Geyser Eruptions on Mars

Every spring on the south polar ice cap of Mars brings violent eruptions of carbon dioxide gas carrying dark sand and dust high aloft.

The seasonal frosting and defrosting of ice results in the appearance of a number of features, such dark dune spots with spider-like rilles or channels below the ice, where spider-like radial channels are carved between the ground and ice, giving it an appearance of spider webs, then, pressure accumulating in their interior ejects gas and dark basaltic sand or mud, which is deposited on the ice surface and thus, forming dark dune spots. This process is rapid, observed happening in the space of a few days, weeks or months.

The geological features called dark dune spots and spiders were separately discovered on images acquired by the MOC camera on board the Mars Global Surveyor during 1998-1999. At first it was generally thought they were unrelated features because of their appearance. The first "Jet" or "Geyser" models start to be proposed and refined from 2000 onwards. The name 'spiders' was coined by Malin Space Science Systems personnel, the developers of the camera. The unusual shape and appearance of these 'spider webs' and spots caused a lot of speculation about their origin. The first years' surveillance showed that during the following Martian years, 70% of the spots appear at the exact same place, and a preliminary statistical study indicated that dark dune spots and spiders are related phenomena as functions of the cycle of CO2 ice condensation and sublimation. Thermal imaging during 2006 revealed that the temperature of these structures are as cold as the ice that covers the area. Soon after their first detection, they were discovered to be negative topographical features: radial troughs or channels of what today are thought to be geyser-like vent systems.

The geysers' two most prominent features (dark dune spots and spider channels) appear at the beginning of the Martian spring on dune fields covered with carbon dioxide (CO2 or 'dry ice'), mainly at the ridges and slopes of the dunes; by the beginning of winter, they disappear. Dark spots' shape is generally round, on the slopes it is usually elongated, sometimes with streams (water?) that accumulate in pools at the bottom of the dunes. Dark dune spots are typically 15 to 46 meters wide and spaced several hundred feet apart. Spider features form a round lobed structure reminiscent of a spider web radiating outward in lobes from a central point. Its radial patterns represent shallow channels or ducts in the ice formed by the flow of the sublimation gas toward the vents. The entire spider channel network is typically 160–300 m across.


Dark dune spots, high resolution color image
by the HiRISE camera (Credit: NASA)

Time-lapsed imagery performed by NASA confirms the apparent ejection of dark material following the radial growth of spider channels in the ice. Small dark spots generally indicate the position of spider features not yet visible; it also shows that spots expand significantly, including dark fans emanating from some of the spots, which increase in prominence and develop clear directionality indicative of wind action.

A number of geophysical models have been investigated to explain the various colors and shapes' development of these geysers on the southern polar ice cap of Mars.

Some teams propose dry venting of carbon dioxide gas and sand, occurring between the ice and the underlying bedrock. It is known that a CO2 ice slab is virtually transparent to solar radiation where 72% of solar energy incident at 60 degrees off vertical will reach the bottom of a 1 m thick layer. In addition, the ice thickness is measured in several target areas, and it was discovered that the greatest thickness of the CO2 frost layer in the geysers' area is about 0.76–0.78 m, supporting the geophysical model of dry venting powered by sunlight. As the southern spring CO2 ice receives enough Sun energy, it starts sublimation of the CO2 ice from the bottom. This vapor accumulates under the slab rapidly increasing pressure and erupting. High-pressure gas flows through at speeds of 161 km/h or more; under the slab, the gas erodes ground as it rushes toward the vents, snatching up loose particles of sand and carving the spidery network of grooves. The dark material falls back to the surface and may be taken up slope by wind, creating dark wind streak patterns on the ice cap.

