Monday, December 20, 2010


Wind is the flow of gases on a large scale. On Earth, wind consists of the bulk movement of air. In outer space, solar wind is the movement of gases or charged particles from the sun through space, while planetary wind is the outgassing of light chemical elements from a planet's atmosphere into space. Winds are commonly classified by their spatial scale, their speed, the types of forces that cause them, the regions in which they occur, and their effect. The strongest observed winds on a planet in our solar system occur on Neptune and Saturn.
In meteorology, winds are often referred to according to their strength, and the direction from which the wind is blowing. Short bursts of high speed wind are termed gusts. Strong winds of intermediate duration (around one minute) are termed squalls. Long-duration winds have various names associated with their average strength, such as breeze, gale, storm, hurricane, and typhoon. Wind occurs on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few hours, to global winds resulting from the difference in absorption of solar energy between the climate zones on Earth. The two main causes of large scale atmospheric circulation are the differential heating between the equator and the poles, and the rotation of the planet (Coriolis effect). Within the tropics, thermal low circulations over terrain and high plateaus can drive monsoon circulations. In coastal areas the sea breeze/land breeze cycle can define local winds; in areas that have variable terrain, mountain and valley breezes can dominate local winds.
In human civilization, wind has inspired mythology, influenced the events of history, expanded the range of transport and warfare, and provided a power source for mechanical work, electricity, and recreation. Wind has powered the voyages of sailing ships across Earth's oceans. Hot air balloons use the wind to take short trips, and powered flight uses it to increase lift and reduce fuel consumption. Areas of wind shear caused by various weather phenomena can lead to dangerous situations for aircraft. When winds become strong, trees and man-made structures are damaged or destroyed.
Winds can shape landforms, via a variety of Aeolian processes such as the formation of fertile soils, such as loess, and by erosion. Dust from large deserts can be moved great distances from its source region by the prevailing winds; winds that are accelerated by rough topography and associated with dust outbreaks have been assigned regional names in various parts of the world because of their significant effects on those regions. Wind affects the spread of wildfires. Winds disperse seeds from various plants, enabling the survival and dispersal of those plant species, as well as flying insect populations. When combined with cold temperatures, wind has a negative impact on livestock. Wind affects animals' food stores, as well as their hunting and defensive strategies.

Wind is caused by differences in pressure. When a difference in pressure exists, the air is accelerated from higher to lower pressure. On a rotating planet the air will be deflected by the Coriolis effect, except exactly on the equator. Globally, the two major driving factors of large scale winds (the atmospheric circulation) are the differential heating between the equator and the poles (difference in absorption of solar energy leading to buoyancy forces) and the rotation of the planet. Outside the tropics and aloft from frictional effects of the surface, the large-scale winds tend to approach geostrophic balance. Near the Earth's surface, friction causes the wind to be slower than it would be otherwise. Surface friction also causes winds to blow more inward into low pressure areas.
Winds defined by an equilibrium of physical forces are used in the decomposition and analysis of wind profiles. They are useful for simplifying the atmospheric equations of motion and for making qualitative arguments about the horizontal and vertical distribution of winds. The geostrophic wind component is the result of the balance between Coriolis force and pressure gradient force. It flows parallel to isobars and approximates the flow above the atmospheric boundary layer in the midlatitudes. The thermal wind is the difference in the geostrophic wind between two levels in the atmosphere. It exists only in an atmosphere with horizontal temperature gradients. The ageostrophic wind component is the difference between actual and geostrophic wind, which is responsible for air "filling up" cyclones over time. The gradient wind is similar to the geostrophic wind but also includes centrifugal force (or centripetal acceleration).

