Aristotle

Aristotle (Greek: Ἀριστοτέλης, Aristotélēs) (384 BC – 322 BC) was a Greek philosopher, a student of Plato and teacher of Alexander the Great. He wrote on many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, politics, government, ethics, biology and zoology.
Together with Plato and Socrates (Plato's teacher), Aristotle is one of the most important founding figures in Western philosophy. He was the first to create a comprehensive system of Western philosophy, encompassing morality and aesthetics, logic and science, politics and metaphysics. Aristotle's views on the physical sciences profoundly shaped medieval scholarship, and their influence extended well into the Renaissance, although they were ultimately replaced by Newtonian Physics. In the biological sciences, some of his observations were confirmed to be accurate only in the nineteenth century. His works contain the earliest known formal study of logic, which was incorporated in the late nineteenth century into modern formal logic. In metaphysics, Aristotelianism had a profound influence on philosophical and theological thinking in the Islamic and Jewish traditions in the Middle Ages, and it continues to influence Christian theology, especially Eastern Orthodox theology, and the scholastic tradition of the Catholic Church. All aspects of Aristotle's philosophy continue to be the object of active academic study today.

Life
Aristotle was born in Stageira, Chalcidice, in 384 BC, about 55 km (34 mi) east of modern-day Thessaloniki. His father Nicomachus was the personal physician to King Amyntas of Macedon. Aristotle was trained and educated as a member of the aristocracy. At about the age of eighteen, he went to Athens to continue his education at Plato's Academy. Aristotle remained at the academy for nearly twenty years, not leaving until after Plato's death in 347 BC. He then traveled with Xenocrates to the court of his friend Hermias of Atarneus in Asia Minor. While in Asia, Aristotle traveled with Theophrastus to the island of Lesbos, where together they researched the botany and zoology of the island. Aristotle married Hermias's adoptive daughter (or niece) Pythias. She bore him a daughter, whom they named Pythias. Soon after Hermias' death, Aristotle was invited by Philip II of Macedon to become the tutor to his son Alexander the Great in 343 B.C.
Aristotle was appointed as the head of the royal academy of Macedon. During that time he gave lessons not only to Alexander, but also to two other future kings: Ptolemy and Cassander. In his Politics, Aristotle states that only one thing could justify monarchy, and that was if the virtue of the king and his family were greater than the virtue of the rest of the citizens put together. Tactfully, he included the young prince and his father in that category. Aristotle encouraged Alexander toward eastern conquest, and his attitude towards Persia was unabashedly ethnocentric. In one famous example, he counsels Alexander to be 'a leader to the Greeks and a despot to the barbarians, to look after the former as after friends and relatives, and to deal with the latter as with beasts or plants'. Near the end of Alexander's life he began to suspect plots, and threatened Aristotle in letters. Aristotle had made no secret of his contempt for Alexander's pretense of divinity, and the king had executed Aristotle's grandnephew Callisthenes as a traitor. A widespread tradition in antiquity suspected Aristotle of playing a role in Alexander's death, but there is little evidence for this.

Early Islamic portrayal of Aristotle

Aristotle's scientific method
Like his teacher Plato, Aristotle's philosophy aims at the universal. Aristotle, however, found the universal in particular things, which he called the essence of things, while Plato finds that the universal exists apart from particular things, and is related to them as their prototype or exemplar. For Aristotle, therefore, philosophic method implies the ascent from the study of particular phenomena to the knowledge of essences, while for Plato philosophic method means the descent from a knowledge of universal Forms (or ideas) to a contemplation of particular imitations of these. For Aristotle, "form" still refers to the unconditional basis of phenomena but is "instantiated" in a particular substance (see Universals and particulars, below). In a certain sense, Aristotle's method is both inductive and deductive, while Plato's is essentially deductive from a priori principles.
In Aristotle's terminology, "natural philosophy" is a branch of philosophy examining the phenomena of the natural world, and includes fields that would be regarded today as physics, biology and other natural sciences. In modern times, the scope of philosophy has become limited to more generic or abstract inquiries, such as ethics and metaphysics, in which logic plays a major role. Today's philosophy tends to exclude empirical study of the natural world by means of the scientific method. In contrast, Aristotle's philosophical endeavors encompassed virtually all facets of intellectual inquiry.
In the larger sense of the word, Aristotle makes philosophy coextensive with reasoning, which he also would describe as "science". Note, however, that his use of the term science carries a different meaning than that covered by the term "scientific method". For Aristotle, "all science (dianoia) is either practical, poetical or theoretical" (Metaphysics 1025b25). By practical science, he means ethics and politics; by poetical science, he means the study of poetry and the other fine arts; by theoretical science, he means physics, mathematics and metaphysics.
If logic (or "analytics") is regarded as a study preliminary to philosophy, the divisions of Aristotelian philosophy would consist of: (1) Logic; (2) Theoretical Philosophy, including Metaphysics, Physics, Mathematics, (3) Practical Philosophy and (4) Poetical Philosophy.

Legacy
Twenty-three hundred years after his death, Aristotle remains one of the most influential people who ever lived. He was the founder of formal logic, pioneered the study of zoology, and left every future scientist and philosopher in his debt through his contributions to the scientific method.
Despite these accolades, many of Aristotle's errors held back science considerably. Bertrand Russell notes that "almost every serious intellectual advance has had to begin with an attack on some Aristotelian doctrine". Russell also refers to Aristotle's ethics as "repulsive", and calls his logic "as definitely antiquated as Ptolemaic astronomy". Russell notes that these errors make it difficult to do historical justice to Aristotle, until one remembers how large of an advance he made upon all of his predecessors. Of course, the problem of excessive devotion to Aristotle is more a problem of those later centuries and not of Aristotle himself.
Aristotle believed that women are colder than men and thus a lower form of life. His assumption unfortunately carried forward unexamined to Galen and others for almost two thousand years until the sixteenth century. He also believed that females could not be fully human. His analysis of procreation is frequently criticized on the grounds that it presupposes an active, ensouling masculine element bringing life to an inert, passive, lumpen female element; it is on these grounds that Aristotle is considered by some feminist critics to have been a misogynist. On the other hand, Aristotle gave equal weight to women's happiness as he did to men's, and commented in his Rhetoric that a society cannot be happy unless women are happy too. In places like Sparta where the lot of women is bad, there can only be half-happiness in society.

