Sunday, October 18, 2009

Eye Candy

The Moon

Most people heard that NASA launched a missile at the moon's south pole last week, followed by the LCROSS spacecraft. The experiment was designed to search for the presence of underground glacial water, which scientists have suspected might be found beneath the Cabeus A crater. The LCROSS spacecraft flew into the plume of dust left by the missile's impact and measured the properties before also colliding with the lunar surface.

The experiment cost $79 billion, cheap in the world of space travel. Millions gathered outside with binoculars and telescopes on the early morning of September 9 to observe the impact. It therefore seems like a good time to post a few comments on the moon, our nearest celestial neighbor, and the only body with details visible without a telescope.

As far as we can tell, it's unusual for a satellite and its host planet to be so close in size as the Earth is to the Moon. Mercury and Venus have no moons, and Mars has two, but they are very tiny. The diameter of our moon is about one-fourth that of Earth (3480 Km, 2160 mi.); but its volume is one-fiftieth of Earth's, and the Earth's mass is 81 times greater than the mass of the moon. Thus the pull of gravity on the lunar surface is only one-sixth of what it is here.

A rocket trip to the moon takes 60-70 hours. If you drove to the moon by car at a steady speed of 75 miles per hour, it would take 135 days to reach your destination. Twelve men and no women have walked on the moon, and the Apollo missions have collected 842 pounds of moon rocks.

Although the strength of the moon's gravity is one-sixth that of Earth's, the gravitational field itself is uneven. There are patches of unexpectedly high gravity , called "mascons", or "mass concentrations" on the lunar surface. Nobody knows for certain what causes them, but they are found in high concentrations where there are thick layers of lava from volcanic activity. Surprisingly, not all areas which were once volcanically active host mascons.

In 2011, NASA will send a probe to study the moon's gravity in minute detail. This will not only allow us to learn more about the moon, but also about how gravity can work here on Earth, and throughout the universe.

Things hardly ever change on the surface of the moon. Neil Armstrong's footprint will be visible for thousands of years, and it is still possible to find rocks on the surface from when the Solar System was created. The astronauts from the Apollo 15 mission found a rock that is 4.5 billion years old. Called the Genesis Rock, it is now on display at the Johnson Space Center in Houston, Texas.

The moon is a very quiet, stable environment, which makes it a terrific place to mount astronomical instruments. In fact, the moon is a perfect observatory, completely free from noise, light, and atmospheric interference such as we have here on Earth.

Some day its craters might be used as dishes for massive radio antennae. It's also an ideal launch pad for deep space exploration. If bases could be established on the moon, deep space exploration would become much easier. To exploit this potential, first we'd need to work out how to live there and build construction facilities. This is where water, native to the moon rather than shipped from Earth, would come in handy. Then we would have to find a way to launch space vehicles in a lunar environment.

No doubt it's a big job, but we're working out the details all the time.

For more information, I recommend checking out the Book of the Moon, by Rick Stroud.

For my previous posts on outer space, click here.

Monday, October 12, 2009

Eye Candy

The Elements

The elements with atomic numbers 57-70 are known collectively as the lanthanides, after the first member of the series, lanthanum. The name is derived from the greek word lanthano, meaning, "to lie hidden". The older name was rare-earth elements, although not all are rare.

The discovery of the lanthanides began with yttrium, which is not a rare-earth element but is very similar to them and often found with them. The mineral gadolinite, from which yttrium was first extracted, also contains trace amounts of several lanthanides.

Lanthanide elements with even atomic numbers are more abundant than those with odd numbers, a common feature of all the elements. The cost of lanthanide metals is in line with their rarity: most command prices of several thousand US dollars per kilogram. World reserves of lanthanide metals are estimated to exceed 110 million tons. The largest deposit is in China, and accounts for 75% of world production.

Today, we focus on the first three lanthanides...

Lanthanum:
Atomic Symbol: La
Atomic Number: 57
Discovered in January 1839 in Stockholm, Sweden by Carl Gustav Mosander, who remained strangely silent about his discovery and did not publish an account of it for several years. Most of his time was taken up running a mineral water business.
Lanthanum is one of the more abundant rare earth elements, being more common than either lead or tin. The element consists of two isotopes, the heavier of which comprises 99.9% of the total. The remaining 0.1%, lanthanum-138, is very weakly radioactive, with a half-life of 100 billion years.

