Hubble Space Telescope

The Hubble Space Telescope, the most productive scientific instrument of all time, is slated for its fifth and final repair mission later this year. The space shuttle astronauts will launch from Kennedy Space Center, Fla., match orbits with the telescope, capture it, service it, upgrade it, and replace its broken parts—on the spot.

Roughly the size of a Greyhound bus, Hubble was launched aboard the space shuttle Discovery in 1990 and already has outlived its 15-year life expectancy. Students in high school today have never known a time without Hubble as their conduit to the cosmos. This new servicing mission will extend Hubble's life several more years. It also will replace burned-out circuit boards to the Advanced Camera for Surveys. That's the instrument responsible for Hubble's most memorable images since it was installed in 2002.

Servicing Hubble is a task that requires exquisite dexterity. Filmed as part of a PBS NOVA segment on the Hubble repair mission, I recently had the opportunity to visit NASA's Goddard Space Flight Center in Maryland. There, I donned puffy, pressurized astronaut gloves, wielded a space-age portable screwdriver, stuck my head in a space helmet, and attempted to extract a faulty circuit board in a model of the Advanced Camera for Surveys, which was embedded within a full-scale mockup of the Hubble Telescope. This was a darn-near impossible feat. And I wasn't weightless. I was not wearing the full-body spacesuit. Nor were Earth and space drifting by.

We normally think of astronauts as brave and noble. But, in this case, having the right stuff includes being a hardware surgeon extraordinaire.

Perhaps you didn't know, but Hubble is not alone up there. About two dozen space telescopes of assorted sizes and shapes orbit Earth and the Moon. Each of them provides a clear view of the cosmos that is unobstructed, unblemished, and undiminished by Earth's turbulent and murky atmosphere. But most of these telescopes were launched with no means of servicing them. Parts wear out. Gyroscopes fail. Batteries die. These hardware realities limit a telescope's life expectancy to anywhere from three to seven years.

These telescopes all advance science, but most perform their duties without the public's awareness or adulation. They are designed to detect bands of light invisible to the human eye, some of which never penetrate Earth's atmosphere. Entire classes of objects and phenomena in the cosmos reveal themselves only through one or more of these invisible cosmic windows. Black holes, for example, were discovered by their X-ray calling card—radiation that was generated by the surrounding, swirling gas just before it descended into the abyss. Telescopes also have captured microwave radiation—the primary physical evidence for the Big Bang.

Hubble, on the other hand, is the first and only space telescope to observe the universe using primarily visible light. Its stunningly crisp, colorful, and detailed images of the cosmos make Hubble a kind of supreme version of human eyes in space. Yet Hubble's appeal to us comes from much more than parades of pretty portraits. Hubble came of age in the 1990s, during an exponential growth of access to the Internet. That's when its digital images were first cast into the public domain. As we all know, anything that's fun, free, and forwardable spreads rapidly online. Hubble images, one more splendorous than the next, became screen savers and desktop wallpaper for computers owned by people who never before would have had the occasion to celebrate, however quietly, our place in the universe.

Indeed, Hubble brought the universe into our backyard. Or, rather, it expanded our backyards to enclose the universe itself. It did that with images so intellectually, visually, and even spiritually fulfilling that most don't even need captions. No matter what Hubble reveals—planets, dense star fields, colorful interstellar nebulae, deadly black holes, graceful colliding galaxies, the large-scale structure of the universe—each image establishes your own private vista on the cosmos.

Hubble's scientific legacy is unimpeachable. More research papers have been published using its data than have ever been published for any other scientific instrument in any discipline. Among Hubble's highlights is settling the decades-old debate about the age of the universe. Previously, the data were so bad that astrophysicists could not agree. Some thought 10 billion years. Others, 20 billion. Yes, it was embarrassing. But Hubble enabled us to measure accurately how the brightness varies in a particular type of star that resides in a distant cluster of galaxies. That information, when plugged into a simple formula, tells us their distance from Earth. And because the entire universe is expanding at a known rate, we can then turn back the clock to determine how long ago everything was in the same place. The answer? The universe was born 14 billion years ago.

