Thursday, December 17, 2009

Eye Candy

The Elements

The elements from lanthanum to ytterbium are known collectively as lanthanides or rare-earth elements. The term rare-earth elements is a misnomer because some are not rare at all. The minerals from which they are extracted are actually quite common. The mineral monazite is mined worldwide, and it contains a complex mixture of nearly all the lanthanide elements.

My last chemistry post discussed the first three lanthanide metals. Today's will cover the next three. Please enjoy...

Neodymium:
Atomic Symbol: Nd
Atomic Number: 60
This is the best known of all the rare-earth elements because of neodymium magnets. These are by far the strongest magnets available, so strong that they are genuinely dangerous to be around, especially if you have more than one. They fly together which such force that they can shatter and send splinters in all directions, and can jump at each other from more than a foot away. Even very small ones can crush a finger, large ones an entire hand. They are used in fake magnetic piercings, which sometimes become impossible to pull apart, requiring a hospital visit for surgical removal.
Neodymium magnets are also used to check for counterfeit currency by detecting the magnetic particles in the ink used to print real currency.

Promethium:
Atomic Symbol: Pm
Atomic Number: 61
There is no way that this element could be successfully extracted from terrestrial sources. Promethium is radioactive with a half-life too short to have survived from when the earth was formed. The longest lived isotope has a half-life of only 17.7 years.
Promethium is obtained in minute quantities from the fission products of nuclear reactors. Its commercial applications are very meager: it was briefly used to create luminous dials for watches, but was soon replaced because its half-life made the glowing dials wear out too quickly to be practical.

Samarium:
Atomic Symbol: Sm
Atomic Number: 62
Surprisingly, samarium is not named for the ancient city of Samaria, but rather for its discoverer, the Russian scientist Vasili Samarsky-Bykhovets.
One of the strangest compounds on earth is samarium sulfide. It exists as a black crystal, but if scratched, it immediately transforms into a golden crystal with the properties of a metal.
Neodymium magnets are the strongest available, but samarium magnets can operate at higher temperatures where others would lose their magnetism.

A favorite book of mine which has been invaluable in writing these chemistry posts is Nature's Building Blocks: An A-Z Guide to the Elements, by John Emsley. A great recent addition is The Elements: A Visual Exploration, by Theodore Gray, which includes a lot of nice pictures and is suitable for a coffee table near you.

For my previous posts on the elements, click here.

Tuesday, December 15, 2009

Eye Candy

Orion

During the winter months, the constellation of Orion dominates the northern sky. This group of stars is among the easiest to recognize because of the three bright stars in a straight line that make up his belt. Orion and the surrounding area contains a number of remarkable stars and other celestial objects.

In Greek mythology, Orion was a mighty hunter who fell in love with Metrope, daughter of the king of Chios, and sought her hand in marriage. The king constantly deferred his consent to the marriage, and eventually had Orion blinded. Orion consulted an oracle who told him he could regain his sight by going to the far east and letting the rays of the rising sun fall on his eyes. His sight restored, Orion went to live on the island of Crete, where he was killed by the sting of a scorpion. After Orion's death, he was placed in the heavens as a constellation.

The orange star at he top left is the star Betelgeuse, 400 light-years from Earth and shining more brightly than 10,000 Suns. This is a star in decline, pulsating in the red supergiant stage. The color of a star gives information about its temperature, size, and life expectancy. Stars change color like a piece of heated metal, becoming progressively red, orange, yellow, white, and blue. For this reason Betelgeuse appears to flash red, contrasting with the pale blue of the surrounding stars.

Orion also contains a number of notable nebulas. Until 1610, nebulas were thought to be stars. Now they are recognized as giant clouds of gas and dust, sometimes luminous and other times dark. Nebulas fascinate astronomy enthusiasts because of their wispy, spiral shapes.

Clearly visible to the naked eye as a bright fuzzy patch, the Orion Nebula is the closest nebula to Earth (1,200 light-years away). Its location in Orion's sword, just south of the leftmost star in the belt, also makes it easy to find. Several thousand stars were probably born here. A few of the youngest are still inside the nebula, and they heat the ambient gas to over 18,000oF.

The Horsehead Nebula is one of the most admired objects in the sky, first observed at the Harvard University Observatory in 1888. The familiar horse head shape is actually a small extension of a much larger cloud, invisible against the night sky's black background. Stellar winds are gradually eroding the magnificent scrolls of this famous nebula, so that the head will lose its familiar shape over the next several thousand years. Enjoy it while you still can.

