What Happened to LED Light Bulbs?

Light-emitting diodes are making their way into everyday life [see “In Pursuit of the Ultimate Lamp”; SciAm, February 2001]. Still, LED versions of 60-watt incandescent bulbs can cost around $100. Scientific American magazine states that just this month engineers at Purdue University reported that they have developed a way to make cheaper blue LED’s. Blue LED’s, along with easier to produce red and green LED’s, are needed to generate white light. Researchers describe making LED’s on silicon with a built-in reflective layer, which reduces cost. With mass manufac­turing they predict that affordable LED lamps could appear in two years.

Why LED’s? LED’s are very efficient at producing light from electricity. Unlike incandescent (filament) light bulbs in which only approximately 20% of the electrical energy is converted to visable light and the other 80% is radiated as thermal energy, nearly all of the electrical energy is converted into visable light. Also, the average incandescent or fluorescent light bulb has a lifetime use of hundreds of hours. LED’s have a lifetime use of tens of thousands of hours.

Black Holes

A black hole is a circular region of space in which the gravity is so powerful that nothing, including light, can escape its pull. Black holes are produced when a very large amount of matter collapses inward and creates a tremendous gravitational pull from matter existing in a very small space. Although the most recent movies and cutting-edge science literature use interest in black holes to make their products more appealing, the idea of a black hole is not new. The idea that an object could be so massive that light could not escape it was first presented in 1783 by John Mitchell. In 1915, Einstein’s theory of relativity gave mathematical evidence that this object could exist. German astronomers have confirmed in February 2009 after completing a sixteen year study that a giant black hole exists at the center of our galaxy. They tracked the movement of 28 stars circling the centre of the Milky Way using two telescopes in Chile.

The black hole is located about 27,000 light years from Earth and is estimated to be four million times bigger than the Sun. According to Dr Robert Massey, of the Royal Astronomical Society (RAS), the results suggest that galaxies form around giant black holes in the way that a pearl forms around grit. They had a role in bringing matter together and if you had a high enough density of matter then you have the conditions in which stars could form. “Thus the first generation of stars and galaxies could have come into existence”.

 One way of finding a black hole is by looking for straight streams of x-rays. As matter spirals inward it increases in temperature to a very high temperature and like a flashlight it emits large amounts of radiation from its center. This beam of radiation can be detected from earthbound and earth-orbiting telescopes. Another method is to look for areas where the light from stars seem to be bent and distorted much like looking through a lens. The light from around the hole will be bent like water going down a drain or like looking through an irregular glass window.  And, a third method of finding black holes is to look for areas of space where it seems that stars and planets are being pulled inward by a very strong gravitational field The researchers who found the black hole used this third method  of observation with the 3.5m New Technology Telescope and the 8.2m Very Large Telescope (VLT) in Chile. Both are operated by the European Southern Observatory (Eso).

 Movies do not describe the properties of black holes realistically. One aspect of black holes that movies do not generally take into account is the ability to survive entering into a black hole. Scientists generally agree that any living thing entering a black hole will be vaporized by the hot gasses and/or pulled in to long thin strings of matter in a process known as spagettification. Although the idea of traveling through a black hole to reach another universe or time is attractive to audiences, black holes do not lead to other universes and if you are pulled into one you will not survive.

 More Resources:

http://www.black-holes.org/explore4.html

The Sun Right Now

Here is a link to the Solar and Heliospheric Observatory (SOHO). Daily posts of pictures of the Sun, Sun’s corona, and other E/M imaging.
 

Deep Space 1

Deep Space 1 was launched from Cape Canaveral on October 24, 1998. During a highly successful primary mission the team tested twelve advanced high-risk technologies in space. In an extremely successful extended mission it encountered Comet Borrelly and returned the best images and other science data ever obtained from a comet. During its successful hyperextended mission, it conducted further technology tests. The spacecraft was retired on December 18, 2001.

  Deep Space 1 was the first spacecraft to utilize ion engines. Ion engines use ejected ionized xenon gas instead of chemical propellants. Only a very small amount of xenon is ejected at a time. It may take four days or more just to use one kilogram of xenon. Becasue of this small ejection mass, the reaction force experienced by the spacecraft is also small. If you rest a piece of paper on your hand, the paper pushes on your hand about as hard as the ion engine pushes on the spacecraft.  The benifit of the xenon ion propulsion is that unlike chemical engines, which generally can only be operated for minutes, ion engines can be operated for years. Even though the force that acts on the craft is small, it is applied over a long period and produces a large impulse. The net effect of this is a large change in momentum (velocity), eventually attaining speeds far beyond the reach of chemical propellants.

Deep Space 1, using less than 74 kg (163 pounds) of xenon, accelerated by about 4.3 kilometers/second (9600 miles/hour) over a period of 678 days. This is greater than any spacecraft has ever been able to change its speed and a longer duration than any previous propulsion system. This was attained while operating conservatively. DS1 could have achieved still higher velocity, but mission controllers had to fulfill defined mission objectives.

The team that developed and flew NASA’s Deep Space 1 spacecraft received the American Institute of Aeronautics and Astronautics’ prestigious Space Systems Award “For the outstanding performance of the team during design, implementation, test, operations, and extended mission including space flight test of 12 important, high-risk technologies.” The award was presented on April 2, 2003, during the Responsive Space Conference in Redondo Beach, Calif.

The First Day

In the spirit of blogging, my entry is a rambling about the fact that this is my first entry. With that out of the way, welcome!