Another model explores the possibility of active water-driven erosive structures, where soil and water derived from the shallow sub-surface layer is expelled up by CO2 gas through fissures eroding joints to create spider-like radiating tributaries capped with mud-like material and/or ice. Data obtained by the Mars Express satellite in 2004, confirmed that the southern polar cap has an average of 3 kilometres thick slab of CO2 ice with varying contents of frozen water, depending on its latitude: the bright polar cap itself, is a mixture of 85% CO2 ice and 15% water ice. The second part comprises steep slopes known as 'scarps', made almost entirely of water ice, that fall away from the polar cap to the surrounding plains. This transition area between the scarps and the permafrost is the 'cryptic region', where clusters of geysers are located.

A team of Hungarian scientists propose that the dark dune spots and channels may be colonies of photosynthetic Martian microorganisms, which over-winter beneath the ice cap, and as the sunlight returns to the pole during early spring, light penetrates the ice, the microorganisms photosynthesise and heat their immediate surroundings. A pocket of liquid water, which would normally evaporate instantly in the thin Martian atmosphere, is trapped around them by the overlying ice. Since their discovery, fiction writer Arthur C. Clarke promoted these formations as deserving of study from an astrobiological perspective.

A multinational European team suggests that if liquid water is present in the spiders' channels during their annual defrost cycle, the structures might provide a niche where certain microscopic life forms could have retreated and adapted while sheltered from UV solar radiation. A British team also considers the possibility that organic matter, microbes, or even simple plants might co-exist with these inorganic formations, especially if the mechanism includes liquid water and a geothermal energy source.


Further reading:
Geology of Mars
NASA Findings Suggest Jets Bursting From Martian Ice Cap
Mars' South Pole Ice Deep and Wide
Water at Martian south pole
Martian spots warrant a close look
Dark Dune Spots: Possible Biomarkers on Mars?

Supermassive Black Holes

A supermassive black hole is a black hole with the mass on the order of hundreds of thousands to billions of solar masses. Most galaxies are believed to contain supermassive black holes at their centers.


This artist's concept depicts a supermassive black hole and its
accretion disk at the center of a galaxy (Credit: NASA)

Supermassive black holes have properties which distinguish them from lower-mass classifications:

• The average density of a supermassive black hole can be very low, and may actually be lower than the density of air. This is because the Schwarzschild radius is directly proportional to mass, while density is inversely proportional to the volume. Since the volume of a spherical object is directly proportional to the cube of the radius, and mass merely increases linearly, the volume increases at a greater rate than mass. Thus, average density decreases for increasingly larger radii of black holes.
• The tidal forces in the vicinity of the event horizon are significantly weaker. Since the central singularity is so far away from the horizon, a hypothetical astronaut travelling towards the black hole center would not experience significant tidal force until very deep into the black hole.

There are several models for the formation of black holes of this size. The most obvious is by slow accretion of matter starting from a black hole of stellar size. Another model of supermassive black hole formation involves a large gas cloud collapsing into a relativistic star of perhaps a hundred thousand solar masses or larger. The star would then become unstable to radial perturbations due to electron-positron pair production in its core, and may collapse directly into a black hole without a supernova explosion, which would eject most of its mass and prevent it from leaving a supermassive black hole as a remnant. Yet another model involves a dense stellar cluster undergoing core-collapse as the negative heat capacity of the system drives the velocity dispersion in the core to relativistic speeds. Finally, primordial black holes may have been produced directly from external pressure in the first instants after the Big Bang.

Astronomers are confident that our own Milky Way galaxy has a supermassive black hole at its center, in a region called Sagittarius A* because:

• The star S2 follows an elliptical orbit with a period of 15.2 years and a pericenter of 17 light hours from the central object.
• Early estimates indicated that the central object contains 2.6 million solar masses and has a radius of less than 17 light hours. Only a black hole can contain such a vast mass in such a small volume.
• Further observations strengthened the case for a black hole, by showing that the central object's mass is about 3.7 million solar masses and its radius no more than 6.25 light-hours.

The Max Planck Institute for Extraterrestrial Physics and UCLA Galactic Center Group have provided the strongest evidence to date that Sagittarius A* is the site of a supermassive black hole, based on data from the ESO and the Keck telescope. Our galactic central black hole is calculated to have a mass of approximately 4.1 million solar masses.


