Death By Black Hole Part 1

Death by black hole: and other cosmic quandaries.

Neil deGra.s.se Tyson.

PREFACE.

I see the universe not as a collection of objects, theories, and phenomena, but as a vast stage of actors driven by intricate twists of story line and plot. So when writing about the cosmos, it feels natural to bring readers into the theater, behind the scenes, to see up close for themselves what the set designs look like, how the scripts were written, and where the stories will go next. My goal at all times is to communicate insight into how the universe works, which is harder than the simple conveyance of facts. Times arise along the way, as for the drama icon itself, to smile or to frown when the cosmos calls for it. Times arise to be scared witless when the cosmos calls for that, too. So I think of see the universe not as a collection of objects, theories, and phenomena, but as a vast stage of actors driven by intricate twists of story line and plot. So when writing about the cosmos, it feels natural to bring readers into the theater, behind the scenes, to see up close for themselves what the set designs look like, how the scripts were written, and where the stories will go next. My goal at all times is to communicate insight into how the universe works, which is harder than the simple conveyance of facts. Times arise along the way, as for the drama icon itself, to smile or to frown when the cosmos calls for it. Times arise to be scared witless when the cosmos calls for that, too. So I think of Death by Black Hole Death by Black Hole as a reader's portal to all that moves, enlightens, and terrifies us in the universe. as a reader's portal to all that moves, enlightens, and terrifies us in the universe.

Each chapter first appeared, in one form or another, on the pages of Natural History Natural History magazine under the heading "Universe" and span the 11-year period of 1995 through 2005. magazine under the heading "Universe" and span the 11-year period of 1995 through 2005. Death by Black Hole Death by Black Hole forms a kind of "Best of the Universe" and includes some of the most requested essays I have written, mildly edited for continuity and to reflect emergent trends in science. forms a kind of "Best of the Universe" and includes some of the most requested essays I have written, mildly edited for continuity and to reflect emergent trends in science.

I submit this collection to you, the reader, for what might be a welcome diversion from your day's routine.

Neil deGra.s.se Tyson New York City October 2006

ACKNOWLEDGMENTS.

My formal expertise in the universe concerns stars, stellar evolution, and galactic structure. And so I could not possibly write with authority about the breadth of subjects in this collection without the careful eyes of colleagues whose comments on my monthly ma.n.u.scripts often made the difference between a simple idea described and an idea nuanced with meaning drawn from the frontier of cosmic discovery. For matters regarding the solar system, I am grateful to Rick Binzel, my former cla.s.smate in graduate school and now professor of Planetary Sciences at MIT. He has received many a phone call from me, in desperate search of a reality-check on what I had written or what I had planned to write about the planets and their environments.

Others in this role include Princeton Astrophysics Professors Bruce Draine, Michael Strauss, and David Spergel whose collective expertise in cosmo-chemistry, galaxies, and cosmology allowed me to reach deeper into that store of cosmic places than would otherwise be possible. Among my colleagues, the ones who are closest to these essays include Princeton's Robert Lupton, who, being properly educated in England, looks to me as though he knows everything about everything. For most of the essays in this volume, Robert's remarkable attention to scientific as well as literary detail provided reliable monthly enhancement to whatever I had penned. Another colleague and generalist who keeps watch over my work is Steven Soter. My writings are somehow incomplete without first pa.s.sing them to his attention.

From the literary world, Ellen Goldensohn, who was my first editor at Natural History Natural History magazine, invited me to write a column in 1995 after hearing me interviewed on National Public Radio. I agreed on the spot. And this monthly task remains one of the most exhausting and exhilarating things I do. Avis Lang, my current editor continues the effort begun by Ellen, ensuring that, without compromise, I say what I mean and mean what I say. I am indebted to both of them for the time they have invested to make me be a better writer. Others who have helped to improve or otherwise enhance the content of one or more essays include Phillip Branford, Bobby Fogel, Ed Jenkins, Ann Rae Jonas, Betsy Lerner, Mordecai Mark Mac-Low, Steve Napear, Michael Richmond, Bruce Stutz, Frank Summers, and Ryan Wyatt. Hayden volunteer Kyrie Bohin-Tinch made a heroic first pa.s.s at helping me to organize the universe of this book. And I offer further thanks to Peter Brown, editor-in-chief of magazine, invited me to write a column in 1995 after hearing me interviewed on National Public Radio. I agreed on the spot. And this monthly task remains one of the most exhausting and exhilarating things I do. Avis Lang, my current editor continues the effort begun by Ellen, ensuring that, without compromise, I say what I mean and mean what I say. I am indebted to both of them for the time they have invested to make me be a better writer. Others who have helped to improve or otherwise enhance the content of one or more essays include Phillip Branford, Bobby Fogel, Ed Jenkins, Ann Rae Jonas, Betsy Lerner, Mordecai Mark Mac-Low, Steve Napear, Michael Richmond, Bruce Stutz, Frank Summers, and Ryan Wyatt. Hayden volunteer Kyrie Bohin-Tinch made a heroic first pa.s.s at helping me to organize the universe of this book. And I offer further thanks to Peter Brown, editor-in-chief of Natural History Natural History magazine, for his overall support of my writing efforts and for granting permission to reproduce the essays of my choice for this collection. magazine, for his overall support of my writing efforts and for granting permission to reproduce the essays of my choice for this collection.

