The Inner Life of the Cell: Video

This explanation video provides a glimpse of the process of the activation of a white blood cell in case of an inflammation response. For more info go here:
http://minimalpotential.wordpress.com/2008/11/24/more-inner-life-of-the-cell-explanations/

Recently Extinct Mammalian Species

This is a short list of recently extinct mammals, their dates of extinction, and some more interesting details. Many of these animals were extinct as a result of human hunting or through the destruction of their natural environment.

Javan Tiger (ext. 1990)

The photograph of a live Javan tiger taken in 1938

The Javan tiger (Panthera tigris sondaica) was a subspeices of tiger limited to the Indonesian island of Java. As a result of hunting and habitat destruction, this subspecies was made extinct in the 1980s, but the extinction became increasingly probable from the 1950s onwards, when fewer than 25 tigers remained in the wild.

In 2008, an unidentified body of a female mountain hiker was found in Central Java, allegedly died from tiger attack. Villagers who found the body also claimed some tiger sightings in the vicinity. But until concrete evidence can be produced, the Javan tiger must be considered yet another tiger subspecies which is probably extinct.


Zanzibar Leopard (ext. 1996)

Panthera pardus adersi, Zanzibar Museum, Helle V. Goldman and Jon Winther-Hansen

The Zanzibar Leopard (Panthera pardus adersi) is an extinct subspecies of leopard endemic to Unguja Island in the Zanzibar archipelago, Tanzania. Efforts to develop a conservation programme in the mid-1990s were stopped when researchers concluded that there was little prospect for the animal's long-term survival.

Rural Zanzibaris’ descriptions of the leopard are coloured by the belief that these carnivores are kept by witches and sent by them to harm or otherwise harass villagers. After the Zanzibar Revolution, a combined anti-witchcraft and leopard-killing campaign was launched under the leadership of the famous witch-finder, Kitanzi. The result of this campaign was to bring leopards to the brink of extinction.


Pyrenean Ibex (ext. January, 2000)

Pyrenean Ibex; Image from Cabrera, A. (1914)

The Pyrenean Ibex (Capra pyrenaica pyrenaica) once ranged across the Pyrenees in Spain and France and the surrounding area, including Navarre, the Basque Country, north Aragon and north Catalonia. The last natural Pyrenean Ibex, was found dead on January 6, 2000, killed by a falling tree.

The biotechnology company Advanced Cell Technology, Inc. used nuclear transfer cloning technology to clone the Pyrenean ibex from the tissue that was taken in 1999. The first attempts to clone the species failed. In 2009, one clone was born alive, but died seven minutes later, due to physical defects in the lungs.


West African Black Rhinoceros (ext. July, 2006)

Black Rhinoceros in Ngorongoro Conservation Area, Tanzania; photo: Yoky

West African Black Rhinoceros (Diceros bicornis longipes) was once widespread in the savanna of central-west Africa but on 7 July 2006, it was (tentatively) declared extinct.

Around 1980 the population was in the hundreds. The illegal poaching contributed to the species' demise, by 2000 only an estimated 10 survived. An intensive survey of the last remaining habitat of the species in early 2006 found none. There are eight western black rhinoceros alive: six are in the Czech republic and two are in the San Diego Zoo's Wild Animal park. It might be possible to save this species with work between these two locations.

Baiji: Chinese River Dolphin (ext. December, 2006)

An illustration of the Baiji; author: Alessio Marrucci

Nicknamed "Goddess of the Yangtze", Baiji is classified by the 2007 IUCN Red List as a possibly extinct species. A late 2006 expedition by scientists from six nations failed to find any Baiji in the Yangtze river.

As China industrialized in recent decades, and used the river for transportation, hydroelectricity, and fishing the Baiji population declined drastically. The last uncontested sighting of a baiji was in 2002. This was the first recorded extinction of a well-studied cetacean species directly attributable to human influence.

A Very Short History of Mathematics

70,000 BC there are drawings that indicate some knowledge of elementary mathematics and of time measurement based on the stars. Paleontologists have discovered ochre rocks adorned with scratched geometric patterns.

