ETHIOPIAN SCIENCE & TECHNOLOGY
Vol. 1, No. 5 ------------ < for cleo community> --------- December 12, 1992
Magnetic Disk vs. Optical (part III)................Section 3/4
The Development of Quantum Theory (part IV).........Section 4/4
Note: A number of articles will be followed in the area of word processing, typesetting, and printing in the future.
This article was published by Dr. Richard Pankhurst with other stuff by the title "The Foundations of Education, Printing, Newspapers, Book Production, Libraries and Literacy in Ethiopia."
The printing press was first introduced into East Africa in Emperor Theodros' time. In October, 1863, Lorenzo Biancheri, a Lazarist Father who had been appointed apostolic vicar of Abyssinia, brought to Massawas, then nominally still under Turkish rule, a small printing press and a sort of Amharic type cast from matrixes made for Antoine d'Abbadie in France. Father Biancheri called himself ``printer to His Majesty Emperor Theodore'' and published an Amharic catechism which appeared early in 1864, but he died a few months later in September after which his press was destroyed.
The first non-religious press in the Italian colony was the Italian Military Press at Massawa which was established not long after the occupation of the port by the Italians in February, 1885. The press, according to Fumagalli, was obtained from the firm of Salvatore Lapi in Citta di Castelli in Italy which also supplied a 17-year-old printer, besides whom there were six or seven assistant workers. Production, which was entirely in Italian, was mainly of regulations, orders and circulars of the military authorities, though a number of books were also printed.
The first commercial press in Massawa appeared a few years later in 1890. It was the Tipographiae Libereria Italiana which was owned by A. Micheli and Co. and began publishing L'Eritreo,a weekly administrative newspaper, in November of the following year.
The press of the Corriere Eritreo was set up in Massawa in 1891 and began a weekly politico- commercial newspaper of that name in June of that year.
Magnetic Disk vs. Optical
Any computer by today's standard, must have a storage device. A computer with out storage is the same as an automobile with out a gas tank. This article addresses and compares two area of storage devices; namely, magnetic disk and optical.
Optical Storage (Part III)
CD = Compact Disc (audio player)
WORM = Write Once Read Many
CD-ROM = Compact Disc-Read Only Memory
MO = Megneto-Optical
MPC = Multimedia PC
How Does It Work?
A storage device consists of mainly two components--a DISK DRIVE and a DISK (or a tape) where data are stored and retrieved. A disk drive reads and writes data onto the disk using the instructions sent by CPU (by the brain of a computer.) A disk maintains a data given by a disk drive. In other words, a disk drive works the same as that of audio cassette player while a disk serves as an audio cassette. By the same token, when we talk about optical storage, we could say Optical Storage drives and Optical media.
An optical storage generally comes with a drive and optical medium. Optical storage device uses a coherent laser beam, which is sometimes called optical stylus, to read or write data from/on the surface of an optical medium.
Optical medium vary according to the type of optical storage, CD, CD-ROM, WORM, or MO. For instance, a CD medium is made of three layers:
1. Polycarbonate (plastic base or injection-molded substrate)
2. Aluminum (a reflective layer)
3. Lacquer (a protective clear coat.)
When data is stored into an optical medium, a coherent laser beam with measured exposure, which would affect the surface of the medium, is sent to mark the pits. Pits are a relative deep holes below the aluminum layer. As usual, data is maintained in the form of bits; technically speaking, as a collection of marks.
On the other hand, data is read, by sending a weaker laser beam to the address of a data on the surface of the medium, and by receiving the reflection of that laser from the surface of the medium and converting it into data.
Advantages of using a laser are quite promising and indicative of the future storage devices, but at this conjuncture, the technology remains far from replacing magnetic storages.
1. A laser can focus a very tiny spot or pit compared to that of magnetic disk drive.
2. A size of an optical storage medium as the same as a magnetic disk can store more data.
3. An optical medium is far stable than a magnetic disk. It is not easily affected by magnetic field, normal temperature, or light.
4. And it is portable.
Since optical storages come with different flavors, examining each and every one them would be helpful. And the next issue will cover CD-ROM, WORM, and MO.
