bloated object as big as the period at the end of this sentence. Bacteria are complete living organisms, which reproduce themselves given only a supply of nutrients.
By contrast, a virus is a tiny object, often less than a hundred-thousandth of an inch long. It is no more than a tiny piece of DNA or RNA, wrapped in a protein coat, and it cannot reproduce at all unless it can find and enter another organism with its own reproducing mechanism. It is different enough from all other life forms that some biologists argue that viruses are not really alive; certainly, they do not fit into any of the known biological kingdoms.
The way in which a virus reproduces is highly ingenious. First, it must find and penetrate the wall of a normal healthy cell, often with the aid of a little tail of protein that serves as a kind of corkscrew or hypodermic syringe. Once inside, the virus takes over the cell's own reproducing equipment. It uses that equipment to make hundreds of thousands of copies of itself, until the chemical supplies within the cell are used up. Then the cell wall bursts open to release the viruses, which go on to repeat the process in another cell. Viruses are, and must be, parasitic on other life forms. They are the ultimate Man Who Came to Dinner, who does not leave until he has eaten everything in the house, and also killed his host.
This explanation of what a virus is and does leads to a bigger mystery: Since a virus totally depends for its reproduction on the availability of other living organisms, how did viruses ever arise in the first place?
Today's biology has no complete answer to this question. However, it seems to me that the only plausible explanation is that viruses were once complete organisms, probably bacteria with their own reproducing mechanisms. They found it advantageous to invade other cells, perhaps to rob them of nutrients. As time went on, the virus found that it could get by with less and less of its own cellular factories, and could more and more use the facilities of its host. Little by little the virus dispensed with its cell wall and its nutrient-producing facilities, and finally retained only the barest necessities needed to copy itself. What we see today is the result of a long process of evolution, which could perhaps more appropriately be called devolution. The end result is one of nature's most perfect creations, reproduction reduced to its absolute minimum.
The virus is a lean, mean copying machine. It may be a comfort to remember this, the next time that you are laid low by what your doctor describes as a viral infection. And we can take greater comfort from the fact that, as our understanding increases, twenty years from now we should have "viral antibiotics" to tackle viruses and have us back on our feet within 24 hours.
A.11. Accelerating universe. For the past year the astronomers of the world have been in a state of high excitement. Observations of supernovasexploding starsbillions of light-years away suggest a surprising result: the universe, which since the 1920s has been known to be expanding, is not simply expanding; it's accelerating. Distant galaxies are not only receding from us, they are flying away faster and faster.
Since these events are taking place at distances so great as to be almost unimaginable, the natural reaction to the new observations might well be, so what? How can things so remote have any possible relevance to human affairs here on Earth?
To answer that question, we need to explain why it is so surprising for far-off galaxies to be moving away increasingly fast. The place to start is with the "standard model" of the universe, the mental picture of the cosmos that scientists have been developing and testing for the past seventy years. According to that model, our universe began somewhere between twelve and twenty billion years ago, in a "Big Bang" that sent all parts of that original tightly-compressed universe rushing away from each other. We have to point out that it is not that other parts of the universe are receding from us, which would imply we are in some special position. All parts are running away from each other. And the first evidence of this expansion was provided in 1929 by Edwin Hubble, after whom the Hubble Space Telescope is named. All observations since then confirm his result.
Will the expansion continue forever, or it will it stop at some future time? That question proved difficult to answer. The force of gravity operates on every galaxy, no matter how far away, and it acts to pull them all closer together. Given enough material in the universe, the expansion might one day slow down and even reverse, with everything falling back together to end in a "Big Crunch." Or, with less density of material, the expansion might go on forever, with the force of gravity gradually slowing the expansion rate. But in either case, gravity can only serve to pull things together. It can't push; and a push is what you need in order to explain how the expansion of the universe can possibly be accelerating.
Where could such a pusha repulsive force between the galaxiespossibly come from? The only possible source, according to today's science, arises from space itself. There must be a "vacuum energy," present even in empty space, and providing an expansion force powerful enough to overcome the attraction of gravity. The idea of such a source of force was introduced by Einstein over eighty years ago, as a so-called "cosmological constant." Einstein used this constant to explain why the universe did not expand (this was before Hubble's observations showing that it did) and Einstein called his failure to imagine an expanding universe the biggest blunder of his life. Until recently, most cosmologists preferred to assume that the value of the cosmological constant was zero, which meant there was no repulsive force associated with space itself.
The new observations of an accelerating universe imply that this is no longer an option. The cosmological constant can't be equal to zero if space itself is to be the origin of a repulsive force more than strong enough to balance gravitational attraction.