20,000 BC - The Ishango bone, found in northeastern Congo, is the earliest known demonstration of sequences of prime numbers and of Ancient Egyptian multiplication.

3,000 BC - The Indus Valley Civilization of North India and Pakistan developed a system of measures that used the decimal system, and an advanced brick technology which utilized ratios.

2,500 BC - The Sumerians wrote multiplication tables on clay tablets and dealt with division problems. The traces of the Babylonian numerals also date back to this period.

1,650 BC - The Rhind papyrus, a major Egyptian mathematical text, is an instruction manual in arithmetic and geometry. It gives area formulas, multiplication methods, working with unit fractions, composite and prime numbers, arithmetic, geometric and harmonic means.

550 BC - Pythagoras of Samos is credited with the first proof of the Pythagorean theorem, though the statement of the theorem has a long history. He expressed the theorem algebraically rather than geometrically.

400 BC - Jaina mathematicians from ancient India began studying mathematics for the sole purpose of mathematics. They developed transfinite numbers, logarithms, fundamental laws of indices, cubic equations, quartic equations, set theory, sequences and progressions, permutations and combinations, etc.

370 BC - Eudoxus developed the method of exhaustion, a precursor of modern integration. The Pythagoreans proved the existence of irrational numbers.

300 BC - Euclid wrote Elements, the most important mathematics book ever written. It is the first example of the format still used in mathematics today: definition, axiom, theorem, proof.

230 BC - Archimedes of Syracuse used the method of exhaustion to calculate the area under the arc of a parabola with the summation of an infinite series, and gave remarkably accurate approximations of Pi.

400 - The Surya Siddhanta, classical Indian mathematician, introduced the trigonometric functions of sine, cosine, and inverse sine, and laid down rules to determine the true motions of the luminaries, which conforms to their actual positions in the sky.

650 - Brahmagupta lucidly explained the use of zero as both a placeholder and decimal digit, and explained the Hindu-Arabic numeral system.

825 - Muhammad ibn Musa al-Kwarizmi wrote several books on the Hindu-Arabic numerals and on methods for solving equations. The word algorithm is derived from the Latinization of his name.

1000 - Al-Karaji, a Persian mathematician, gives the first known proof by mathematical induction. He proved the binomial theorem, Pascal's triangle, and the sum of integral cubes.

1170 - Bhaskara, another Indian mathematician first conceived differential calculus, the concept of the derivative, differential coefficient and differentiation. He also stated Rolle's theorem and investigated the derivative of the sine function.

1202 - Fibonacci produced the first significant mathematics in Europe since the time of Eratosthenes, a gap of more than a thousand years. His book introduced Hindu-Arabic numerals to Europe, and discussed many other mathematical problems.

1654 - Blaise Pascal and Pierre de Fermat set the groundwork for the investigations of probability theory and the corresponding rules of combinatorics in their discussions over a game of gambling.

1665 - Isaac Newton brought together the concepts now known as calculus. Independently, Gottfried Wilhelm Leibniz developed calculus and much of the calculus notation still in use today.

1736 - Leonhard Euler, the most influential mathematician of the 18th century, solved the Koenigsberg bridge problem. He founded the study of graph theory named the square root of -1 with the symbol i, made contributions to the study of topology, etc.

1799 - Karl Friedrich Gauss proves that every polynomial equation has a solution among the complex numbers. Gauss did revolutionary work on functions of complex variables, in geometry, and on the convergence of series.

1807 - Joseph Fourier announced his discoveries about the trigonometric decomposition of functions, but the demonstration was not altogether satisfactory. The final solution of the problem was given in 1829 by Jacques Charles François Sturm.

1822 - Augustin Louis Cauchy proved the Cauchy integral theorem for integration around the boundary of a rectangle. He started the project of formulating and proving the theorems of infinitesimal calculus in a rigorous manner and was thus a pioneer of analysis.