Sagittarius A* (centre) and two light echoes
from a recent explosion (Credit: NASA)

It is now widely accepted that the center of nearly every galaxy contains a supermassive black hole. The close observational correlation between the mass of this hole and the velocity dispersion of the host galaxy's bulge, known as the M-sigma relation, strongly suggests a connection between the formation of the black hole and the galaxy itself.

The explanation for this correlation remains an unsolved problem in astrophysics. It is believed that black holes and their host galaxies coevolved between 300-800 million years after the Big Bang, passing through a quasar phase and developing correlated characteristics, but models differ on the causality of whether black holes triggered galaxy formation or vice versa, and sequential formation cannot be excluded. The unknown nature of dark matter is a crucial variable in these models.

At least one galaxy, Galaxy 0402+379, appears to have two supermassive black holes at its center, forming a binary system. Should these collide, the event would create strong gravitational waves. Binary supermassive black holes are believed to be a common consequence of galaxy mergers. As of November 2008, another binary pair, in OJ 287, contains the most massive black hole known, with a mass estimated at 18 billion solar masses.

Self-Replicating Robots Might Take Over the World

"Grey goo" is a hypothetical end-of-the-world scenario involving molecular nanotechnology in which out-of-control self-replicating robots consume all matter on Earth while building more of themselves. This scenario is known as "ecophagy" -- the literal consuming of an ecosystem. The term "grey goo" is usually used in a science fiction context. In the worst postulated scenarios, matter beyond Earth would also be turned into goo, a large mass of replicating nanomachines. The disaster is posited to result from a deliberate doomsday device, or from an accidental mutation in a self-replicating nanomachine used only for other purposes, but designed to operate in a natural environment.


A simple form of self-replicating machine (Credit: NASA)

Self-replicating machines were originally described by mathematician John von Neumann. They are artificial constructs capable of autonomously manufacturing copies of themselves using raw materials taken from their environment. The concept of self-replicating machines has been advanced and examined by Edward F. Moore, Homer Jacobsen, Freeman Dyson, and in more recent times by K. Eric Drexler. The future development of such technology has featured as an integral part of several plans involving the mining of moons and asteroid belts for ore and other materials, the creation of lunar factories and even the construction of solar power satellites in space. Von Neumann also worked on what he called the universal constructor, a self-replicating machine that would operate in a cellular automata environment.

Ecophagy is a term coined by Robert Freitas. He used the term to describe a scenario involving molecular nanotechnology gone awry. In this situation out-of-control self-replicating nanorobots consume entire ecosystems, resulting in global ecophagy. However, the word "ecophagy" is now applied more generally in reference to any event -- nuclear war, the spread of monoculture, massive species extinctions -- that might fundamentally alter the planet. These events might result in ecocide in that they would undermine the capacity of the earth's biological population to repair itself. Some scientists suggest that more mundane and less spectacular events -- the unrelenting growth of the human population, the steady transformation of the natural world by human beings -- will eventually result in a planet that is considerably less vibrant, and one that is, apart from humans, essentially lifeless.

In his original paper Freitas wrote:

Perhaps the earliest-recognized and best-known danger of molecular nanotechnology is the risk that self-replicating nanorobots capable of functioning autonomously in the natural environment could quickly convert that natural environment (e.g., "biomass") into replicas of themselves (e.g., "nanomass") on a global basis, a scenario usually referred to as the "grey goo problem" but perhaps more properly termed "global ecophagy".

As the use of industrial automation has advanced over time, some factories have begun to approach a semblance of self-sufficiency that is suggestive of self-replicating machines. Since safety is a primary goal of all legislative consideration of regulation of such development, future development efforts may be limited to systems which lack either control, matter, or energy closure. Fully-capable machine replicators are most useful for developing resources in dangerous environments which are not easily reached by existing transportation systems -- such as outer space. An artificial replicator can be considered to be a form of artificial life. Depending on its design, it might be subject to evolution over an extended period of time. However, with robust error correction, and the possibility of external intervention, the common science fiction scenario of robotic life run amok will remain extremely unlikely for the foreseeable future.