This page would be incomplete without a brief expression of debt to Stephen Jay Gould, whose Natural History Natural History column "This View of Life" ran for three hundred essays. We overlapped at the magazine for seven years, from 1995 through 2001, and not a month pa.s.sed where I did not feel his presence. Stephen practically invented the modern essay form, and his influence on my work is manifest. Wherever I am compelled to reach deep into the history of science, I would acquire and turn the fragile pages of rare books from centuries past, as Gould so often did, drawing from them a rich sampling of how those who came before us attempted to understand the operations of the natural world. His premature death at age 60, like that of Carl Sagan at age 62, left a vacuum in the world of science communication that remains to this day unfilled. column "This View of Life" ran for three hundred essays. We overlapped at the magazine for seven years, from 1995 through 2001, and not a month pa.s.sed where I did not feel his presence. Stephen practically invented the modern essay form, and his influence on my work is manifest. Wherever I am compelled to reach deep into the history of science, I would acquire and turn the fragile pages of rare books from centuries past, as Gould so often did, drawing from them a rich sampling of how those who came before us attempted to understand the operations of the natural world. His premature death at age 60, like that of Carl Sagan at age 62, left a vacuum in the world of science communication that remains to this day unfilled.

PROLOGUE:.

The Beginning of Science

The success of known physical laws to explain the world around us has consistently bred some confident and c.o.c.ky att.i.tudes toward the state of human knowledge, especially when the holes in our knowledge of objects and phenomena are perceived to be small and insignificant. n.o.bel laureates and other esteemed scientists are not immune from this stance, and in some cases have embarra.s.sed themselves.

A famous end-of-science prediction came in 1894, during the speech given by the soon-to-be n.o.bel laureate Albert A. Michelson on the dedication of the Ryerson Physics Lab, at the University of Chicago: The more important fundamental laws and facts of physical science have all been discovered, and these are now so firmly established that the possibility of their ever being supplanted in consequence of new discoveries is exceedingly remote.... Future discoveries must be looked for in the sixth place of decimals. (Barrow 1988, p. 173) (Barrow 1988, p. 173) One of the most brilliant astronomers of the time, Simon Newcomb, who was also cofounder of the American Astronomical Society, shared Michelson's views in 1888 when he noted, "We are probably nearing the limit of all we can know about astronomy" (1888, p. 65). Even the great physicist Lord Kelvin, who, as we shall see in Section 3, had the absolute temperature scale named after him, fell victim to his own confidence in 1901 with the claim, "There is nothing new to be discovered in physics now. All that remains is more and more precise measurement" (1901, p.1). These comments were expressed at a time when the luminiferous ether was still the presumed medium in which light propagated through s.p.a.ce, and when the slight difference between the observed and predicted path of Mercury around the Sun was real and unsolved. These quandaries were perceived at the time to be small, requiring perhaps only mild adjustments to the known physical laws to account for them.

Fortunately, Max Planck, one of the founders of quantum mechanics, had more foresight than his mentor. Here, in a 1924 lecture, he reflects on the advice given to him in 1874: When I began my physical studies and sought advice from my venerable teacher Philipp von Jolly...he portrayed to me physics as a highly developed, almost fully matured science.... Possibly in one or another nook there would perhaps be a dust particle or a small bubble to be examined and cla.s.sified, but the system as a whole stood there fairly secured, and theoretical physics approached visibly that degree of perfection which, for example, geometry has had already for centuries. (1996, p. 10) (1996, p. 10) Initially Planck had no reason to doubt his teacher's views. But when our cla.s.sical understanding of how matter radiates energy could not be reconciled with experiment, Planck became a reluctant revolutionary in 1900 by suggesting the existence of the quantum, an indivisible unit of energy that heralded an era of new physics. The next 30 years would see the discovery of the special and general theories of relativity, quantum mechanics, and the expanding universe.

