Physics Envy

There are the so-called “hard sciences,” like physics and chemistry. Then there are the “soft sciences,” like psychology, biology, and economics, which have often aspired to build models that are as precise, quantitative, and “hard” as those of physics. The appeal of Newtonian physics these last 400 years has been its simplicity and its ability to derive equations that elegantly express the behavior of the natural world. 

But the allure of physics is much more than its basic equations such as Newton's F = ma or Einstein's E = mc²; it's the capability to predict the future behavior of things. These straightforward equations allow one to predict what will happen tomorrow, based on what we see today. That ability to prognosticate shows us that there is order to the physical universe.

This capacity to predict has a great attraction to soft-science economists and psychologists. If they can boil down their social sciences into similar elegant equations or postulates, they will then achieve what physicists have long done: simply describe how things behave and how they will go in the future.

The problem with economics is that it is nowhere near as mathematically precise as physics. This annoys economists, because every lay person feels qualified to weigh in on economics (thinking they understand this very complex process), as they tend to leave physics and its often complicated equations to the erudite scientists. For example, what happens in the theoretical world of particle physics seems to have little to do with my daily existence (or my ability to understand it), but what happens to the Federal Reserve's interest rate, I can feel in my bank account.

A central issue here is that science is studying the natural world—which is consistent and repeatable—while economics studies the unpredictable, if not sometimes whimsical, behavior of human beings. So in the late 19^th century and into the 20^th, several leading economists tried very hard to give economics a solid mathematical foundation. The school of economics led by Milton Friedman at the University of Chicago helped to put economics on what they believed to be a rational, mathematical basis. This process reached an apogee in the 1990s, when economists like Alan Greenspan (who spent nearly 20 years as the chairman of the Fed) became lionized as the gurus of economic “scientism.”

Instead of realizing the prosperous future that their models predicted, however, things went disastrously wrong. Greenspan's policies—implemented by Bill Clinton—fueled a speculative bubble that badly burst in 2008. So today a number of economists are waking up to the fact that economics is a field that is neither as quantifiable nor predictable as they'd thought. 
 
Furthermore, research shows that people do not make economic decisions based on rational thinking. We are impulsive and many of our choices are driven by our subconscious urges. We are not mathematical in our behavior. Thus, market transactions do not behave as straightforwardly as the laws of nature, in a concise mathematical way.

So physics envy on the part of “soft” scientists has largely been a misplaced attempt to quantify the squishy discipline of economics. This was outlined nicely in a 2010 paper: “Warning: Physics Envy May Be Hazardous to Your Wealth,” by two professors at MIT. It's taken a few years for some economists to accept that their discipline is not precisely mathematical or even very predictable. The authors of this paper point out that, although the attempt to make economics a mathematical science has brought some insights into the market place, “physics envy has also created a false sense of mathematical precision in some cases.” 
 
My former career was in physics, largely because I liked the simplicity and consistency of that hard science. Economists have learned in recent years to give more weight to the erratic choices that we make in the market place. Maybe that might help avoid another Great Recession, as happened in 2008.

Ultimately Untestable?

Contemporary physics is facing a problem—some physicists would even describe it as a crisis. And as is true for most crises, controversy erupts. Factions appear and engage in debate. Emotions bubble up. Yes, even staid physicists can become emotional, and a few of them even become impassioned.

The cause of this particular crisis is the shortcomings of what has come to be known as the “standard model” of physics. It describes the fundamental behavior of matter—which is essentially the core of physics. But the standard model, although it has been very successful in describing most of the behavior of aggregate matter, does not explain the behavior of elementary particles. The model does very well at the macro level, but is quite useless at the micro level.

Beginning about 100 years ago, a few physicists developed a new micro-matter theory that's come to be called quantum mechanics. It does a very nice job of describing the behavior of subatomic particles—such as electrons, protons, and neutrons. The problem—the crisis—lies in physicists being unable to reconcile the two theories.

What's worse, while the standard model has been verified by countless experiments, that's not true for several aspects of quantum theory. While many predictions of quantum mechanics have been verified by tests, there are some aspects of the theory that seem to be beyond experimental investigation. And that really bothers some physicists. The time-tested scientific principle is that scientific theories must be proven by experiment. So what do you do, when you can't put your theory to the test?

