This year is the 150th anniversary of the publishing of Darwin’s On the Origin of Species by Means of Natural Selection, or the Preservation of Favored Races in the Struggle for Life. It’s useful to see that complete title (a short one, compared to some titles of his day!), as a reminder of the actual message Darwin gave us. He described far more than evolution in that astounding book. In fact, the word evolution is not even in the title. In fact, evolution had already been an accepted process for decades before Darwin published his insights. What was not understood in his time was how the process unfolded. What caused new species to appear? Why did some persevere and others disappear?
Darwin’s contribution was to achieve a brilliant synthesis of an incredibly wide range of scientific observations of the natural world that he and others had been accumulating. The time—the middle of the 19th century—was ripe for his insights to appear. Science in England was brewing some mighty potent stews, as many good minds fed off each other.
It is not easy to describe Darwin’s insight, largely because it pulls together such a wide ranging and complex set of descriptions of the variability and propagation of life on Earth. Recently I read an elegant description of Darwin’s concept of natural selection, written by Chet Raymo, an author/astronomer who has repeatedly inspired me. It’s a neat four-step summary:
1. Species are variable (there’s great diversity in the world).
2. Variations are maintained during reproduction.
3. Individuals produce more offspring than are needed for the species to survive.
4. Those individuals who are well adapted to their environment will be more likely to survive and reproduce, thereby passing on their traits to succeeding generations.
That’s it in a nutshell! Straightforward Darwin. Note that this description is of the process of natural selection, not evolution. Or put another way, natural selection is what drives evolution.
A second thing to note is that Darwin’s insight occurred long before anyone knew that genes and DNA existed. Now we know that errors in the copying of DNA—mutations—can cause these variations. We also know that once the error pops up, it gets passed on to one’s offspring—preserved in the DNA. Most mutations are so minor as to have no influence on adaptability or ability to survive. But when an important mutation comes along, it either favors that individual and all her or his progeny or condemns them. In the former case they become Darwin’s “favored races in the struggle for life.”
Life is a struggle. It’s a relentless competition that causes every critter to be constantly looking over its shoulder, seeking any advantage to stay alive. Nature weeds out those less fit, the less adaptable—continually refining, changing the balance, and spawning diversity. We have Darwin to thank for this profound insight; as well as his courage to publish and stand behind this controversial discovery. By the way, this year is also Darwin’s 200th birthday.
Sunday, September 13, 2009
Friday, September 11, 2009
Wednesday, September 9, 2009
Life is Delightful
To be alive is a precious gift. Whether we’re in human form or are an insect, every one of us inherently knows that being alive is special. Every creature will valiantly struggle to stay alive, whenever death threatens. Nature has placed a tremendously strong drive in every one of us to hold on to our life.
One reason we embrace life so dearly, I think, is its promise to bring us countless forms of delight. The taste of exquisite food, the sight of a sunset sky, the love of another person—these are rewards we experience, and experiences from which we take great joy. Watch a bird soar, a dog chase a ball, a bear dive into a stream full of fish—and know that animals have the same ability to experience delight.
Some folks might point to a gloomier side of life, however. Life is fragile, they would say. We constantly are but a heartbeat away from death. Circumstances beyond our control can snatch this existence from us at any moment. We face constant threats. An animal inherently knows that it can be eaten—that a predator may lurk around the next bend. These threats can dampen our joy of life and fill us with dread.
Additionally, we humans fear death in our own special way—burdened with the knowledge that our mortality may come calling the next minute. Disease and violence may rob us of this precious life, and there may be little we can do about it. As Carlo Strenger (a philosopher and psychoanalyst) puts it, “…we all need protection from the unbearable knowledge that we are mortal.”
Rather than let these dark thoughts intrude on our enjoyment of life, I believe we can allow them to heighten our sense of the preciousness of living. Life’s very fragility and shortness makes it all the more cherished. Gold and diamonds are valued by many people simply because they are rare and thus expensive. Isn’t it the same for life?
Another author I have learned much from—Bernd Heinrich, a biologist—describes how we all (humans and animals) do things out of an urge to survive, without any conscious understanding of why we do them. We act in so many ways to enhance our staying alive. Why do we do this—simply to hang on to this existence or to take delight in all that life brings us? Heinrich also ponders the drive to stay alive, not as an effort to become immortal, but just to taste those delights. He writes, “I try to imagine what it would be like if I had the assurance that I’d never die, and wonder if life would be so sweet.” It seems to me that immortality would probably be excruciatingly boring.