Cerium:
Atomic Symbol: Ce
Atomic Number: 58
There is only a small demand for cerium metal. One use is in so called "self cleaning" ovens, in which it is sprayed on the walls to catalyze the disintegration of cooking residue, which is mostly carbon.
Cerium has some environmentally friendly characteristics: cerium oxide cleans up vehicle exhaust, and cerium is an essential part of long life, low energy light bulbs.

Praseodymium:
Atomic symbol: Pr
Atomic Number: 59
Carl Mosander believed he discovered two elements, which he named lanthanum and didymium. The first of these was a true element, the second was not, although it was accepted as such for more than 40 years.
Didymium was later discovered to be a mixture of two components: praseodymium and neodymium.
Praseodymium glass is used to make goggles for welders because it filters out heat radiation. It is one of the most abundant rare-earth elements, and is four times more abundant than tin.

There's a terrific book about all the elements called Nature's Building Blocks: An A-Z Guide to the Elements, by John Emsley. Highly recommended if you're one of the statistically insignificant number of people who's interested in this sort of thing.

For more geeky fun, check out my posts on the previous elements, hydrogen through barium, by clicking here.

Thursday, October 8, 2009

Eye Candy

Japan: The Early Centuries

There are 4,223 islands in the archipelago called Japan. Six hundred of them are inhabited, but only five are of any considerable size. The largest, Hondo or Honshu, is 1,130 miles long, averages about 73 miles wide, and contains 81,000 square miles, more than half the land area of the nation.

Population: 127,463,611
Total area: 145,882 sq. mi. (slightly smaller than California)
Capital: Tokyo
Prime Minister: Yukio Hatoyama (since September 2009)
Constitution: May 3, 1947
Language: Japanese
Religion: most Japanese observe both Shinto and Buddhist rites; about 16% belong to other religions, including 0.7% Christianity
GDP: $4.018 trillion, $31,500 per capita

No other nation is so afflicted by earthquakes. In the year 599, an earthquake swallowed entire villages. Comets streaked across the sky, asteroids crashed into the earth, and Japan was mysteriously blanketed in snow in mid-July. Drought and famine followed, and millions of Japanese died. In 1703 an earthquake killed 32,000 in Tokyo alone. In 1923 earthquake, tsunami, and fire caused 100,000 deaths in Tokyo. Kamakura, so kind to Buddha, was nearly totally destroyed. All modern Japanese buildings are now constructed to withstand seismic activity as a result.

Research has shown that the Ainu, a tribal people whose origins are unknown, were the first inhabitants of the Japanese Archipelago. They may have populated the islands from the 2nd and 1st millenia BC. Invading peoples from nearby areas in Asia began expeditions of conquest to the islands, forcing the Ainu to the northern portions of Honshu.

About AD 360 Empress Jingu, who would eventually be considered a goddess, took over the government after the death of her husband, Emperor Chuai. She led Japan to invade and conquer a portion of nearby Korea. During the next several centuries, cultural influence passed between Korea and Japan. Chinese writing, literature, and philosophy became popular.

The most important event of the period was the importation of Buddhism. This is usually dated in 552, when a king from southwestern Korea sent Buddhist priests to Japan, together with religious images, scriptures, and calendars. The imported culture soon became deeply rooted in the islands, and while contact between the two countries weakened after the Japanese were driven out of Korea in 562, by the early 7th century Buddhism had become the official religion of Japan.

In 604, the first Japanese constitution was drafted. A great council, the Dajokan, ruled alongside the emperor through local governors sent from the capital. Nara in Yamato became the first fixed capital in 710. In 794 Kyoto was made the imperial residence and, with few interruptions, remained the capital until 1868. By the 9th century, the emperor and Dajokan ruled all of the main islands except Hokkaido.

During the 9th century the emperors began to withdraw from public life, delegating the affairs of state to subordinates until they came to be regarded as abstractions in the national life rather than its directors. This political void was filled by the rising power of the Fujiwara, the leading family of court nobles. In 858 the Fujiwara became virtual masters of Japan, maintaining their power for the next three centuries.

The period of Fujiwara supremacy hosted a great flowering of Japanese culture; influenced, but no longer dominated by China and Korea. Wealth accumulated, and was centered on a life of luxury and refinement. Kyoto became as elegant as Paris in poetry and dress, setting the nation's standards for learning and taste.

I've stopped trying to summarize the Nations of the World in a single post. My short history of Japan will be continued...

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