This may appear to be late, but that's just an illusion. LOL.

Here's the link to this year's contribution to Christmas, and one year ending and another starting. I hope you find it useful and maybe a little entertaining.

A recent article in TIME magazine ("Evolving Darwin," by Carl Zimmer, February 23, 2009, issue) about Darwin's theories and scientists' more recent findings using DNA had some rare gems in it that I'd like to share. The basis of the article is a book -- Why Evolution is True -- by Jerry Coyne, an evolutionary biologist a the University of Chicago.

Note that Darwin's theories were first published in his book On the Origin of Species on 24 November 1859. In it he recognized that

variation and heredity were the twin engines that made evolution possible, [but] he didn't know what made them possible. It would take almost a century after the publication of On the Origin of Species for biologists to determine that the answer was DNA.

DNA is like a genetic cookbook, using four molecular "letters" to spell out recipes for everything from hormones to heart valves...

Time and again, biologists are finding that Darwin had it right: evolution is the best way to explain the patterns of nature.

Here's a compendium of nuggets from the article:

• Besides studying fossils, biologists can discover the genealogy of species by looking at their DNA. The fossil record points to hippos and other hoofed mammals as being the closest living relatives of whales. So does their DNA. Our own DNA contains clues to the bonds we share with the rest of life — it turns out, for instance, that we are closer kin to mushrooms than to sunflowers.
• In fact, a lot of mutations that all humans carry neither helped nor harmed our ancestors. They spread just by chance. And a lot of our genome is not made up of protein-coding genes. In fact, 98.8% of it is not. Some of that 98.8% consists of "pseudogenes" — genes that once encoded proteins but no longer can because of a crippling mutation. They are the molecular equivalent of a vestigial tail, allowing us to see evolution's track.
• [Referring to Darwin's metaphor for evolution, the tree of life] ... there's more to the history of life than the branching of a tree. Viruses ferry genes from one host to another. Bacteria swap genes inside our bodies, evolving resistance to antibiotics in our own gut. Some 2 billion years ago, one of our single-celled ancestors took in an oxygen-consuming bacterium. That microbe became the thousands of tiny sacs found in each of our cells today, known as mitochondria, that let us breathe oxygen. When genes move this way, it's as if two brances of the tree of life are being grafted together.
• There are 10,000 species of bacteria in a spoonful of dirt, twice as many species as all the mammals in the world.

This article also contains a table comparing Darwin's theory to current findings, here quoted:

A while back I started a series of pieces about "things electrical." Published to date are entries titled

• "A drift of electrons"
• "Sweet induction"

This is the third installment.

When I first started studying electronics, I came across this statement in my textbook and was intrigued:

A charged particle moving in an electric field generates magnetism.

Searching on "charged particle in electric field", I couldn't find this statement anywhere to verify that I remembered it correctly. Then I remembered my son's series of books on science.

In 1819, a Danish scientist, Hans Chrisian Oersted, discovered electromagnetism. Oersted found that a nearby compass needle would move each time he switched some electrical equipment on or off. Normally, the needle pointed in a north-south direction. But, when Oersted switched on his equipment, the needle swung around to point in a different direction. It returned to its original position when the equipment was switched off.

Oersted found that the effect was caused by the electric current flowing through a wire near the compass. For some reason, the wire acted like a magnet when the current flowed through it. ... Oersted had discovered electromagnetism, although he did not discover why electricity should give rise to magnetism. In fact, even today, scientists do not understand electromagnetism fully...

Growing Up with Science: vol.5, "Electromagnetism;" H.S.Stuttman; 1987
[I've omitted a lot of the repetition--it's a children's book, after all.]

As far as I'm concerned this answers my guery. But, during my search, I found other information that is also intriguing. One interesting reference to Einstein's paper "On the Electrodynamics of Moving Bodies" in the wikipedia states that it

...reconciles Maxwell's equations for electricity and magnetism with the laws of mechanics, by introducing major changes to mechanics close to the speed of light. This later became known as Einstein's Special theory of relativity.

In some of the articles I found online, the only particles referred to are photons. Other sources stated that light is an electromagnetic wave. Be careful though. If you consider the double-slit experiment, it's a toss-up on whether and when light is a particle or a wave or a charged particle is a particle or a wave. It can get pretty messy. Here's a great animation from YouTube explaining the experiment.