A rough parallel is the theory that was put forth by the Ptolemaic model for the universe—the nearly 2,000-year-old idea that placed the Earth at the center of the universe. Ptolemy's model was very cumbersome and complex, but it explained various phenomena for centuries. It was finally replaced by the far simpler Copernican (sun-centered) model in the 17^th century by Kepler, but his model's proof had to wait until science had the tools to do the experiment and irrefutably demonstrate that the new model was correct. The crucial tool that did the job: the telescope.

Quantum physics today is in a rather similar place. It could be that we may someday have the tools to run the experiments and confirm the correct theory (or correct theories). Yet some physicists are convinced we may never be able to do the experiments. If so, do we abandon the venerable rule that all theories must be testable, or just abandon those theories that can't be tested? The debate continues. Emotions are roiling.

Science Struggles—Part 2

There's a related struggle that is going on—primarily in academia—that illustrates another misunderstanding that the public has about science. It also stems from too many science educators teaching science as a simple sequential series of facts. I believe this is why so many students dislike and even dread the most basic science subject: physics.

I taught physics at the university level for a few years and was taken aback by the fact that many students were very anxious and were fretting over a subject that I loved. I soon realized that the physics text that the college had selected before I arrived was filled with intimidating equations and expected students to memorize those equations and their associated facts, with little emphasis on gaining any insight into their meaning. The second year of teaching I switched to a delightful physics text that stressed the concepts behind the equations, while minimizing their manipulation. I was delighted to see that many students now responded with far more receptivity to this most basic science. Class time now included lively discussions that had not been there before.

Without realizing it at the time, I was introducing a little of the philosophy of physics to my students. I have since become much more aware of the relevance of the philosophy of science—a subject that is even more misunderstood than science itself. Many people—particularly college students—are resistant to including a philosophical perspective to science. After all, isn't science a very tangible and concrete subject, while philosophy is fuzzy and mostly a matter of opinion?

It is a mistake to treat science mostly as a dry, objective study of the nature of things. Unfortunately, many scientists seem to encourage that kind of thinking, but it can lead to the perception that science has nothing to do with emotions, ethics, and moral choices. This may be partly why the public looks upon scientists as self-involved, introspective, and out of touch with the real world—and possibly even contributes to public distrust of science.

There is a lively field of study called the “philosophy of science,” that too many people—including a fair number of scientists—are either unaware of or distrust. But this field asks crucial questions that we all should be asking. It addresses questions that mere facts alone can't. It probes the understanding of science, rather than just its knowledge. It asks how we know these things, and are there some things we can't know? Is our understanding valid? Can our scientific knowledge guide us ethically or not? When we feel that we've improved our knowledge about a subject, how do we know that? How do we evaluate the improvement? What are the limitations of science? How do we discern true science from pseudoscience? These are important philosophical questions to be asking. If scientists were more open to them, it's possible that the disconnect between scientists and the public could be repaired some.

So there are many reasons why science is struggling in the eyes of the public. At a time when scientific discoveries are coming at a speedy pace and technology (the application of science) is rushing onward, this is not the time for poor communication between scientists and citizens; let alone mistrust and misunderstanding. The near future will be bringing many serious challenges to humanity. Those challenges need to be met by a robust science community working with a scientifically literary populace.

Hard Science

My formal education and former career were in the so-called “hard science” of physics. I also taught college physics for a brief stint, and was taken aback by how many students came to the course apprehensive—if not downright fearful—about surviving the experience. Physics, it seems, has acquired a frightful reputation. I soon took it as a challenge to demonstrate that this most basic of sciences is remarkably straightforward and even engaging. I tried to make it fascinating... with modest success at best. Within the department that I taught, there were other science classes in biology and chemistry. I don't think that their instructors dealt with students who were as intimidated as I did—and I never quite understood why.