Another result, long suspected to be true but confirmed by Hubble, was the discovery that every large galaxy, such as our own Milky Way, has a supermassive black hole in its center that dines on stars, gas clouds, and other unsuspecting matter that wanders too close. The centers of galaxies are so densely packed with stars that Earth-based telescopes see only a mottled cloud of light—the merged image of hundreds or thousands of stars. From space, Hubble's sharp imagery allows us to see each star individually and to track its motion around the galactic center. Behold, these stars move much, much faster than they have any right to. A small, unseen yet powerful source of gravity must be tugging on them. Crank the equations, and we are forced to conclude that a black hole lurks in their midst.

In 2005, the Bush Administration announced that Hubble would not receive the needed funds for this last servicing mission. Curiously, the loudest voices of dissent were not from the scientists but from the general public. Akin to a modern version of a torch-wielding mob, angry editorials, snippy letters to the editor, and no end of radio and television talk shows all urged NASA to restore the funding and keep Hubble alive. Congress ultimately listened and reversed NASA's decision. Democracy had a shining moment: Hubble would indeed be serviced, one last time. For the first time in the history of civilization, the public took ownership of a scientific instrument—they took ownership of the Hubble Space Telescope.

Of course, nothing lasts forever—except, perhaps, the universe itself. So Hubble eventually will die. But in the meantime, NASA is building the James Webb Space Telescope, specially designed to see deeper into the universe than Hubble ever could. When launched early next decade, it will allow us to plumb the depths of gas clouds in our own Milky Way galaxy in search of stellar nurseries, as well as probe the earliest epochs of the universe in search of the formation of galaxies themselves.

Meanwhile, NASA plans to retire the aging space shuttle by 2010. This step will enable its aerospace engineers, assembly lines, and funding streams to focus on a new suite of launch vehicles that will do what the shuttles are not designed to do—return us to the Moon and take us on to Mars and beyond.

The march of discovery continues, driven by our timeless and collective urge to explore.

Every now and then, a single photograph appears in the press that somehow forces you to take pause and reassess your place in the universe. In the 1960s, the first photograph of Earth from space reminded us that, as geologists had been telling us for some time, land masses do not have political boundaries drawn upon them—we were all together on spaceship Earth. Then there was the well-publicized photograph of Earth-rise over the barren lunar horizon taken by the astronauts of Apollo 8, the first manned mission to orbit the Moon. Earth looked small, fragile, and distant—just another orb out there in space.

For me, one of the Hubble Space Telescope's recently released photographs, now known as the Hubble deep field, ranks among the world's most profound images. It seems to have the right ingredients. It is unfamiliar. It is otherworldly. And it lures me someplace I have never been before.

What makes the Hubble deep field so special? The image grants the viewer a peek at a remarkably detailed subset of the billions and billions of galaxies in the universe, captured in a time line that spans from the first few billion years after the big bang, all the way to the present. Astrophysicists have been peeking at the universe with telescopes for 400 years, so the act of peeking itself is nothing new. But what the Hubble Telescope provides (by virtue of its above-the-atmosphere venue) is the highest resolution, and thus the clearest view, of the universe ever achieved in the history of optical telescopes.

Many ground-based pictures already exist of the seemingly countless galaxies in the outer universe, but in all cases the galaxies appear as undistinguished smudges. If you had bad vision you would encounter a similar problem when you looked at a lawn: you are told it is a lawn; you know in your mind it is a lawn; but all you notice is a sea of green, and you are not forced to think deep thoughts about what's there. With good vision, however, the green lawn is revealed to be composed of multitudes of blades of grass. There are even insects crawling about. You are now forced to recognize the lawn to be a world unto itself.