With all this myopic precedence you would think that the brilliant and prolific physicist Richard Feynman would have known better. In his charming 1965 book The Character of Physical Law The Character of Physical Law, he declares: We are very lucky to be living in an age in which we are still making discoveries.... The age in which we live is the age in which we are discovering the fundamental laws of nature, and that day will never come again. It is very exciting, it is marvelous, but this excitement will have to go. (Feynman 1994, p. 166) (Feynman 1994, p. 166) I claim no special knowledge of when the end of science will come, or where the end might be found, or whether an end exists at all. What I do know is that our species is dumber than we normally admit to ourselves. This limit of our mental faculties, and not necessarily of science itself, ensures to me that we have only just begun to figure out the universe.

Let's a.s.sume, for the moment, that human beings are the smartest species on Earth. If, for the sake of discussion, we define "smart" as the capacity of a species to do abstract mathematics then one might further a.s.sume that human beings are the only smart species to have ever lived.

What are the chances that this first and only smart species in the history of life on Earth has enough smarts to completely figure out how the universe works? Chimpanzees are an evolutionary hair's-width from us yet we can agree that no amount of tutelage will ever leave a chimp fluent in trigonometry. Now imagine a species on Earth, or anywhere else, as smart compared with humans as humans are compared with chimpanzees. How much of the universe might they figure out?

Tic-tac-toe fans know that the game's rules are sufficiently simple that it's possible to win or tie every game-if you know which first-moves to make. But young children play the game as though the outcome were remote and unknowable. The rules of engagement are also clear and simple for the game of chess, but the challenge of predicting your opponent's upcoming sequence of moves grows exponentially as the game proceeds. So adults-even smart and talented ones-are challenged by the game and play it as though the end were a mystery.

Let's go to Isaac Newton, who leads my list of the smartest people who ever lived. (I am not alone here. A memorial inscription on a bust of him in Trinity College, England, proclaims Qui genus humanum ingenio superavit Qui genus humanum ingenio superavit, which loosely translates from the Latin to "of all humans, there is no greater intellect.") What did Newton observe about his state of knowledge?

I do not know what I appear to the world; but to myself I seem to have been only like a boy playing on a seash.o.r.e, and diverting myself in now and then finding a smoother pebble or a prettier sh.e.l.l than ordinary, whilst the great ocean of truth lay undiscovered before me. (Brewster 1860, p. 331) (Brewster 1860, p. 331) The chessboard that is our universe has revealed some of its rules, but much of the cosmos still behaves mysteriously-as though there remain secret, hidden regulations to which it abides. These would be rules not found in the rule book we have thus far written.

The distinction between knowledge of objects and phenomena, which operate within the parameters of known physical laws, and knowledge of the physical laws themselves is central to any perception that science might be coming to an end. The discovery of life on the planet Mars, or beneath the floating ice sheets of Jupiter's moon Europa, would be the greatest discovery of any kind ever. You can bet, however, that the physics and chemistry of its atoms will be the same as the physics and chemistry of atoms here on Earth. No new laws necessary.

But let's peek at a few unsolved problems from the underbelly of modern astrophysics that expose the breadth and depth of our contemporary ignorance, the solutions of which, for all we know, await the discovery of entirely new branches of physics.

While our confidence in the big bang description of the origin of the universe is very high, we can only speculate what lies beyond our cosmic horizon, 13.7 billion light-years from us. We can only guess what happened before the big bang or why there should have been a big bang in the first place. Some predictions, from the limits of quantum mechanics, allow our expanding universe to be the result of just one fluctuation from a primordial s.p.a.ce-time foam, with countless other fluctuations sp.a.w.ning countless other universes.

Shortly after the big bang, when we try to get our computers to make the universe's hundred billion galaxies, we have trouble simultaneously matching the observational data from early and late times in the universe. A coherent description of the formation and evolution of the large-scale structure of the universe continues to elude us. We seem to be missing some important pieces of the puzzle.

Newton's laws of motion and gravity looked good for hundreds of years, until they needed to be modified by Einstein's theories of motion and gravity-the relativity theories. Relativity now reigns supreme. Quantum mechanics, the description of our atomic and nuclear universe, also reigns supreme. Except that as conceived, Einstein's theory of gravity is irreconcilable with quantum mechanics. They each predict different phenomena for the domain in which they might overlap. Something's got to surrender. Either there's a missing part of Einstein's gravity that enables it to accept the tenets of quantum mechanics, or there's a missing part of quantum mechanics that enables it to accept Einstein's gravity.