In contrast, biology is not a “hard” science—although when put that way, the contrast makes it seem as if biology is easier... or even “soft,” whatever that means. Whatever the descriptive terms used, physics and biology are two contrasting sciences—the former is far more basic. One of the fundamental differences in the two sciences is that most researchers in the so-called hard science of physics have a pretty good idea of what things they are looking for in their research. As an example, a major effort in physics for decades now has been the so-called “grand unified theory,” that integrates the four fundamental forces of nature: gravity, electromagnetism, and the strong and weak nuclear forces. Physicists know pretty much where they are headed (to realize that unification)—the struggle is deciphering the fierce mathematics to get there. Another example: last year a huge team of physicists demonstrated the existence of the Higgs boson—a particle that had been predicted to exist for decades. Its discovery had to wait for a powerful enough machine to expose it.

Biology, however, is neither elegant nor straightforward, like physics. Biology deals with the messy living world—a domain rife with variety and unpredictable complexity. Life is the result of a long process of historical accidents—unpredictable events that have brought about species that responded well to those random historical incidents. For example, the ascendancy of mammals began about 65 million years ago, in the wake of an unlikely collision that brought a massive meteorite to impact Earth and did away with the dinosaurs. No one could have seen that impact coming. Sudden and haphazard climate changes have similarly caused many species to evolve in manners that no “grand unified theory” could ever have anticipated.

As a result, biologists are often left hanging as to why certain organisms developed the way they did. They are often forced to project back in time, surmising causal factors for the observations they make. At times these factors are discovered through a process of complex scientific sleuthing. At other times it seems as if they might never fully be understood.

Biology is a frustratingly complex and difficult science. At least it seems that way to me—having been trained in what is considered a more basic science. In recent years I have become increasingly fascinated with biology, but struggle with its complicated and manifold divisions. It seems as if I have to memorize hundreds of terms and all of their relationships, in order to get anywhere with it. I'm glad I'm not a college student sitting in a biology class—trying to understand such a difficult subject.

Ear of the Beholder--Part 2

So the students and I faced an ongoing struggle that is created when an objective scientist is trying to reach a group of subjective musicians. They often were skeptical of the scientific material in our text. Luckily, I was teaching a laboratory course, so I was able to introduce them to the experimental method, wherein they could prove to themselves the truth of the physical properties of their musical instruments.

I ran into stiff resistance when we studied acoustic properties of their instruments that sometimes countered the message they were given by the conservatory staff. For example, brass players had been taught that the specific metal alloy of their instrument had a defining role in its sound quality. Woodwind players had been taught that the quality of sound they made was strongly dependent on whether the clarinet or oboe was made of an exotic tropical wood or a good grade of plastic. In fact, tests have shown that the material of a musical instrument has minimal influence on its tone. It’s much more a function of the shape of the instrument’s inner air column and the qualities of the player’s embouchure (the way that the player applies her lips and tongue to the mouthpiece). Unfortunately, there are no unequivocal tests that we could conduct in a college lab that would unambiguously evaluate sound quality, so our credibility gap in that area remained.

I did manage to come up with one lab test that was able to refute one of their main beliefs. We were studying in our text the subject of what distinguishes the sound of one musical instrument from another. How does one tell the sound of a violin from a trombone, or a clarinet from a trumpet? The answer seems obvious to anyone who has listened to music. They are very distinctive. The author of our text described that the main distinguishing characteristic was not the nature of the tone of an instrument, but unique qualities that can be heard at the very beginning and ending of a note. It’s not the steady tone that is distinctive, it’s the transient sounds on each end of a note.

This result seems to go against the experience of anyone who is at all familiar with music. As expected, the students were very resistant to the message. So, together we designed an experiment to test it out in our next lab. They all brought their instruments—clarinet, trombone, flute, trumpet, guitar, violin, cello, French horn, oboe, saxophone, and even voice. We picked a note that every instrument could play at the same pitch—I think it was A above middle C.

Each student stepped to the microphone and played that note for about 30 seconds, as we recorded it on tape. We chose one student to go alone into another room and erase the first and last couple of seconds from each recording—leaving only the steady, middle part of the note. He then scrambled the order of the recordings—making his secret notes as to the new sequence.