Usage of wind
There are many different forms of sailing ships, but they all have certain basic things in common. Except for rotor ships using the Magnus effect, every sailing ship has a hull, rigging and at least one mast to hold up the sails that use the wind to power the ship. Ocean journeys by sailing ship can take many months, and a common hazard is becoming becalmed because of lack of wind, or being blown off course by severe storms or winds that do not allow progress in the desired direction. A severe storm could lead to shipwreck, and the loss of all hands. Sailing ships can only carry a certain quantity of supplies in their hold, so they have to plan long voyages carefully to include appropriate provisions, including fresh water.
While aircraft usually travel under an internal power source, tail winds affect groundspeed and in the case of hot air balloons and other lighter-than-air vehicles, wind may play a significant role in their movement and ground track. In addition, the direction of wind plays a role in the takeoff and landing of fixed-wing aircraft and airfield runways are usually aligned to take the direction of wind into account. Of all factors affecting the direction of flight operations at an airport, wind direction is considered the primary governing factor. While taking off with a tailwind may be permissible under certain circumstances, it is generally considered the least desirable choice because of performance and safety considerations, with a headwind the desirable choice. A tailwind will increase takeoff distance and decrease climb gradient such that runway length and obstacle clearance may become limiting factors. An airship, or dirigible, is a lighter-than-air aircraft that can be steered and propelled through the air using rudders and propellers or other thrust. Unlike other aerodynamic aircraft such as fixed-wing aircraft and helicopters, which produce lift by moving a wing, or airfoil, through the air, aerostatic aircraft, such as airships and hot air balloons, stay aloft by filling a large cavity, such as a balloon, with a lifting gas. The main types of airship are non-rigid (or blimps), semi-rigid and rigid. Blimps are small airships without internal skeletons. Semi-rigid airships are slightly larger and have some form of internal support such as a fixed keel. Rigid airships with full skeletons, such as the massive Zeppelin transoceanic models, all but disappeared after several high-profile catastrophic accidents during the mid-20th century.

Power source
Historically, the ancient Sinhalese of Anuradhapura and in other cities around Sri Lanka used the monsoon winds to power furnaces as early as 300 BCE. The furnaces were constructed on the path of the monsoon winds to exploit the wind power, to bring the temperatures inside up to 1,200 °C (2,190 °F). An early historical reference to a rudimentary windmill was used to power an organ in the first century CE. The first practical windmills were later built in Sistan, Afghanistan, from the 7th century CE. These were vertical-axle windmills, which had long vertical driveshafts with rectangle shaped blades. Made of six to twelve sails covered in reed matting or cloth material, these windmills were used to grind corn and draw up water, and were used in the gristmilling and sugarcane industries. Horizontal-axle windmills were later used extensively in Northwestern Europe to grind flour beginning in the 1180s, and many Dutch windmills still exist. High altitude wind power is the focus of over 30 companies worldwide using tethered technology rather than ground-hugging compressive-towers. Oil is being saved by using wind for powering cargo ships by use of the mechanical energy converted from the wind's kinetic energy using very large kites.

Wind figures prominently in several popular sports, including recreational hang gliding, hot air ballooning, kite flying, snowkiting, kite landboarding, kite surfing, paragliding, sailing, and windsurfing. In gliding, wind gradients just above the surface affect the takeoff and landing phases of flight of a glider. Wind gradient can have a noticeable effect on ground launches, also known as winch launches or wire launches. If the wind gradient is significant or sudden, or both, and the pilot maintains the same pitch attitude, the indicated airspeed will increase, possibly exceeding the maximum ground launch tow speed. The pilot must adjust the airspeed to deal with the effect of the gradient. When landing, wind shear is also a hazard, particularly when the winds are strong. As the glider descends through the wind gradient on final approach to landing, airspeed decreases while sink rate increases, and there is insufficient time to accelerate prior to ground contact. The pilot must anticipate the wind gradient and use a higher approach speed to compensate for it.

Monday, July 12, 2010


Ice, technically, is one of the 15 known crystalline phases of water. In non-scientific contexts, the term usually means ice Ih, which is known to be the most abundant of these solid phases. It can appear transparent or opaque bluish-white colour, depending on the presence of impurities or air inclusions. The addition of other materials such as soil may further alter the appearance.
The most common phase transition to ice Ih occurs when liquid water is cooled below 0°C (273.15K, 32°F) at standard atmospheric pressure. It can also deposit from vapour with no intervening liquid phase, such as in the formation of frost.
Ice appears in nature in forms of precipitation as varied as snowflakes, hail, icicles, glaciers, pack ice, and entire polar ice caps. It is an important component of the global climate, and plays an important role in the water cycle. Furthermore, ice has numerous cultural applications, from ice cooling of drinks to winter sports and the art of ice sculpting.
The word is derived from Old English ís, which in turn stems from Proto-Germanic *isaz.

Ice that is found at sea may be in the form of sea ice, pack ice, or icebergs. The term that collectively describes all of the parts of the Earth's surface where water is in frozen form is the cryosphere. Ice is an important component of the global climate, particularly in regard to the water cycle. Glaciers and snowpacks are an important storage mechanism for fresh water; over time, they may sublimate or melt. Snowmelt is often an important source of seasonal fresh water.
Rime is a type of ice formed on cold objects when drops of water crystallize on them. This can be observed in foggy weather, when the temperature drops during the night. Soft rime contains a high proportion of trapped air, making it appear white rather than transparent, and giving it a density about one quarter of that of pure ice. Hard rime is comparatively denser.
Aufeis is layered ice that forms in Arctic and subarctic stream valleys. Ice, frozen in the stream bed, blocks normal groundwater discharge, and causes the local water table to rise, resulting in water discharge on top of the frozen layer. This water then freezes, causing the water table to rise further and repeat the cycle. The result is a stratified ice deposit, often several meters thick. Ice can also form icicles, similar to stalactites in appearance, or stalagmite-like forms as water drips and re-freezes.
Clathrate hydrates are forms of ice that contain gas molecules trapped within its crystal lattice. Pancake ice is a formation of ice generally created in areas with less calm conditions.
Candle Ice is a form of Rotten Ice that develops in columns perpendicular to the surface of a lake.
Ice discs are circular formations of ice surrounded by water in a river.

