Friday, August 14, 2009
Thursday, August 13, 2009
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.
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.
Tuesday, August 11, 2009
Monday, August 10, 2009
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.
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.
Saturday, August 8, 2009
Tuesday, August 4, 2009
Cardinal Window Woes
While our homestead may host a small flock of chickadees and titmice, we’ve never had more than one mating pair of cardinals. The resident male cardinal has consistently been intolerant of having any other guy of his species hang around. For a few years after we moved here the male was devilishly irritating; he kept attacking his own image in our windows, assuming it was his dreaded foe. Some days he’d land on a sill and bash away at himself for an hour or two. When that hour or two was at five in the morning, I was ready to throttle him.
I began to think that he’d addled his brain, turning it to mush, in his compulsive assaults that seemed to grow ever longer. I read with great trepidation that cardinals could live more than 20 years. That longevity, however, was achieved by a bird in captivity. Wild songbirds are lucky to live to an age of five. It made me wonder how old this guy was. How many more years would he pester us? Would he break the wild record and live with us for many more years? And would his replacement just carry on the tradition? I found my fondness for cardinals waning.
I tried taping pictures of hawks, owls, and other birds of prey to the inside of the windows, in a futile attempt to intimidate him. The fierce photos didn’t faze him. He pecked in their faces. I finally hit on the idea of tacking strips of chicken wire over some windows—just to keep him from reaching the glass. After attacking the wire a few times, he finally gave up.
A related problem had been disturbing us during that period: birds flying headlong into the windows and either becoming stunned or killed by breaking their neck. When a bird flies toward a window it sees the reflection of the sky behind it, not realizing it’s about to meet hard glass. We coddled a few birds until they regained consciousness, but it was heartbreaking to hold a bird whose life ebbed away.
After several failed experiments (like my earlier taping up of raptor photos) I hit upon an idea: fasten small tree branches to the outside of the window, so a bird perceives a tree, not open sky. It even allowed me to remove the ugly chicken wire, as the cardinal had by now apparently changed his ways. Window collisions dropped drastically, and cardinal peckings continued to be lacking.
Mom and pop cardinal even eventually became adapted to our presence—if not exactly tame. Once too shy to come to the feeder, they’ve now grown to be regular customers. They are usually the first at dawn and the last at dusk. It’s quite a sight, when light levels are diminishing, to see the brilliant red of the male fly to the feeder and sit there for several minutes, cracking sunflower seeds and spitting out the shells.
Just recently I was treated to the sight of the father feeding one of his fledged offspring, who’d scarcely acquired flying skills. Dad would pick up a seed, discard the shell, and fly to a tree. The youngster would immediately and awkwardly fly to him and get its reward: the seed stuffed into his gaping bill. The father always flew to a different spot, making his baby fly to him. It seemed to be both feeding and flying practice.
A couple of days later we heard a crash against the window and we once again sickeningly looked at each other, knowing this was a hard impact. I went out to find an immature cardinal lying on the ground, bleeding from its bill, quickly expiring. I winced yet one more time at a death that we had caused, while in vain trying to prevent it. Casing the situation out, I guessed that the inexperienced bird had tried to aim between two twigs on the branch that was tacked to the window, but failed.
I was greatly relieved later that day, when I saw the father feeding another of his offspring. I apologized to him for placing a window in his baby’s way and wished him success in his current parental investment. Could he also pass on the lesson of avoiding those branches on the windows?
I began to think that he’d addled his brain, turning it to mush, in his compulsive assaults that seemed to grow ever longer. I read with great trepidation that cardinals could live more than 20 years. That longevity, however, was achieved by a bird in captivity. Wild songbirds are lucky to live to an age of five. It made me wonder how old this guy was. How many more years would he pester us? Would he break the wild record and live with us for many more years? And would his replacement just carry on the tradition? I found my fondness for cardinals waning.
I tried taping pictures of hawks, owls, and other birds of prey to the inside of the windows, in a futile attempt to intimidate him. The fierce photos didn’t faze him. He pecked in their faces. I finally hit on the idea of tacking strips of chicken wire over some windows—just to keep him from reaching the glass. After attacking the wire a few times, he finally gave up.
A related problem had been disturbing us during that period: birds flying headlong into the windows and either becoming stunned or killed by breaking their neck. When a bird flies toward a window it sees the reflection of the sky behind it, not realizing it’s about to meet hard glass. We coddled a few birds until they regained consciousness, but it was heartbreaking to hold a bird whose life ebbed away.
After several failed experiments (like my earlier taping up of raptor photos) I hit upon an idea: fasten small tree branches to the outside of the window, so a bird perceives a tree, not open sky. It even allowed me to remove the ugly chicken wire, as the cardinal had by now apparently changed his ways. Window collisions dropped drastically, and cardinal peckings continued to be lacking.
Mom and pop cardinal even eventually became adapted to our presence—if not exactly tame. Once too shy to come to the feeder, they’ve now grown to be regular customers. They are usually the first at dawn and the last at dusk. It’s quite a sight, when light levels are diminishing, to see the brilliant red of the male fly to the feeder and sit there for several minutes, cracking sunflower seeds and spitting out the shells.
Just recently I was treated to the sight of the father feeding one of his fledged offspring, who’d scarcely acquired flying skills. Dad would pick up a seed, discard the shell, and fly to a tree. The youngster would immediately and awkwardly fly to him and get its reward: the seed stuffed into his gaping bill. The father always flew to a different spot, making his baby fly to him. It seemed to be both feeding and flying practice.
A couple of days later we heard a crash against the window and we once again sickeningly looked at each other, knowing this was a hard impact. I went out to find an immature cardinal lying on the ground, bleeding from its bill, quickly expiring. I winced yet one more time at a death that we had caused, while in vain trying to prevent it. Casing the situation out, I guessed that the inexperienced bird had tried to aim between two twigs on the branch that was tacked to the window, but failed.
I was greatly relieved later that day, when I saw the father feeding another of his offspring. I apologized to him for placing a window in his baby’s way and wished him success in his current parental investment. Could he also pass on the lesson of avoiding those branches on the windows?
Saturday, August 1, 2009
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