And now for the so what?: Can such esoteric ideas, originating so far away, have any relevance to everyday life?
I can't really answer that. But I will point out that the proposed vacuum energy is present here on Earth, as well as in remote locations. And notions equally abstract, published by Einstein in 1905 and concerning the nature of space and time, led very directly to atomic energy and the atomic bomb. That development took less than forty years. If history is any guide, many of us might live to see practical consequences of a non-zero cosmological constant.
A.12. Nothing but blue skies . . . Let me describe a condition: it is a physical disability that affects more than twenty million Americans; it is usually congenital, and almost always incurable; it is at best a nuisance, and it is at worst life-threatening.
You might think that such an ailment would be a major item on the agenda of the National Institutes of Health, perhaps even the subject of a Presidential Commission to seek urgent action.
No such thing. The condition I have described is color blindness. It is strongly sex-linked. One man in every twelve suffers from it to some extent, compared with only one woman in two hundred. And the whole subject enjoys little attention.
Part of the reason for our lack of emphasis on color blindness is its invisibility. You can't tell that a man has such a disability, though his choice of shirt and matching tie may be a bit of a giveaway. In fact, you may suffer some form of it yourself and become aware of that fact only in special circumstances. In my own case I have difficulty distinguishing blues and greens, but I only notice it when playing "Trivial Pursuit"; then I am never sure if I have a blue or a green question coming.
A more commonand a more dangerousform cannot distinguish red from green. John Dalton, the chemist, a colorblind person and one of the first people to write about it, reported that "blood looks like bottle-green and a laurel leaf is a good match for sealing wax." In more modern times, sufferers are forced to distinguish the condition of traffic lights by their vertical placement, and they are at risk in situations where a red "Stop" light or a green "Go" light offers no other information to back it up.
The problem originates in the retina, at the back of our eyes. The retina contains two different kinds of light-sensitive objects, each microscopic in size. The retinal rods do not perceive color at all, and they are most useful at low light levels. The retinal cones are responsible for all color vision, but they need a higher light level before they become sensitive. Recall that, on a moonlit walk, your surroundings are rendered only in black and white.
In a person with normal vision, the signals generated by the cones and transmitted by nerve cells to the brain permit all color to be distinguished. If you are color blind, however, certain colors will produce the same signals as each other. Green and red may be confused, or pale green and yellow, or, in my case, certain greens and blues.
Unlike some other conditions, color blindness has few compensating advantages. In a military situation, a color blind person may detect camouflage which fools ordinary eyes, but in general, color blindness is nothing but a nuisance. So can we do anything about it?
As I said at the beginning, this disability is usually incurable. It can, however, often be alleviated by the use of special eyeglasses. These contain filters that modify the light passing through them, in such a way that they convert different colors to combinations that the wearer can perceive.
That's today, and even if impressive it's pretty crude. Twenty years from now we will be able to go much farther, with personalized "false color" eyeglasses. These will employ sensors and displays that transform any light falling on them into color regions for which the wearer's retina is able to generate distinguishable signals.
You might argue that a person with such eyeglasses is still color blind, because his perception of blue, green, or red will be different from yours. If you make this point, I will ask the question: how do you know that what you perceive when you see colors is at all the same as other people's?
A.13. Thinking small. The launch of a space shuttle is an impressive event. It is impressively big, impressively noisy, and impressively expensive. During the first few minutes of ascent, energy is used at a rate enough to power the whole United States. Most of us love fireworks, and I have never met anyone who did not enjoy watching this fireworks display on the grandest scale.
On the other hand, is this a necessary display of size and power? We are in the habit of thinking that sending something into space requires a vast and powerful rocket, but could we be wrong?
We could, and we are. Most of our preconceived ideas about rocket launches go back to the early days of the "space race" between the United States and the Soviet Union, and in the 1950s and 1960s the name of the game was placing humans into orbit. There were good psychological and practical reasons for wanting to send astronauts and cosmonauts. First, the public is always far more interested in men than in machines; and second, the computers of the early days of the space program were big, primitive and limited in what they could do. People, by contrast, possessedand possessfar more versatility than any computer, and can perform an endless variety of tasks.
On the other hand, people come in more-or-less standard sizes. They also need to eat, drink and breathe. Once you decide that humans are necessary in space, you have no alternative to big rockets; but today's applications satellites, for communications, weather observation, and resource mapping, neither need nor want a human presence.
As computers become smarter and more powerful, they are also shrinking in size and weight. The personal computer in your home today is faster and has far more storage than anything in the Apollo program spacecraft. Other electronics, for observing instruments and for returning data to the ground, is becoming micro-miniaturized. Payloads can weigh less. So how bigor how smallcan a useful rocket be?
