Tuesday, October 26, 2010

You've got c-mail?

J.J. Thomson & Ernest Rutherford
How does one go about discovering a particle so small that nobody can see it? The British physicist J.J. Thomson won the Nobel prize in 1906 for doing just that—discovering the electron. At Cambridge University, Thomson was the epitome of an absentminded professor, sporting a tweed jacket, round-rimmed spectacles, mustache and dishevelled hair. 
  While exploring the nature of cathode rays, he discovered that he could deflect their path with an electric field. Measuring the amount of deflection under various strength fields, he was able to determine the mass of these particles, which he found to be about 1,800 times lighter than the hydrogen atom. 
  He called these particles “corpuscles,” and (incorrectly) suggested that they make up all of the matter in atoms. Most scientists at the time believed that the atom was the most fundamental unit of matter and indivisible, so to them this was a shocking concept.
The "plum pudding" model of the atom
  Thompson proposed a “plum pudding” model for the atom, in which thousands of tiny, negatively charged corpuscles move about inside a massless cloud of positive charge. This theory was disproved by a former student of Thomson, Ernest Rutherford. By examining how alpha particles scattered after colliding with a thin sheet of gold foil, Rutherford found that the atom must have a small core, or nucleus. Rutherford proposed that the atom might resemble a tiny solar system, with a massive, positively-charged center orbited by electrons.
Rutherford's gold foil experiment
  Luckily the name corpuscles did not stick or else today we would be going to corpuscular stores like Radio Shack, or reading c-mail instead of e-mail. Eventually the word electron gained favor. It comes from the Greek word for amber, which was known for its ability to electrostatically attract small objects when rubbed with fur.

Monday, October 18, 2010

America's Secret Canyon

A Fremont petroglyph

Hidden away in a rugged and remote corner of eastern Utah lies one of the most unique archeological sites in North America—Range Creek Canyon. Native Americans known as the Fremonts lived there for several hundred years up until about 1,300 AD when their way of life came to a sudden and mysterious end. Similar to the Anasazi, the Fremonts were ancestors of today’s Pueblo peoples.
  The site remains largely untouched today thanks to Waldo Wilcox. He is the rancher that owned the land and protected this secret for 50 years until he eventually sold it to the state of Utah in 2001. Currently, the land is under the care of the University of Utah’s Archeology Department.
A stone and adobe granary
  The Fremonts hunted and farmed. They grew corn and stored it in stone and adobe granaries that they built in out-of-the-way cliff sides. Over 38 have been identified so far. These granaries are at many different elevations and often located in extremely precarious spots. It is thought that in lean years they stored their corn in higher, more difficult to reach areas in order to protect their limited food supply. 
A Fremont petroglyph
  They were also prolific artists, creating many carvings into the cliff walls (know as petroglyphs) and paintings in caves and on rocks (known as pictograms). Their cave dwellings were well crafted and a rich source of artifacts: pottery, stone tools, arrowheads and other items. This unique find will no doubt be carefully studied for years to come and promises to reveal many details of their lives.

1) True of false: Ranch Creek Canyon was home to the Fremont people a thousand years ago.

2) The Fremonts relied on the farming of ______________ which they stored in stone and adobe ______________________
a) corn, baskets  b) wheat, caves  c) corn, granaries  d) wheat, granaries

3) True or false: Petroglyphs are paintings on rock or cave walls.

4) Range Creek Canyon is being studied by _________________.
a) the state of Utah  b) the Utah University Geology Department  c) Waldo Wilcox  d) the Utah University Archeology Department.

5) The Fremonts are similar to what other ancient tribe?

Sunday, October 10, 2010

Apollo 15

Apollo 15's Lunar Rover
Genesis Rock


Sunday, October 3, 2010

Plutonium Pacemakers

A Medtronic plutonium pacemaker from 1974.

How ironic that the heaviest naturally-occurring element, plutonium, was named after the dwarf planet Pluto.
   Plutonium was discovered in 1940 by Glenn Seaborg and his team at Berkeley University. His research became part of the top-secret Manhattan Project, so its discovery would not be made public until after the atomic bomb called Fat Man was dropped on Nagasaki to end World War II. Seaborg would receive the Nobel Prize in Chemistry in 1951 for the discovery of the transuranium elements, including: plutonium, americium, curium, berkelium and californium.
   There are five isotopes of plutonium but only two have commercial uses: P-238 and P-239. P-239 is what is used in nuclear weapons and to fuel nuclear power plants. With a half-life of about 24,000 years, this is some pretty nasty stuff. In 1945 and 1946, during research for the Manhattan Project, two scientists died and many others had their lives cut short in two separate incidents with the same plutonium core that briefly went critical: first because a researcher accidentally dropped a brick on it, and once when a researcher accidentally encased it in a neutron reflector. Due to these accidents, the core would become known infamously as the Demon Core.
   P-238 has a half life of only 88 years and is much less dangerous—its radioactivity is known as alpha decay, where it emits a helium ion instead of gamma or X-rays. This type of radiation is much easier to shield and since a kilogram of P-238 can generate over 500 watts of power for decades, it’s perfect as an onboard power plant for space probes: Viking, Galileo and Cassini to name a few. 
   For a while in the 1970s, P-238 was used to power pacemakers for patients who did not want to risk repeated surgeries every time their battery wore out, and although pacemakers now use lithium-iodide batteries, there are still 50-100 people still living with functioning P-238 pacemakers.