Meteorite

A meteorite is a meteoroid (a solid piece of debris from such sources as asteroids or comets) originating in outer space that survives impact with the Earth's surface. A meteorite's size can range from small to extremely large. Most meteorites derive from small astronomical objects called meteoroids, but they are also sometimes produced by impacts of asteroids. When a meteoroid enters the atmosphere, frictional, pressure, and chemical interactions with the atmospheric gasses cause the body to heat up and emit light, thus forming a fireball, also known as a meteor or shooting/falling star. The term bolide refers to either an extraterrestrial body that collides with the Earth, or to an exceptionally bright, fireball-like meteor regardless of whether it ultimately impacts the surface.

More generally, a meteorite on the surface of any celestial body is a natural object that has come from elsewhere in space. Meteorites have been found on the Moon and Mars. Meteorites that are recovered after being observed as they transited the atmosphere or impacted the Earth are called falls. All other meteorites are known as finds. As of February 2010, there are approximately 1,086 witnessed falls having specimens in the world's collections. In contrast, there are over 38,660 well-documented meteorite finds.

Meteorites have traditionally been divided into three broad categories: stony meteorites are rocks, mainly composed of silicate minerals; iron meteorites are largely composed of metallic iron-nickel; and, stony-iron meteorites contain large amounts of both metallic and rocky material. Modern classification schemes divide meteorites into groups according to their structure, chemical and isotopic composition and mineralogy. Meteorites smaller than 2mm are classified as micrometeorites.

Platonic Solids

In Euclidean geometry, a Platonic solid is a regular, convex polyhedron. The faces are congruent, regular polygons, with the same number of faces meeting at each vertex.  There are five Platonic solids; their names are derived from their numbers of faces.

The aesthetic beauty and symmetry of the Platonic solids have made them a favorite subject of geometers for thousands of years. They are named for the ancient Greek philosopher Plato, who theorized that the classical elements were constructed from the regular solids.

The Platonic solids have been known since antiquity. Ornamented models of them can be found among the carved stone balls created by the late neolithic people of Scotland at least 1000 years before Plato.

The ancient Greeks studied the Platonic solids extensively. Some sources (such as Proclus) credit Pythagoras with their discovery. Other evidence suggests he may have only been familiar with the tetrahedron, cube, and dodecahedron, and that the discovery of the octahedron and icosahedron belong to Theaetetus, a contemporary of Plato.

Euclid gave a complete mathematical description of the Platonic solids in the Elements, the last book (Book XIII) of which is devoted to their properties. Propositions 13–17 in Book XIII describe the construction of the tetrahedron, octahedron, cube, icosahedron, and dodecahedron in that order. For each solid Euclid finds the ratio of the diameter of the circumscribed sphere to the edge length. In Proposition 18 he argues that there are no further convex regular polyhedra. Much of the information in Book XIII is probably derived from the work of Theaetetus.

In the 16th century, the German astronomer Johannes Kepler attempted to find a relation between the five extraterrestrial planets known at that time and the five Platonic solids. In Mysterium Cosmographicum, published in 1596, Kepler laid out a model of the solar system in which the five solids were set inside one another and separated by a series of inscribed and circumscribed spheres. Kepler proposed that the distance relationships between the six planets known at that time could be understood in terms of the five Platonic solids, enclosed within a sphere that represented the orbit of Saturn. The six spheres each corresponded to one of the planets (Mercury, Venus, Earth, Mars, Jupiter, and Saturn). The solids were ordered with the innermost being the octahedron, followed by the icosahedron, dodecahedron, tetrahedron, and finally the cube. In this way the structure of the solar system and the distance relationships between the planets was dictated by the Platonic solids. In the end, Kepler's original idea had to be abandoned, but out of his research came his three laws of orbital dynamics, the first of which was that the orbits of planets are ellipses rather than circles, changing the course of physics and astronomy. He also discovered the Kepler solids.