1829 - Nikolai Ivanovich Lobachevsky publishes his work on hyperbolic non-Euclidean geometry, where uniqueness of parallels no longer holds.

1832 - Evariste Galois presents a general condition for the solvability of algebraic equations. Galois and Niels Henrik Abel proved that there is no general algebraic method for solving polynomial equations of degree greater than four.

1843 - William Rowan Hamilton in Ireland discovers the calculus of quaternions and deduces that they are non-commutative.

1847 - George Boole devised Boolean algebra, in which the only numbers were 0 and 1 and in which, famously, 1 + 1 = 1. Boolean algebra is the starting point of mathematical logic and has important applications in computer science.

1854 - Bernhard Riemann introduces Riemannian geometry, which unifies and vastly generalizes the three types of geometry, and he defined the concept of a manifold, which generalize the ideas of curves and surfaces.

1899 - David Hilbert presents a set of self-consistent geometric axioms in Foundations of Geometry. In 1900, he set out a list of 23 unsolved problems in mathematics. These problems formed a central focus for much of 20th century mathematics.

1928 - John von Neumann, a Hungarian American mathematician who made major contributions to a vast range of fields, begins devising the principles of game theory and proves the minimax theorem.

1931 - Kurt Goedel shows that mathematical systems are not fully self-contained. One of the most significant logicians of all time, Goedel made an immense impact upon scientific and philosophical thinking in the 20th century.

1950 - Stanislaw Ulam and John von Neumann present cellular automata dynamical systems. Stanislaw Marcin Ulam was a Polish mathematician who participated in the Manhattan Project and proposed the Teller–Ulam design of thermonuclear weapons.

1961 - Daniel Shanks and John Wrench compute pi to 100,000 decimal places using an inverse-tangent identity and an IBM-7090 computer. Shanks is best known for his book Solved and Unsolved Problems in Number Theory.

1983 - Gerd Faltings shows that there are only finitely many whole number solutions for each exponent of Fermat's Last Theorem.

1987 - Yasumasa Kanada, Jonathan Borwein, Peter Borwein, and David Bailey, use iterative modular equation approximations to elliptic integrals and a NEC SX-2 supercomputer to compute pi to 134 million decimal places.

1995 - Sir Andrew John Wiles, working in secrecy, proves Fermat's Last Theorem. This surprisingly lengthy proof has stood up to the scrutiny of the world's experts.


Sources & further reading:

MacTutor History of Mathematics archive
History of Mathematics Home Page
The History of Mathematics
Biographies of Women Mathematicians
Fred Rickey's History of Mathematics Page
Wikipedia.org: History of Mathematics

Exceptionally Deep View of NGC 4921

Yet another amazing video created from images taken by the NASA/ESA Hubble Space Telescope. The video reveals lots of new details of the galaxy, as well as a rich background of remote galaxies stretching back to the early Universe.

3D animation of galaxies

This video was produced by Frank Summers, currently working as an astronomer for NASA. This animation of galaxies from the Hubble Space Telescope shows galaxies distributed over 10 billion years of cosmic time.

Einstein’s own popular book on relativity

The present book is intended as far as is possible to give an exact insight into the theory of Relativity to those readers who, from a general scientific and philosophical point of view, are interested in the theory, but are not conversant with the mathematical apparatus of theoretical physics.
Albert Einstein, from the preface.

Read the book online or download it.

Relativity: the Special and General Theory was written in 1916. This is a revised edition from 1924.

Grinstead and Snell's Introduction to Probability

This excellent introductory probability book is now available for free download in pdf format. It has been licensed under the terms of the GNU Free Documentation License: it is freely redistributable, and you can do whatever you like with the text, as long as you don't prevent anyone else from doing the same.

This book was written for an introductory probability course taken by sophomores, juniors, and seniors in mathematics, physical sciences, computer science, and engineering. It gives a thorough treatment of probability ideas and techniques necessary for a firm understanding of the subject.