He then came back into the lab and played the 20-second samples, as the students listened and made their choices of which instrument made which tone. It surprised me at how similar the notes sounded, as I watched looks of consternation and perplexity cross their faces. They were clearly taken aback. When all tones had been played, I asked them if they wanted to listen to them again, before making their final choices. All heads nodded approvingly, brows knitted.

At the end of the second round, we tallied the scores. It was quite astonishing: on average, the class had correctly identified only one-third of the instruments. Their response to the test was somewhere between being awestruck and disbelief. I don’t think they became instant converts to the scientific principle, but it sure made an impression on them. They had proved to themselves something about the physics of sound that countered their subjective experience. For the rest of the course, the communication gap between us seemed a bit narrower.

Is Beauty Truth?—Part 1

For a couple of centuries scientists, mathematicians, and philosophers have argued about the validity of the last two lines of John Keats Ode on a Grecian Urn: “Beauty is truth, truth beauty—that is all/ Ye know on earth, and all ye need to know.” Keats seems to be equating truth and beauty in these lines, and there are many who agree with him. However, there is an equally adamant group of folks who take issue with Keats and find all sorts of reasons why beauty and truth are not the same, or at least that one does not necessarily imply the other.

As often happens when parties disagree, they frequently are using different definitions, and there are few words that have more contradictory interpretations than beauty and truth. Beauty certainly is a relative term—one person’s beauty is another’s ugly. Truth, although it infers an absolute state, can at best be only partially fathomed by us humans. Truth, if we pursue it unwaveringly, may slowly reveal itself, but we can never fully own it. So the arguments persist. If people can’t even agree on whether something is true or not, or whether it’s beautiful or not, how do they ever expect to settle the dispute of whether or not they are equivalent?

I recently read a book by the eminent British mathematician and prolific writer Ian Stewart, that unequivocally takes a stand on the issue. Stewart titled his book Why Beauty is Truth. It’s really “a history of symmetry” (that’s the subtitle of his book), but along the way he builds a pretty strong case for why “beauty must be true,” but he does so in a rather narrow definition of each term.

One of my frustrations in reading the book (besides having my brain become numb by all the pure mathematics he goes into) is that Stewart never clearly defines what he means by either beauty or truth. He seems to assume that anyone brash enough to tackle his book will already know what truth and beauty are, as he uses them. He’s kind of like the musician who delves into a detailed lecture on timbre and counterpoint rhythms, assured that everyone is familiar with those words.

The book was still rewarding for me to tough out, though. Afterwards I kept pondering what beauty and truth are, as Stewart uses them. Here’s what I came up with, thanks one more time to wonderful Internet resources. (I really appreciate Wikipedia!)

Stewart—being a mathematician—is primarily concerned with mathematical beauty. Pure mathematicians love to refer to a mathematical concept or proof as beautiful, and when they do they usually mean that it is elegant, in the sense of being (1) clean, with a minimum of details, (2) succinct, and/or (3) original and unexpected (as in a discovery of some fundamental mathematical relationship). In other words, it must be simple, straightforward, unique, and balanced.

When a mathematician plays with theoretical concepts in algebra, geometry, and number theory, and eventually comes upon a pure, simple insight, he literally gets a feeling of aesthetic pleasure and considers it beautiful. The Babylonian and Greek mathematicians fell in love with the beauty they found (particularly Pythagoras’s geometrical discoveries).

Next time, truth…

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.

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.

A Physics Digest—Part 6: Light

Last time I described how the electromagnetic spectrum spans a huge frequency range—from radio waves to gamma rays, a factor of a trillion or so. Only the tiniest part (one billionth) of that range, in the very middle, is the light visible to our eyes. Everything we see is confined to that incredibly narrow strip—it’s our constricted view of life.

One property of visible light that’s crucial to our sense of sight is reflection. If ordinary objects didn’t reflect the sun’s light, we’d not see them (sort of like the Klingon cloaking device on Star Trek). Ordinary things don’t emit light on their own, so we need reflections from the sun or other light source to know they’re there.

While light waves reflect from opaque objects, they penetrate materials like glass and water—wherein they move more slowly. When a light wave is forced to slow down upon entering a transparent medium, it will bend or refract. If you look at a spoon sitting in a glass of water, it appears bent. Refraction is also used in eyeglasses and telescopes, to focus rays of light.