Muhammad ibn Zakariya al-Razi

Abū Bakr Muhammad ibn Zakariyā Rāzī (Zakariā-ye Rāzi: Persian: زكريای رازی), known as Rhazes or Rasis after medieval Latinists, (August 26 865, Rayy— 925, Rayy) was a Persian alchemist, chemist, physician, philosopher and scholar. He is recognised as a polymath and often referred as "probably the greatest and most original of all the Muslim physicians, and one of the most prolific as an author".
He made fundamental and enduring contributions to the fields of medicine, alchemy, music, and philosophy, recorded in over 184 books and articles in various fields of science. He was well-versed in Persian, Greek and Indian medical knowledge and made numerous advances in medicine through own observations and discoveries.


Well educated in music, mathematics, philosophy, and metaphysics, he finally chose medicine as his professional field. As a physician, he was an early proponent of experimental medicine and is considered the father of pediatrics. He was also a pioneer of neurosurgery and ophthalmology. He was among the first to use Humoralism to distinguish one contagious disease from another. In particular, Razi was the first physician to distinguish smallpox and measles through his clinical characterization of the two diseases. And as an alchemist, Rhazes is known for his study of sulfuric acid and for his discovery of ethanol and its refinement to use in medicine. He became chief physician of Rayy and Baghdad hospitals.


Rhazes was a rationalist and very confident in the power of ratiocination; he was widely regarded by his contemporaries and biographers as liberal and free from any kind of prejudice and very bold and daring in expressing his ideas without a qualm.
He traveled extensively but mostly in Persia. As a teacher in medicine, he attracted students of all disciplines and was said to be compassionate and devoted to the service of his patients, whether rich or poor.

European depiction of the Persian doctor Al-Razi, in Gerard of Cremona "Receuil des traites de medecine" 1250-1260

Biography

Rhazes was born on 28 August 865 AH and died on 6 October 925AH. His name Razi in Persian means from the city of Rayy, an ancient town called Ragha in old Persian and Ragâ in Avestan. It is located on the southern slopes of the Elburz Range situated near Tehran, Iran. In this city (like Ibn Sina) he accomplished most of his work.

In his early life he could have been a musician or singer (see Ibn abi Usaibi'ah) but more likely a lute-player who shifted his interest from music to alchemy (cf. ibn Juljul, Sa'id, ibn Khallikan, Usaibi'ah, al-Safadi). At the age of 30 (Safadi says after 40) he stopped his study of alchemy because his experimentation had caused an eye-disease (Cf. al-Biruni), obliging him to search for physicians and medicine to cure it. al-Biruni, Beyhaqi and others, say this was the reason why he began his medical studies.

Contributions to medicine

Smallpox vs. measles

As chief physician of the Baghdad hospital, Razi formulated the first known description of smallpox:
"Smallpox appears when blood 'boils' and is infected, resulting in vapours being expelled. Thus juvenile blood (which looks like wet extracts appearing on the skin) is being transformed into richer blood, having the color of mature wine. At this stage, smallpox shows up essentially as 'bubbles found in wine' - (as blisters) - ... this disease can also occur at other times - (meaning: not only during childhood) -. The best thing to do during this first stage is to keep away from it, otherwise this disease might turn into an epidemic."
This diagnosis is acknowledged by the Encyclopaedia Britannica (1911), which states: "The most trustworthy statements as to the early existence of the disease are found in an account by the 9th-century Persian physician Rhazes, by whom its symptoms were clearly described, its pathology explained by a humoral or fermentation theory, and directions given for its treatment."

Razi, treating a patient

Razi's book: al-Judari wa al-Hasbah (On Smallpox and Measles) was the first book describing smallpox and measles as distinct diseases. It was translated more than a dozen times into Latin and other European languages. Its lack of dogmatism and its Hippocratic reliance on clinical observation show Razi's medical methods.

Uranium

Uranium (pronounced /jʊˈreɪniəm/) is a silvery-white metallic chemical element in the actinide series of the periodic table that has the symbol U and atomic number 92. Besides its 92 protons, a uranium nucleus can have between 141 and 146 neutrons, with 146 (U-238) and 143 (U-235) in its most common isotopes. The number of electrons in a uranium atom is 92, 6 of them valence electrons. Uranium has the highest atomic weight of the naturally occurring elements. Uranium is approximately 70% denser than lead, but not as dense as gold or tungsten. It is weakly radioactive. It occurs naturally in low concentrations (a few parts per million) in soil, rock and water, and is commercially extracted from uranium-bearing minerals such as uraninite.

silvery gray metallic; corrodes to a spalling black oxide coat in air

Uranium is used as a colorant in uranium glass, producing orange-red to lemon yellow hues. It was also used for tinting and shading in early photography. The 1789 discovery of uranium in the mineral pitchblende is credited to Martin Heinrich Klaproth, who named the new element after the planet Uranus. Eugène-Melchior Péligot was the first person to isolate the metal, and its radioactive properties were uncovered in 1896 by Antoine Becquerel. Research by Enrico Fermi and others starting in 1934 led to its use as a fuel in the nuclear power industry and in Little Boy, the first nuclear weapon used in war. An ensuing arms race during the Cold War between the United States and the Soviet Union produced tens of thousands of nuclear weapons that used enriched uranium and uranium-derived plutonium. The security of those weapons and their fissile material following the breakup of the Soviet Union in 1991 is an ongoing concern for public health and safety.

