Category: Science

The Feynman Lectures on Physics

feynman

“The whole thing was basically an experiment,” Richard Feynman said late in his career, looking back on the origins of his lectures. The experiment turned out to be hugely successful, spawning a book that has remained a definitive introduction to physics for decades. Ranging from the most basic principles of Newtonian physics through such formidable theories as general relativity and quantum mechanics, Feynman’s lectures stand as a monument of clear exposition and deep insight. (Feynman Lectures)

The timeless lectures are now being put online for free, these are “not just for students of physics but for anyone seeking an introduction to the field from the inimitable Feynman.”

An iconoclastic and influential theoretical physicist, not to mention Nobel Laureate, Richard Feynman(1918-1988) touched the lives of many.

Feynman is best known for his role in Los Alamos and the challenger investigation, but he was also an amazing teacher.

Now, at long last, his famous physics lectures, thanks to Caltech and The Feynman Lectures website, are being put online. Starting with the 52 chapters of volume one. Of course, you can always watch a few of them in video.

These are the lectures in physics that I gave last year and the year before to the freshman and sophomore classes at Caltech. The lectures are, of course, not verbatim—they have been edited, sometimes extensively and sometimes less so. The lectures form only part of the complete course.

See: Volume I: mainly mechanics, radiation and heat.

It’s impossible to learn very much by simply sitting in a lecture, or even by simply doing problems that are assigned. But in our modern times we have so many students to teach that we have to try to find some substitute for the ideal. Perhaps my lectures can make some contribution. Perhaps in some small place where there are individual teachers and students, they may get some inspiration or some ideas from the lectures. Perhaps they will have fun thinking them through—or going on to develop some of the ideas further.

This is all a work in progress, volumes II and II “will be posted as time and funds permit.” If you can’t wait, or you don’t want to kill your printer, you can always buy the paperbound set.

Coevolution and Artificial Selection

“The ancient relationship between bees and flowers is a classic example of coevolution. In a coevolutionary bargain like the one struck by the bee and the apple tree, the two parties acton each other to advance their individual interests but wind up trading favors: food for the bee, transportation for the apple genes. Consciousness needn’t enter into it on either side …”

***

In The Botany of Desire: A Plant’s-Eye View of the World Michael Pollan tells the story of four domesticated species—the apple, the tulip, cannabis, and the potato—and the human desires that link their destinies to our own.

“Its broader subject,” he writes, “is the complex reciprocal relationship between the human and natural world.”

It’s a simple question really: Did I choose to plant these tulips or did they make me do it? Pollan concludes that, in fact, both statements are true.

Did the plant make him do it? Only in the sense that the flower “makes” the bee pay it a visit.

Evolution doesn’t depend on will or intention to work; it is almost by definition, and unconscious, unwilled process. All it requires are beings compelled, as all plants and animals are, to make more of themselves by whatever means trial and error present. Sometimes an adaptive trait is so clever it appears purposeful: the ant that “cultivates” its own gardens of edible fungus, for instance, or the pitcher plant that “convinces” a fly it’s a piece of rotting meat. But such traits are clever only in retrospect. Design in nature is but a concatenation of accidents, culled by natural selection until the result is so beautiful or effective as to seem a miracle of purpose.

The book is as much about the human desires that connect us to plants as it is about the plants themselves.

“Our grammar,” Pollan writes, “might teach us to divide the world into active subjects and passive objects, but in a coevolutionary relationship every subject is also an object, every object a subject.”

Charles Darwin didn’t start out The Origin of Species with an account of his new theory, rather, he began with a foundation he felt would be easier for people to get their heads around. The first chapter was a special case of natural selection called artificial selection.

Artificial wasn’t used in the sense of fake but as in things that reflect human will. He wrote about a wealth of variation of species from which humans selected the traits that will be passed down to future generations. In this sense, human desire plays the role of nature, determining what constitutes “fitness.” If people could understand that, they would understand nature’s evolution.