We are in the process of finding out. Miniature thrust chambers for rocket engines have already been built, each one smaller and lighter than a dime. A group of about a hundred of these should be able to launch into orbit something about the size of a Coke can. That's more than big enough to house a powerful computer, plus an array of instruments. One of these "microsats" could well become an earth resources or weather observing station.
We are at the very beginning of thinking small in space. How small might we go? Since our experience with space vehicles is limited, let us draw an analogy with aircraft. Today's aircraft, like today's spacecraft, are designed to carry people. Suppose, however, that we just want a flying machine that can carry a small payload (maybe a few grams, enough for a powerful computer). How small and light can it be? We don't have a final answer to that question, although today a jet engine the size of a shirt button is being built at MIT. However, Nature provides us with an upper limit on size. Swallows, weighing just a few ounces, every year migrate thousands of miles without refueling. We should be able to do at least this well.
And if you want to think really small, look at what the swallows eat: flying insects, each with its own on-board navigation and observing instruments. Imagine a swarm of space midges, all launched on a rocket no bigger than a waste paper basket, each one observing the Earth or the sky and returning their coordinated observations back to the ground. Imagination could become reality in less than half a century.
A.14. New maps for old. Map-making in ancient times was not a job for the faint-hearted.
Even without the early worries of going too far and sailing off the edge of the world, anyone interested in determining the positions of land masses and shore lines had to face the dangers of reefs, shoals, storms at sea, scurvy, shipwreck, and starvation. Perhaps even worse were the hostile natives met along the way, who killed, among others, the famous explorers Ferdinand Magellan and Captain James Cook.
Mapping the interior of a country was just as difficult. The hardy surveyor had to face deserts, glaciers, avalanches, impassable rivers, infectious diseases, dangerous animals, and still more hostile natives.
And yet maps were early recognized as vitally important. Within settled countries they were needed to define property ownership, set taxes, measure land use, and establish national boundaries. Farther afield, the lack of good maps and accurate knowledge of position led to countless shipwrecks. In 1707, an English fleet commanded by the splendidly-named Sir Cloudesley Shovel made an error in navigation, ran ashore on the Scilly Isles which they thought were many miles away, and lost more than two thousand sailors.
Why was map-making so hard? It sounds easy. All you need to define a point on the surface of the Earth uniquely are three numbers: latitude, longitude, and height above some reference surface (usually sea-level). Measure a few thousand or tens of thousands of such points, and you have an accurate map of the Earth.
Unfortunately, it was difficult verging on impossible to determine absolute locations. The fall-back position was to measure relative locations. Starting with a baseline a few miles long, a distant point was identified, and accurate angles from each end of the baseline were measured. This allowed the other two sides of the triangle to be calculated; from these as new baselines, new angle measurements led to more triangles, which led to still more triangles, until finally the whole country or region was covered by a network. In practice, because there could be small errors in each measurement, all the angles and lengths in the network were adjusted together to produce the most consistent result.
What we describe sounds straightforward, but the amount of measurement and computation in a large mapping survey was huge. The calculations were, of course, all done by hand. A survey of this type could take years, or even decades. There was also no substitute for going out and making ground measurements. Even fifty years ago, it was possible for a leading expert on maps to declare, with perfect confidence, "there is only one way to compile an accurate map of the earth . . . and that is to go into the field and survey it."
Today, that is not the case at all. The new generation of map-makers sit in their offices, while far above them, satellites look down on the Earth and send back a continuous stream of images revealing details as small as a few feet across. In perennially cloudy regions, spaceborne radar systems see through to the ground below. The location of the images is known fairly well, but not accurately enough to make good maps. However, the images can be cross-referenced, by identifying common ground features on neighboring and overlapping images. Also, the position of selected points on the ground can be found absolutely, to within a few tens of meters, using another satellite system known as GPS (the Global Positioning System).
Finally, all the image data and all the cross-reference data can be adjusted simultaneously, in a computer calculation of a size that would have made all early map-makers blench. The result is not just a map of the Earthit is an accurate map and a recent map, in which a date can be assigned to any observed feature.
As the people involved in this will tell you, it is still hard workbut it sure beats cannibals and shipwrecks.
A.15. The ears have it. I am one of those unfortunate people who have trouble singing the "Star-Spangled Banner." It's not that I don't know the tune, it's that my useful vocal range is only about one octave. The National Anthem spans an octave and a half. No matter where I start with "Oh say can you see," by the time I get to "the rockets' red glare" I sound like a wolf baying at the moon.