Adjacent to the Orion Nebula is a cloud of microscopic, bluish gas known as the Witch Head Nebula. The color is derived from the reflected light of the blue supergiant star Rigel, which shines more brightly than 40,000 suns. The nebula is actually a more vibrant blue than the star itself. Like the particles in the Earth's atmosphere, the nebula reflects more blue radiation because it absorbs blue less than other colors.

Next to Orion is the constellation Taurus, which contains the Pleiades, the most visible open cluster in the night sky. Single stars like our sun are relatively rare: stars usually come in groups of two or more that orbit one another. The Pleiades appears to contain seven stars in tight formation, although there are actually more than seven. They have been celebrated since ancient times: Homer's Odyssey mentions the Pleiades, as do the Old Testament books of Job and Amos. The cluster will dissipate over the next few million years, and each star will follow its own path through the galaxy.

All these objects near Orion are visible during December and January. For a clear view, use a telescope, but most can be spotted simply by looking up at the night sky on a clear night.

If you're interested in outer space, check out Astronomy: A Visual Guide, by Mark A. Garlick, and Cosmos, by Sylvia Arditi and Marc Lachieze-Rey. Both contain fascinating astronomy facts, along with lots of gorgeous glossy pictures.

For my previous posts on outer space, click here.

Monday, December 14, 2009

Eye Candy

Medieval Japan

Medieval Japan began in 1185. Before you begin today's blog post, I recommend that you check out the first part of the story, Japan: The Early Centuries. This includes a map, some basic statistics about modern Japan, and recounts the rise of Japanese culture from the dawn of civilization to the Fujiwara ascendancy. While today's post is perfectly enjoyable on its own, it might be a bit confusing without the back story.

Also please note that I am not Japanese, nor am I any sort of expert on Japanese culture. If you're more informed than I am, please feel free to comment.

Feudalism came to Japan the same way it did to Europe: local sources of authority grew in power as a central and distant emperor failed to maintain security and order. The peasants, no longer protected by imperial armies, paid taxes to the shogun, or general. The emperor himself was more helpless every day.

The resulting anarchy caused a series of conflicts between various clans struggling for dominance, collectively known as the Gempei War. Ultimate victory went to Minamoto Yoritomo, whose power was based on the new warrior class, which he established and maintained as a privileged order. Stressing the almost complete division between civil and military government, Yoritomo set up a separate military capital at Kamakura in 1185.

During the Kamakura Period, which lasted until 1333, Japanese art flourished, and feudalism developed until it was stronger than the imperial administration had ever been.

Through his military network, Yoritomo was already virtual ruler of Japan. The emperor and court were mostly powerless before the shogun. Kamakura became the true court and government, while Kyoto remained a titular capital, with no real power.

Originally the term samurai was applied to the whole military system of Japan, both nobles and vassals. By Yoritomo's time, it denoted the military retainers of the shogun, or military governor. The samurai was generally a mounted warrior, wearing two swords as a symbol of their position and following a rigid code of ethics known as the Bushido. They reorganized Japan as a police state, maintaining power on behalf of feudal barons, protecting the territory and ensuring the obedience of the peasants. This remained the dominant military force until feudalism was abolished in 1871, and the wearing of swords was forbidden.

The great Yoritomo died suddenly in 1198, thrown from his horse which panicked upon seeing the ghost of a brother whom Yoritomo had murdered. He was succeeded by his weakling sons.

In 1219, the rival Hojo family came to power by means of a series of conspiracies and assassinations that eliminated Minamoto heirs and their supporters. The Hojo regency lasted for 134 years. In 1274 and again in 1281 the Mongols, then in control of China and Korea, attempted to invade Japan, both times unsuccessfully. The invasions were a serious drain on Hojo resources, and they were soon unable to reward the vassals whom they relied on for support.

A talented emperor, Daigo II (1287-1339) led a rebellion to restore imperial administration which climaxed in 1333 with the capture of Kamakura and the downfall of the Hojo.

One of Daigo's supporters, Ashikaga Takauji, turned against the emperor and established a rival court. Daigo II was forced to flee from the capital, and for the next 56 years civil war between Daigo's and Ashikaga's supporters ravaged Japan. Finally, in 1392, an Ashikaga diplomat persuaded the true emperor to relinquish his throne. With their nominees acknowledged as rightful emperors, the Ashikaga were empowered to establish their own feudal control over the entire country.

To be continued...

There are a lot of great books on Japan, of course. One that's been especially helpful to me in writing these posts is Japan: Its History and Culture, by W. Scott Morton and J. Kenneth Olenik. There's also a very enjoyable travel memoir called A Year in Japan, by Kate T. Williamson. Both are available in the Hansisgreat Bookstore, or online at Barnes & Noble.

For my posts on other Nations of the World, click here.