One reason we embrace life so dearly, I think, is its promise to bring us countless forms of delight. The taste of exquisite food, the sight of a sunset sky, the love of another person—these are rewards we experience, and experiences from which we take great joy. Watch a bird soar, a dog chase a ball, a bear dive into a stream full of fish—and know that animals have the same ability to experience delight.
Some folks might point to a gloomier side of life, however. Life is fragile, they would say. We constantly are but a heartbeat away from death. Circumstances beyond our control can snatch this existence from us at any moment. We face constant threats. An animal inherently knows that it can be eaten—that a predator may lurk around the next bend. These threats can dampen our joy of life and fill us with dread.
Additionally, we humans fear death in our own special way—burdened with the knowledge that our mortality may come calling the next minute. Disease and violence may rob us of this precious life, and there may be little we can do about it. As Carlo Strenger (a philosopher and psychoanalyst) puts it, “…we all need protection from the unbearable knowledge that we are mortal.”
Rather than let these dark thoughts intrude on our enjoyment of life, I believe we can allow them to heighten our sense of the preciousness of living. Life’s very fragility and shortness makes it all the more cherished. Gold and diamonds are valued by many people simply because they are rare and thus expensive. Isn’t it the same for life?
Another author I have learned much from—Bernd Heinrich, a biologist—describes how we all (humans and animals) do things out of an urge to survive, without any conscious understanding of why we do them. We act in so many ways to enhance our staying alive. Why do we do this—simply to hang on to this existence or to take delight in all that life brings us? Heinrich also ponders the drive to stay alive, not as an effort to become immortal, but just to taste those delights. He writes, “I try to imagine what it would be like if I had the assurance that I’d never die, and wonder if life would be so sweet.” It seems to me that immortality would probably be excruciatingly boring.
Monday, September 7, 2009
Friday, September 4, 2009
A Physics Digest—Part 8: Relativity and Astrophysics
This is the final entry of my physics digest and is appropriate as a conclusion: turning to look outwards at our magnificent and unimaginably large universe. When we attempt to comprehend the vastness of the universe we can’t help but see how tiny, alone, and precious our little planet is.
Albert Einstein founded the concept of relativity a little over a hundred years ago, by conducting brilliant thought experiments. (His experiments had to be conducted in his head, since he had no way to check them out in a lab. Years later technological developments allowed others to confirm his theories.)
Einstein realized that space and time are linked; whereas Newtonian mechanics assumes they are independent. When we move through space, for example, our sense of time can be altered. Motion, in fact, is relative; how it appears to someone at rest differs from someone who is moving. If I drive alongside a car on the interstate, it appears to hardly be moving; while someone standing by the roadside sees us both zipping past.
The first postulate of relativity is that all of nature’s laws are the same in any uniformly moving (constant speed) reference frame. If I toss up a ball while riding in that car, it will fall back into my hand, just as it will if I’m standing at roadside.
The second postulate of relativity is a little trickier: the speed of light is absolute; it's the same, regardless of one’s frame of reference. While things are relative at slower speeds (as when I’m driving in my car), the speed of light never changes (it would be measured the same for me as for the person standing by the roadside). How can light be absolute? Einstein realized that at near-light speeds both time and space contract, and they do so in a manner that, no matter how fast one goes, the speed of light is observed as constant. This happens because time slows down and objects mysteriously become squashed. It only happens for subatomic particles moving near the speed of light, not for plodding objects like people.
These results are all from the “special theory of relativity.” It’s special because it describes those objects moving at a constant speed. Einstein’s general theory—dealing with accelerating objects—took him another ten years to decode. He saw that an accelerating object behaves the same as if were under the influence of gravity. Release an apple (gravity acting upon it) and it will accelerate towards the ground. If you’re in an elevator that’s starting upward (accelerating), you feel heavier, as if suddenly under a stronger gravitational field. When the elevator starts down, you feel lighter, as if momentarily under less gravity. So motion and gravity are also linked.
Einstein realized that gravitational effects were still true for light waves—even though they have no mass. How can this be? It’s because huge bodies, like the sun, literally warp space around them. Light waves simply follow bent space. That’s another concept that physicists are still trying to wrap their minds around.