Pollan argues that the crisp conceptual lie “that divided artificial from natural selection has blurred.”

Whereas once humankind exerted its will in the relatively small arena of artificial selection (the arena I think of, metaphorically, as a garden) and nature held sway everywhere else, today the force of our presence is felt everywhere. It has become much harder, in the past century, to tell where the garden leaves off an pure nature begins.

We are shaping things in ways that Darwin could never have imagined.

For a great many species today, “fitness” means the ability to get along in a world in which humankind has become the most powerful evolutionary force.

Artificial selection, it appears, has become at least as powerful as natural selection.

Nature’s success stories from now on are probably going to look a lot more like the apple’s than the panda’s or white leopard’s. If those last two species have a future, it will be because of human desire; strangely enough, their survival now depends on what amounts to a form of artificial selection.

The main characters of the book—the apple, the tulip, cannabis, and the potato—are four of the world’s success stories. “The dogs, cats, and horses of the plant world, these domesticated species are familiar to everyone,” Pollan writes.

Apples

In the wild a plant and its pests are continually coevolving, in a dance of resistance and conquest that can have no ultimate victor. But coevolution ceases in an orchard of grafted trees, since they are genetically identical from generation to generation. The problem very simply is that the apple trees no longer reproduce sexually, as they do when they’re grown from seed, and sex is nature’s way of creating fresh genetic combinations. At the same time the viruses, bacteria, fungi, and insects keep very much at it, reproducing sexually and continuing to evolve until eventually they hit on the precise genetic combination that allows them to overcome whatever resistance the apples may have once possessed. Suddenly total victory is in the pests’ sight — unless, that is, people come to the tree’s rescue, wielding the tools of modern chemistry.

Put another way, the domestication of the apple has gone too far, to the point where the species’ fitness for life in nature (where it still has to live, after all) has been dangerously compromised. Reduced to the handful of genetically identical clones that suit our taste and agricultural practice, the apple has lost the crucial variability — the wildness — that sexual reproduction confers.

The Tulip

The tulip’s genetic variability has in fact given nature–or, more precisely, natural selection–a great deal to play with. From among the chance mutations thrown out by a flower, nature preserves the rare ones that confer some advantage–brighter color, more perfect symmetry, whatever. For millions of years such features were selected, in effect, by the tulip’s pollinators–that is, insects–until the Turks came along and began to cast their own votes. (The Turks did not learn to make deliberate crosses till the 1600s; the novel tulips they prized were said simply to have “occurred.”) Darwin called such a process artificial, as opposed to natural, selection, but from the flower’s point of view, this is a distinction without a difference: individual plants in which a trait desired by either bees or Turks occurred wound up with more offspring. Though we self-importantly regard domestication as something people have done to plants, it is at the same time a strategy by which the plants have exploited us and our desires–even our most idiosyncratic notions of beauty–to advance their own interests. Depending on the environment in which a species finds itself, different adaptations will avail. Mutations that nature would have rejected out of hand in the wild sometimes prove to be brilliant adaptations in an environment that’s been shaped by human desire.

In the environment of the Ottoman Empire the best way for a tulip to get ahead was to have absurdly long petals drawn to a point fine as a needle. In drawings, paintings, and ceramics (the only place the Turks’ ideal of tulip beauty survives; the human environment is an unstable one), these elongated blooms look as though they’d been stretched to the limit by a glassblower. The metaphor of choice for this form of tulip petal was the dagger. … Though these … traits are not uncommon in species tulips, attenuated petals are virtually unknown in the wild, which suggests that the Ottoman ideal of tulip beauty—elegant, sharp, and masculine—was freakish and hard-won and conferred no advantage in nature.

All in all The Botany of Desire is one of the best books I’ve read on how our Apollonian desire for control and order increasingly butts up against the natural Dionysian wildness.

Richard Feynman — The Key to Science

“If it disagrees with experiment, it is wrong.”

In this video from the 60s, Richard Feynman explains, very simply, the key to science with his timeless wisdom. It is the capacity to be wrong that moves us forward.