In air or in a vacuum all the colors (all frequencies) of light move at the same speed, but in glass the low frequencies (reds) move faster than high frequencies (blues). Thus light can get separated into its constituent colors upon entering a glass prism and becoming refracted. The same process creates a rainbow; each raindrop acts like a tiny prism.

Sunlight appears white because it contains all colors mixed together. (Actually, it’s a little yellowish, since the sun emits a little more light energy at yellow wavelengths.) So how does a red balloon appear red, when only “white” sunlight strikes it? The balloon absorbs all light frequencies other than red; only the red wavelengths are reflected. If all the colors get absorbed, it’s a black balloon.

Why is the sky blue? White sunlight enters our atmosphere and some of it gets scattered by particles in the air. Blue (high) frequencies get scattered more than any other color, so the sky gets filled with “blue rays” of light. Why is the sunset red? When overhead, the sun is whitish-yellow, but as it sets (or rises) its rays must then travel a longer path through the atmosphere to reach our eyes. The lowest frequencies (reds) are the least scattered color. So red rays penetrate the thick atmosphere best and are the ones we see.

Our eyes’ retinas contain light sensing rods and cones. Cones (at the center) respond to color and also give us acute central vision. Rods (surrounding the center) do not sense color and give us less detail in peripheral vision. They can “see” at light levels a hundredth of what cones need, however, so in dim light we can still see, but with fewer details and no color.

Two or more overlapping electromagnetic light waves can either reinforce or interfere with each other. Scientists have learned much about light—its speed, its color composition, and the nature of the media it’s traversing—by studying the reinforcement and interference patterns that the waves make.

Although we see most objects by the sunlight they reflect, a few things emit light themselves. Fireflies do it beautifully. An incandescent light does it by getting heated up so much that it glows. When some types of gas are zapped by electrical energy, the electrons in their atoms are bumped up to a higher energy state. These excited electrons quickly drop back to their usual lower energy level, and emit photons of light. This is how neon and fluorescent lamps glow.

The electrons in some elements don’t immediately jump back down to a lower energy state right away, but hold on for a while. This is phosphorescence. And when the emitted light waves are all in step with each other (reinforcing each other) we get the intense beam of a laser.

Every element emits its own unique signature of photons (i.e., color of light) when excited electrically. Astronomers use these signatures to determine what elements are present in various stars, so we don’t have to travel there to sample them directly.

A Physics Digest—Part 5: Electricity and Magnetism

Our world is filled with electrical devices—in fact, all matter is electrical in nature. Every atom contains negatively-charged electrons orbiting a positive nucleus of protons. Positives and negatives attract each other. This is what holds an atom together. So what keeps all those mutually repulsive protons squeezed into an atom’s nucleus? The strong nuclear force—which we’ll get to in a later entry.

Some materials can be charged with static electricity by rubbing them. Shuffle across a rug in winter (when the humidity is low) and touch a door handle—watch the spark. Rub a balloon on your shirt and stick it to a wall: electrical attraction.

Some materials are good conductors of electricity; e.g., metals, which also conduct heat well. Other materials are poor conductors; e.g., rubber, so we coat electrical wires with rubber, in order to be able to handle them without a shock.

When electrical charges move along a wire, we have an electrical current; which can be thought of as analogous to water flowing through a hose. Voltage corresponds to pressure in the hose, and a battery is like the pump that pushes the water.

We can have direct current (DC), in which all the electric charge flows in one direction, or alternating current (AC), in which the charge reverses direction (60 times a second for the electric power coming into our houses). Voltage can do work as it pushes current, such as when it turns an electric motor. We measure the work that is done by the power it produces—in watts.

The discovery of magnetism predated our grasp of electricity by a few millennia. The Greeks played with magnetic stones they found. Material gets magnetized when clusters of atoms line up, military style. That lineup creates directional properties, for which we assign a north and a south pole to the magnet. Where did we get that convention? The Earth’s iron core creates a magnetic field that points towards the north and south poles. A magnetized compass needle aligns itself with this field. Some birds have a built-in magnetic compass to navigate themselves via Earth’s magnetic field.