The Hubble deep field is a small, specially chosen, random, boring patch of sky that covers less than one one-hundredth the area of the full moon. To be specially chosen, yet random, simply means that a random field was selected among all fields that: 1) could be monitored continuously by the Hubble Space Telescope, without the Sun or the Earth getting in the way; 2) was away from the plane of the Milky Way galaxy, where densely packed stars, gas and dust clouds obscure our view of the rest of the universe; 3) was void of bright stars that might become over-exposed; and 4) was not coincident with clusters of galaxies that have already been cataloged.

The Hubble deep field, a full-color image created from 342 repeated exposures, was taken by the Hubble Space Telescope during a continuous stretch of orbits that spanned ten consecutive days, which represents far more observing time than is ever granted to an individual research project. In practice, long exposures are created by adding together many repeated, shorter exposures. With each added image, objects in the field of view become more and more pronounced against the background, which enables dimmer and dimmer objects come into view. One of several reasons for this tactic is that if a hardware or software problem arises within a single image, then you still have all the rest of the images to add together, which may still enable you to accomplish your scientific objectives.

To observe with the Hubble normally requires that an astrophysicist write a detailed proposal that states and defends the scientific motivations of a project, the target objectives, and why the project must be accomplished from orbit rather than from the many available ground-based telescopes. The proposal is then reviewed and critiqued by a committee of peers and awarded observing time on the basis of merit. Often, more than twice as much observing time is requested than is available, so most proposals are awarded no time at all. But thanks to something called director's discretionary time, Robert Williams, the Director of the Space Telescope Science Institute, was able to do what nobody else would have been permitted to do: point the telescope in a random place just to see what's there.

At about 1/100 the area of the full moon, the Hubble deep field sampled only about 1/15,000,000 of the 41,000 square degrees of the entire sky. Even so, this single image reveals thousands galaxies. If we diligently count every one of them—from the large, bright ones, down to the small, faint ones—and then multiply the result by 15,000,000, we get a fast estimate for the total number of observable galaxies in the universe. When the Hubble deep field image was released, media accounts (based on the NASA press release that accompanied it) widely reported that there are five times as many galaxies in the universe than previously estimated, raising the count from 10 to 50 billion. Actually, even from fuzzy ground-based images, the estimates had already ranged from a lower limit of about 10 billion to an upper limit of about 100 billion, depending on how thoroughly you believed that the population of under-luminous dwarf galaxies had been counted. What the headlines should have said was that data from the Hubble deep field allow us to confidently raise the previous lower limit from 10 to 50 billion galaxies.

As you watch astrophysicists bandy billions, it may look as though we are clueless about the galactic contents of the universe. But when you consider that all numbers above a trillion (of which there are many) and all numbers below a billion, are not in the running, then the range in our ignorance is quite small.

For me, what is most striking about the Hubble deep field is the richness in morphology revealed in even the tiniest of galaxies. The photogenic spirals, kindred forms to our own Milky Way, show the characteristic central bulges and the knots of freshly made stars that dot the spiral arms. Each of these galaxies, however small they appear in the image, is its own collection of hundreds of billion of stars. There are other galactic forms such as elliptical and irregular galaxies. Though less photogenic, they too are part of the cosmic census.

The colors of galaxies are dominated by the colors of the most luminous resident stars. Bluish galaxies tend to have active areas where stars are forged; assortments of freshly made stars typically contain extremely hot (at least 20,000 kelvins), ultra luminous blue giants. Reddish galaxies contain relatively cool (3,000 kelvins), yet ultra luminous, red giant stars. In any galaxy, the absence of blue reveals the absence of stellar nurseries, which generally implies that the gas content (from which stars are made) was exhausted long ago.