Colonization of Jupiter's moon Europa

Europa, the fourth-largest moon of Jupiter, is a subject in both science fiction and scientific speculation for future human colonization. Europa's geophysical features, including a possible subglacial water ocean, make it a strong possibility that human life could be sustained on or beneath the surface.


At just over 3,100 kilometres in diameter, Europa is slightly smaller than Earth's Moon
and is the sixth-largest moon in the Solar System. (Credit: Galileo Project, JPL, NASA)

Europa is primarily made of silicate rock and likely has an iron core. It has a tenuous atmosphere composed primarily of oxygen. Its surface is composed of ice and is one of the smoothest in the Solar System. This water ice, liquid water, and organic compounds that might be useful for sustaining human life. The young surface is striated by cracks and streaks, while craters are relatively infrequent. The apparent youth and smoothness of the surface have led to the hypothesis that a water ocean exists beneath it. Heat energy from tidal flexing ensures that the ocean remains liquid and drives geological activity.


Model of Europa's subsurface structure. (Credit: NASA)

Colonies in the outer solar system could serve as centers for long term investigation of the planet and the other moons. In particular, robotic devices could be controlled by humans without the very long time delays needed to communicate with Earth. The colonization of Europa presents numerous difficulties; one is the high level of radiation from Jupiter's radiation belt, which is about 10 times as strong as Earth's Van Allen radiation belts. As Europa receives 540 rem of radiation per day, a human would not survive at or near the surface of Europa for long without significant radiation shielding. Colonists on Europa would have to descend beneath the surface, and stay in buried habitats. Another problem is that the surface temperature of Europa normally rests at −170 °C. It is also speculated that alien organisms may exist on Europa, possibly in the water underlying the moon's ice shell. If this is so, human colonists may come into conflict with harmful microbes. Even if life on Europa is found to be benign, human colonization of Europa raises ethical questions of ecocide.

Artist's concept of the cryobot, a large nuclear-powered probe, which
would melt through the ice until it hit the ocean below. (Credit: NASA)

Europa plays a role in the book and film of Arthur C. Clarke's 2010: Odyssey Two (1982) and its sequels. Super-advanced aliens aiding the development of life take an interest in the primitive life forms under Europa's ice and transform Jupiter into a star to kick-start their evolution. The aliens grant humans the other three Galilean moons of Jupiter to settle, but the humans are instructed not to land on Europa in order to allow the local life to develop. In 2061: Odyssey Three (1988), Europa has become a tropical ocean world.

Further reading:

Europa, a Continuing Story of Discovery
Moon Miners' Manifesto: Europa II Workshop Report
Preventing Forward Contamination of Europa
Humans on Europa: A Plan for Colonies on the Icy Moon

Effect of Psychoactive Drugs on Animals

Psychoactive drugs, such as caffeine, amphetamine, mescaline, strychnine, LSD, benzedrine, marijuana, chloral hydrate, theophylline, IBMX and others, have a strong effect on animals. At small concentrations, they reduce the feeding rate of insects and molluscs, and at higher doses kill them. Spiders build more disordered webs after consuming most drugs than before. It is believed that some plants developed caffeine in their leaves as a natural protection against insects.


Drugs affect spider's ability to build a web (Credit: NASA)

Spiders

In 1948, German pharmocologist P. N. Witt started his research on the effect of drugs on spiders. The initial motivation for the study was a request from his colleague, zoologist H. M. Peters, to shift the time when garden spiders build their webs from 2am-5am, which apparently annoyed Peters, to earlier hours. Witt tested spiders with a range of psychoactive drugs, including amphetamine, mescaline, strychnine, LSD and caffeine, and found that the drugs affect the size and shape of the web rather than the time when it is built. At small doses of caffeine (10 µg/spider), the webs were smaller; the radii were uneven, but the regularity of the circles was unaffected. At higher doses (100 µg/spider), the shape changed more, and the web design became irregular. All the drugs tested reduced web regularity except for small doses (0.1-0.3 µg) of LSD, which resulted in more ordered webs.