Applications
The major application of uranium in the military sector is in high-density penetrators. This ammunition consists of depleted uranium (DU) alloyed with 1–2% other elements. At high impact speed, the density, hardness, and flammability of the projectile enable destruction of heavily armored targets. Tank armor and the removable armor on combat vehicles are also hardened with depleted uranium plates. The use of DU became a contentious political-environmental issue after the use of DU munitions by the US, UK and other countries during wars in the Persian Gulf and the Balkans raised questions of uranium compounds left in the soil (see Gulf War Syndrome).
Depleted uranium is also used as a shielding material in some containers used to store and transport radioactive materials. Other uses of DU include counterweights for aircraft control surfaces, as ballast for missile re-entry vehicles and as a shielding material. Due to its high density, this material is found in inertial guidance devices and in gyroscopic compasses. DU is preferred over similarly dense metals due to its ability to be easily machined and cast as well as its relatively low cost. Counter to popular belief, the main risk of exposure to DU is chemical poisoning by uranium oxide rather than radioactivity (uranium being only a weak alpha emitter).
During the later stages of World War II, the entire Cold War, and to a lesser extent afterwards, uranium has been used as the fissile explosive material to produce nuclear weapons. Two major types of fission bombs were built: a relatively simple device that uses uranium-235 and a more complicated mechanism that uses uranium-238-derived plutonium-239. Later, a much more complicated and far more powerful fusion bomb that uses a plutonium-based device in a uranium casing to cause a mixture of tritium and deuterium to undergo nuclear fusion was built.

The most visible civilian use of uranium is as the thermal power source used in nuclear power plants.

After Marie Curie discovered radium in uranium ore, a huge industry developed to mine uranium so as to extract the radium, which was used to make glow-in-the-dark paints for clock and aircraft dials. This left a prodigious quantity of uranium as a 'waste product', since it takes three metric tons of uranium to extract one gram of radium. This 'waste product' was diverted to the glazing industry, making uranium glazes very inexpensive and abundant. In addition to the pottery glazes, uranium tile glazes accounted for the bulk of the use, including common bathroom and kitchen tiles which can be produced in green, yellow, mauve, black, blue, red and other colors.
Uranium was also used in photographic chemicals (esp. uranium nitrate as a toner), in lamp filaments, to improve the appearance of dentures, and in the leather and wood industries for stains and dyes. Uranium salts are mordants of silk or wool. Uranyl acetate and uranyl formate are used as electron-dense "stains" in transmission electron microscopy, to increase the contrast of biological specimens in ultrathin sections and in negative staining of viruses, isolated cell organelles and macromolecules.
The discovery of the radioactivity of uranium ushered in additional scientific and practical uses of the element. The long half-life of the isotope uranium-238 (4.51 × 109 years) makes it well-suited for use in estimating the age of the earliest igneous rocks and for other types of radiometric dating (including uranium-thorium dating and uranium-lead dating). Uranium metal is used for X-ray targets in the making of high-energy X-rays.

Uranium glass used as lead-in seals in a vacuum capacitor

Limestone

Limestone is a sedimentary rock composed largely of the mineral calcite (calcium carbonate: CaCO3). The deposition of limestone strata is often a by-product and indicator of biological activity in the geologic record. Calcium (along with nitrogen, phosphorus, and potassium) is a key mineral to plant nutrition: soils overlying limestone bedrock tend to be pre-fertilized with calcium. Limestone is an important stone for masonry and architecture, vying with only granite and sandstone to be the most commonly used architectural stone. Limestone is a key ingredient of quicklime, mortar, cement, and concrete. The solubility of limestone in water and weak acid solutions leads to important phenomena. Regions overlying limestone bedrock tend to have fewer visible groundwater sources (ponds and streams), as surface water easily drains downward through cracks in the limestone. While draining, water slowly (over thousands or millions of years) enlarges these cracks; dissolving the calcium-carbonate and carrying it away in solution. Most well-known natural cave systems are through limestone bedrock.

Description
Limestone often contains variable amounts of silica in the form of chert and/or flint, as well as varying amounts of clay, silt and sand as disseminations, nodules, or layers within the rock. The primary source of the calcite in limestone is most commonly marine organisms. These organisms secrete shells that settle out of the water column and are deposited on ocean floors as pelagic ooze or alternatively are conglomerated in a coral reef (see lysocline for information on calcite dissolution). Secondary calcite may also be deposited by supersaturated meteoric waters (groundwater that precipitates the material in caves). This produces speleothems such as stalagmites and stalactites. Another form taken by calcite is that of oolites (oolitic limestone) which can be recognized by its granular appearance.
Limestone makes up about 10% of the total volume of all sedimentary rocks. Limestones may also form in both lacustrine and evaporite depositional environments.
Calcite can be either dissolved by groundwater or precipitated by groundwater, depending on several factors including the water temperature, pH, and dissolved ion concentrations. Calcite exhibits an unusual characteristic called retrograde solubility in which it becomes less soluble in water as the temperature increases.
When conditions are right for precipitation, calcite forms mineral coatings that cement the existing rock grains together or it can fill fractures.
Karst topography and caves develop in carbonate rocks due to their solubility in dilute acidic groundwater. Cooling groundwater or mixing of different groundwaters will also create conditions suitable for cave formation.