Robert Bunsen

Robert Wilhelm Eberhard Bunsen (30 March 1811 – 16 August 1899) was a German chemist. He investigated emission spectra of heated elements, and discovered caesium (in 1860) and rubidium (in 1861) with Gustav Kirchhoff. Bunsen developed several gas-analytical methods, was a pioneer in photochemistry, and did early work in the field of organoarsenic chemistry. With his laboratory assistant, Peter Desaga, he developed the Bunsen burner, an improvement on the laboratory burners then in use. The Bunsen–Kirchhoff Award for spectroscopy is named after Bunsen and Kirchhoff.

Joseph Paul Jernigan

Joseph Paul Jernigan (January 31, 1954 – August 5, 1993) was a Texas murderer who was killed by lethal injection at 12:31 a.m, August 5, 1993.

In 1981, Jernigan was sentenced to death for stabbing and shooting 75-year-old Edward Hale, who discovered him stealing a microwave oven. Jernigan spent 12 years in prison before his final plea for clemency was denied. At the prompting of a prison chaplain, he agreed to donate his body for scientific research or medical use.

After execution, Jernigan's corpse was encased and frozen in a gelatin and water mixture in order to stabilize the specimen for cutting. The specimen was then “cut” in the axial plane at 1 millimeter intervals. Each of the resulting 1,871 “slices” were photographed in both analog and digital, yielding 15 gigabytes of data. In 2000, the photos were rescanned at a higher resolution, yielding more than 65 gigabytes.

The data is supplemented by axial sections of the whole body obtained by computed tomography, axial sections of the head and neck obtained by magnetic resonance imaging, and coronal sections of the rest of the body also obtained by magnetic resonance imaging.

The scanning, slicing and photographing took place at the University of Colorado's Health Sciences Center, where additional cutting of anatomical specimens continues to take place.

Kelvin

The kelvin is a unit of measurement for temperature. It is one of the seven base units in the International System of Units (SI) and is assigned the unit symbol K. The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all thermal motion ceases in the classical description of thermodynamics. The reference point that defines the Kelvin scale is the triple point of water at 273.16K

(0.01 degrees Celsius). The kelvin is defined as 1/273.16 of the difference between these two reference points.

The Kelvin scale is named after the Belfast-born physicist and engineer William Thomson, 1st Baron Kelvin (1824–1907), who wrote of the need for an "absolute thermometric scale". Unlike the degree Fahrenheit and degree Celsius, the kelvin is not referred to or typeset as a degree. The kelvin is the primary unit of measurement in the physical sciences, but is often used in conjunction with the degree Celsius, which has the same magnitude. 0kelvin is −273.15 degrees Celsius.

Periodic Table

The periodic table of the chemical elements is a tabular display of the chemical elements. Although precursors to this table exist, its invention is generally credited to Russian chemist Dmitri Mendeleev in 1869, who intended the table to illustrate recurring ("periodic") trends in the properties of the elements. The layout of the table has been refined and extended over time, as new elements have been discovered, and new theoretical models have been developed to explain chemical behavior. The periodic table is now ubiquitous within the academic discipline of chemistry, providing a useful framework to classify, systematize, and compare all of the many different forms of chemical behavior. The table has found many applications in chemistry, physics, biology, and engineering, especially chemical engineering. The current standard table contains 118 elements to date.

Magdeburg Hemispheres

The Magdeburg hemispheres were a pair of large copper hemispheres with mating rims. When the rims were sealed with grease and the air was pumped out, the sphere contained a vacuum and could not be pulled apart by teams of horses. The Magdeburg hemispheres were designed by German scientist and mayor of Magdeburg, Otto von Guericke in 1650 to demonstrate the air pump which he had invented, and the concept of atmospheric pressure.

The first artificial vacuum had been produced a few years earlier by Evangelista Torricelli, and had inspired von Guericke to design the world's first vacuum pump, which consisted of a piston and cylinder with one-way flap valves.