A wonderful property of matter is that electricity and magnetism are coupled. When electricity flows in a wire, it sets up a magnetic field around it. Conversely, if you move a wire through a magnetic field, it causes an electric current to flow in the wire. Better yet, if you move a wire carrying current through a magnetic field a force on the wire can be felt. This is the essence of electric motors. That force can do work rotating a motor, maybe even moving an electric car.

One more fascinating property of electricity and magnetism is that their interaction creates electromagnetic radiation. If we vibrate a wire that’s carrying an electric current back and forth, we cause the wire’s surrounding magnetic field to similarly vibrate. This interaction sends out an electromagnetic wave, which happens to travel at the speed of light. In fact, these waves are light! They can move through the vacuum of space, like the heat radiation we saw earlier.

How fast we wave the wire back and forth determines the frequency of the electromagnetic wave. At low frequencies we get radio and microwaves (the latter can cook food). At mid frequencies we get infrared, visible light, and ultraviolet radiation. At high frequencies we get X-rays and gamma rays. These are all the same kind of waves, all moving at the speed of light.

On to more light next time.

A Physics Digest—Part 4: Sound

Sound begins when something vibrates—sending a sound wave through the air. The ear then gets stimulated and electrical impulses reach the brain. So does a tree make a sound when it falls? By this definition, only if an ear and a brain are present to sense the air’s vibrations.

While light and heat waves can travel through a vacuum, sound waves need a medium—a solid, liquid, or gas. (So a tree falling in outer space would be silent.) Sound waves travel at different speeds in different materials (they move faster in solids than air). A sound wave is transmitted within a medium when something makes a part of that medium vibrate. That part jostles neighboring parts, and the disturbance moves along—just like heat. Throw a stone into a pond and watch the circular vibration waves move outward. While the disturbance (energy) flows along, the material itself doesn’t. Watch a cork on the surface of the water bob up and down and notice that the cork doesn’t move outward with the wave.

The rate of vibration of sound is defined as its frequency. Our ears can register frequencies as low as 20 vibrations per second (Hertz), up to as high as 20,000 Hertz (although my aging ears quit at about 12,000). Sound waves transmit energy, which is often measured as loudness. Our remarkable ear can sense loudness levels of greater than a range of a factor of a trillion, so we squeeze that down into a workable logarithmic range of about 120 decibels.

Sound can become particularly attractive when we talk about music—although it can be very subjective. One person’s music is another’s noise. As a less subjective evaluation, we’d pretty much all of us define a jet engine as making a lot of noise.

Qualities of musical sounds that describe their properties are pitch (the same as frequency) and timbre. When a musical instrument makes a sound, it is composed of a fundamental tone (the basic pitch) and various overtones, which are whole-number multiples of the fundamental. The particular mix of these multiple tones defines the timbre of the instrument—its unique sound quality.

Musical instruments make sounds in three ways: by vibrating strings, vibrating air columns (horns and woodwinds) and vibrating surfaces (cymbals and drums). All of these sounds are simulated in a stereo system when an electrical signal causes a speaker surface to vibrate.

Our ear loves regular mathematical relationships between musical pitches. When the pitch of one sound is twice that of another, we hear an octave. When the ratios of pitches are whole number fractions—like 5/4 and 4/3—we hear musical intervals of a third and a fourth, respectively. That’s harmony!

A Physics Digest—Part 3: Heat

All matter we’re familiar with possesses some amount of heat, which means its atoms and molecules constantly jiggle about. The hotter something is, the greater the jiggle. Atoms in a solid can jiggle only so much, before they break loose and form a liquid. Heat it some more and atoms jiggle even more and spread out into a gas.

Temperature: it’s a measure of the thermal energy of something—it’s a way to quantify of the amount of kinetic (jiggling) energy of the atoms and molecules. The calorie: it’s a measure of the amount of heat energy it takes to raise the temperature of a body. We convert food calories (heat energy) into the energy of walking or doing the work of lifting things (like our bodies off the couch).