Perhaps there's a third option: the need for a larger, inclusive theory that supplants them both. Indeed, string theory has been invented and called upon to do just that. It attempts to reduce the existence of all matter, energy, and their interactions to the simple existence of higher dimensional vibrating strings of energy. Different modes of vibration would reveal themselves in our measly dimensions of s.p.a.ce and time as different particles and forces. Although string theory has had its adherents for more than 20 years, its claims continue to lie outside our current experimental capacity to verify its formalisms. Skepticism is rampant, but many are nonetheless hopeful.

We still do not know what circ.u.mstances or forces enabled inanimate matter to a.s.semble into life as we know it. Is there some mechanism or law of chemical self-organization that escapes our awareness because we have nothing with which to compare our Earth-based biology, and so we cannot evaluate what is essential and what is irrelevant to the formation of life?

We've known since Edwin Hubble's seminal work during the 1920s that the universe is expanding, but we've only just learned that the universe is also accelerating, by some antigravity pressure dubbed "dark energy" for which we have no working hypothesis to understand.

At the end of the day, no matter how confident we are in our observations, our experiments, our data, or our theories, we must go home knowing that 85 percent of all the gravity in the cosmos comes from an unknown, mysterious source that remains completely undetected by all means we have ever devised to observe the universe. As far as we can tell, it's not made of ordinary stuff such as electrons, protons, and neutrons, or any form of matter or energy that interacts with them. We call this ghostly, offending substance "dark matter," and it remains among the greatest of all quandaries.

Does any of this sound like the end of science? Does any of this sound like we are on top of the situation? Does any of this sound like it's time to congratulate ourselves? To me it sounds like we are all helpless idiots, not unlike our kissing cousin, the chimpanzee, trying to learn the Pythagorean theorem.

Maybe I'm being a little hard on h.o.m.o sapiens h.o.m.o sapiens and have carried the chimpanzee a.n.a.logy a little too far. Perhaps the question is not how smart is an individual of a species, but how smart is the collective brain-power of the entire species. Through conferences, books, other media, and of course the Internet, humans routinely share their discoveries with others. While natural selection drives Darwinian evolution, the growth of human culture is largely Lamarckian, where new generations of humans inherit the acquired discoveries of generations past, allowing cosmic insight to acc.u.mulate without limit. and have carried the chimpanzee a.n.a.logy a little too far. Perhaps the question is not how smart is an individual of a species, but how smart is the collective brain-power of the entire species. Through conferences, books, other media, and of course the Internet, humans routinely share their discoveries with others. While natural selection drives Darwinian evolution, the growth of human culture is largely Lamarckian, where new generations of humans inherit the acquired discoveries of generations past, allowing cosmic insight to acc.u.mulate without limit.

Each discovery of science therefore adds a rung to a ladder of knowledge whose end is not in sight because we are building the ladder as we go along. As far as I can tell, as we a.s.semble and ascend this ladder, we will forever uncover the secrets of the universe-one by one.

DEATH BY BLACK HOLE.

SECTION 1.

THE NATURE OF KNOWLEDGE.

THE CHALLENGES OF KNOWING WHAT IS KNOWABLE IN THE UNIVERSE.

ONE.

COMING TO OUR SENSES.

Equipped with his five senses, man explores the universe around him and calls the adventure science.-EDWIN P. H P. HUBBLE (18891953), (18891953), The Nature of Science The Nature of Science Among our five senses, sight is the most special to us. Our eyes allow us to register information not only from across the room but also from across the universe. Without vision, the science of astronomy would never have been born and our capacity to measure our place in the universe would have been hopelessly stunted. Think of bats. Whatever bat secrets get pa.s.sed from one generation to the next, you can bet that none of them is based on the appearance of the night sky.

When thought of as an ensemble of experimental tools, our senses enjoy an astonishing acuity and range of sensitivity. Our ears can register the thunderous launch of the s.p.a.ce shuttle, yet they can also hear a mosquito buzzing a foot away from our head. Our sense of touch allows us to feel the magnitude of a bowling ball dropped on our big toe, just as we can tell when a one-milligram bug crawls along our arm. Some people enjoy munching on habanero peppers while sensitive tongues can identify the presence of food flavors on the level of parts per million. And our eyes can register the bright sandy terrain on a sunny beach, yet these same eyes have no trouble spotting a lone match, freshly lit, hundreds of feet across a darkened auditorium.