Ice and transportation
Ice can also be an obstacle; for harbours near the poles, being ice-free is an important advantage; ideally, all year long. Examples are Murmansk (Russia), Petsamo (Russia, formerly Finland) and Vardø (Norway). Harbours which aren't ice-free are opened up using icebreakers.
Ice forming on roads is a dangerous winter hazard. Black ice is very difficult to see, because it lacks the expected frosty surface. Whenever there is freezing rain or snow which occurs at a temperature near the melting point, it is common for ice to build up on the windows of vehicles. Driving safely requires the removal of the ice build-up. Ice scrapers are tools designed to break the ice free and clear the windows, though removing the ice can be a long and laborious process.
Far enough below the freezing point, a thin layer of ice crystals can form on the inside surface of windows. This usually happens when a vehicle has been left alone after being driven for a while, but can happen while driving, if the outside temperature is low enough. Moisture from the driver's breath is the source of water for the crystals. It is troublesome to remove this form of ice, so people often open their windows slightly when the vehicle is parked in order to let the moisture dissipate, and it is now common for cars to have rear-window defrosters to solve the problem. A similar problem can happen in homes, which is one reason why many colder regions require double-pane windows for insulation.
When the outdoor temperature stays below freezing for extended periods, very thick layers of ice can form on lakes and other bodies of water, although places with flowing water require much colder temperatures. The ice can become thick enough to drive onto with automobiles and trucks. Doing this safely requires a thickness of at least 30 centimetres (one foot).
For ships, ice presents two distinct hazards. Spray and freezing rain can produce an ice build-up on the superstructure of a vessel sufficient to make it unstable, and to require it to be hacked off or melted with steam hoses. And icebergs — large masses of ice floating in water (typically created when glaciers reach the sea) — can be dangerous if struck by a ship when underway. Icebergs have been responsible for the sinking of many ships, the most famous probably being the Titanic.
For aircraft, ice can cause a number of dangers. As an aircraft climbs, it passes through air layers of different temperature and humidity, some of which may be conducive to ice formation. If ice forms on the wings or control surfaces, this may adversely affect the flying qualities of the aircraft. During the first non-stop flight of the Atlantic, the British aviators Captain John Alcock and Lieutenant Arthur Whitten Brown encountered such icing conditions - Brown left the cockpit and climbed onto the wing several times to remove ice which was covering the engine air intakes of the Vickers Vimy aircraft they were flying.
A particular icing vulnerability associated with reciprocating internal combustion engines is the carburetor. As air is sucked through the carburettor into the engine, the local air pressure is lowered, which causes adiabatic cooling. So, in humid near-freezing conditions, the carburettor will be colder, and tend to ice up. This will block the supply of air to the engine, and cause it to fail. For this reason, aircraft reciprocating engines with carburettors are provided with carburettor air intake heaters. The increasing use of fuel injection—which does not require carburettors—has made "carb icing" less of an issue for reciprocating engines.
Jet engines do not experience carb icing, but recent evidence indicates that they can be slowed, stopped, or damaged by internal icing in certain types of atmospheric conditions much more easily than previously believed. In most cases, the engines can be quickly restarted and flights are not endangered, but research continues to determine the exact conditions which produce this type of icing, and find the best methods to prevent, or reverse it, in flight.

Wednesday, June 2, 2010


A hiccup or hiccough (pronounced /ˈhɪkʌp/ HICK-up) is a contraction of the diaphragm that repeats several times per minute. In humans, the abrupt rush of air into the lungs causes the epiglottis to close, creating a "hic" sound.
In medicine it is known as synchronous diaphragmatic flutter (SDF), or singultus, from the Latin singult, "the act of catching one's breath while sobbing". The hiccup is an involuntary action involving a reflex arc. A bout of hiccups, in general, resolves itself without intervention, although many home remedies claim to shorten the duration, and medical treatment is occasionally necessary in cases of chronic hiccups.