The drugs were administered by dissolving them in sugar water, and a drop of solution was touched to the spider's mouth. In some later studies, spiders were fed with drugged flies. For qualitative studies, a well-defined volume of solution was administered through a fine syringe. The webs were photographed for the same spider before and after drugging.

Witt's research was discontinued, but it became reinvigorated in 1984 after a paper by Nathanson in the journal Science, which is discussed below. In 1995, a NASA research group repeated Witt's experiments on the effect of caffeine, benzedrine, marijuana and chloral hydrate on European garden spiders. NASA's results were qualitatively similar to those of Witt, but the novelty was that the pattern of the spider web was quantitatively analyzed with modern statistical tools, and proposed as a sensitive method of drug detection.



Other arthropods and molluscs

In 1984, Nathanson reported an effect of methylxanthines on larvae of the tobacco hornworm. He administered solutions of finely powdered tea leaves or coffee beans to the larvae and observed, at concentrations between 0.3 and 10% for coffee and 0.1 to 3% for tea, inhibition of feeding, associated with hyperactivity and tremor. At higher concentrations, larvae were killed within 24 hours. He repeated the experiments with purified caffeine and concluded that the drug was responsible for the effect, and the concentration differences between coffee beans and tea leaves originated from 2-3 times higher caffeine content in the latter. Similar action was observed for IBMX on mosquito larvae, mealworm larvae, butterfly larvae and milkweed bug nymphs, that is, inhibition of feeding and death at higher doses. Flour beetles were unaffected by IBMX up to 3% concentrations, but long-term experiments revealed suppression of reproductive activity.

Further, Nathanson fed tobacco hornworm larvae with leaves sprayed with such psychoactive drugs as caffeine, formamidine pesticide didemethylchlordimeform (DDCDM), IBMX or theophylline. He observed a similar effect, namely inhibition of feeding followed by death. Nathanson concluded that caffeine and related methylxanthines could be natural pesticides developed by plants as protection against worms: Caffeine is found in many plant species, with high levels in seedlings that are still developing foliage, but are lacking mechanical protection; caffeine paralyzes and kills certain insects feeding upon the plant. High caffeine levels have also been found in the soil surrounding coffee bean seedlings. It is therefore understood that caffeine has a natural function, both as a natural pesticide and as an inhibitor of seed germination of other nearby coffee seedlings, thus giving it a better chance of survival.

Coffee borer beetles seem to be unaffected by caffeine, in that their feeding rate did not change when they were given leaves sprayed with caffeine solution. It was concluded that those beetles have adapted to caffeine. This study was further developed by changing the solvent for caffeine. Although aqueous caffeine solutions had indeed no effect on the beetles, oleate emulsions of caffeine did inhibit their feeding, suggesting that even if certain insects have adjusted to some caffeine forms, they can be tricked by changing minor details, such as the drug solvent.

These results and conclusions were confirmed by a similar study on slugs and snails. Cabbage leaves were sprayed with caffeine solutions and fed to Veronicella cubensis slugs and Zonitoides arboreus snails. Cabbage consumption reduced over time, followed by the death of the molluscs. Inhibition of feeding by caffeine was also observed for caterpillars.

(Source: Wikipedia)

IK Pegasi B: The Nearest Supernova Candidate

IK Pegasi is a binary star system in the constellation Pegasus. White dwarf IK Pegasi B, a massive star that is no longer generating energy through nuclear fusion, is the nearest known supernova candidate. When the primary evolves into a red giant, it will grow to a radius where the white dwarf can attract more matter from the expanded envelope. When the white dwarf approaches the limit of 1.44 solar masses, it is going to explode as a Type Ia supernova.


In IK Pegasi binary system, gas is being stripped away
from a giant star to form an accretion disc around
a compact companion (NASA image).

The primary is a main sequence star that displays minor pulsations in luminosity. It is categorized as a Delta Scuti variable star with a period of about an hour. Its companion is a massive white dwarf — a star that has evolved past the main sequence. They orbit each other every 21.7 days with a separation of about astronomical units. This is smaller than the orbit of Mercury around the Sun.