Uses
Limestone is very common in architecture, especially in North America and Europe. Many landmarks across the world, including the Great Pyramid and its associated Complex in Giza, Egypt, are made of limestone. So many buildings in Kingston, Ontario, Canada were constructed from it that it is nicknamed the 'Limestone City'. On the island of Malta, a variety of limestone called Globigerina limestone was for a long time the only building material available, and is still very frequently used on all types of buildings and sculptures. Limestone is readily available and relatively easy to cut into blocks or more elaborate carving. It is also long-lasting and stands up well to exposure. However, it is a very heavy material, making it impractical for tall buildings, and relatively expensive as a building material.

Limestone was most popular in the late 19th and early 20th centuries. Train stations, banks and other structures from that era are normally made of limestone. Limestone is used as a facade on some skyscrapers, but only in thin plates for covering rather than solid blocks. In the United States, Indiana, most notably the Bloomington area, has long been a source of high quality quarried limestone, called Indiana limestone. Many famous buildings in London are built from Portland limestone.
Limestone was also a very popular building block in the Middle Ages in the areas where it occurred since it is hard, is durable, and commonly occurs in easily accessible surface exposures. Many medieval churches and castles in Europe are made of limestone. Beer stone was a popular kind of limestone for medieval buildings in southern England.
Limestone and marble are very reactive to acid solutions, making acid rain a significant problem. Many limestone statues and building surfaces have suffered severe damage due to acid rain. Acid-based cleaning chemicals can also etch limestone, which should only be cleaned with a neutral or mild alkaline-based cleaner.

Other uses include:
1) The manufacture of quicklime (calcium oxide) and slaked lime (calcium hydroxide);
2) Cement and mortar;
3) Pulverized limestone is used as a soil conditioner to neutralize acidic soil conditions;
4) Crushed for use as aggregate—the solid base for many roads;
5) Geological formations of limestone are among the best petroleum reservoirs;
6) As a reagent in desulfurizations;
7) Glass making, in some circumstances;
8) Added to paper, plastics, paint, tiles, and other materials as both white pigment and a cheap
filler.
9) Toothpaste
10) Suppression of methane explosions in underground coal mines
11) Added to bread and cereals as a source of calcium
12) Calcium supplement for poultry (when ground up)