Hiccups are caused by many central and peripheral nervous system disorders, all from injury or irritation to the phrenic and vagus nerves, as well as toxic or metabolic disorders affecting the aforementioned systems. Hiccups often occur after drinking carbonated beverages or alcohol or ingesting spicy foods. Prolonged laughter is also known to cause hiccups. Eating too fast can also cause the hiccups. Persistent or intractable hiccups may be caused by any condition which irritates or damages the relevant nerves. Chemotherapy—which can include a huge number of different drugs—has been implicated in hiccups (some data states 30 percent of patients), while other studies have not proven such a relationship. Many times chemotherapy is applied to tumors sitting at places that are by themselves prone to cause hiccups, if irritated.

Ordinary hiccups are cured easily without medical intervention. However, there are a number of anecdotal treatments for casual cases of hiccups. Some of the more common home remedies include giving the afflicted a fright or shock, eating peanut butter, taking a teaspoon of vinegar, drinking water (sometimes in an unorthodox manner), holding one's breath and altering one's breathing patterns. A solution involving sugar placed on or under the tongue was cited in the December 23, 1971 issue of the New England Journal of Medicine.
Hiccups are treated medically only in severe and persistent (termed "intractable") cases, such as in the case of a 15-year-old girl who, in 2007, hiccuped continuously for five weeks.
Haloperidol (Haldol, an anti-psychotic and sedative), metoclopramide (Reglan, a gastrointestinal stimulant), and chlorpromazine (Thorazine, an anti-psychotic with strong sedative effects) are used in cases of intractable hiccups. In severe or resistant cases, baclofen, an anti-spasmodic, is sometimes required to suppress hiccups. Effective treatment with sedatives often requires a dose that renders the person either unconscious or highly lethargic. Hence, medicating singultus is done short-term, as the affected individual cannot continue with normal life activities while taking the medication.
Persistent and intractable hiccups due to electrolyte imbalance (hypokalemia, hyponatremia) may benefit from drinking a carbonated beverage containing salt to normalize the potassium-sodium balance in the nervous system. The carbonation promotes quicker absorption. Carbonated beverages by themselves may have a tendency to provoke hiccups in some people.
The administration of intranasal vinegar was found to ease the chronic and severe hiccups of a three-year old Japanese girl. Vinegar may stimulate the dorsal wall of the nasopharynx, where the pharyngeal branch of the glossopharyngeal nerve (the afferent of the hiccup reflex arc) is located.
Dr. Bryan R. Payne, a neurosurgeon at the Louisiana State University Health Sciences Center in New Orleans, has had some success with an experimental procedure in which a vagus nerve stimulator is implanted in the upper chest of patients with an intractable case of hiccups. "It sends rhythmic bursts of electricity to the brain by way of the vagus nerve, which passes through the neck. The Food and Drug Administration approved the vagus nerve stimulator in 1997 as a way to control seizures in some patients with epilepsy".

Getting the wind knocked out of you
Getting the wind knocked out of you is a phrase and a commonly used idiom that mainly refers to a kind of diaphragm spasm that occurs when sudden force is applied to the abdomen which puts pressure on the solar plexus. It results in a temporary paralysis of the diaphragm that makes it difficult to breathe for a short period of time. It can also occur from a strong blow to the back.
When the abdomen is struck, a large difference in pressure occurs across the diaphragm. The diaphragm then stretches, which also stretches the diaphragm's nerves. The resulting mechanical force puts the diaphragm into a muscle spasm, comparable to having a charley horse in the leg. It takes a few seconds for the diaphragm to relax again before breathing can resume normally. Martial artists are often taught to breathe out heavily when struck in the stomach, to minimize this effect.
Often, the laryngeal muscles contract during diaphragm spasm producing an inspiratory sound known as stridor which can be heard for several cycles as breathing resumes.
Singultus, commonly known as the hiccups, is also a form of diaphragm spasm, although much milder. A singultus episode impairs voluntary breathing control for brief moments (measured in milliseconds) rather than for several seconds.
It may also be referred to as Rat Gut, getting winded or just winded.

Society and culture
American man Charles Osborne had the hiccups for 68 years, from 1922 to 1990, and was entered in the Guinness World Records as the man with the longest attack of hiccups.
In 2007, a teenager from Washington State in the United States named Cheyenne Motland hiccuped around 50 times a minute for more than five weeks. After her hiccups returned, her neurologist suggested that she may have Tourette syndrome, and the hiccups may be a "tic" caused by Tourette's.
Christopher Sands from the UK had hiccups for a period of almost three years which was eventually discovered to be due to a tumor located on the part of the brain that controls vascular activities, once 2/3 of the tumor was removed the hiccups appeared to settle and Sands no longer suffers from his condition.