But long ago is looking straight at us. On average, we expect the smaller galaxies to be farther away than the larger galaxies. And their light has been traveling longest in time to reach us. In other words, we see them not as they are, but as they used to be. As sedimentary deposits on Earth indicate a geological time line, distant objects betray a time long passed in the history of the universe. No new concepts here: Light from your elbow, provided it is where it belongs (hinged from your shoulder) is about a nanosecond (a billionth of a second) away in light travel time from your body's light detector known as the retina. The Moon: about 1.5 seconds away. The Sun: 500 light-seconds. The nearest star: 4.1 light years. The beautiful spiral galaxy M100: 65 million light years. (Yes, voyeuristic residents of M100 could now be watching Earth's dinosaurs go extinct.) Most of the galaxies in the Hubble deep field are billions and billions of light years away. The light we now see left their stars before single-celled life began on Earth. And in some cases, before Earth, itself.

With images of the quality of the Hubble deep field, one can even begin to test for evolutionary trends in galaxy colors. As stars are forged out of interstellar gas, less and less gas remains to create subsequent generations of stars. Eventually, stars stop forming. We would thus, on average, expect the more distant galaxies to be bluer than the nearby galaxies. A first estimate of the distances to these galaxies can be made from the Hubble data, but more reliable distances must be obtained from follow-up measurements. Until that happens, our evolutionary interpretation retains a level of uncertainty: are the smallest galaxies on the image small because they are normal-sized galaxies that happen to be far away? Or are they small because they are, indeed, dwarf galaxies that happen to be right in front of our noses? The real answer is likely to be some combination of these scenarios, with the distant galaxy description being the dominant of the two.

Let there be no misunderstanding: large, ground-based telescopes (such as the 10-meter Keck telescope in Hawaii) have detected galaxies as far away as the farthest galaxies in the Hubble deep field. Telescopes of the ten-meter class have over twenty times the light gathering power of the Hubble Space Telescope. But somehow, the relatively fuzzy, ground based images do not act as powerfully on my imagination. I am captured intellectually, but not emotionally. Only with sharp images am I viscerally reminded me that there are other worlds out there. Billions and billions of them.

In spite of the quality and beauty of the Hubble data, many scientific questions remain unanswered: Do we have the right to extrapolate what we learn from one postage stamp-sized region of the sky to the entire universe? How many more galaxies might have revealed themselves with an even longer exposure? How far away is the farthest galaxy? How soon after the big bang did galaxies form?

Many questions also remain that do not lend themselves to immediate scientific inquiry: Is there some undiscovered law of physics that will completely change our modern understanding of the cosmos the way Einstein's theories of relativity redefined our understanding of the physical universe? On planets around stars in the galaxies of the Hubble deep field, are there life forms that are contemplating the universe the way we are? Or are they not paying attention because they are just looking for shelter, food, and sex, as does most life on Earth?

As I galaxy-gaze through time upon their diversity of colors, shapes, sizes, brightnesses, and structural detail, the boundary between knowledge and ignorance calls to me. When I reach for the edge of the universe, I do it knowing that along some paths of cosmic discovery, there are times when, at least for now, one must be content to love the questions themselves.

More than a year has passed since the space shuttle Columbia broke into pieces over central Texas. This past January President Bush announced a long-term program of space exploration that would return human beings to the Moon, and thereafter send them to Mars and beyond. As this magazine goes to press, the twin Mars Exploration Rovers, Spirit and Opportunity, are wowing the scientists and engineers at the rovers' birthplace—NASA's Jet Propulsion Laboratory (JPL)—with their skills as robotic field geologists. JPL's official rover Web site is being stampeded by visitors.

The confluence of these and other events resurrects a perennial debate: with two shuttle failures out of 112 missions, and the astronomical expense of the manned space program, can sending people into space be justified, or should robots do the job alone? Or, given society's sociopolitical ailments, is space exploration something we simply cannot afford to pursue? As an astrophysicist, as an educator, and as a citizen, I must speak my mind on these issues.