I comfort myself with the thought that humans are primarily visual animals. Eighty percent, maybe even ninety percent, of the information that we receive about the world comes to us as visual inputs. Bats, by comparison, depend mainly on sound, "seeing" the world by echolocation of reflected sound signals that they themselves generate. And as for the other senses, any dog owner will tell you that an object without a smell counts as little or nothing in the canine world.
Being human, we have a tendency to argue for the superiority of "our" primary way of perceiving the world. After all, we have stereoscopic, high-definition, full color vision, and that's a rare ability in the animal kingdom. But would an intelligent bat agree with us, or would it be able to make a good case for its own superior form of perception?
Let's compare sound and light. They may seem totally different, but they have many similarities. Both travel as wave forms, and both can be resolved into waves of different single frequencies (colors, in the case of light). The note that we hear as middle C has a wavelength of a little more than four feet, whereas what we see as the color yellow has a wavelength of only one twenty-millionth of that. Also, sound waves need somethingair, water, metalto travel through, while light waves travel perfectly well through a vacuum. No bat can ever see the stars. However, I would argue that these are unimportant differences. We have equipment that can readily translate sounds to light, or convert different colored light to sounds.
Our intelligent bats would agree with all of this; but what they would point out, quite correctly, is that our visual senses lack range. We can hear, with no difficulty, sounds that go all the way from thirty cycles a second, the lowest note on a big pipe organ, to fifteen thousand cycles a second, beyond the highest note of the piccolo. That is a span of nine octaves (an octave is just the doubling of the frequency of a note). Compare this with our eyesight. The longest wavelength of visible light (dark red) is not quite twice the wavelength of the shortest light that our eyes can detect (violet). The range of what we can see is less than one octave. If we were to convert "The Star-Spangled Banner" to equivalent light, not a person on earth would be able to see the whole thing.
Why can we observe such a limited range of wavelengths, while hearing over a vastly greater one? It is a simple matter of the economy of nature. Our eyes have adapted over hundreds of millions of years to be sensitive in just the wavelength region where the sun produces its maximum illumination. The amount of radiation coming from the sun falls off rapidly in the infrared, at wavelengths longer than what we can see, while waves much shorter than violet are absorbed strongly by the atmosphere (lucky for us, or we would fry).
Of course, being the inventive monkeys that we are, humans have found ways around the natural limitations of our eyes. Today we have equipment that provides pictures using everything from ultra-short X-rays to mile-long radio waves. We roam the universe, from the farthest reaches of space to the insides of our own bodies. With the help of our instruments, we can observe not just nine or ten octaves, but more than forty. Let's see the bats match that one.
A.16. Memories are made ofwhat? Over the years I have met many people in many professions: actors, writers, biologists, computer pioneers, artists, astronomers, composers, even a trio of Nobel Prize winners in physics. They had numerous and diverse skills. What none of them had was a good memory. Or rather, what none of them would admit to was a good memory. Their emphasis was the other way round: how hard it was to recall people's faces, or names, or birthdays, or travel directions.
History records examples of people with prodigious memories. Mozart, at thirteen, went to the Sistine Chapel in Rome to hear a famous Miserere by Allegri, then wrote out the whole work. The mathematician, Gauss, did not need to look up values in logarithm tables, because he knew those tables by heart. And Thomas Babington, Lord Macaulay, seemed to have read so much and remembered it so exactly that one of his exasperated colleagues, Lord Melbourne, said, "I wish I was as cocksure of anything as Tom Macaulay is of everything."
To the rest of us, hard-pressed to remember our own sister's phone number, such monster memories seem almost inhuman. My bet, however, is that even these people would, if asked, complain of their poor memories and emphasize what they forgot. And each of us, without ever thinking about it, has enormous amounts of learned information stored away in our brain.
I say "learned information," because some of what we know is hard-wired, and we call that instinct. We don't learn to suck, to crawl, or to walk by committing actions to memory, and we normally reserve the word "memorize" to things that we learn about the world through observation and experience. I am going to stick with this distinction between instinct and memory, though sometimes the borderline becomes blurred. We don't remember learning to talk, but we accept that it relies on memory because others tell us we did (though there is good evidence that the ability to acquire language is hard-wired). And most of us would not say that riding a bicycle depends on memory, although clearly this is a learned and not an inborn activity.
I want to concentrate on factual information that is definitely learned, stored, and recalled, and ask two simple questions: Where is it stored, and how is it stored?
The easy part first: information is stored in the brain. But when we ask where in the brain, and ask for the form of storage, we run at once into problems. The tempting answer, that a piece of data is stored in a single definite location, as it would be in a computer, proves to be wrong. Although many people believe that the brain ultimately operates like a computera "computer made of meat"in this case the analogy is more misleading than helpful.