Sunday, May 23, 2010


Anemia (pronounced /əˈniːmiə/, also spelled anaemia and anæmia; from Ancient Greek ἀναιμία anaimia, meaning lack of blood) is a decrease in normal number of red blood cells (RBCs) or less than the normal quantity of hemoglobin in the blood. However, it can include decreased oxygen-binding ability of each hemoglobin molecule due to deformity or lack in numerical development as in some other types of hemoglobin deficiency.
Because hemoglobin (found inside RBCs) normally carries oxygen from the lungs to the tissues, anemia leads to hypoxia (lack of oxygen) in organs. Because all human cells depend on oxygen for survival, varying degrees of anemia can have a wide range of clinical consequences.
Anemia is the most common disorder of the blood. There are several kinds of anemia, produced by a variety of underlying causes. Anemia can be classified in a variety of ways, based on the morphology of RBCs, underlying etiologic mechanisms, and discernible clinical spectra, to mention a few. The three main classes of anemia include excessive blood loss (acutely such as a hemorrhage or chronically through low-volume loss), excessive blood cell destruction (hemolysis) or deficient red blood cell production (ineffective hematopoiesis).
There are two major approaches: the "kinetic" approach which involves evaluating production, destruction and loss, and the "morphologic" approach which groups anemia by red blood cell size. The morphologic approach uses a quickly available and cheap lab test as its starting point (the MCV). On the other hand, focusing early on the question of production may allow the clinician more rapidly to expose cases where multiple causes of anemia coexist.

Signs and symptoms
Anemia goes undetected in many people, and symptoms can be minor or vague. The signs and symptoms can be related to the anemia itself, or the underlying cause.
Most commonly, people with anemia report non-specific symptoms of a feeling of weakness, or fatigue, general malaise and sometimes poor concentration. They may also report shortness of breath, dyspnea, on exertion. In very severe anemia, the body may compensate for the lack of oxygen carrying capability of the blood by increasing cardiac output. The patient may have symptoms related to this, such as palpitations, angina (if preexisting heart disease is present), intermittent claudication of the legs, and symptoms of heart failure.
On examination, the signs exhibited may include pallor (pale skin, mucosal linings and nail beds) but this is not a reliable sign. There may be signs of specific causes of anemia, e.g., koilonychia (in iron deficiency), jaundice (when anemia results from abnormal break down of red blood cells — in hemolytic anemia), bone deformities (found in thalassaemia major) or leg ulcers (seen in sickle cell disease).
In severe anemia, there may be signs of a hyperdynamic circulation: a fast heart rate (tachycardia), flow murmurs, and cardiac enlargement. There may be signs of heart failure.
Pica, the consumption of non-food based items such as dirt, paper, wax, grass, ice, and hair, may be a symptom of iron deficiency, although it occurs often in those who have normal levels of hemoglobin.
Chronic anemia may result in behavioral disturbances in children as a direct result of impaired neurological development in infants, and reduced scholastic performance in children of school age.
Restless legs syndrome is more common in those with iron deficiency anemia.
Less common symptoms may include swelling of the legs or arms, chronic heartburn, vague bruises, vomiting, increased sweating, and blood in stool.

Possible complications
Anemia diminishes the capability of affected individuals to perform physical activities, a result of one's muscles being forced to depend on anaerobic metabolism. The lack of iron associated with anemia can cause many complications, including hypoxemia, brittle or rigid fingernails, cold intolerance, and possible behavioral disturbances in children. Hypoxemia resulting from anemia can worsen the cardio-pulmonary status of patients with pre-existing chronic pulmonary disease. Cold intolerance occurs in one in five patients with iron deficiency anemia, and becomes visible through numbness and tingling.

There are many different treatments for anemia and the treatment depends on severity and the cause.
Iron deficiency from nutritional causes is rare in non-menstruating adults (men and post-menopausal women). The diagnosis of iron deficiency mandates a search for potential sources of loss such as gastrointestinal bleeding from ulcers or colon cancer. Mild to moderate iron deficiency anemia is treated by oral iron supplementation with ferrous sulfate, ferrous fumarate, or ferrous gluconate. When taking iron supplements, it is very common to experience stomach upset and/or darkening of the feces. The stomach upset can be alleviated by taking the iron with food; however, this decreases the amount of iron absorbed. Vitamin C aids in the body's ability to absorb iron, so taking oral iron supplements with orange juice is of benefit.
Vitamin supplements given orally (folic acid) or subcutaneously (vitamin B-12) will replace specific deficiencies.
In anemia of chronic disease, anemia associated with chemotherapy, or anemia associated with renal disease, some clinicians prescribe recombinant erythropoietin, epoetin alfa, to stimulate red cell production.
In severe cases of anemia, or with ongoing blood loss, a blood transfusion may be necessary.