Modern societies have been sending robots into space since 1957, and people since 1961. Fact is, it's vastly cheaper to send robots: in most cases, a fiftieth the cost of sending people. Robots don't much care how hot or cold space gets; give them the right lubricants, and they'll operate in a vast range of temperatures. They don't need elaborate life-support systems, either. Robots can spend long periods of time moving around and among the planets, more or less unfazed by ionizing radiation. They do not lose bone mass from prolonged exposure to weightlessness, because, of course, they are boneless. Nor do they have hygiene needs. You don't even have to feed them. Best of all, once they've finished their jobs, they won't complain if you don't bring them home. So if my only goal in space is to do science, and I'm thinking strictly in terms of the scientific return on my dollar, I can think of no justification for sending people into space. I'd rather send the fifty robots.

But there's a flip side to this argument. Unlike even the most talented modern robots, a person is endowed with the ability to make serendipitous discoveries that arise from a lifetime of experience. Until the day arrives when bioneurophysiological computer engineers can do a human-brain download on a robot, the most we can expect of the robot is to look for what it has already been programmed to find. A robot—which is, after all, a machine for embedding human expectations in hardware and software—cannot fully embrace revolutionary scientific discoveries. And those are the ones you don't want to miss.

In the old days, people generally pictured robots as a hunk of hardware with a head, neck, torso, arms, and legs—or maybe some wheels to roll around on. They could be talked to, and would talk back (sounding, of course, robotic). The standard robot looked more or less like a person. The fussbudget character C3PO, from the Star Wars movies, is a perfect example. Even when a robot doesn't look humanoid, its handlers might present it to the public as a quasi-living thing. Each of NASA's Mars rovers, for instance, is described in JPL press packets as having a body, brains, a 'neck and head,' eyes and other 'senses,' an arm, 'legs,' and antennas for 'speaking' and 'listening.' On February 5, 2004, according to the status reports, Spirit woke up earlier than normal today . . . in order to prepare for its memory 'surgery.' On the 19th the rover remotely examined the rim and surrounding soil of a crater dubbed Bonneville, and after all this work, Spirit took a break with a nap lasting slightly more than an hour.

In spite of all this anthropomorphism, it's pretty clear that a robot can have any shape: it's simply an automated piece of machinery that accomplishes a task—either by repeating an action faster or more reliably than the average person can, or by performing an action that a person, relying solely on the five senses, would be unable to accomplish. Robots that paint cars on assembly lines don't look much like people. The Mars rovers look a bit like toy flatbed trucks, but they can grind a pit in the surface of a rock, mobilize a combination microscope-camera to examine the freshly exposed surface, and determine the rock's chemical composition—just as a geologist might do in a laboratory on Earth.

It's worth noting, by the way, that even a human geologist doesn't go it alone. Unaided by some kind of equipment, a person cannot grind down the surface of a rock; that's why a field geologist carries a hammer. To analyze a rock further, the geologist deploys another kind of apparatus, one that can determine its chemical composition. Therein lies a conundrum. Almost all the science likely to be done in an alien environment would be done by some piece of equipment. Field geologists on Mars would schlep it on their daily strolls across a Martian crater or outcrop, where they might take measurements of the soil, the rocks, the terrain, and the atmosphere. But if you can get a robot to do the schlepping and deploy all the same instruments, why send a field geologist to Mars at all?

One good reason is the geologist's common sense. Each Mars rover is designed to move for about ten seconds, then stop and assess its immediate surroundings for twenty seconds, move for another ten seconds, and so on. If the rover moved any faster, or moved without stopping, it might stumble on a rock and tip over, becoming as helpless as a Galápagos tortoise on its back. In contrast, a human explorer would just stride ahead; people are quite good at watching out for rocks and cliffs.

Back in the late 1960s and early 1970s, in the days of NASA's manned Apollo flights to the Moon, no robot could decide which pebbles to pick up and bring home. But when the Apollo 17 astronaut Harrison Schmitt, the only geologist (in fact, the only scientist) to have walked on the Moon, noticed some odd, orange and black soil on the lunar surface, he immediately collected a sample. It turned out to be minute beads of volcanic glass. Today a robot can perform staggering chemical analyses and transmit amazingly detailed images, but it still can't react, as Schmitt did, to a surprise. By contrast, packed inside the 150-pound mechanism of a field geologist are the capacities to walk, run, dig, hammer, see, communicate, interpret, and invent.