The distance to the IK Pegasi system can be measured directly by observing its parallax shifts against the distant stellar background as the Earth orbits around the Sun. This shift was measured to high precision by the Hipparcos spacecraft, and the distance was estimated as 150 light years. Hipparcos also measured the proper motion — the small angular motion of IK Pegasi across the sky because of its motion through space. The combination of the distance and proper motion of this system was used to compute the transverse velocity of IK Pegasi as 16.9 km/s.

The interior of IK Pegasi B may be composed wholly of carbon and oxygen, or alternatively, it may have a core of oxygen and neon, surrounded by a mantle enriched with carbon and oxygen. The exterior is covered by an atmosphere of almost pure hydrogen. Any helium in the envelope will have sunk beneath the hydrogen layer. The entire mass of the star is supported by electron degeneracy pressure — a quantum mechanical effect that limits the amount of matter that can be squeezed into a given volume.


A comparison between the IK Pegasi B (center), its companion
IK Pegasi A (left) and the Sun (right). (Credit: RJHall)

IK Pegasi B is considered to be a high-mass white dwarf, at an estimated 1.15 solar masses. Its radius can be estimated from known theoretical relationships between the mass and radius of white dwarfs, giving a value of about 0.60% of the Sun's radius. Thus this star packs a mass greater than the Sun into a volume roughly the size of the Earth. The massive, compact nature of a white dwarf produces a strong surface gravity — over 900,000 times the gravitational force on the Earth. The surface temperature is about 35,500K, making it a strong source of ultraviolet radiation. Under normal conditions this white dwarf would continue to cool for more than a billion years, while its radius would remain unchanged.

At some point in the future, IK Pegasi A will consume the hydrogen fuel at its core and form a red giant. The envelope of a red giant can extend up to a hundred times its previous radius. Once IK Pegasi A expands to the point where its outer envelope overflows the Roche lobe of its companion, a gaseous accretion disk will form around the white dwarf. This mass transfer between the stars will also cause their mutual orbit to shrink. Should the white dwarf's mass approach the Chandrasekhar limit of 1.44 solar masses it will no longer be supported by electron degeneracy pressure and it will undergo a collapse. If the core is made of carbon-oxygen, increasing pressure and temperature will initiate carbon fusion in the center prior to attainment of the Chandrasekhar limit. The dramatic result is a runaway nuclear fusion reaction that consumes a substantial fraction of the star within a short time. This will be sufficient to unbind the star in a cataclysmic, Type Ia supernova explosion.

A supernova would need to be within about 26 light years of the Earth to effectively destroy the Earth's ozone layer, which would severely impact the planet's biosphere. IK Pegasi system is not likely to pose a threat to life on the Earth, however. It is thought that the primary star is unlikely to evolve into a red giant in the immediate future. As shown previously, the space velocity of this star relative to the Sun is 20.4 km/s. This is equivalent to moving a distance of one light year every 14,700 years. After 5 million years, this star will be separated from the Sun by more than 500 light years. This is outside the radius where a Type Ia supernova is thought to be hazardous.


This video shows a thermonuclear flame burning its way through a white dwarf star. The flame produces hot ash, which buoyantly rises as the flame burns. The ash breaks out of but remains gravitationally bound to the surface of the star and collides at a point on the opposite side of the star from the breakout location. The blue shows the approximate surface of the star and the orange shows the interface between the star and the hot ash produced by the flame. (Credit: DOE NNSA ASC/Alliance Flash Center at the University of Chicago)

The Story of Gamma-ray Bursts

Gamma-ray bursts are flashes of gamma rays connected with extremely energetic explosions in distant galaxies. They are the most luminous electromagnetic events occurring in the universe.