Finally, astrophysics: from the minute to the immense. The study of astrophysics often parallels the passage of time: how our universe began and is unfolding. It all apparently got underway with the Big Bang, about 14 billion years ago. An unimaginably tiny hot spot blew up and expanded into an unimaginably big universe. That’s the current best guess. Physicists continue to struggle with the mathematical description of that beginning.
The early universe—as it expanded outward—was composed almost entirely of hydrogen, with a dash of helium thrown in. That’s all. No carbon, oxygen, iron, lead. The first stars got formed when clouds of hydrogen collapsed, at which time the high pressure and temperature set off a nuclear fusion process. Those early stars burned hot and fast—lasting but a few million years. As they burned out they collapsed yet a little more, bringing crushing pressures inside, which created even more fusion into other elements. They then blew up in a super nova, spraying all those new elements into space.
Later forming stars (like our sun, born five billion years ago) were created when the new debris collapsed. But now there was only 99% hydrogen. Most of the other elements became fashioned into planets. Our sun is currently at its mid life. In another five billion years it will begin to die. It will do so at first by expanding, consuming, and frying the inner planets. What further evolutionary developments will alter life on our little planet in that upcoming five billion years? No one knows; we’ve just begun.
New tools have recently allowed astronomers to observe planets orbiting other stars. It gives us our first proof that Earth and her sister planets are not alone. We also recently have found that life is far more robust than we once thought, and that conditions exist elsewhere (on some of Saturn’s moons, for example) that likely are conducive to these tough forms of life. Will we find that our planet is not alone in harboring life in this vast universe? No one knows. It’s all speculation for now. But I’m doubtful that extraterrestrial life—if it’s out there—will be bipedal and speak English, as Star Trek would have us believe.
Albert Einstein founded the concept of relativity a little over a hundred years ago, by conducting brilliant thought experiments. (His experiments had to be conducted in his head, since he had no way to check them out in a lab. Years later technological developments allowed others to confirm his theories.)
Einstein realized that space and time are linked; whereas Newtonian mechanics assumes they are independent. When we move through space, for example, our sense of time can be altered. Motion, in fact, is relative; how it appears to someone at rest differs from someone who is moving. If I drive alongside a car on the interstate, it appears to hardly be moving; while someone standing by the roadside sees us both zipping past.
The first postulate of relativity is that all of nature’s laws are the same in any uniformly moving (constant speed) reference frame. If I toss up a ball while riding in that car, it will fall back into my hand, just as it will if I’m standing at roadside.
The second postulate of relativity is a little trickier: the speed of light is absolute; it's the same, regardless of one’s frame of reference. While things are relative at slower speeds (as when I’m driving in my car), the speed of light never changes (it would be measured the same for me as for the person standing by the roadside). How can light be absolute? Einstein realized that at near-light speeds both time and space contract, and they do so in a manner that, no matter how fast one goes, the speed of light is observed as constant. This happens because time slows down and objects mysteriously become squashed. It only happens for subatomic particles moving near the speed of light, not for plodding objects like people.
These results are all from the “special theory of relativity.” It’s special because it describes those objects moving at a constant speed. Einstein’s general theory—dealing with accelerating objects—took him another ten years to decode. He saw that an accelerating object behaves the same as if were under the influence of gravity. Release an apple (gravity acting upon it) and it will accelerate towards the ground. If you’re in an elevator that’s starting upward (accelerating), you feel heavier, as if suddenly under a stronger gravitational field. When the elevator starts down, you feel lighter, as if momentarily under less gravity. So motion and gravity are also linked.
Einstein realized that gravitational effects were still true for light waves—even though they have no mass. How can this be? It’s because huge bodies, like the sun, literally warp space around them. Light waves simply follow bent space. That’s another concept that physicists are still trying to wrap their minds around.
Finally, astrophysics: from the minute to the immense. The study of astrophysics often parallels the passage of time: how our universe began and is unfolding. It all apparently got underway with the Big Bang, about 14 billion years ago. An unimaginably tiny hot spot blew up and expanded into an unimaginably big universe. That’s the current best guess. Physicists continue to struggle with the mathematical description of that beginning.