Heat always moves from hotter to colder bodies (cold doesn’t move); and does so in three ways. (1) Conduction—warmer jiggling atoms in a solid pass their jiggle on down the line. Good conductors (metals) pass it on faster than insulators. (2) Convection—hotter molecules and atoms in a liquid or gas move to cooler places and warm them. (3) Radiation—heat energy gets transferred by electromagnetic waves (we’ll look at them later).

Now comes the hard part: thermodynamics. No undergraduate class gave me more grief than thermo. Thermodynamics is the study of heat and how it’s transformed into mechanical energy. It’s a macroscopic discipline—not caring about the jiggling of individual atoms, just the net impact of what they do in concert. Thermodynamics is the basic study of how engines transform heat into useful energy: your car, a refrigerator, a nuclear power plant.

One of the basic concepts in thermodynamics is the temperature of absolute zero (there is no maximum temperature). Energy can always be extracted from any warm body; but when we get that body down to absolute zero, there is no energy at all (no more jiggle). Thus it’s the absolute ground floor for all heat calculations.

Similar to Newton’s discoveries for forces, thermodynamicists have discovered two basic laws. The First Law of Thermodynamics describes the conservation of energy—that it can neither be created nor destroyed, just transformed from one type into another. Thus when we add heat to a system we can then transform it into various forms of energy, knowing we can account for every portion without something mysteriously disappearing.

The Second Law of Thermodynamics tells us that heat always flows from hot to cold locations—always downhill. Thus energy always dissipates, is always deteriorating into less useful forms; eventually into waste heat. Entropy is a measure of this disorder.

A Physics Digest—Part 2: Properties of Matter

Matter is what physics is all about—in contrast to mind and spirit (which are the province of other specialties). All matter is composed of identical, infinitesimal building blocks: quarks and leptons. They come together to form a little bit bigger building blocks we call electrons, protons, and neutrons—which then form atoms. Everything in this wide universe is made up of only about a hundred kinds of atoms, arranged in endless possibilities. It’s all in how it’s assembled.

Of those 100 kinds of atoms, only about a dozen are used in the common stuff we see every day (most commonly carbon). When the universe was very young it consisted almost exclusively of hydrogen atoms—which are the simplest: one proton, one electron. Gradually, over time, other kinds of atoms got manufactured in the explosive belly of stars. We are stardust!

Atoms are ageless—once created, they’re pretty much forever. They move through us continually. Oxygen atoms you inhale today were once inhaled by Jesus (or maybe a gnat on his neck). Atoms are mostly nothing—each one is the tiniest speck of a nucleus, surrounded by vast space. We’re mostly nothing!

Matter comes in three basic flavors: solids, liquids, and gases. When atoms combine into molecules and get firmly locked into a structure, we call it a solid. When the molecules are ordered in a precise fashion, we call it a crystal—like the sodium chloride molecules in salt. An electrical attraction between atoms and molecules in a solid binds them tightly together. Solids possess density (how much mass is squeezed into a given volume)—thus the iron atoms in steel are heavier and packed together more tightly than the carbon atoms in wood.

Some solids also possess elasticity: the ability to distort under force and then bounce back, once the force is removed. But inelastic solids, like a lump of clay, get bent and stay bent.

In liquids the molecules are not fixed—there’s less electrical attraction between them—so they slide over each other and can assume the shape of the container they’re in. Analogous to the weight of a solid is pressure in a liquid: the force that a liquid exerts on the surface that contains it. Liquids also possess density; thus less dense oil will float on denser water. Useful properties of a liquid are hydraulics (a property of pressure) and capillarity (which allows trees to suck up water).

The third flavor of matter is gas—in which the molecules are even freer from each other. A gas will expand to fill its container, as its molecules spread out. But gas does have weight (also expressed as pressure), so we experience atmospheric pressure, when all that air piles up above us. Gas can also float less dense objects, such as air floating a helium-filled balloon. Gases can exert forces: hold your hand out of a moving car’s window and you’ll feel it.

The force of gas also holds up an airplane—which is far denser than air. How? Air flowing over the curved top of a wing must travel farther (and thus faster) than that across the flat bottom of the wing. Bernoulli showed us that the faster air moves, the lower is its pressure; so more pressure (force) is applied to the bottom of the wing, lifting it—along with the solid airplane attached to it.

