Death By Black Hole & Other Cosmic Quandaries

by Neil DeGrasse Tyson

  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 seashore, and diverting myself in now and then finding a smoother pebble or a prettier shell than ordinary, whilst the great ocean of truth lay undiscovered before me. (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 space-time foam, with countless other fluctuations spawning 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 space 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 circumstances or forces enabled inanimate matter to assemble 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 Homo sapiens and have carried the chimpanzee analogy 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 accumulate 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 assemble 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. HUBBLE (1889–1953), 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 passed 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 space 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 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 analyze anything they encountered, living or inanimate, for its basic properties. As the tricorder was waved over the object in question, it made an audible spacey 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 space, appearing as an unresolved point of light in the sky, our five senses would offer us no insight to its distance, velocity through space, 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 analysis, 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 mass 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 eyeballs. 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 principal 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 titanic 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 compass 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 analyzers 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, nobody 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 basement 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 pass 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 pass judgment in the unfamiliar underworld of the atom or in the mind-bending domain of higher-dimensional space. 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)

  Our five senses even interfere with sensible answers to stupid metaphysical questions like, “If a tree falls in the forest and nobody 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 analogy, “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 orbit 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, mass, 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.