But before we get carried away in praise of ourselves, note that what we gain in breadth we lose in precision: we register the world's stimuli in logarithmic rather than linear increments. For example, if you increase the energy of a sound's volume by a factor of 10, your ears will judge this change to be rather small. Increase it by a factor of 2 and you will barely take notice. The same holds for our capacity to measure light. If you have ever viewed a total solar eclipse you may have noticed that the Sun's disk must be at least 90 percent covered by the Moon before anybody comments that the sky has darkened. The stellar magnitude scale of brightness, the well-known acoustic decibel scale, and the seismic scale for earthquake severity are each logarithmic, in part because of our biological propensity to see, hear, and feel the world that way.

WHAT, IF ANYTHING, lies beyond our senses? Does there exist a way of knowing that transcends our biological interfaces with the environment?

Consider that the human machine, while good at decoding the basics of our immediate environment-like when it's day or night or when a creature is about to eat us-has very little talent for decoding how the rest of nature works without the tools of science. If we want to know what's out there then we require detectors other than the ones we are born with. In nearly every case, the job of a scientific apparatus is to transcend the breadth and depth of our senses.

Some people boast of having a sixth sense, where they profess to know or see things that others cannot. Fortune-tellers, mind readers, and mystics are at the top of the list of those who lay claim to mysterious powers. In so doing, they instill widespread fascination in others, especially book publishers and television producers. The questionable field of parapsychology is founded on the expectation that at least some people actually harbor such talents. To me, the biggest mystery of them all is why so many fortune-telling psychics choose to work the phones on TV hotlines instead of becoming insanely wealthy trading futures contracts on Wall Street. And here's a news headline none of us has seen, "Psychic Wins the Lottery."

Quite independent of this mystery, the persistent failures of controlled, double-blind experiments to support the claims of parapsychology suggest that what's going on is nonsense rather than sixth sense.

On the other hand, modern science wields dozens of senses. And scientists do not claim these to be the expression of special powers, just special hardware. In the end, of course, the hardware converts the information gleaned from these extra senses into simple tables, charts, diagrams, or images that our inborn senses can interpret. In the original Star Trek Star Trek sci-fi series, the crew that beamed down from their starship to the uncharted planet always brought with them a tricorder-a handheld device that could a.n.a.lyze anything they encountered, living or inanimate, for its basic properties. As the tricorder was waved over the object in question, it made an audible s.p.a.cey sound that was interpreted by the user. sci-fi series, the crew that beamed down from their starship to the uncharted planet always brought with them a tricorder-a handheld device that could a.n.a.lyze anything they encountered, living or inanimate, for its basic properties. As the tricorder was waved over the object in question, it made an audible s.p.a.cey sound that was interpreted by the user.

Suppose a glowing blob of some unknown substance were parked right in front of us. Without some diagnostic tool like a tricorder to help, we would be clueless to the blob's chemical or nuclear composition. Nor could we know whether it has an electromagnetic field, or whether it emits strongly in gamma rays, x-rays, ultraviolet, microwaves, or radio waves. Nor could we determine the blob's cellular or crystalline structure. If the blob were far out in s.p.a.ce, appearing as an unresolved point of light in the sky, our five senses would offer us no insight to its distance, velocity through s.p.a.ce, or its rate of rotation. We further would have no capacity to see the spectrum of colors that compose its emitted light, nor could we know whether the light is polarized.

Without hardware to help our a.n.a.lysis, and without a particular urge to lick the stuff, all we can report back to the starship is, "Captain, it's a blob." Apologies to Edwin P. Hubble, the quote that opens this chapter, while poignant and poetic, should have instead been: Equipped with our five senses, along with telescopes and microscopes and ma.s.s spectrometers and seismographs and magnetometers and particle accelerators and detectors across the electromagnetic spectrum, we explore the universe around us and call the adventure science.

Think of how much richer the world would appear to us and how much earlier the nature of the universe would have been discovered if we were born with high-precision, tunable eyeb.a.l.l.s. Dial up the radio-wave part of the spectrum and the daytime sky becomes as dark as night. Dotting that sky would be bright and famous sources of radio waves, such as the center of the Milky Way, located behind some of the princ.i.p.al stars of the constellation Sagittarius. Tune into microwaves and the entire cosmos glows with a remnant from the early universe, a wall of light set forth 380,000 years after the big bang. Tune into x-rays and you immediately spot the locations of black holes, with matter spiraling into them. Tune into gamma rays and see t.i.tanic explosions scattered throughout the universe at a rate of about one per day. Watch the effect of the explosion on the surrounding material as it heats up and glows in other bands of light.