Courthouse built of limestone in Manhattan, Kansas

Alcázar of Segovia in Spain

Unta Patah Rancangan Abu Jahal

Setelah pelbagai usaha oleh kaum Quraisy untuk menyekat dan menghapuskan penyebaran agama Islam menemui kegagalan, maka Abu Jahal semakin benci terhadap Rasulullah S.A.W. Kebencian Abu Jahal ini tidak ada tolok bandingnya, malah melebihi kebencian Abu Lahab terhadap Rasulullah S.A.W. Melihatkan agama Islam semakin tersebar, Abu Jahal pun berkata kepada kaum Quraisy di dalam suatu perhimpunan, "Hai kaumku! Janganlah sekali-kali membiarkan Muhammad menyebarkan ajaran barunya dengan sesuka hatinya. Ini adalah kerana dia telah menghina agama nenek moyang kita, dia mencela tuhan yang kita sembah. Demi Tuhan, aku berjanji kepada kamu sekalian, bahawa esok aku akan membawa batu ke Masjidil Haram untuk dibalingkan ke kepala Muhammad ketika dia sujud. Selepas itu, terserahlah kepada kamu semua samada mahu menyerahkan aku kepada keluarganya atau kamu membela aku dari ancaman kaum kerabatnya. Biarlah orang-orang Bani Hasyim bertindak apa yang mereka sukai." Tatkala mendengar jaminan daripada Abu Jahal, maka orang ramai yang menghadiri perhimpunan itu berkata secara serentak kepadanya, "Demi Tuhan, kami tidak akan sekali-kali menyerahkan engkau kepada keluarga Muhammad. Teruskan niatmu." Orang ramai yang menghadiri perhimpunan itu merasa bangga mendengar kata-kata yang diucapkan oleh Abu Jahal bahawa dia akan menghapuskan Muhammad kerana jika Abu Jahal berjaya menghapuskan Nabi Muhammad S.A.W bererti akan terhapuslah segala keresahan dan kesusahan mereka selama ini yang disebabkan oleh kegiatan Rasulullah S.A.W menyebarkan agama Islam di kalangan mereka. Dalam pada itu, terdapat juga para hadirin di situ telah mengira-ngira perbelanjaan untuk mengadakan pesta sekiranya Nabi Muhammad S.A.W berjaya dihapuskan. Pada pandangan mereka adalah mudah untuk membunuh Nabi Muhammad S.A.W yang dikasihi oleh Tuhan Yang Maha Esa serta sekalian penghuni langit. Padahal Allah tidak akan sekali-kali membiarkan kekasih-Nya diancam dan diperlakukan seperti binatang. Dengan perasaan bangga, keesokan harinya di sebelah pagi, Abu Jahal pun terus pergi ke Kaabah iaitu tempat biasa Nabi Muhammad S.A.W bersembahyang. Dengan langkahnya seperti seorang satria, dia berjalan dengan membawa seketul batu besar di tangan sambil diiringi oleh beberapa orang Quraisy yang rapat dengannya. Tujuan dia mengajak kawan-kawannya ialah untuk menyaksikan bagaimana nanti dia akan menghempapkan batu itu di atas kepala Nabi Muhammad S.A.W. Sepanjang perjalanan itu dia membayangkan bagaimana keadaan Nabi Muhammad nanti setelah kepalanya dihentak oleh batu itu. Dia tersenyum sendirian apabila membayangkan kepala Nabi Muhammad S.A.W pecah dan tidak bergerak lagi. Dan juga membayangkan bagaimana kaum Quraisy akan menyambutnya sebagai pahlawan yang telah berjaya membunuh musuh nombor satu mereka. Sebaik sahaja Abu Jahal tiba di perkarangan Masjidil Haram, dilihatnya Rasulullah S.A.W baru sahaja sampai dan hendak mengerjakan sembahyang. Dalam pada itu, Nabi Muhammad S.A.W tidak menyedari akan kehadiran Abu Jahal dan kawan-kawannya di situ. Baginda tidak pernah terfikir apa yang hendak dilakukan oleh Abu Jahal terhadap dirinya pada hari itu. Sebaik-baik sahaja Abu Jahal melihat Rasulullah S.A.W telah mula bersembahyang, dia berjalan perlahan-lahan dari arah belakang menuju ke arah Nabi Muhammad S.A.W. Abu Jahal melangkah dengan berhati-hati, setiap pergerakannya dijaga, takut disedari oleh baginda. Dari jauh kawan-kawan Abu Jahal memerhatikan dengan perasaan cemas bercampur gembira. Dalam hati mereka berkata, "Kali ini akan musnahlah engkau hai Muhammad." Sebaik sahaja Abu Jahal hendak menghampiri Nabi Muhammad S.A.W dan menghayun batu yang dipegangnya itu, tiba-tiba secepat kilat dia berundur ke belakang. Batu yang dipegangnya juga jatuh ke tanah. Mukanya yang tadi merah kini menjadi pucat lesi seolah-olah tiada berdarah lagi. Rakan-rakannya yang amat ghairah untuk melihat Nabi Muhammad S.A.W terbunuh, tercengang dan saling berpandangan. Kaki Abu Jahal seolah-olah terpaku ke bumi. Dia tidak dapat melangkahkan kaki walaupun setapak. Melihatkan keadaan itu, rakan-rakannya segera menarik Abu Jahal dari situ sebelum disedari oleh baginda. Abu Jahal masih terpinga-pinga dengan kejadian yang dialaminya. Sebaik sahaja dia sedar dari kejutan peristiwa tadi, rakan-rakannya tidak sabar untuk mengetahui apakah sebenarnya yang telah berlaku. Kawannya bertanya, "Apakah sebenarnya yang terjadi kepada engkau, Abu Jahal? Mengapa engkau tidak menghempapkan batu itu ke kepala Muhammad ketika dia sedang sujud tadi?" Akan tetapi Abu Jahal tetap membisu, rakan-rakannya semakin kehairanan. Abu Jahal yang mereka kenali selama ini seorang yang lantang berpidato dan menyumpah seranah Nabi S.A.W, tiba-tiba sahaja diam membisu. Dalam pada itu, Abu Jahal masih terbayang-bayang akan kejadian yang baru menimpanya tadi. Dia seolah-olah tidak percaya dengan apa yang dilihatnya, malah dia sendiri tidak menyangka perkara yang sama akan berulang menimpa dirinya. Perkara yang sama pernah menimpa Abu Jahal sewaktu Rasulullah S.A.W pergi ke rumah Abu Jahal apabila seorang Nasrani mengadu kepada baginda bahawa Abu Jahal telah merampas hartanya. Pada masa itu Abu Jahal tidak berani berkata apa-apa pada baginda apabila dia terpandang dua ekor harimau menjadi pengawal peribadi Rasulullah S.A.W. Kemudian setelah habis mereka menghujani Abu Jahal dengan pelbagai soalan, maka Abu Jahal pun mula bersuara, "Wahai sahabatku! Untuk pengetahuan kamu semua, sebaik sahaja aku menghampiri Muhammad hendak menghempapkan batu itu ke kepalanya, tiba-tiba muncul seekor unta yang besar hendak menendang aku. Aku amat terkejut kerana belum pernah melihat unta yang sebegitu besar seumur hidupku. Sekiranya aku teruskan niatku, nescaya akan matilah aku ditendang oleh unta itu, sebab itulah aku berundur dan membatalkan niatku." Rakan-rakan Abu Jahal berasa amat kecewa mendengar penjelasan itu, mereka tidak menyangka orang yang selama ini gagah dan beria-ia hendak membunuh Nabi Muhammad S.A.W hanya tinggal kata-kata sahaja. Orang yang selama ini diharapkan boleh menghapuskan Nabi Muhammad S.A.W dan pengaruhnya hanya berupaya bercakap seperti tin kosong sahaja. Setelah mendengar penjelasan dari Abu Jahal yang tidak memuaskan hati itu, maka mereka pun berkata kepada Abu Jahal dengan perasaan kehairanan, "Ya Abu Jahal, semasa kau menghampiri Muhammad tadi, kami memerhatikan engkau dari jauh tetapi kai tidak napak akan unta yang engkau katakan itu. Malah bayangnya pun kami tidak nampak." Rakan-rakan Abu Jahal mula sangsi dengan segala keterangan yang diberikan oleh Abu Jahal. Mereka menyangka Abu Jahal sentiasa mereka-reka cerita yang karut itu, mereka mula hilang kepercayaan terhadapnya. Akhirnya segala kata-kata Abu Jahal mereka tidak berapa endahkan lagi.

Netizen @ Cybercitizen

A Netizen (a portmanteau of Internet and citizen) or cybercitizen is a person actively involved in online communities.

Description
Netizens can use the Internet to engage in activities of extended social groups, such as giving and receiving viewpoints, furnishing information, fostering the Internet as an intellectual and a social resource, and making choices for the self-assembled communities. Generally, a netizen can be any user of the worldwide, unstructured forums of the Internet. The word netizen itself was coined by Michael Hauben. Netizens are Internet users who utilize the networks from their home, workplace, or school (among other places). Netizens try to be conducive to the Internet's use and growth. Netizens, who use and know about the network of networks, usually have a self-imposed responsibility to make certain that it is improved in its development while encouraging free speech and open access. Netizens' use of the Internet around the world has been marked by:

Medium Description
E-mail : Delivery of letters by means of the Internet, as a
replacement to the traditional based paper
correspondence letters.