Blood transfusions
Doctors attempt to avoid blood transfusion in general, since multiple lines of evidence point to increased adverse patient clinical outcomes with more intensive transfusion strategies. The physiological principle that reduction of oxygen delivery associated with anemia leads to adverse clinical outcomes is balanced by the finding that transfusion does not necessarily mitigate these adverse clinical outcomes.
In severe, acute bleeding, transfusions of donated blood are often lifesaving. Improvements in battlefield casualty survival is attributable, at least in part, to the recent improvements in blood banking and transfusion techniques.
Transfusion of the stable but anemic hospitalized patient has been the subject of numerous clinical trials, and transfusion is emerging as a deleterious intervention.
Four randomized controlled clinical trials have been conducted to evaluate aggressive versus conservative transfusion strategies in critically ill patients. All four of these studies failed to find a benefit with more aggressive transfusion strategies.
In addition, at least two retrospective studies have shown increases in adverse clinical outcomes with more aggressive transfusion strategies.

Hyperbaric oxygen
Treatment of exceptional blood loss (anemia) is recognized as an indication for hyperbaric oxygen (HBO) by the Undersea and Hyperbaric Medical Society. The use of HBO is indicated when oxygen delivery to tissue is not sufficient in patients who cannot be transfused for medical or religious reasons. HBO may be used for medical reasons when threat of blood product incompatibility or concern for transmissible disease are factors.
In 2002, Van Meter reviewed the publications surrounding the use of HBO in severe anemia and found that all publications report a positive result.

Thursday, May 20, 2010

Ibn Bajjah

Abū-Bakr Muhammad ibn Yahya ibn al-Sāyigh (Arabic أبو بكر محمد بن يحيى بن الصائغ), known as Ibn Bājjah (Arabic: ابن باجة‎), was an Andalusian-Arab Muslim polymath: an astronomer, logician, musician, philosopher, physician, physicist, psychologist, Botany, poet and scientist. He was known in the West by his Latinized name, Avempace. He was born in Zaragoza in what is today Spain and died in Fes, Morocco in 1138. Avempace worked as vizir for Abu Bakr ibn Ibrahim Ibn Tîfilwît, the Almoravid governor of Saragossa. Avempace also wrote poems (panegyrics and 'muwasshahat') for him, and they both enjoyed music and wine. Avempace joined in poetic competitions with the poet al-Tutili. He later worked, for some twenty years, as the vizir of Yahyà ibn Yûsuf Ibn Tashufin, another brother of the Almoravid Sultan Yusuf Ibn Tashufin (died 1143) in Morocco. He was the famous author of the Kitab al-Nabat (The Book of Plants), a popular work on Botany, which defined the sex of Plants.
His philosophic ideas had a clear effect on Ibn Rushd and Albertus Magnus. Most of his writings and book were not completed (or well organized) because of his early death. He had a vast knowledge of Medicine, Mathematics and Astronomy. His main contribution to Islamic Philosophy is his idea on Soul Phenomenology, but unfortunately not completed.
His beloved expressions were Gharib غريب and Mutawahhid متوحد, two approved and popular expressions of Islamic Gnostics.
Ibn Bajjah was also a renowned poet. In his explanation of the Zajal E.G. Gomes writes: "There is some evidence for the belief that it was invented by the famous philosopher and musician known as Avempace. Its chief characteristic being that it is written entirely in the vernacular. ” (Emilio Gracia Gomes in his essay “Moorish Spain")
Though many of his works have not survived, his theories on astronomy and physics were preserved by Maimonides and Averroes respectively, which had a subsequent influence on later astronomers and physicists in the Islamic civilization and Renaissance Europe, including Galileo Galilei.

In Islamic astronomy, Maimonides wrote the following on the planetary model proposed by Ibn Bajjah:
"I have heard that Abu Bakr [Ibn Bajja] discovered a system in which no epicycles occur, but eccentric spheres are not excluded by him. I have not heard it from his pupils; and even if it be correct that he discovered such a system, he has not gained much by it, for eccentricity is likewise contrary to the principles laid down by Aristotle.... I have explained to you that these difficulties do not concern the astronomer, for he does not profess to tell us the existing properties of the spheres, but to suggest, whether correctly or not, a theory in which the motion of the stars and planets is uniform and circular, and in agreement with observation."