A Physics Digest—Part 1: Motion

A discussion of the mechanics (the physics) of motion is pretty much a look at the early history of European physics—as it morphed from a general topic of natural philosophy into a precise science of physics. It began, however, with the Greeks. (What doesn’t, in Western culture?) A few of the Greek natural philosophers arrived at very accurate understandings of motion, while others conducted “thought experiments”—never testing out their ideas—that were shaky at best. Some of their misinterpretations hung around for nearly 2000 years, before they were fixed.

One of the key fixers was Galileo, who became one of the first natural philosophers to put his ideas to test—in 16th century Italy. He introduced the concept of inertia: that a body at rest wants to stay inactive until something budges it. More importantly, Galileo also showed us that inertia means that a moving body wants to keep in motion (at a constant speed), until something either slows it down or accelerates it. His insights paved the way for the understanding of the motion of projectiles and satellites. The moon is a satellite of Earth, as we are a satellite of the sun.

These Galilean insights opened the door for Isaac Newton to formulate his three laws of forces. He understood that a force was the thing that overcame the inertia of a body—getting it moving or slowing it down. He also discovered that every body has mass: an inherent quality that provides a measure of its inertia. Massive things have a lot of inertia. It takes more force to push them. So what is weight? It’s just a measure of how much force Earth’s gravity pulls on a body.

Newton was also the first person to grasp the essence of gravity. As I wrote in an earlier posting (5/26/09), Kepler got some hunches about gravity—believing it to be some kind of force that the sun exerts on planets—but never quite got the full picture. Newton did. The popular image has him getting his inspiration when an apple (being pulled down by gravitational force) hit him on the head. Whatever really happened, Newton understood that gravity is the force that pulls the apple and keeps us circling the sun. He came up with an elegant equation to describe it.

A Physics Digest

Over two millennia ago the Greeks founded the study of philosophy—fundamentally defined as the love or pursuit of wisdom. It is the search for underlying causes and principles of reality. That love of wisdom soon divided itself into two fields of study: (1) discerning the truth of existence as we humans perceive it (what is today’s philosophy) and (2) seeking to understand the reality of the universe, independent of human perception (i.e., not filtered through human senses). The latter branch of philosophy became known as natural philosophy: the study of natural phenomenon. Today we call it physics—the most basic of the modern sciences. (Other physical sciences: chemistry and astronomy. Life sciences: biology, botany, and zoology.)

Some 25 years ago I had the opportunity of teaching physics at the local college. Physics had been one of my stronger subjects when I was in school, so I looked forward to passing on the insights of this most basic of sciences. I love physics, but I also know that it intimidates most people. It needn’t. It scares people mostly because it’s usually taught by constantly throwing equations at students and then making them mindlessly crank out solutions, with minimal understanding of the concepts. So I made it my mission to get students excited about physics—rather than becoming frightened of it. My success was uneven, but I had fun at it for a few years.

I love physics because it is so basic. It’s the foundation of all other sciences. It’s also the most elegant science; the most graceful and simple. Now, I never used the word simple with students who considered physics to be devilishly hard, but it is simple, in the manner of being unadorned. Physics shows us the “how” of this universe—not necessarily the “why”. That’s the province of metaphysics.

To me, physics is the study of nature’s fundamental behavior—often expressed in elegant equations. I think it is beautiful and wonderful that the natural world behaves in such a straightforward, dependable, and honest manner. God doesn’t play capricious games with creation; the basic truths and beauty are constant and await anyone who puts attention to them.

I believe that as we develop an understanding of our world, we cannot have anything other than awe and a reverential attitude towards it all. The loveliness and harmony of nature are exquisitely expressed in the so-called laws of physics. Physicists do not create these laws; they are nature’s rules of conduct. They ain’t just equations; they’re sacred rules.

Over the next several posts I will attempt to provide a very brief digest of a year’s physics course. It won’t provide anyone a detailed comprehension of natural philosophy, but it will touch most of the bases of what the study of physics encompasses: the basic structure of this divine creation.