From the wikipedia again, here's a definition of electromagnetic radiation:

...a time-varying electric field generates a magnetic field and vice versa. Therefore, as an oscillating electric field generates an oscillating magnetic field, the magnetic field in turn generates an oscillating electric field, and so on. These oscillating fields together form an electromagnetic wave.

For an interactive illustration of an electromagnetic wave, try Molecular Expressions. You may be prompted to download and install the Java Runtime Environment to view the animation. It's well worth the effort.

Journal entry dated 6 May 2007
Category: Whatis Aquarian, Food for thought

This is part 2 of my "things electrical" series.

Sweet induction

Before we get into the specifics of induction and inductors, transformers and windings, let me give a word to why talk about them. It seems to me that the aura is an example of induction in action and some forms of telepathy may be due to induction. The chakras may use induction to step up and step down energy, but I'm at a loss to explain how.

An inductor is an insulated, current-carrying wire wrapped around a magnetic or air core (think of thread on a spool). Because electricity (more properly electro-magnetic radiation or force) has electrical and magnetic components, current moving through the wire generates a magnetic field. When an inductor is placed near a second inductor, voltage is induced in it, that is, the current flowing in the first inductor causes current to flow in the second inductor. The two inductors don't have to have a common magnetic core, but it's more efficient. For this to work, something has to be changing: the current may be alternating, the magnetic core may be changing position, the voltage may be switched on and off repeatedly.

The inductor with the greater number of windings, or turns, will produce the larger voltage. If the inductor on the incoming side of the circuit has more turns, the voltage is stepped down by the second inductor; if the inductor on the incoming side of the circuit has fewer turns, the voltage is stepped up.

As an example, look at the inductor in a cathode-ray tube (CRT) or television. The incoming line voltage, usually 120 volts AC is converted to approximately 30 volts DC, then stepped up by the fly-back transformer to about 20,000 volts (depending on frequency) to produce a picture on the tube. A picture of a flyback transformer from Andy's high voltage page at geocities is included.

The following diagrams illustrate the methods for inducing electromagnetic force (EMF). Loop A is the conducting loop; causing a change in the flux linkage induces a change in current level. If we know the value of the resistor and the value of the incoming voltage, we can calculate the current (I = V/R).

	Changing the current in loop B, by means of a variable resistor, induces a current in A.
Changing the positions of the coils induces a current.
	Open and close a switch.
Push/pull a magnet with respect to the loop. (Induced current is shown by pulling the magnet away.)

So there are three rules for induction:

• A circuit with a power source
• proximity
• something changing

Journal entry dated 18 March 2007
Category: Food for thought

Lately things electrical have been coming to mind. Namely

• the drift of electrons in electric current
• the operation of inductors
• Electricity -- a mixture of electricity and magnetism
• Electrical potential

A drift of electrons

When I was first studying electronics, I asked an electrical engineer about the flow of electricity. He said it was comparable to water. So for a long time I thought of electrical flow as being like water flowing in a river.

Then, when studying electricity in physics, I came across this equation for electric current:

Rearranging the members of this equation so that the relationships between the quantities is unchanged in order to find

Hang in there, I know this can be boring. If you must, skip to the last paragraph. I think you'll find it interesting.

Where

• I  = current in amps
• n  = number of electrons per cubic meter (using a value of 1 electron per atom contributing to the current flow)
• e  = electronic charge
• A  = cross-sectional area of the wire carrying the current
• v_d = drift velocity of the electrons travelling throught the wire

Using the following values (after computing them where necessary)

• I  = 1 amp (value selected for convenience)
• n  = 8.45 X10²⁸ electrons per cubic meter
• e  = 1.602 X 10^-19 Coulomb per electron
• A  = 1 mm² or 10^-6 meters² (value selected for convenience)

And the answer is --
v_d = 7.39 X 10^-5 meters per second, less than 0.1 millimeter per second.

If electrons drift along lazily about the width of a hair per second, why does the light in my room go on as soon as I flip the switch?

According to my physics textbook (University Physics, Alvin Hudson and Rex Nelson, Harcourt Brace Jovanovich, 1982)

...when a circuit is connected to a source of [power], the electric field is established in all parts of the circuit a nearly the speed of light. So when the final connection is made, forming a complete closed path with the [power source], electrons start to flow more or less simultaneously in all parts of the circuit. Even though the average drift speed of each electron is slow, all parts of the circuit feel the effects of the current almost instantaneously. ...

Journal entry dated 23 March 2007