In his commentary on Aristotle's Meteorology, Ibn Bajjah presented his own theory on the Milky Way galaxy. Aristotle believed the Milky Way to be caused by "the ignition of the fiery exhalation of some stars which were large, numerous and close together" and that the "ignition takes place in the upper part of the atmosphere, in the region of the world which is continuous with the heavenly motions." On the other hand, Aristotle's Arabic commentator Ibn al-Bitriq considered "the Milky Way to be a phenomenon exclusively of the heavenly spheres, not of the upper part of the atmosphere" and that the "light of those stars makes a visible patch because they are so close." Ibn Bajjah's view differed from both, as he considered "the Milky Way to be a phenomenon both of the spheres above the moon and of the sublunar region." The Stanford Encyclopedia of Philosophy describes his theory and observation on the Milky Way as follows:
"The Milky Way is the light of many stars which almost touch one another. Their light forms a “continuous image” (khayâl muttasil) on the surface of the body which is like a “tent” (takhawwum) under the fierily element and over the air which it covers. Avempace defines the continuous image as the result of refraction (in‛ikâs) and supports its explanation with an observation of a conjunction of two planets, Jupiter and Mars which took place in 500/1106-7. He watched the conjunction and “saw them having an elongate figure” although their figure is circular."

Ibn Bajjah also reported observing "two planets as black spots on the face of the Sun." In the 13th century, the Maragha astronomer Qotb al-Din Shirazi identified this observation as the transit of Venus and Mercury. However, Ibn Bajjah cannot have observed a Venus transit, as there were no Venus transits in his lifetime.

In Islamic physics, Ibn Bajjah's law of motion was equivalent to the principle that uniform motion implies absence of action by a force. This principle would later form the basis of modern mechanics and have a subsequent influence on the classical mechanics of physicists such as Galileo Galilei. Ibn Bajjah's definition of velocity was also equivalent to Galileo's definition of velocity:

Velocity = Motive Power - Material Resistance

where the motive power is measured by the specific gravity of the mobile body and the material resistance is the resisting medium whose resistive power is measured by its specific gravity.
Ibn Bajjah was among the first to state that there is always a reaction force for every force exerted, a precursor to Gottfried Leibniz's idea of force which underlies Newton's third law of motion or law of reciprocal actions. However,the history of the principle of action and reaction can be traced as far as Aristotle.

Ibn Bajjah also had an influence on Thomas Aquinas' analysis of motion. In his Systeme du Monde, the pioneering historian of medieval science, Pierre Duhem, stated:
"For the first time we have seen human reason distinguish two elements in a heavy body: the motive force, that is, in modern terms, the weight; and the moved thing, the corpus quantum, or as we say today, the mass. For the first time we have seen the notion of mass being introduced in mechanics, and being introduced as equivalent to what remains in a body when one has suppressed all forms in order to leave only the prime matter quantified by its determined dimensions. Saint Thomas Aquinas's analysis, completing Ibn Bajja's, came to distinguish three notions in a falling body: the weight, the mass, and the resistance of the medium, about which physics will reason during the modern era....This mass, this quantified body, resists the motor attempting to transport it from one place to another, stated Thomas Aquinas."

In Islamic psychology, Ibn Bajjah "based his psychological studies on physics." In his essay, Recognition of the Active Intelligence, he wrote that active intelligence is the most important ability of human beings, and he wrote many other essays on sensations and imaginations. He concluded that "knowledge cannot be acquired by senses alone but by Active Intelligence, which is the governing intelligence of nature." He begins his discussion of the soul with the definition that "bodies are composed of matter and form and intelligence is the most important part of man—sound knowledge is obtained through intelligence, which alone enables one to attain prosperity and build character." He viewed the unity of the rational soul as the principle of the individual identity, and that by its contact with the Active Intelligence, it "becomes one of those lights that gives glory to God." His definition of freedom is "that when one can think and act rationally". He also writes that "the aim of life should be to seek spiritual knowledge and make contact with Active Intelligence and thus with the Divine."