Von Guericke's demonstration was performed on 8 May 1654 in front of the Reichstag and the Emperor Ferdinand III in Regensburg. Thirty horses, in two teams of 15, could not separate the hemispheres until the valve was opened to release the vacuum. In 1656 he repeated the demonstration with 16 horses (2 teams of 8) in his hometown of Magdeburg, where he was mayor. In 1663 the demonstration was given in Berlin before Frederick William, Elector of Brandenburg with 24 horses.

The hemispheres became popular in physics lectures as an illustration of the power of air pressure, and are still used in education. The original hemispheres are preserved in the Deutsches Museum in Munich.

Prince Rupert's Drops

Prince Rupert's Drops are a glass curiosity created by dripping hot molten glass into cold water. The glass cools into a tadpole-shaped droplet with a long, thin, tail. The water rapidly cools the molten glass on the outside of the drop, while the inner portion of the drop remains significantly hotter. When the glass on the inside eventually cools, it contracts inside the already-solid outer part. This contraction sets up very large compressive stresses on the exterior, while the core of the drop is in a state of tensile stress. It can be said to be a kind of tempered glass.

The very high residual stress within the drop gives rise to unusual qualities, such as the ability to withstand a blow from a hammer on the bulbous end without breaking, while the drops will disintegrate explosively if the tail end is even slightly damaged.

When the tail end is damaged, the large amount of potential energy stored in the drop's crystalline or amorphous atomic structure is released, causing fractures to propagate through the material at very high speed. Recently an examination of the shattering of Prince Rupert's Drops by the use of extremely high speed video made by Dr. Srinivasan Chandrasekar at Purdue University has revealed that the "crack front" which is initiated at the tail end propagates in a disintegrating drop within the tensile zone towards the drop's head at a very high velocity (~ 1450-1900 m/s, or up to ~4,200 miles per hour, a number that in air would be Mach 5.5).

Post-Prandial Somnolence

Post-prandial somnolence is a state of drowsiness or lassitude following a meal. Post-prandial somnolence has two components – a general state of low energy related to activation of the parasympathetic nervous system in response to nutrients in the gastrointestinal tract, and a specific state of sleepiness caused by hormonal and neurochemical changes related to the rate at which glucose enters the bloodstream and its downstream effects on amino acid transport in the central nervous system.

Although the passage of food into the gastrointestinal tract results in increased blood flow to the stomach and intestines, this is achieved by diversion of blood primarily from skeletal muscle tissue and by increasing the volume of blood pumped forward by the heart each minute. The flow of oxygen and blood to the brain is extremely tightly regulated by the circulatory system and does not drop after a meal, and is not a cause of post-meal sleepiness.

A common myth holds that turkey is especially high in tryptophan, resulting in sleepiness after it is consumed, as may occur at the traditional meal of the American holiday of Thanksgiving. However, the tryptophan content of turkey is comparable to chicken, beef, and other meats and does not result in higher blood tryptophan levels than other common foods. Certain foods, such as soybeans, sesame and sunflower seeds, and certain cheeses, are high in tryptophan. Although it is possible these may induce sleepiness if consumed in sufficient quantities, this is not well studied.

When alcohol is consumed with a meal, this may contribute to sleepiness after the meal, but is a nonspecific response to alcohol consumption and can occur independent of eating.

Bioplastics

Bioplastics are a form of plastics derived from renewable biomass sources, such as vegetable oil, corn starch, pea starch, or microbiota, rather than fossil-fuel plastics which are derived from petroleum. Some, but not all, bioplastics are designed to biodegrade.

Biodegradable bioplastics are used for disposable items, such as packaging and catering items (crockery, cutlery, pots, bowls, straws). Biodegradable bioplastics are also often used for organic waste bags, where they can be composted together with the food or green waste. Some trays and containers for fruit, vegetables, eggs and meat, bottles for soft drinks and dairy products and blister foils for fruit and vegetables are manufactured from bioplastics.