Animal Evolution: Phanerozoic Eon

The Phanerozoic Eon is the eon in which we live, the one during which abundant animal life has existed. I've just found this amazing video on YouTube, it shows the evolution of fish, amphibians, reptiles, dinosaurs, mammals, and primates, starting more than 500,000,000 years ago, and ending today.

World's Most Expensive Engineering Projects

Here is a list of the world's most expensive engineering projects with estimated costs and short descriptions of each project (sources: iCivilEngineer, China Daily, Wikipedia). Some of the projects are already completed, some are under construction, so the cost estimates are not definitive. This list is also under construction: if you know big engineering projects which are not listed, please post your comments.


5. Gerald R. Ford Class Aircraft Carrier: 8.1 billion USD
Artist’s concept of CVN 21 one of a new class of aircraft carriers

The Gerald R. Ford-class aircraft carriers (CVN-78) will be the next generation supercarrier for the United States Navy. Construction began in the spring of 2007, and is planned to finish in 2015. With the addition of the most modern equipment and automation they will reduce the crew requirement and the total cost of future aircraft carriers.

Carriers of the Ford class will incorporate many new design features: new nuclear reactor design, stealthier features to reduce radar profile, electromagnetic catapults, advanced arresting gear, and reduced crewing requirements. It will be constructed at Northrop Grumman Shipbuilding in Virginia, the only shipyard in the U.S. capable of building nuclear powered aircraft carriers. It is estimated to cost at least $8.1 billion excluding the $5 billion spent on research and development. A total of three carriers has been authorized for construction, but eleven carriers could be constructed over the life of the program.

4. Big Dig, Boston: 14.6 billion USD
Interstate I-93 Tunnel in Boston, part of the Big Dig; photography by Rene Schwietzke

The Big Dig is a megaproject that rerouted the Central Artery, the chief highway through the heart of Boston, into a 3.5 mile tunnel under the city. When the project concluded on December 31, 2007, it was the most expensive highway project in the U.S. The project incurred criminal arrests, escalating costs, death, leaks, and charges of poor execution and use of substandard materials.

This project was developed in response to traffic congestion on Boston's streets, which were laid out before the advent of the automobile. The project faced several environmental and engineering obstacles. The area through which the tunnels were to be dug was largely landfill, and included existing subway lines, pipes and utility lines, many unexpected geological barriers, glacial debris, foundations of buried houses, sunken ships, etc. Unusual engineering challenges required unusual solutions and methods to address them. Engineers figured out the safest way to build the tunnel without endangering the existing highway above.

By the January 13, 2006, Big Dig was completed. It remains the largest and most complex highway and tunnel project in the nation's history.

3. Three Gorges Dam, China: 24 billion USD
Three Gorges Dam in construction 2002; photography by Frank Matthes

The Three Gorges Dam is a hydroelectric river dam that spans the Yangtze River in Sandouping, China. This is the largest hydroelectric power station in the world. The original plan of the project was completed in 2008. Six additional generators in the underground power plant will be installed until around 2011, when total electric generating capacity of the dam will reach 22,500 MW.

Some interesting facts: the concrete dam wall is 2,309 meters long, 101 meters high, 115 meters thick on the bottom and 40 meters thick on top. The project used 27,200,000 cubic meters of concrete, 463,000 tonnes of steel (enough to build 63 Eiffel Towers), and moved about 102,600,000 cubic meters of earth. When the water level is maximum at 91 meters above river level, the reservoir created by the Three Gorges Dam is about 660 kilometers in length and 1.12 kilometers in width on average. The total surface area of the reservoir is 1045 km2. The reservoir will flood a total area of 632 km2 of land.

The dam provides a vast amount of clean electricity, controls flooding, and enhances navigation. However, it has also flooded cultural and archaeological sites, displaced more than million people, and is causing dramatic ecological changes. The decision to build the dam has been deeply controversial.