Sunday, May 16, 2010


Pan-STARRS (an acronym for Panoramic Survey Telescope And Rapid Response System) is a planned astronomical survey that will conduct astrometry and photometry of much of the entire sky on a continuous basis. By detecting any differences from previous observations of the same areas of the sky, it is expected to discover a very large number of new asteroids, comets, variable stars and other celestial objects. Its primary mission is to detect near-Earth objects that threaten to cause impact events. It is expected to create a database of all objects visible from Hawaii (three-quarters of the entire sky) down to apparent magnitude 24.
Pan-STARRS' first telescope, called PS1, is located at the summit of Haleakala in Maui Island, and went online on December 6, 2008, under the administration of the University of Hawaii. The other three telescopes completing the array will be completed by 2012 at a total cost of USD 100 million for the entire array.
The Pan-STARRS is a collaboration between the University of Hawaii Institute for Astronomy, MIT Lincoln Laboratory, Maui High Performance Computing Center and Science Applications International Corporation. Telescope construction is funded by the US Air Force. Once PS1 reaches the milestone of passing its Operational Readiness Review, expected Fall 2008, the Pan-STARRS Project will focus on building PS4.
The operations for the first Pan-STARRS telescope (PS1) are funded by The PS1 Science Consortium or PS1SC a consortium including the Max Planck Society in Germany, National Central University in Taiwan, Edinburgh, Durham and Queen's Belfast Universities in the UK, and Johns Hopkins and Harvard Universities in the USA and the Las Cumbres Observatory Global Telescope Network.

Systematically surveying the entire sky on a continuous basis is an unprecedented project and is expected to produce a dramatically larger number of discoveries of various types of celestial objects. For instance, the current leading asteroid discovery project Catalina Sky Survey only goes down to apparent magnitude 20-20.5 and concentrates its searches mostly near the ecliptic; Pan-STARRS will go four magnitudes fainter and cover the entire sky visible from Hawaii. The ongoing survey will also complement the efforts to map the infrared sky by the NASA WISE orbital telescope, with the results of one survey complementing and extending the other.

Solar system
In addition to the large number of expected discoveries in the main asteroid belt, Pan-STARRS is expected to detect at least 100,000 Jupiter Trojan asteroids (compared to 2900 known as of end-2008); at least 20,000 Kuiper belt objects (compared to 800 known as of mid-2005); thousands of Trojan asteroids of Saturn, Uranus and Neptune (currently six Neptune Trojans are known, and none for the other planets excluding Mars and Jupiter); and large numbers of Centaurs and comets.
Apart from drastically adding to the number of known solar system objects, Pan-STARRS will remove or mitigate the observational bias inherent in many current surveys. For instance, among currently known objects there is a bias favoring low orbital inclination, and thus an object such as Makemake escaped detection until recently despite its bright apparent magnitude of 17, which is not much fainter than Pluto. Also, among currently known comets there is a bias favoring those with short perihelion distances. Reducing the effects of this observational bias will enable a more complete picture of solar system dynamics. For instance it is expected that the number of Jupiter Trojans larger than 1 km may in fact roughly match the number of main asteroid belt objects, although the currently known population of the latter is several orders of magnitude larger.
One intriguing possibility is that Pan-STARRS may detect "interstellar debris" or "interstellar interlopers" flying through the solar system. During the formation of a planetary system it is thought that a very large number of objects are ejected due to gravitational interactions with planets (as many as 1013 such objects in the case of our solar system). Objects ejected by planetary systems around other stars might plausibly be flying throughout the galaxy and some may pass through our solar system.
Another intriguing possibility is that Pan-STARRS may actually detect collisions involving small asteroids. These are quite rare and none have yet been observed, but with the drastically larger number of asteroids that will be discovered it is expected from statistical considerations that some collision events may be observed.
Pan-STARRS will also likely detect a number of Kuiper belt objects the size of Pluto or larger, similar to Eris.

Beyond the solar system
It is expected that Pan-STARRS will discover an extremely large number of variable stars, including such stars in other nearby galaxies; in fact, this may lead to the discovery of hitherto unknown dwarf galaxies. In discovering a large number of Cepheid variables and eclipsing binary stars, it will help determine distances to nearby galaxies with greater precision. It is expected to discover a large number of Type Ia supernovae in other galaxies, which are important in studying the effects of dark energy, and also optical afterglows of gamma ray bursts.
Because very young stars (such as T Tauri stars) are usually variable, Pan-STARRS should discover a large number of these and improve our understanding of them. It is also expected that Pan-STARRS may discover a large number of extrasolar planets by observing their transits across their parent stars, as well as gravitational microlensing events.
Pan-STARRS will also measure proper motion and parallax and should thereby discover a large number of brown dwarfs and white dwarfs and other nearby faint objects, and it should be able to conduct a complete census of all stars within 100 parsecs of the Sun. Prior proper motion and parallax surveys often did not detect faint objects such as the recently-discovered Teegarden's star, which are too faint for projects such as Hipparcos.
Also, by identifying stars with large parallax but very small proper motion for followup radial velocity measurements, Pan-STARRS may even be able to permit the detection of hypothetical Nemesis-type objects if these actually exist.

SN 2008id (type 1a supernova), confirmed by Keck observatory via redshift.
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