Online chat : Establishing of one-on-one or group conversations by
means of the Internet.

Instant messaging : Software which enables real time conversations without the
need of using a website (in contrast to online chats).

Internet fora : Web Sites which serve to hold discussions in defined
subjects.

Online games : Multiplayer Computer games which are played through the
Internet.

Blog : A kind of log in which the writer(s) writes in it in any
possible subject in which he or she desires to talk discuss at
any time the author(s) so desires, and in which the writer(s)
control access to.

Feedback comment system : A Mechanism used in web sites to post responses from the
internet users, which is mostly used in the news web sites, in
blogs and in the other additional sites

File sharing : A technology which enables the internet users to share files
from their computers with other internet users, and in
return the same internet user is capable of downloading files
from the computer of other internet users. This enables the
fast distribution, not always legal, of software, music, etc.

Gopher : A distributed document search and retrieval network protocol
designed for the Internet. Its goal is to function as an
improved form of Anonymous FTP, enhanced with
hyperlinking features similar to that of the World Wide Web.

Wiki : A collection of web pages designed to enable anyone who
accesses it to contribute or modify content, using a simplified
markup language.

Internet Commerce: Netizens are citizens of the internet community dedicated to
the participation and civic responsibility of providing Internet
commerce resources to the netizens of the global Internet
community.

The term has been used most frequently recently in Korea where there are vigorous netizens movements. The election of President Roh Moo-hyun of South Korea in 2002 is widely attributed to the support for him among South Korean netizens, especially OhmyNews.

Kuiper belt

The Kuiper belt (pronounced /ˈkaɪpər/, rhyming with "viper"), sometimes called the Edgeworth-Kuiper belt, is a region of the Solar System beyond the planets extending from the orbit of Neptune (at 30 AU) to approximately 55 AU from the Sun. It is similar to the asteroid belt, although it is far larger—20 times as wide and 20–200 times as massive. Like the asteroid belt, it consists mainly of small bodies (remnants from the Solar System's formation). But while the asteroid belt is composed primarily of rock and metal, the Kuiper belt objects are composed largely of frozen volatiles (termed "ices"), such as methane, ammonia and water. It is home to at least three dwarf planets – Pluto, Haumea and Makemake.
Since the first discovery in 1992, the number of known Kuiper belt objects (KBOs) has increased to over a thousand, and more than 70 000 KBOs over 100 km in diameter are believed to reside there. The Kuiper belt was initially believed to be the main repository for periodic comets, those with orbits lasting less than 200 years. However, studies since the mid-1990s have shown that the Kuiper belt is dynamically stable, and that it is the farther scattered disc, a dynamically active region created by the outward motion of Neptune 4.5 billion years ago, that is their true place of origin. Scattered disc objects such as Eris are KBO-like bodies with extremely large orbits that take them as far as 100 AU from the Sun. The centaurs, comet-like bodies that orbit among the gas giants, are believed to originate there. Neptune's moon Triton is believed to be a captured KBO. Pluto, a dwarf planet, is the largest known member of the Kuiper belt. Originally considered a planet, it is similar to many other objects of the Kuiper belt, and its orbital period is identical to that of the KBOs known as "Plutinos".
The Kuiper belt should not be confused with the hypothesized Oort cloud, which is a thousand times more distant. The objects within the Kuiper belt, together with the members of the scattered disc and any potential Hills cloud or Oort cloud objects, are collectively referred to as trans-Neptunian objects (TNOs)

Known objects in the Kuiper belt, derived from data from the Minor Planet Center. Objects in the main belt are coloured green, while scattered objects are coloured orange. The four outer planets are blue. Neptune's few known Trojan asteroids are yellow, while Jupiter's are pink. The scattered objects between the Sun and the Kuiper belt are known as centaurs. The scale is in astronomical units. The pronounced gap at the bottom is due to obscuration by the band of the Milky Way.

The precise origins of the Kuiper belt and its complex structure are still unclear, and astronomers are awaiting the completion of several wide-field survey telescopes such as Pan-STARRS and the future LSST, which should reveal many currently unknown KBOs. These surveys will provide data that will help determine answers to these questions. The Kuiper belt is believed to consist of planetesimals; fragments from the original protoplanetary disc around the Sun that failed to fully coalesce into planets and instead formed into smaller bodies, the largest less than 3000 km in diameter.
Modern computer simulations show the Kuiper belt to have been strongly influenced by Jupiter and Neptune, and also suggest that neither Uranus nor Neptune could have formed in situ beyond Saturn, as too little primordial matter existed at that range to produce objects of such high mass. Instead, these planets are believed to have formed closer to Jupiter, and migrated outwards during the course of the Solar System's early evolution. Eventually, the orbits shifted to the point where Jupiter and Saturn existed in an exact 2:1 resonance; Jupiter orbited the Sun twice for every one Saturn orbit. The gravitational pull from such a resonance ultimately disrupted the orbits of Uranus and Neptune, causing Neptune's orbit to move outward into the primordial planetesimal disk, which sent the disk into temporary chaos. As Neptune traveled along this modified orbit, it excited and scattered many TNO planetesimals into higher and more eccentric orbits, depleting the primordial population. However, the present most popular model still fails to account for many of the characteristics of the distribution and, quoting one of the scientific articles, the problems "continue to challenge analytical techniques and the fastest numerical modeling hardware and software".