And of course when something goes wrong, an on-the-spot human being becomes a robot's best friend. Give a person a wrench, a hammer, and some duct tape, and you'd be surprised what can get fixed. After landing on Mars this past January 3, did the Spirit rover just roll right off its lander platform and start checking out the neighborhood? No, its airbags were blocking the path. Not until January 15 did Spirit's remote controllers manage to get all six of its wheels rolling on Martian soil. Anyone on the scene on January 3 could have just lifted the airbags out of the way and given Spirit a little shove.

Let's assume, then, that we can agree on a few things: People notice the unexpected, react to unforeseen circumstances, and solve problems in ways that robots cannot. Robots are cheap to send into space, but can make only a preprogrammed analysis. Cost and scientific results, however, are not the only relevant issues. There's also the question of exploration.  The first troglodytes to cross the valley or climb the mountain ventured forth from the family cave not because they wanted to make a scientific discovery but because something unknown lay beyond the horizon. Perhaps they sought more food, better shelter, or a more promising way of life. In any case, they felt compelled to explore. The drive to explore may be hardwired, lying deep within the behavioral identity of the human species. To send a person to Mars who can look under the rocks or find out what's down in the valley is the natural extension of what ordinary people have always done on Earth.

Many of my colleagues assert that plenty of science can be done without putting people in space. But if they are between forty and sixty years old, and you ask what inspired them to become scientists, nearly every one (at least in my experience) will cite the high-profile Apollo program. It took place when they were young, and it's what got them excited. It's that simple. In contrast, even if they also mention the launch of Sputnik I, which gave birth to the space era, very few of those scientists credit their interest to the numerous other unmanned satellites and space probes launched by both the United States and the Soviet Union shortly thereafter.

So if you're a first-rate scientist drawn to the space program because you'd initially been inspired by astronauts rocketing into the great beyond, it's somewhat disingenuous of you to contend that people should no longer go into space. To take that position is, in effect, to deny the next generation of students the thrill of following the same path you did: enabling one of our own kind, not just a robotic emissary, to walk on the frontier of exploration.

Whenever we hold an event at the Hayden Planetarium that includes an astronaut, I've found there's a small but noticeable uptick in attendance. People invariably seek the astronaut's autograph. This celebrity status holds even for astronauts most people have never heard of. Any astronaut will do. The one-on-one encounter makes a difference in the hearts and minds of Earth's armchair space travelers—whether retired science teachers, hardworking bus drivers, thirteen-year-old kids, or ambitious parents.

Of course, people have been excited about robots lately, too. From January 3 through January 5, 2004, the NASA Web site that tracks the doings of the Mars rovers got more than half a billion hits—506,621,916 to be exact. That's a record for NASA.

The solution to the quandary seems obvious to me: send both robots and people into space. Space exploration needn't be an either/or transaction, because there's no avoiding the fact that robots are better suited for certain tasks, and people for others. One thing is certain: in the coming decades, the U.S. will need to call upon multitudes of scientists and engineers from scores of disciplines, and astronauts will have to be extraordinarily well trained. The search for evidence of past life on Mars, for instance, will require top-notch biologists. But what does a biologist know about planetary terrains?  Geologists and geophysicists will have to go, too. Chemists will be needed to check out the atmosphere and sample the soils. If life once thrived on Mars, the remains might now be fossilized, and so perhaps we'll need a few paleontologists to join the fray. People who know how to drill through kilometers of soil and rock will also be must-haves, because that's where Martian water reserves might be hiding.

Where will all those talented scientists and technologists come from? Who's going to recruit them? Personally, when I give talks to students old enough to decide what they want to be when they grow up, but young enough not to get derailed by raging hormones, I need to offer them a tasty carrot to get them excited enough to become scientists. That task is made easy if I can introduce them to astronauts looking for the next generation to share their grand vision of exploration and join them in space. Without such inspiring forces behind me, I'm just that day's entertainment. My reading of history tells me that people need heroes. Nobody ever gave a ticker-tape parade for a robot.