Much of what we know about memory comes from the study of unfortunate individuals with brains damaged by accident or disease. This is hardly surprising, since volunteers for brain experiments are hard to come by (as Woody Allen remarked, "Not my brain. It's my second favorite organ."). Studies of abnormal brains can be misleading, but they show unambiguously that a human memory does not sit in a single defined place. Rather, each memory seems to be stored in a distributed form, scattered somehow in bits and pieces at many different physical locations. Although ultimately the information must be stored in the brain's neurons (we know of nowhere else that it could be stored), we do not yet understand the mechanism. Some unknown process hears the question, "Who delivered the Gettysburg address?", goes off into the interior of the brain, finds and assembles information, and returns the answer (or occasionally, and frustratingly, fails to return the answer): "Abraham Lincoln."
And it does the job fast. The brain contains a hundred billion neurons, but the whole process, from hearing the question to retrieving and speaking the answer, takes only a fraction of a second.
We may not be Mozart, but each of us possesses an incredible ability to store and recall information. And are we impressed by this? Not at all. Instead of being pleased by such a colossal capability, we are like the celebrated Mr. X, always complaining about his sieve-like memory.
I would give Mr. X's name, but at the moment I cannot quite recall it.
A.17. In defense of Chicken Little. Chicken Little wasn't completely wrong. Some of the sky does fall, some of the time. When a grit-sized particle traveling at many miles a second streaks into the Earth's atmosphere and burns up from friction with the air before reaching the ground, we call it a shooting star or a meteor. Some of us make a wish on it. We think of meteors as harmless and beautiful, especially when they come in large groups and provide spectacular displays such as the Leonid and Perseid meteor showers.
Meteors, however, have big brothers. These exist in all sizes from pebbles to basketballs to space-traveling mountains. If the speeding rock is large enough, it can remain intact all the way to the ground and it is then known as a meteorite. The reality of meteorites was denied for a long timeThomas Jefferson said, "I could more easily believe that two Yankee professors would lie than that stones would fall from heaven"but today the evidence is beyond dispute.
If one of these falling rocks is big enough, its great speed gives it a vast amount of energy, all of which is released on impact with the Earth. Even a modest-sized meteorite, twenty meters across, can do as much damage as a one-megaton hydrogen bomb. This sounds alarming, so let us ask three questions: How many rocks this size or larger are flying around in orbits that could bring them into collision with the Earth? How often can impact by a rock of any particular size be expected? And how does damage done vary with the size of the meteorite?
Direct evidence of past impacts with Earth is available only for large meteorites. For small ones, natural weathering by wind, air, and water erases the evidence in a few years or centuries. However, we know that a meteorite, maybe two hundred meters across, hit a remote region of Siberia called Tunguska, on June 30, 1908. It flattened a thousand square kilometers of forest and put enough dust into the atmosphere to provide colorful sunsets half a continent away. About 20,000 years ago, a much bigger impact created Meteor Crater in Arizona, more than a kilometer across. And 65 million years ago, a monster meteorite, maybe ten kilometers across, struck in the Gulf of Mexico. It caused global effects on weather, and is believed to have led to the demise of the dinosaurs and the largest land reptiles.
The danger of impact is real, and beyond argument. But is it big enough for us to worry about? After all, sixty-five million years is an awfully long time. How do we make an estimate of impact frequency?
The answer may seem odd: we look at the Moon. The Moon is close to us in space, and hit by roughly the same meteorite mix. However, the Moon is airless, waterless, and almost unchanging, so the history of impacts there can be discovered by counting craters of different sizes. Combining this with other evidence about the general size of objects in orbits likely to collide with Earth, we can calculate numbers for frequency and energy release. They are not totally accurate, but they are probably off by no more than a factor of three or four.
I will summarize the results by size of body, and translate that to the equivalent energy released as number of megatons of H-bombs. About once a century, a "small" space boulder about five meters across will hit us and produce a matching "small" energy equal to that released by the Hiroshima atomic bomb. It will probably burn up in the atmosphere and never reach the ground, but the energy release will be no less. Once every two thousand years, on average, we will get hit by a twenty-meter boulder, with effects a little bigger than a one-megaton H-bomb. Every two million years, a five-hundred-meter giant will arrive, delivering as much energy as a full-scale nuclear war.
I found these numbers disturbing, so a few years ago I sent them to the late Gene Shoemaker, an expert on the bombardment of Earth by rocks from space. He replied, not reassuringly, that he thought my numbers were in the right ballpark, but too optimistic. We will be hit rather more often than I have said.
Even if I were exactly right, that leaves plenty of room for worry. Being hit "on average" every 100,000 years is all very well, but that's just a statistical statement. A big impact could happen any time. If one did, we would have no way to predict it, ordespite what recent movies would have you believeprevent it.