The early universe—as it expanded outward—was composed almost entirely of hydrogen, with a dash of helium thrown in. That’s all. No carbon, oxygen, iron, lead. The first stars got formed when clouds of hydrogen collapsed, at which time the high pressure and temperature set off a nuclear fusion process. Those early stars burned hot and fast—lasting but a few million years. As they burned out they collapsed yet a little more, bringing crushing pressures inside, which created even more fusion into other elements. They then blew up in a super nova, spraying all those new elements into space.
Later forming stars (like our sun, born five billion years ago) were created when the new debris collapsed. But now there was only 99% hydrogen. Most of the other elements became fashioned into planets. Our sun is currently at its mid life. In another five billion years it will begin to die. It will do so at first by expanding, consuming, and frying the inner planets. What further evolutionary developments will alter life on our little planet in that upcoming five billion years? No one knows; we’ve just begun.
New tools have recently allowed astronomers to observe planets orbiting other stars. It gives us our first proof that Earth and her sister planets are not alone. We also recently have found that life is far more robust than we once thought, and that conditions exist elsewhere (on some of Saturn’s moons, for example) that likely are conducive to these tough forms of life. Will we find that our planet is not alone in harboring life in this vast universe? No one knows. It’s all speculation for now. But I’m doubtful that extraterrestrial life—if it’s out there—will be bipedal and speak English, as Star Trek would have us believe.
Wednesday, September 2, 2009
Tuesday, September 1, 2009
A Physics Digest—Part 7: Atomic and Nuclear Physics
Up to this point my physics digest has taken the classical or Newtonian viewpoint. Now it’s time to pass beyond and enter quantum theory. This is a term that’s been severely misused in recent years, as we’ve heard of everything from quantum Zen to quantum force—whenever someone wants to sound esoteric.
Around the end of the 19th century, experimental physicists were first able to explore elementary particles of matter: electrons, protons, and even smaller entities. The first surprise they met: while energy and radiation at the macroscopic level appear continuous, when you get down to the microscopic level, energy comes in discrete bundles, called quanta. The study of nature’s workings at wee scales is called quantum mechanics. It extends and modifies Newtonian mechanics into this realm.
A second surprise physicists discovered was that you cannot nail down both the speed and position of a tiny particle. If you constrain its location, you lose information on its speed. If you can accurately observe its speed, you’re not really sure just where it is. This vagueness is called Heisenberg’s Uncertainty Principle.
A third surprise: photons of light can behave either as a stream of particles or as a continuous wave. It all depends on how you observe them… literally. Before you observe them they exist only as possibilities. The observer impacts the observation. There is no separate, objective reality at the quantum level.
These findings threw many scientists (including, and especially, Einstein) for a loop. The quantum world is counterintuitive to us macroscopic beings. Physicists are still trying to come to terms with these bizarre results.
These findings also brought about a reconsideration of the structure of the atom. We now understand that the nucleus is surrounded, not by individual electrons in orbit, but by a cloud of electrons in some probabilistic state somewhere between a wave and a particle. Either? Both? Yes.
This uncertain nature of electrons is described by a wave equation—the microscopic world’s equivalent of Newton’s laws—which describes the probabilities of the behavior of electrons and other elementary things. We can only state what’s likely to be—not precisely what is—until we look at it. We then sort of make it come into being. Isn’t that weird?
If we move inward from the atom’s electron probability cloud, we find a lump of positively-charged protons—jammed tightly together in the atom’s nucleus. To keep the electrical repulsive force between them from breaking the nucleus apart, something called the strong (attractive) nuclear force was discovered. But when the nucleus gets rather big—like for uranium—an opposing force called the weak nuclear force comes into play and makes the nucleus rather unstable. Science is still trying to bring the description of these various forces under one umbrella (in the so-called Grand Unified Theory, or GUT).
The counteracting forces in a large nucleus like uranium causes it to be rather unstable and so it will slowly break down, emitting high-energy radiation. A uranium atom decays to the metal lead in some 14-15 steps, passing through nine different elements along the way. In nature this decay is slow—maybe on the order of thousands of years.
Each time a nucleus splits a little mass disappears, becoming transformed into pure energy. Einstein’s famous equation E = mc2 then comes into play. “E” is the energy released, “m” is the tiny bit of mass that is lost, and “c” is the speed of light. In English units c2 is about 2 followed by 20 zeroes, so the energy is large, even though the lost mass is small.