If we were born with magnetic detectors, the compa.s.s would never have been invented because we wouldn't ever need one. Just tune into Earth's magnetic field lines and the direction of magnetic north looms like Oz beyond the horizon. If we had spectrum a.n.a.lyzers within our retinas, we would not have to wonder what we were breathing. We could just look at the register and know whether the air contained sufficient oxygen to sustain human life. And we would have learned thousands of years ago that the stars and nebulae in the Milky Way galaxy contain the same chemical elements found here on Earth.

And if we were born with big eyes and built-in Doppler motion detectors, we would have seen immediately, even as grunting troglodytes, that the entire universe is expanding-with distant galaxies all receding from us.

If our eyes had the resolution of high-performance microscopes, n.o.body would have ever blamed the plague and other sicknesses on divine wrath. The bacteria and viruses that made us sick would be in plain view as they crawled on our food or as they slid through open wounds in our skin. With simple experiments, we could easily tell which of these bugs were bad and which were good. And of course postoperative infection problems would have been identified and solved hundreds of years earlier.

If we could detect high-energy particles, we would spot radioactive substances from great distances. No Geiger counters necessary. We could even watch radon gas seep through the bas.e.m.e.nt floor of our homes and not have to pay somebody to tell us about it.

THE HONING OF our senses from birth through childhood allows us, as adults, to pa.s.s judgment on events and phenomena in our lives, declaring whether they "make sense." Problem is, hardly any scientific discoveries of the past century flowed from the direct application of our five senses. They flowed instead from the direct application of sense-transcendent mathematics and hardware. This simple fact is entirely responsible for why, to the average person, relativity, particle physics, and 10-dimensional string theory make no sense. Include in the list black holes, wormholes, and the big bang. Actually, these ideas don't make much sense to scientists either, or at least not until we have explored the universe for a long time, with all the senses that are technologically available. What emerges, eventually, is a newer and higher level of "common sense" that enables a scientist to think creatively and to pa.s.s judgment in the unfamiliar underworld of the atom or in the mind-bending domain of higher-dimensional s.p.a.ce. The twentieth-century German physicist Max Planck made a similar observation about the discovery of quantum mechanics: our senses from birth through childhood allows us, as adults, to pa.s.s judgment on events and phenomena in our lives, declaring whether they "make sense." Problem is, hardly any scientific discoveries of the past century flowed from the direct application of our five senses. They flowed instead from the direct application of sense-transcendent mathematics and hardware. This simple fact is entirely responsible for why, to the average person, relativity, particle physics, and 10-dimensional string theory make no sense. Include in the list black holes, wormholes, and the big bang. Actually, these ideas don't make much sense to scientists either, or at least not until we have explored the universe for a long time, with all the senses that are technologically available. What emerges, eventually, is a newer and higher level of "common sense" that enables a scientist to think creatively and to pa.s.s judgment in the unfamiliar underworld of the atom or in the mind-bending domain of higher-dimensional s.p.a.ce. The twentieth-century German physicist Max Planck made a similar observation about the discovery of quantum mechanics: Modern Physics impresses us particularly with the truth of the old doctrine which teaches that there are realities existing apart from our sense-perceptions, and that there are problems and conflicts where these realities are of greater value for us than the richest treasures of the world of experience. (1931, p. 107) (1931, p. 107) Our five senses even interfere with sensible answers to stupid metaphysical questions like, "If a tree falls in the forest and n.o.body is around to hear it, does it make a sound?" My best answer is, "How do you know it fell?" But that just gets people angry. So I offer a senseless a.n.a.logy, "Q: If you can't smell the carbon monoxide, then how do you know it's there? A: You drop dead." In modern times, if the sole measure of what's out there flows from your five senses then a precarious life awaits you.

Discovering new ways of knowing has always heralded new windows on the universe that tap into our growing list of nonbiological senses. Whenever this happens, a new level of majesty and complexity in the universe reveals itself to us, as though we were technologically evolving into supersentient beings, always coming to our senses.

TWO.

ON EARTH AS IN THE HEAVENS.

Until Isaac Newton wrote down the universal law of gravitation, there was little reason to presume that the laws of physics on Earth were the same as everywhere else in the universe. Earth had earthly things going on and the heavens had heavenly things going on. Indeed, according to many scholars of the day, the heavens were unknowable to our feeble, mortal minds. As further detailed in Section 7, when Newton breached this philosophical barrier by rendering all motion comprehensible and predictable, some theologians criticized him for leaving nothing for the Creator to do. Newton had figured out that the force of gravity pulling ripe apples from their branches also guides tossed objects along their curved trajectories and directs the Moon in its...o...b..t around Earth. Newton's law of gravity also guides planets, asteroids, and comets in their orbits around the Sun and keeps hundreds of billions of stars in orbit within our Milky Way galaxy.