A.18. Language problems and the Theory of Everything. A couple of weeks ago I received a letter in Spanish. I don't know Spanish. I was staring at the text, trying and failing to make sense of it by using my primitive French, when my teenage daughter wandered by. She picked up my letter and cockily gave me a quick translation.
I was both pleased and annoyedaren't I supposed to know more than my children?but the experience started me thinking: about language, and the importance of the right language if you want to do science in general, and physics in particular.
Of course, every science has its own special vocabulary, but so does every other subject you care to mention. Partly it's for convenience, although sometimes I suspect it's a form of job security. Phrases like "stillicide rights," "otitis mycotica," and "demultiplexer" all have perfectly good English equivalents, but they also serve to sort out the insiders from the outsiders.
One subject, though, is more like an entire language than a special vocabulary, and we lack good English equivalents for almost all its significant statements. I am referring to mathematics; and, like it or not, modern physics depends so heavily on mathematics that non-mathematical versions of the subject mean very little. To work in physics today, you have to know the language of mathematics, and the appropriate math vocabulary and methods must already exist.
On the face of it, you might think this would make physics an impossibly difficult subject. What happens if you are studying some aspect of the universe, and the piece of mathematical language that you need for its description has not yet been invented? In that case you will be out of luck. But oddlyalmost uncannilythroughout history, the mathematics had already been discovered before it was needed in physics.
For example, in the seventeenth century Kepler wanted to show that planets revolved around the Sun not in perfect circles, but in other more complex geometrical figures. No problem. The Greeks, fifteen hundred years earlier, had proved hundreds of results about conic sections, including everything Kepler needed to know about the ellipses in which planets move. Two hundred years later, Maxwell wanted to translate Michael Faraday's experiments into a formal theory. The necessary mathematics, of partial differential equations, was sitting there waiting for him. And, to give one more example, when Einstein's theory of general relativity needed a precise way to describe the properties of curved space, the right mathematics had been created by Riemann and others and was already in the text books.
Of course, there can be no guarantee that the mathematical tools and language you want will be there when you need it. And that brings me to the central point of this column. One of the hottest subjects in physics today is the "Theory Of Everything," or TOE. The "Everything" promised here is highly limited. It won't tell you how a flower grows, or explain the IRS tax codes. But a TOE, if successful, will pull together all the known basic forces of physics into one integrated set of equations.
Now for the tricky bit. The most promising efforts to create a TOE involve something known as string theory, and they call for a description of space and time far more complicated than the height-width-length-time we find adequate for most purposes. The associated mathematics is fiendishly difficult, and is not just sitting in the reference books waiting to be applied. New tools are being created, by the same people doing the physics, and it is quite likely that these will prove inadequate. The answers may just have to wait, until, ten or fifty years from now, the right mathematical language has been evolved and can be applied.
It's one of my minor personal nightmares. Mathematics, more than almost any other subject, is a game played best by the young. Suppose that, five or fifteen years from now, we have a TOE that explains everything from quarks to quasars in a single consistent set of equations. It will, almost certainly, require for its understanding some new mathematical language. By that time I may just be too old or set in my ways ever to learn what's needed.
It's a dismal prospect. You wait your whole life for something, and then when it finally comes along you find you can't understand it.
A.19. Fellow travelers. My mother grew up in a household with nine children and little money. Not much was wasted. Drop a piece of food on the floor and you picked it up, dusted it off, and ate it. This doesn't seem to have done my mother much harm, since she is still around at ninety-seven. Her philosophy toward food and life can be summed up in her comment, "You eat a peck of dirt before you die."
Contrast this with the television claim I heard a couple of weeks ago: "Use this product regularly, and you will rid yourself and your house completely of germs and pests."
The term "pest" was not described. It probably didn't include your children's friends. But whatever the definition, the advertisers are kidding themselves and the public by making such extravagant claims. Your house, and you yourself, are swarming with small organisms, whose entry to either place was not invited but whose banishing is a total impossibility.
I have nothing against cleanliness, and certainly no one wants to encourage the presence in your home of the micro-organisms that cause cholera, malaria, bubonic plague, and other infectious diseases. Such dangers are, however, very much in the minority. Fatal diseases are also the failures among the household invaders. What's the point of invading a country, if the invasion makes the land uninhabitable? In our case, that amounts to the organism infecting and killing its host. Successful invaders don't kill you, or even make you sick. The most successful ones become so important to you that you could not live without them.
Biologists set up a hierarchy of three types of relationship between living organisms. When one organism does nothing but harm to its host, that's called parasitism. In our case, this includes things like ringworm, pinworms, athlete's foot, ticks, and fleas. All these have become rarer in today's civilized nations, but most parents with children in elementary school have heard the dread words "head lice," and have probably dealt with at least one encounter.