Twentieth-century America owed much of its security and economic strength to its support for science and technology. Some of the most revolutionary (and marketable) technology of the past several decades has been spun off the research done under the banner of U.S. space exploration: kidney dialysis machines, implantable pacemakers, corrosion-resistant coatings for bridges and monuments (including the Statue of Liberty), hydroponic systems for growing plants, collision-avoidance systems on aircraft, digital imaging, infrared hand-held cameras, cordless appliances, athletic shoes, scratch-resistant sunglasses, virtual reality. And that list doesn't even include Tang.

Although solutions to a problem are often the fruit of direct investments in targeted research, the most revolutionary solutions tend to emerge from cross-pollination with other disciplines. Medical investigators might never have known of X rays, since they do not naturally occur in biological systems. It took a physicist, Wilhelm Conrad Röntgen, to discover them—light rays that could probe the body's interior with nary a cut from a surgeon.

Here's a more recent example of cross-pollination. Soon after the Hubble Space Telescope was launched in April 1990, NASA engineers realized that the telescope's primary mirror—which gathers and reflects the light from celestial objects into its cameras and spectrographs—had been ground to an incorrect shape. In other words, the billion-and-a-half-dollar telescope was producing fuzzy images.

That was bad.

As if to make lemonade out of lemons, though, computer algorithms came to the rescue. Investigators at the Space Telescope Science Institute in Baltimore, Maryland, developed a range of clever and innovative image-processing techniques to compensate for some of Hubble's shortcomings. Turns out, maximizing the amount of information that could be extracted from a blurry astronomical image is technically identical to maximizing the amount of information that can be extracted from a mammogram. Soon the new techniques came into common use for detecting early signs of breast cancer.

But that's only part of the story. In 1997, for Hubble's second servicing mission (the first, in 1993, corrected the faulty optics), shuttle astronauts swapped in a brand-new, high-resolution digital detector—designed to the demanding specs of astronomers whose careers are based on being able to see small, dim things in the cosmos. That technology is now incorporated in a minimally invasive, low-cost system for doing breast biopsies, the next stage after mammograms in the early diagnosis of cancer.

So why not ask investigators to take direct aim at the challenge of detecting breast cancer? Why should innovations in medicine have to wait for a Hubble-size blunder in space? My answer may not be politically correct, but it's the truth: when you organize extraordinary missions, you attract people of extraordinary talent who might not have been inspired by or attracted to the goal of saving the world from cancer or hunger or pestilence.

Today, cross-pollination between science and society comes about when you have ample funding for ambitious, long-term projects. America has profited immensely from a generation of scientists and engineers who, instead of becoming lawyers or investment bankers, responded to a challenging vision posed in 1961 by President John F. Kennedy. We intend to land a man on the Moon, proclaimed Kennedy, welcoming the citizenry to aid in the effort. That generation, and the one that followed, was the same generation of technologists who invented the personal computer. Bill Gates, co-founder of Microsoft, was thirteen years old when the U.S. landed an astronaut on the Moon; Steve Jobs, co-founder of Apple Computer, was fourteen. The PC did not arise from the mind of a banker or artist or professional athlete. It was invented and developed by a technically trained workforce, who had responded to the dream unfurled before them, and were thrilled to become scientists and engineers.

Yes, the world needs bankers and artists and even professional athletes. They, among countless others, create the breadth of society and culture. But if you want tomorrow to come—if you want to spawn entire economic sectors that didn't exist yesterday—those are not the people you turn to. It's technologists who create that kind of future. And it's visionary steps into space that create that kind of technologist. I look forward to the day when human beings travel the solar system as if it's our own backyard—not only with robots, but with real live people, guided by our timeless and boundless need to explore.