This universality of physical laws drives scientific discovery like nothing else. And gravity was just the beginning. Imagine the excitement among nineteenth-century astronomers when laboratory prisms, which break light beams into a spectrum of colors, were first turned to the Sun. Spectra are not only beautiful but also contain oodles of information about the light-emitting object, including its temperature and composition. Chemical elements reveal themselves by their unique patterns of light or dark bands that cut across the spectrum. To people's delight and amazement, the chemical signatures on the Sun were identical to those in the laboratory. No longer the exclusive tool of chemists, the prism showed that as different as the Sun is from Earth in size, ma.s.s, temperature, location, and appearance, both contained the same stuff-hydrogen, carbon, oxygen, nitrogen, calcium, iron, and so forth. But more important than a laundry list of shared ingredients was the recognition that whatever laws of physics prescribed the formation of these spectral signatures on the Sun, the same laws were operating on Earth, 93 million miles away.

So fertile was this concept of universality that it was successfully applied in reverse. Further a.n.a.lysis of the Sun's spectrum revealed the signature of an element that had no known counterpart on Earth. Being of the Sun, the new substance was given a name derived from the Greek word helios helios (the Sun). Only later was it discovered in the lab. Thus, "helium" became the first and only element in the chemist's periodic table to be discovered someplace other than Earth. (the Sun). Only later was it discovered in the lab. Thus, "helium" became the first and only element in the chemist's periodic table to be discovered someplace other than Earth.

OKAY, THE LAWS of physics work in the solar system, but do they work across the galaxy? Across the universe? Across time itself? Step by step, the laws were tested. The nearby stars also revealed familiar chemicals. Distant binary stars, bound in mutual orbit, seem to know all about Newton's laws of gravity. For the same reason, so do binary galaxies. of physics work in the solar system, but do they work across the galaxy? Across the universe? Across time itself? Step by step, the laws were tested. The nearby stars also revealed familiar chemicals. Distant binary stars, bound in mutual orbit, seem to know all about Newton's laws of gravity. For the same reason, so do binary galaxies.

And, like the geologist's stratified sediments, the farther away we look, the further back in time we see. Spectra from the most distant objects in the universe show the same chemical signatures that we see everywhere else in the universe. True, heavy elements were less abundant back then-they are manufactured primarily in subsequent generations of exploding stars-but the laws describing the atomic and molecular process that created these spectral signatures remain intact.

Of course, not all things and phenomena in the cosmos have counterparts on Earth. You've probably never walked through a cloud of glowing million-degree plasma, and you've probably never stumbled upon a black hole on the street. What matters is the universality of the laws of physics that describe them. When spectral a.n.a.lysis was first turned to the light emitted by interstellar nebulae, an element appeared that, once again, had no counterpart on Earth. But the periodic table of elements had no missing boxes; when helium was discovered there were several. So astrophysicists invented the name "nebulium" as a placeholder, until they could figure out what was going on. Turned out that in s.p.a.ce, gaseous nebulae are so rarefied that atoms go long stretches without colliding with each other. Under these conditions, electrons can do things within atoms that had never before been seen in Earth labs. Nebulium was simply the signature of ordinary oxygen doing extraordinary things.

This universality of physical laws tells us that if we land on another planet with a thriving alien civilization, they will be running on the same laws that we have discovered and tested here on Earth-even if the aliens harbor different social and political beliefs. Furthermore, if you wanted to talk to the aliens, you can bet they don't speak English or French or even Mandarin Chinese. You don't even know whether shaking their hands-if indeed they have hands to shake-would be considered an act of war or of peace. Your best hope is to find a way to communicate using the language of science.