Simulation showing Outer Planets and Kuiper Belt: a)Before Jupiter/Saturn 2:1 resonance b)Scattering of Kuiper Belt objects into the solar system after the orbital shift of Neptune c)After ejection of Kuiper Belt bodies by Jupiter

Kisah Nabi Musa a.s dan Nabi Khidir a.s

Lalu mereka dapati seorang dari hamba-hamba Kami (Nabi Khidir) yang telah kami kurniakan kepadanya rahmat dari Kami, dan Kami telah mengajarnya sejenis ilmu; dari sisi Kami.
Nabi Musa berkata kepadanya: “Bolehkah aku mengikutmu, dengan syarat engkau mengajarku dari apa yang telah diajarkan oleh Allah kepadamu, ilmu yang menjadi petunjuk bagiku?” Dia menjawab: “Sesungguhnya engkau (wahai Musa), tidak sekali-kali akan dapat bersabar bersamaku. Dan bagaimana engkau akan sabar terhadap perkara yang engkau tidak mengetahuinya secara meliputi?”

Nabi Musa berkata: ”Engkau akan dapati aku, InsyaAllah, orang yang sabar; dan aku tidak akan membantah sebarang perintahmu.” Dia (Nabi Khidir) menjawab: “Sekiranya engkau mengikutku, maka janganlah engkau bertanya kepadaku akan sesuatupun sehingga aku ceritakan halnya kepadamu.”

Lalu berjalanlah keduanya sehingga apabila mereka menaiki sebuah perahu, dia (Nabi Khidir) membocorkannya. Nabi Musa berkata: “Patutkah engkau membocorkannya sedang akibat perbuatan itu menenggelamkan penumpang-penumpangnya? Sesungguhnya engkau telah melakukan satu perkara yang besar.”

Dia (Nabi Khidir) menjawab: “Bukankah aku telah katakan, bahawa engkau tidak sekali-kali akan dapat bersabar bersamaku?” Nabi Musa berkata: “Janganlah engkau marah akan daku disebabkan aku lupa (akan syaratmu); dan janganlah engkau memberati daku dengan sebarang kesukaran dalam urusanku (menuntut ilmu).”

Kemudian keduanya berjalan lagi sehingga apabila mereka bertemu dengan seorang pemuda lalu dia (Nabi Khidir) membunuhnya. Nabi Musa berkata “Patutkah engkau membunuh satu jiwa yang bersih, yang tidak berdosa membunuh orang? Sesungguhnya engkau telah melakukan satu perbuatan yang mungkar!”

Dia (Nabi Khidir) menjawab: “Bukankah, aku telah katakana kepadamu, bahawa engkau tidak sekali-kali akan dapat bersabar bersamaku?” Nabi Musa berkata: “Jika aku bertanya kepadamu tentang sebarang perkara sesudah ini, maka janganlah engkau jadikan daku sahabatmu lagi; sesungguhnya engkau telah cukup mendapat alasan-alasan berbuat demikian disebabkan pertanyaan-pertanyaan dan bantahanku.”

Kemudian keduanya berjalan lagi, sehingga apabila mereka sampai kepada penduduk sebuah bandar, mereka meminta makan kepada orang-orang di situ, lalu orang-orang itu enggan menjamu mereka. Kemudian mereka dapati di situ sebuah tembok yang hendak runtuh, lalu dia (Nabi Khidir) emmbinanya. Nabi Musa berkata: “Jika engkau mahu, tentulah engkau berhak mengambil upah mengenainya!”

Dia (Nabi Khidir) menjawab: “Inilah masanya perpisahan antaraku denganmu, aku akan terangkan kepadamu maksud (kejadian-kejadian yang dimusykilkan) yang engkau tidak dapat bersabar mengenainya.

Adapun perahu itu adalah dipunyai oleh orang-orang miskin yang bekerja di laut; oleh itu aku bocorkan dengan tujuan hendak mencacatkannya kerana di belakang mereka nanti ada seorang raja yang merampas tiap-tiap sebuah perahu yang tidak cacat.

Adapun pemuda itu, kedua ibu bapanya adalah orang-orang yang beriman, maka kami bimbang bahawa dia akan mendesak mereka melakukan perbuatan yang zalim dan kufur. Oleh itu kami ingin dan berharap supaya Tuhan mereka gantikan bagi mereka anak yang lebih baik daripadanya tentang kebersihan jiwa dan lebih mesra kasih sayangnya.

Adapun tembok itu pula, adalah ia dipunyai oleh dua orang anak yatim di bandar itu; dan di bawahnya ada harta terpendam kepunyaan mereka; dan bapa mereka pula adalah orang yang shalih. Maka Tuhanmu menghendaki supaya mereka cukup umur dan dapat mengeluarkan harta mereka yang terpendam itu, sebagai satu rahmat dari Tuhanmu (kepada mereka). Dan (ingatlah) aku tidak melakukannya menurut fikiranku sendiri. Demikianlah penjelasan tentang maksud dan tujuan perkara-perkara yang engkau tidak dapat bersabar mengenainya.” (sumber - Al-Kahfi : 65-82)

Fata Morgana (mirage)

Fata Morgana are usually seen in the morning after a cold night which has resulted in the radiation of heat into space. In this form of mirage, objects on the horizon or even beyond the horizon, such as islands, cliffs, ships or icebergs, appear elongated and elevated, like "fairy tale castles".
This is how the mirage is caused: in calm weather, when warm air lies over cold dense air near the surface of the ground, the undisturbed interface between these two air masses can act as a refracting lens, producing an upside-down image, over which the distant direct image appears to hover.
The first mention of the "Fata Morgana" phenomenon in English was in 1818, when this type of mirage was observed in the Strait of Messina, between Calabria and Sicily. It is also commonly seen in high mountain valleys, such as the San Luis Valley of Colorado where the effect is exaggerated due to the curvature of the floor of the valley canceling out the curvature of the Earth. These mirages are also seen in Arctic seas on very still mornings, and are common on Antarctic ice shelves.