Parasites we can do without. This includes everything from the influenza virus, far too small to see, to the tapeworm that can grow to twenty feet and more inside your small intestine.
Much more common, however, are the creatures that live on and in us and do neither harm nor good. This type of relationship is known to biologists as commensalism. We provide a comfortable home for tiny mites that live in our eyelashes, to others that dine upon cast-off skin fragments, and to a wide variety of bacteria. We are unaware of their presence, and we would have great difficulty ridding ourselves of them. It might even be a bad idea, since we can't be sure that they do not serve some useful function.
And then there is symbiosis, where we and our fellow-traveling organisms are positively good for each other. What would happen if you could rid yourself of all organisms that do not possess the human genetic code?
The answer is simple. You would die, instantly. In every cell of your body are tiny objects called mitochondria. They are responsible for all energy generation, and they are absolutely essential to your continued existence. But they have their own genetic material and they reproduce independently of normal cell reproduction. They are believed to be bacteria, once separate organisms, that long ago entered a symbiotic relationship with humans (and also with every other animal on earth).
If the absence of mitochondria didn't kill you in a heartbeat, you would still die in days. We depend on symbiotic bacteria to help digest our food. Without them, the digestive system would not function and we would starve to death.
"We are not alone." More and more, we realize the truth of that statement. We are covered on the outside and riddled on the inside by hundreds of different kinds of living organisms, and we do not yet understand the way that we all relate to each other. For each, we have to ask, is this parasitism, commensalism, or symbiosis?
Sometimes, the answers are surprising. Twenty years ago, gastric ulcers were blamed on diet or stress. Today, we know that the main cause is the presence in the stomach of a particular bacterium known as Helicobacter pylori. Another organism, Chlamydia, is a suspect for coronary disease and hardening of the arteries. A variety of auto-immune diseases may be related to bacterial action.
All these facts encourage a new approach for biologists and physicians: The best way to study humans is not as some pure and isolated life form; rather, each of us should be regarded as a "superorganism." The life-cycles and reproductive patterns of us and all our fellow travellers should be regarded as one big interacting system.
Disgusting, to be lumped in with fleas and mites and digestive bacteria, as a single composite object? I don't think so. In a way it's a comforting thought. We are not alone, and we never will be.
A.20. How do we know what we know? At the moment there is a huge argument going on about the cause of AIDS. Most people in this countrybut by no means allbelieve that the disease is caused by a virus known as HIV, the Human Immunodeficiency Virus. In Africa, however, heads of governments have flatly stated that they don't accept this. They blame a variety of other factors, from diet to climate to genetic disposition.
The available scientific evidence ought to be the same for everyone. So how can there be such vast differences in what people believe?
Part of the reason is what we might call the "Clever Hans" effect. Clever Hans was a horse who lived in Germany early in the twentieth century, and he seemed to be smarter than many of the humans around him. He could answer arithmetic problems by tapping out the correct answers with a fore-hoof, and give yes or no answers to other questionsIs London the capital of France?by shaking or nodding his head, just like a human.
His owner, a respected Berliner named Wilhelm von Osten, was as astonished as anyone by Clever Hans' abilities. There seemed no way that he would commit fraud, particularly since Clever Hans could often provide correct answers when von Osten was out of the room, or even in a different town. The Prussian Academy of Sciences sent an investigating committee, and they too were at first amazed by the horse's powers. True, there were inconsistencies in the level of performance, but those could often be explained away.
Finally, almost reluctantly, the truth was discovered. Clever Hans could not do arithmetic, and did not know geography and history. He was responding to the body language of the audience. Most observers, including members of the investigating committee, wanted Hans to get the right answers. So they would instinctively tense at the question, and relax when Hans gave the right answer. The body movements were very subtle, but not too subtle for Hans. He really was cleverclever at reading non-verbal cues from the humans around him.
We are no different from the groups who met Clever Hans. We all want certain answers to be true. Given a mass of evidence, we tend to notice the facts that agree with our preferences, while explaining away the inconvenient ones that would tell us otherwise. And AIDS is a disease so complex and so widespread that you can find what appear to be exceptions to any general rules about its cause, spread, or inevitable effects.
That, however, is only half the story. The other reason there can be such intense arguments about AIDS applies equally well to half the thingsor maybe today it's ninety-nine percent of the thingsin our lives. We have actual experience in certain areas: boiling water hurts; you can jump off a ten-foot ladder but you can't jump back up; the moon will be full about once a month; it's colder in winter than in summer; coffee with salt instead of sugar tastes terrible.