If we gather enough uranium together (far more concentrated than ever occurs in nature) we can reach a critical mass. Now the atoms decay almost instantaneously and achieve the explosive power of the atomic bombs dropped on Hiroshima and Nagasaki. But we can also slow down this process of fission by controlling it with graphite rods, and create a nuclear reactor. The released energy is used to boil water and spin an electrical turbine.
There’s a process even more powerful than the fission (splitting) of uranium atoms: the fusion (merging) of hydrogen atoms. It’s more powerful partly because we can jam together a lot more hydrogen than we can scarce uranium. (Hydrogen is the most plentiful element in the universe.) The hope is that we may soon create a peaceful use for nuclear fusion—in the generation of electricity. Its byproducts are far cleaner than the radioactive remains of current nuclear reactors.
Around the end of the 19th century, experimental physicists were first able to explore elementary particles of matter: electrons, protons, and even smaller entities. The first surprise they met: while energy and radiation at the macroscopic level appear continuous, when you get down to the microscopic level, energy comes in discrete bundles, called quanta. The study of nature’s workings at wee scales is called quantum mechanics. It extends and modifies Newtonian mechanics into this realm.
A second surprise physicists discovered was that you cannot nail down both the speed and position of a tiny particle. If you constrain its location, you lose information on its speed. If you can accurately observe its speed, you’re not really sure just where it is. This vagueness is called Heisenberg’s Uncertainty Principle.
A third surprise: photons of light can behave either as a stream of particles or as a continuous wave. It all depends on how you observe them… literally. Before you observe them they exist only as possibilities. The observer impacts the observation. There is no separate, objective reality at the quantum level.
These findings threw many scientists (including, and especially, Einstein) for a loop. The quantum world is counterintuitive to us macroscopic beings. Physicists are still trying to come to terms with these bizarre results.
These findings also brought about a reconsideration of the structure of the atom. We now understand that the nucleus is surrounded, not by individual electrons in orbit, but by a cloud of electrons in some probabilistic state somewhere between a wave and a particle. Either? Both? Yes.
This uncertain nature of electrons is described by a wave equation—the microscopic world’s equivalent of Newton’s laws—which describes the probabilities of the behavior of electrons and other elementary things. We can only state what’s likely to be—not precisely what is—until we look at it. We then sort of make it come into being. Isn’t that weird?
If we move inward from the atom’s electron probability cloud, we find a lump of positively-charged protons—jammed tightly together in the atom’s nucleus. To keep the electrical repulsive force between them from breaking the nucleus apart, something called the strong (attractive) nuclear force was discovered. But when the nucleus gets rather big—like for uranium—an opposing force called the weak nuclear force comes into play and makes the nucleus rather unstable. Science is still trying to bring the description of these various forces under one umbrella (in the so-called Grand Unified Theory, or GUT).
The counteracting forces in a large nucleus like uranium causes it to be rather unstable and so it will slowly break down, emitting high-energy radiation. A uranium atom decays to the metal lead in some 14-15 steps, passing through nine different elements along the way. In nature this decay is slow—maybe on the order of thousands of years.
Each time a nucleus splits a little mass disappears, becoming transformed into pure energy. Einstein’s famous equation E = mc2 then comes into play. “E” is the energy released, “m” is the tiny bit of mass that is lost, and “c” is the speed of light. In English units c2 is about 2 followed by 20 zeroes, so the energy is large, even though the lost mass is small.
If we gather enough uranium together (far more concentrated than ever occurs in nature) we can reach a critical mass. Now the atoms decay almost instantaneously and achieve the explosive power of the atomic bombs dropped on Hiroshima and Nagasaki. But we can also slow down this process of fission by controlling it with graphite rods, and create a nuclear reactor. The released energy is used to boil water and spin an electrical turbine.
There’s a process even more powerful than the fission (splitting) of uranium atoms: the fusion (merging) of hydrogen atoms. It’s more powerful partly because we can jam together a lot more hydrogen than we can scarce uranium. (Hydrogen is the most plentiful element in the universe.) The hope is that we may soon create a peaceful use for nuclear fusion—in the generation of electricity. Its byproducts are far cleaner than the radioactive remains of current nuclear reactors.
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