2. Yucca Mountain Nuclear Waste Repository Project: 57 billion USD
Looking west atop Yucca Mountain towards Beatty and Death Valley

The U.S. Department of Energy have been studying Yucca Mountain, Nevada, since 1978 to determine whether it would be suitable for a long-term geologic repository for high-level radioactive waste, a result of nuclear power generation and national defense programs. Yucca Mountain is located in a remote desert within the secure boundaries of the Nevada Test Site in Nye County, 90 miles northwest of Las Vegas.

Yucca Mountain was created by several large eruptions from a caldera volcano and is composed of layers of tuff. Tuff has special physical and chemical characteristics that make it a suitable material to entomb radioactive waste for the hundreds of thousands of years required for the waste to become safe through radioactive decay. After 20 years of research and carefully planned scientific field work, the Department of Energy has found that the repository brings together the location and natural barriers most likely to protect the safety of the public, including those Americans living in the immediate vicinity.

The Obama Administration rejected the use of the site in the 2009 United States Federal Budget proposal, which would eliminate all funding except that needed to answer inquiries from the Nuclear Regulatory Commission, while the Administration devises a new strategy toward nuclear waste disposal. On March 5, 2009, Energy Secretary told a Senate hearing that the Yucca Mountain site no longer was viewed as an option for storing reactor waste.

1. International Space Station: 80 billion USD
International Space Station as seen from the departing Space Shuttle Atlantis; source: NASA

The International Space Station (ISS) is a joint project among the space agencies of the United States (NASA), Japan (JAXA), Russia (RKA), Canada (CSA) and the European Space Agency. The space station is in a low Earth orbit, at an altitude of 350 km, and you can see it from Earth's surface even with the naked eye.

The International Space Station is the largest research laboratory ever launched into orbit. Long-term expedition crews conduct science across a variety of fields: life sciences, human research, Earth observation, physical sciences, education and technology demonstrations. Scientific findings are being published every month. ISS provides educational opportunities for students back home on Earth, including educational demonstrations, student-developed experiments, student participation in ISS experiments, ISS engineering activities, and NASA investigator experiments.

As a multinational project, the financial and legal aspects of the ISS are complex. Giving a precise cost estimate is not straightforward, because it is not easy to determine which costs should actually be attributed to the programme. Cost estimates range from 35 billion to 100 billion USD. The ESA estimates €100 billion for the entire station over a period of 30 years.

Hypatia of Alexandria: the ancient Greek mathematician

Hypatia was the first woman who was studying and teaching advanced mathematics. During her lifetime, Alexandria had the world’s greatest library. She was a teacher and the school’s director at the Neoplatonic School of Philosophy. Hypatia was famous for her books on philosophy, mathematics, and other subjects. It is thought that Hypatia invented the astrolabe.

The comprehensive article on Hypatia at wikipedia

Impact Crater Formation

(Moon crater Dedal as photographed by the crew of Apollo 11)

Four billion years ago the Earth, the Moon, and every other Solar System object were heavily shot by impact comets and asteroids. You can see craters on rocky planets, on most moons and asteroids. Large craters usually have several rings around, intermediate have a central peak, and small craters are bowl-shaped.

The theory of impact crater formation must be very complex, searching the web I haven't found any simple (or simplified) explanation to reproduce here. In a lack of an easy theory, however you can conduct experiments, see the video below.

Exceptional Thermal Characteristics of Water

(Frozen lake on Mather Island, Antarctica; Author: Hannes Grobe, Alfred Wegener Institute)

The expansion of water with temperature is approximately linear. However, on a fine scale it is not exactly linear. In the temperature range from 0°C to 4°C water decreases in volume with increasing temperature, its coefficient of volume expansion is negative. Water also expands when it freezes, while most materials contract when they freeze. This has important consequences for plant and animal life in lakes. A lake cools at the surface, the cooler and denser water from the surface flows to the bottom. But when the air temperature drops below 4°C, the surface water is less dense than the water below, the downward flow ceases. The ice is less dense than water, and it floats. The water at the bottom always remains at 4°C unless the entire lake is frozen.

Related link: Water Structure and Science, an excellent web site on physics and chemistry of water.