But there are a million other things in everyday life for which we have no direct experience and explanation. Can you tell me how a digital watch works? Why is a tetanus shot effective for ten years, while even with an annual flu shot you are still likely to get the flu? What does that computer of yours do when you switch it on? How does e-mail from your computer travel across the country to a friend on the opposite coast, or halfway around the world? Just what is plastic, and how is it made? How does your refrigerator work? When you flip a light switch, where does the electricity come from? It's not like turning on a faucet, where we know that somewhere a huge reservoir of water sits waiting to be tapped. So how come the electricity is there just when you need it?
I can give answers to these, in a hand-waving sort of fashion, but if I want any sort of details I have to go and ask questions of specialists whom I trust. And most of the questions that I've just asked are not new, or even close to new. The refrigerator was patented in 1834. The first plastics, like our electricity supply, go back to the beginning of the twentieth century.
Good answers are available to every one of my questions, all we have to do is seek them out. But what about the newer areas of research, for which AIDS forms a fine example? When the experts themselves are still groping their way toward understanding, and still disagreeing with each other, what chance do the rest of us have?
Not much, provided that we insist on direct evidence. Every one of us must decide for ourselves who and what to believe. We, like the audience of Clever Hans, are going to believe what we want to believe until evidence to the contrary becomes awfully strong.
And maybe even after that. We, as ornery humans, tend to go on believing what we prefer to believe.
A.21. Where are they? Our "local" galaxy contains about a hundred billion stars. We see only a few thousand of the closest as actual points of light, though millions of others merge into a broad and diffuse glow that we notice on clear nights and call the Milky Way.
A hundred billion is such a big number that it's hard to have a real feel for it, so let's put it this way: there are enough stars in our galaxy for every human on earth to own sixteen apiece. Not only that, our galaxy is just one of the hundred billion galaxies that make up the known universe. If humans owned the whole cosmos, each of us could lay claim to more than a trillion stars. That's the astronomical equivalent of everyone being owed the National Debt, with each star and its planets priced at about a dollar.
Of course, there's a big "if" in there. We can only claim the universe if no others are out there to stake counterclaims and assert property rights. Which leads to the big question: Are there other living beings in the universe, at least as intelligent as we are; or are we the only smart, self-aware objects in creation? As the late Walt Kelly remarked, long ago, either way it's a mighty sobering thought.
Some people insist that intelligent aliens in the universe have appeared right here on Planet Earth, occasionally taking selected individuals for a space ride but otherwise keeping a low profile. I am not in that group of believers. I can't see why anyone would bother to travel such gigantic distances and then remain in hiding. The idea that aliens have actually crash-landed in remote parts of the country, and had their presence covered up by the government, has even less appeal. If anywhere, Washington, D.C., is the place to look for aliens.
Let's take another approach. We have a rough idea of the total number of stars in all the galaxies. How many of those stars have planets? Ten years ago we had no direct evidence of any, but today some new planet around another star is discovered at least once a month. Suppose, then, that only one star in a thousand has a planet around ita very low estimate. That still gives us a hundred million planets as candidates right here in our own galaxy. If just one percent of those can support life, a million other worlds have living things on them.
The next step is the hardest one. If a world has life, what are the chances that one of those living creatures will develop intelligence and technology, enough to build a starship, or at least to send out a signal to us?
We don't know. Let me state that more strongly: we have not the slightest idea. But we can listen, and we do, for evidence of alien existence. We listen not with sound waves, but with radio waves. For the past forty years, a search for extraterrestrial intelligence (SETI) program has been carried on in this country and around the world. Using radio telescopes capable of picking up the tiniest trickle of energy, we eavesdrop on the sky and hope to discover the organized series of pulses that would announce the presence of other thinking beings.
So far we have found nothing. This is sometimes called the Great Silence, sometimes the Fermi Paradox (Fermi asked the simple question, "Where are they?"). On the other hand, forty years of listening is no time at all in a universe at least ten billion years old, particularly since the SETI program is run on a shoestring. It has no government funding. It is paid for and operated by people who believe that a positive result to the search would change the way we think about everything.
Speaking for myself, I would just love to change the way we think. For instance, if we were willing to spend as much money listening to the stars as we do on, say, land mines, we might detect and decipher that world-altering message from the sky.
Are we alone in this galaxy, as an intelligent life form? It is hard to imagine a more profound question. I'd gladly give up any claim to the trillion-plus stars that represent my share of the universe, to know the answer.
And while I'm at it, I'll gladly give up my share of land mines.
Note: If you own a personal computer and a modem, you can become directly involved in analyzing radio data that may contain evidence of alien signals. Contact me if you would like to know how.