Such an attempt was made in the 1970s with the Pioneer 10 Pioneer 10 and and 11 11 and and Voyager 1 Voyager 1 and and 2 2 s.p.a.cecraft, the only ones given a great enough speed to escape the solar system's gravitational pull. s.p.a.cecraft, the only ones given a great enough speed to escape the solar system's gravitational pull. Pioneer Pioneer donned a golden etched plaque that showed, in pictograms, the layout of our solar system, our location in the Milky Way galaxy, and the structure of the hydrogen atom. donned a golden etched plaque that showed, in pictograms, the layout of our solar system, our location in the Milky Way galaxy, and the structure of the hydrogen atom. Voyager Voyager went further and included diverse sounds from mother Earth including the human heartbeat, whale "songs," and musical selections ranging from the works of Beethoven to Chuck Berry. While this humanized the message, it's not clear whether alien ears would have a clue what they were listening to-a.s.suming they have ears in the first place. My favorite parody of this gesture was a skit on went further and included diverse sounds from mother Earth including the human heartbeat, whale "songs," and musical selections ranging from the works of Beethoven to Chuck Berry. While this humanized the message, it's not clear whether alien ears would have a clue what they were listening to-a.s.suming they have ears in the first place. My favorite parody of this gesture was a skit on Sat.u.r.day Night Live Sat.u.r.day Night Live, appearing shortly after the Voyager Voyager launch. NASA receives a reply from the aliens who recovered the s.p.a.cecraft. The note simply requests, "Send more Chuck Berry." launch. NASA receives a reply from the aliens who recovered the s.p.a.cecraft. The note simply requests, "Send more Chuck Berry."

AS WE WILL see in great detail in Section 3, science thrives not only on the universality of physical laws but also on the existence and persistence of physical constants. The constant of gravitation, known by most scientists as "big G," supplies Newton's equation of gravity with the measure of how strong the force will be, and has been implicitly tested for variation over eons. If you do the math, you can determine that a star's luminosity is steeply dependent on big G. In other words, if big G had been even slightly different in the past, then the energy output of the Sun would have been far more variable than anything that the biological, climatological, or geological records indicate. In fact, no time-dependent or location-dependent fundamental constants are known-they appear to be truly constant. see in great detail in Section 3, science thrives not only on the universality of physical laws but also on the existence and persistence of physical constants. The constant of gravitation, known by most scientists as "big G," supplies Newton's equation of gravity with the measure of how strong the force will be, and has been implicitly tested for variation over eons. If you do the math, you can determine that a star's luminosity is steeply dependent on big G. In other words, if big G had been even slightly different in the past, then the energy output of the Sun would have been far more variable than anything that the biological, climatological, or geological records indicate. In fact, no time-dependent or location-dependent fundamental constants are known-they appear to be truly constant.

Such are the ways of our universe.

Among all constants, the speed of light is surely the most famous. No matter how fast you go, you will never overtake a beam of light. Why not? No experiment ever conducted has ever revealed an object of any form reaching the speed of light. Well-tested laws of physics predict and account for this. These statements sound closed-minded. True, some of the most embarra.s.sing science-based proclamations in the past have underestimated the ingenuity of inventors and engineers: "We will never fly." "Flying will never be commercially feasible." "We will never fly faster than sound." "We will never split the atom." "We will never go to the Moon." You've heard them. What they have in common is that no established law of physics stood in their way.

The claim "We will never outrun a beam of light" is a qualitatively different prediction. It flows from basic, time-tested physical principles. No doubt about it. Highway signs for interstellar travelers of the future will surely read:

The Speed of Light:It's Not Just a Good IdeaIt's the Law.

The good thing about the laws of physics is that they require no law enforcement agencies to maintain them, although I once owned a nerdy T-shirt that loudly proclaimed, "OBEY GRAVITY."

Many natural phenomena reflect the interplay of multiple physical laws operating at once. This fact often complicates the a.n.a.lysis and, in most cases, requires supercomputers to calculate things and to keep track of important parameters. When comet Shoemaker-Levy 9 plunged into and then exploded within Jupiter's gas-rich atmosphere in 1994, the most accurate computer model of what was to happen combined the laws of fluid mechanics, thermodynamics, kinematics, and gravitation. Climate and weather represent other leading examples of complicated (and difficult-to-predict) phenomena. But the basic laws governing them are still at work. Jupiter's Great Red Spot, a raging anticyclone that has been going strong for at least 350 years, is driven by the identical physical processes that generate storms on Earth and elsewhere in the solar system.

THE CONSERVATION LAWS, where the amount of some measured quant.i.ty remains unchanged no matter what no matter what are another cla.s.s of universal truths. The three most important are the conservation of ma.s.s and energy, the conservation of linear and angular momentum, and the conservation of electric charge. These laws are in evidence on Earth and everywhere we have thought to look in the universe-from the domain of particle physics to the large-scale structure of the universe. are another cla.s.s of universal truths. The three most important are the conservation of ma.s.s and energy, the conservation of linear and angular momentum, and the conservation of electric charge. These laws are in evidence on Earth and everywhere we have thought to look in the universe-from the domain of particle physics to the large-scale structure of the universe.