Non-disposable applications include mobile phone casings, carpet fibres, and car interiors, fuel line and plastic pipe applications, and new electroactive bioplastics are being developed that can be used to carry electrical current. In these areas, the goal is not biodegradability, but to create items from sustainable resources.

Munroe Effect

The Munroe effect refers to the partial focusing of blast energy caused by a hollow or void cut into a piece of explosive, a property which is exploited by a shaped charge.

Explosive energy is released directly away from (normal to) the surface of an explosive, so shaping the explosive will concentrate the explosive energy in the void. If the void is properly shaped (usually conically), a high-velocity jet of plasma will form.

It is named after Charles E. Munroe, who discovered it in 1888. Whilst working at the Naval Torpedo Station at Newport, Rhode Island in the United States, he noticed that when a block of guncotton with the manufacturer's name stamped into it was detonated next to a metal plate, the lettering was cut into the plate. If letters were raised in relief above the surface of the guncotton then the letters on the plate would also be raised above its surface. In 1910, Egon Neumann of Germany discovered that a block of TNT which would normally dent a steel plate would cut a hole right through it if the explosive contained a conical indentation. However, the military usefulness of this effect was not appreciated until the Second World War.

In modern military applications, a Munroe-effect shaped-charge warhead can be expected to penetrate solid steel armor of thickness equal to 150–250% of the warhead diameter, though it will tend to be somewhat less effective against modern composite armors and reactive armor, which was developed specifically as a counter to shaped-charge weapons.

In non-military applications, shaped charges are valued for their versatility and speed. Shaped charges are used in the explosive demolition of buildings: a few hundred pounds of well-placed shaped charges can raze a building faster than several hundred tons of machinery. In steelmaking, small shaped charges are often used to pierce taps that have become plugged with slag.

A device called a "Jet-Axe" was also used sometime around the 1960s or 1970s by fire brigades in the United Kingdom to cut holes through reinforced doors and walls to help gain access to fight fires or rescue people. The "Jet-Axe" was the shape of a flattened doughnut with a hole in the middle and contained a ring of a shaped charge. The device, which was roughly 2 feet (60 cm) in diameter, would be hung on a door or wall with the shaped charge facing the door or wall and when detonated it would cut a circular hole through it.

Heavy Water

Heavy water is water that contains a higher proportion than normal of the isotope deuterium, as deuterium oxide, D₂O or ²H₂O, or as deuterium protium oxide, HDO or ¹H²HO. Its physical and chemical properties are somewhat similar to those of water, H₂O.

Relatively pure heavy water was produced in 1933, soon after the discovery of deuterium, the stable heavy isotope of hydrogen. With the discovery of nuclear fission in late 1938 and the need for a neutron moderator which captured few neutrons, heavy water soon achieved importance in relation to early nuclear programs during World War II. Due in part to German reliance on scarce heavy water for reactor research in this war, Germany did not succeed in producing a functioning reactor during World War II. Since this war, heavy water has played a part in a number of reactor designs, both in designs for power and for nuclear weapon-making. Reactors which use enriched uranium, however, are able to use normal “light water” for neutron moderation, and remain the most common type of reactor in use today.

Heavy water itself is not radioactive, and has physical properties similar to water save for being about 11% more dense. However, as commercially made, heavy water contains whatever tritium was present in the water from which it was isolated. When the water in eukaryotic organisms is replaced by more than about 25 to 50% heavy water, they experience toxicity due to interference by the deuterium with the mitotic apparatus of these cells. Higher organisms, including mammals, if given only heavy water, soon become ill and die at the point that about half their body water has been replaced. Bacteria, however, are able to grow slowly in pure heavy water.

Small concentrations of heavy water are nontoxic. The adult human body naturally contains deuterium equivalent to the amount in about 5 grams of heavy water, and comparable doses of heavy water are still used as safe non-radioactive tracers for metabolic experiments in humans and other animals.