Superior mirage

A superior mirage occurs when the air below the line of sight is colder than that above. This is called a temperature inversion, since it does not represent the normal equilibrium temperature gradient of the atmosphere. Since in this case the light rays are bent down, the image appears above the true object, hence the name superior. They are in general less common than inferior mirages, but when they do occur they tend to be more stable, as cold air has no tendency to move up and warm air no tendency to move down.
Superior mirages are most common in polar regions, especially over large sheets of ice with a uniform low temperature. They also occur at more moderate latitudes, however, although in that case they are weaker and not so smooth. For example a distant shoreline may be made towering, looking higher (and thus perhaps closer) than it is in reality, but because of the turbulences there seem to be dancing spikes, towers and so forth. This type of mirage is also called the Fata Morgana or, in Icelandic, halgerndingar.
Superior images can be right-side-up or upside down, depending on the distance of the true object and the temperature gradient. Often the image appears as a distorted mixture of up and down parts.
If the Earth were flat, superior images would not be as interesting. Light rays which bent down would soon hit the ground, and only close objects would be affected. Since the Earth is round, if the amount of downward bending is about equal to the curvature of the Earth, light rays can travel large distances, perhaps from beyond the horizon. This was observed for the first time in 1596, when a ship under the command of Willem Barents looking for the Northeast passage got stuck in the ice at Novaya Zemlya, and the crew had to endure the polar winter there. They saw their midwinter night ending with the rise of a distorted sun about 2 weeks earlier than expected. It was not until the 20th century that Europeans understood the reason: the real sun had still been under their horizon, but its light rays followed the curvature of the Earth. This effect is often called a Novaya Zemlya mirage. For every 100 kilometres (62 mi) the light rays can travel parallel to the Earth's surface, the sun will appear 1° higher on the horizon. The inversion layer must have just the right temperature gradient over the whole distance to make this possible. In the same way, ships which are in reality so far away that they should not be visible above the geometric horizon may appear on the horizon, or even above the horizon, as superior mirages. This may explain some stories about flying ships or coastal cities in the sky, as described by some polar explorers. These are examples of so-called Arctic mirages, or hillingar in Icelandic.
If the vertical temperature gradient is +11°C per 100 meters (reminder: positive means getting hotter when going up), horizontal light rays will just follow the curvature of the Earth, and the horizon will appear flat. If the gradient is less the rays are not bent enough and get lost in space. That is the normal situation of a spherical, convex horizon. But if the gradient gets larger, say 18°C per 100 meters, the observer will see the horizon turned upwards, being concave, as if he were standing at the bottom of a saucer.

A hot road mirage, "fake water" on the road, the most
common example of an inferior mirage

An inferior mirage on the Mojave Desert in spring

Speed of light

The speed of light normally refers the speed of light in a vacuum, and is an important physical constant in modern physics. Light travels at different speeds through different materials, but in vacuum light travels fastest, and the speed does not vary with the color, intensity, or direction of travel. Perhaps more surprisingly, the speed also does not depend on the motion of the light emitter or the observer. Therefore it makes sense to speak of the speed of light, which is the speed of light in vacuum and usually written as c. The speed of light factors into much of modern physics, including special relativity, general relativity, and quantum mechanics.

By everyday standards, light travels very rapidly - approximately 300,000 km each second, in vacuum or air. This is roughly a million times faster than sound, and fast enough to circle the Earth more than 7 times in one second Such a rapid speed is very hard to measure without specialized techniques, and in ancient times the speed of light was the subject of speculation. The first effective measurements of the speed of light were made in the seventeenth century, and were progressively refined. Today, time intervals can be measured extremely precisely, to the point where the metre is now defined officially as the distance light travels in "vacuum" in 1⁄299,792,458 of a second. As a consequence, according to NIST: "… the effect of this definition is to fix the speed of light in vacuum at exactly 299 792 458 m/s."

Speed of light in different units
metres per second : 299,792,458 (exact)
km per hour : 1,079,252,848.8 (exact)
miles per hour : ≈ 670,616,629.3844
miles per second : ≈ 186,282.39705122

Approximate length of time for light to travel...
One foot :0.98 nanoseconds
One metre : 3.3 nanoseconds
One km : 3.3 microseconds
One mile : 5.4 microseconds
Around Earth's equator : 0.13 seconds
From Earth to geostationary orbit and back : 0.24 seconds
From Earth to the moon : 1.3 seconds
From Earth to the sun : 8.3 minutes
To Earth from Alpha Centauri : 4.4 years
From edge to edge of the Milky Way : 100,000 years

Practical effect of the finite speed of light

The speed of light plays an important part in many modern sciences and technologies. Radar systems measure the distance to a target by measuring the time taken for an echo of the light pulse to return. Similarly, a global positioning system (GPS) receiver measures its distance to satellites based on how long it takes for a radio signal to arrive from the satellite. The distances to the moon, planets, and spacecraft are determined by measuring the round-trip travel time.
Another effect of the finite speed of light is stellar aberration. Suppose we look at a star with a telescope idealized as a narrow tube. The light enters the tube from a star at angle θ and travels at speed c taking a time h/c to reach the bottom of the tube, where our eye detects the light. Suppose observations are made from Earth, which is moving with a speed v. During the transit of the light, the tube moves a distance vh/c. Consequently, for the photon to reach the bottom of the tube, the tube must be inclined at an angle φ different from θ , resulting in an apparent position of the star at angle φ.
In astronomy beyond the solar system, distances are often measured in light-years, the distance light travels in a year.
In electronic systems, despite their small size, the speed of light can become a limiting factor in their maximum speed of operation.

As light propagates down the telescope, the telescope moves requiring a tilt to the telescope that depends on the speed of light. The apparent angle of the star φ differs from its true angle θ, a phenomenon called stellar aberration

The blue glow in this "swimming pool" nuclear reactor is Čerenkov radiation, emitted as a result of electrons traveling faster than the speed of light in water.