In general, we look for a new law by the following process: First we guess it; then we compute the consequences of the guess to see what would be implied if this law that we guessed is right; then we compare the result of the computation to nature, with experiment or experience, compare it directly with observation, to see if it works. If it disagrees with experiment, it is wrong. In that simple statement is the key to science. It does not make any difference how beautiful your guess is, it does not make any difference how smart you are, who made the guess, or what his name is — if it disagrees with experiment, it is wrong.

Scientists and researchers, or really, anyone who experiments, are wrong more often than they are right. After all, what is the purpose of a hypothesis? To test whether or not an idea is wrong or right; to carry us toward a definitive answer to a problem. By its very nature, it will yield more disappointments than breakthroughs. In science, if something “disagrees with experiment”, it gets tossed into the treasure trove of failed experiments. Adulation is not usually reserved for things proven to be false. In science, what’s true is more likely to survive the sands of time.

Ask anyone to name the top ten smartest people in the world, dead or alive, and Albert Einstein (Richard Feynman too) would probably appear on that list. His genius is eternal, forever changing the world, but he was not impervious to reaching incorrect conclusions. For example, we know that the universe is constantly expanding but in 1917, Einstein theorized that it was static (“temporally infinite but spatially finite”).

There is something beautiful about ignorance…as long as one has the desire to expand the limits of their knowledge so that ignorance remains ephemeral. Oxymoronic as it may be, being wrong leads us to a better understanding of the world and ourselves.

The Honeybee Conjecture: What Is It About Bees And Hexagons?

honeycomb

Why is every cell in this honeycomb a hexagon?

More than 2,000 years ago, Marcus Terentius Varro, a roman citizen, proposed an answer, which ever since has been called “The Honeybee Conjecture.” He thought that if we better understood, there would be an elegant reason for what we see.

“The Honeybee Conjecture” is an example of mathematics unlocking a mystery of nature. And luckily, NPR, with the help of physicist/writer Alan Lightman, (who wrote The Accidental Universe: The World You Thought You Knew) helps explains Varro’s hunch.

Why the preference for hexagons? Is there something special about a six-sided shape?

“It is a mathematical truth,” Lightman writes, “that there are only three geometrical figures with equal sides that can fit together on a flat surface without leaving gaps: equilateral triangles, squares and hexagons.”

So which to choose? The triangle? The square? Or the hexagon? Which one is best? Here’s where our Roman, Marcus Terentius Varro made his great contribution. His “conjecture” — and that’s what it was, a mathematical guess — proposed that a structure built from hexagons is probably a wee bit more compact than a structure built from squares or triangles. A hexagonal honeycomb, he thought, would have “the smallest total perimeter.” He couldn’t prove it mathematically, but that’s what he thought.

Compactness matters. The more compact your structure, the less wax you need to construct the honeycomb. Wax is expensive. A bee must consume about eight ounces of honey to produce a single ounce of wax. So if you are watching your wax bill, you want the most compact building plan you can find.

In 1999 Thomas Hales produced a mathematical proof, confirming that Varro was right.

Why are they all the same size?

For bees to assemble a honeycomb the way bees actually do it, it’s simpler for each cell to be exactly the same. If the sides are all equal — “perfectly” hexagonal — every cell fits tight with every other cell. Everybody can pitch in. That way, a honeycomb is basically an easy jigsaw puzzle. All the parts fit.

Update: I ran across this interesting paper, which argues the honeybee comb have a circular shape at first and then transform into the hexagon.

We report that the cells in a natural honeybee comb have a circular shape at ‘birth’ but quickly transform into the familiar rounded hexagonal shape, while the comb is being built. The mechanism for this transformation is the flow of molten visco-elastic wax near the triple junction between the neighbouring circular cells. The flow may be unconstrained or constrained by the unmolten wax away from the junction. The heat for melting the wax is provided by the ‘hot’ worker bees.

Still Curious? Learn more about The Honeycomb Conjecture.