--to be continued
THE DEVELOPMENT OF QUANTUM THEORY
Max Plank and the Origin of Quantum Theory
At the end of nineteenth century, the effort to reduce every aspect of physics to mechanics was fading. As the Maxwellians had hoped, electromagnetism couldn't be reduced to mechanics, which created another dimension or pillar in the field of physics. Thermodynamics was another very important science that was different from mechanics or electromagnetism. Thermodynamics shows the distinction between reversible and irreversible phenomena. For instance, the perfect elastic collision between two spheres is reversible, but the expansion of a gas in a vacuum is irreversible. However, one critical question became a serious challenge that led to a new concept, a statistical mechanics. The question was, as Segre stated, ``If all elementary phenomena are reversible and all physical phenomena are a combination of them, where does the obvious irreversibility of the macroscopic world come from?''. Many physicists, in the 19th century, had worked hard to answer this question. Their efforts led to introduce the new science of statistical mechanics, which consists of the concepts of ``probability.''
Statistical mechanics were critically studied by Boltzmann (1844-1908) and many other physicists who established very important theoretical results known today as statistical mechanics.
At a meeting of the German Physics Society on Dec. 14, 1900, Max Planck who had made some progress to find the emissive power, or the specific form of spectrum of a heated body, introduced a new pillar of physics, quantum physics.
Planck was born on April 18, 1858, at a place called Kiel, Germany. His father was a respected professor of law. After his family moved to Munich in 1867, Planck attended the gymnasium at Munich, later the University of Munich. Following this, Planck went to Berlin to join another university, where he took courses from Kirchhoff and Helmholtz, and graduated in. In 1879, Planck's dissertation was on thermodynamics and reversibility.
When Kirchhoff died in 1889, the University of Berlin asked Ludwig Boltzmann of Vienna to take his place, but Boltzmann who first accepted the position changed his mind because of the Prussian atmosphere of Berlin. The University of Berlin then offered the position to Planck.
A big problem was that of the `blackbody problem, where classical thermodynamics couldn't solve. Max Planck took an interest in the `blackbody' problem and in 1897, he started working on it. His work was partially based on Wien's result which was presented in 1893. Using thermodynamics, Wien was led to believe that he had found the properties of the emissive law and gave general formula. Planck tried to drive the formula combining electrodynamics with thermodynamics.Planck's reasoning was accepted neither by Boltzmann nor even by his own student because he didn't carry out the proper statistical analysis to obtain equilibrium conditions.
However, by continuing his work on the same subject, Max Planck concluded that thermodynamics shows that the radiation in a black body is independent of the nature of the wall, but dependent on its temperature. Furthermore, after making different assumptions about the blackbody, Planck concluded that the emissive power of the blackbody had to be proportional to the average energy of the oscillators which were used as a wall in the blackbody.
The experiments began to show a significant difference at low frequency, (A FORMULA IS OMITTED HERE.) Thus, Max Planck tried to change his expression for the ``entropy'' of the radiation by generalizing it. ``The entropy of a system is a quantity that pertains to it in the same manner as its volume or energy, and can be measured by suitable experiments.'' From his new expression, he calculated backward to obtain the emissive power and found a formula. On the night of October 19, 1900, at a Physics Seminar of the University of Berlin, Plank presented his new formula. The same night, when Rubens and Kurlbaum investigated Planck's formula against their experimental data, they found accurate agreement. It was thus clear that Planck had found the blackbody formula. The next task that laid ahead of Planck was justifying his expression of the entropy radiation; however, the problem couldn't be solved only with classical thermo-dynamics because it requires statistical mechanics.
According to classical mechanics and electricity the harmonic oscillator could have any energy, but Planck discovered that to fit the experimental spectrum the energy had to be limited to discrete values which were multiplies of integral of h\nu where h is Planck constant and \nu is frequency. Planck's formula:
(***the formula and its explanation is omitted***)
The discovery was fundamental and revolutionary. In later years, Planck became a secretary of the Prussian Academy of Sciences and the most respected German physicist. On the other hand, Planck suffered personal losses. In 1909, his first wife died, and during First World War, his two daughters succumbed in childbirth and his eldest son died at front. His fourth child from his second wife was killed by the Nazis in 1944. Planck survived the Second World War. While a great preparation was underway for his ninetieth birthday, Planck died on October 4, 1947.
--to be continued~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ email@example.com/ Abass Belay Alamnehe / ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~