This illustration shows the life of a massive star as nuclear fusion converts lighter elements into heavier ones. When fusion no longer generates enough pressure to counteract gravity, the star rapidly collapses into a black hole. Energy may be released during the collapse along the axis of rotation to form a gamma-ray burst. (Credit: Nicolle Rager Fuller/NSF)

"The death star": BBC documentary on the first stars in the universe and gamma-ray bursts.

Moebius transformation

Moebius transformation of the plane is a rational function of the form
f(z)=(az+b)/(cz+d)
The variable z and the coefficients a, b, c, d are complex numbers satisfying ad − bc ≠ 0. Moebius transformations are named in honor of August Ferdinand Moebius.

Here is a short movie depicting the beauty of Moebius Transformations in mathematics, it shows how moving to a higher dimension can make the transformations easier to understand.

The Key to the Cosmos

Prof. Jim Al-Khalili investigates the atom by looking at radioactivity, the Atom Bomb and the Big Bang, and even why we are here and how we were made. He shows that, in the quest to understand the atom, the mystery of how the entire universe was created became revealed.

The Clash of the Titans - 60min Video

Nuclear physicist Jim Al-Khalili looks at what led to the discovery that everything is made of atoms. The program looks at how the discovery affected the scientific world including the atomic energy theories of Albert Einstein and Werner Heisenberg and quantum mechanics.

Science History: the Babylonians and Egyptians

Sumerian god Enki, with characteristic symbols: bird, goat and water flows

The early Sumerians and Babylonians have contributed to later generations important units for the measurement of time and of angles. Babylonian in origin is the week of seven days, also the division of the day and of the night into twelve hours each. The Babylonians made quite extensive use of the sexagesimal scale in writing integral numbers and fractions; using the same scale, they divided the hour into 60 minutes and the minute into 60 seconds. The circle was subdivided into 360 degrees, the degree into 60 minutes of are, and the minute into 60 seconds. The most humble worker of the present day measures the time of work by the hour, as did the Babylonians of perhaps 5000 years ago. The most noted engineer and the most distinguished astronomer of the present time measure angles in degrees, minutes and seconds, much as did the astronomers at the Euphrates and Tigris eons ago. Early Babylonian astronomical records indicate a surprising precision. An achievement of the first magnitude was the discovery of that slow motion of the equinoctial points on the ecliptic called the precession of the equinoxes. This was done by the Babylonian astronomer Cidenas, who directed an astronomical school at Sippra, on the Euphrates, about 343 B.C.

Primitive sun-dials and water-clocks served for measuring time. For finding the angular altitude of the sun (at noon time), they used the gnomon which consisted essentially of a vertical rod of known length. The length and direction of its solar shadow afforded the necessary data. The beam-balance served for weighing medicine and precious articles. The medical recipes described in the Egyptian papyrus Ebers indicate the use of weights as small as 0.71 grams.

Evolution Misconceptions

Evolution: 10-minute video addressing some misconceptions and explaining some of the basics.

A Very Short History of Astronomy

2,500 BC - Stonehenge, one of the most famous sites in the world today, once served as a burial ground. Archaeoastronomers claim that Stonehenge represents an ancient observatory, and that the site had astrological and spiritual significance as well.

650 BC - Babylonian Venus tablet of Ammisaduqa is the oldest significant astronomical text that we possess. This document, recorded on cuneiform tablets, lists the first and last visible risings of Venus over a period of 21 years.


Stonehenge (Andrew Dunn); ................. Solar eclipse (Luc Viatour); .......... Thales; .................. Hipparchus

585 BC - Thales of Miletus predicts a solar eclipse. A battle in progress between the Lydians and the Medes is spontaneously halted by this eclipse.

150 BC - Hipparchus, the greatest astronomer of antiquity, uses parallax to determine that the distance to the Moon. In 134 BC, he discovers the precession of the equinoxes. Hipparchus ranks stars in six magnitude classes according to their brightness: he assignes '1' to the brightest stars, and '6' to the stars which can be barely seen with the naked eye.

46 BC - Julius Caesar adopted a calendar based upon the 365 1/4 day year length originally proposed by Greek astronomer Callippus. 46 BC had 445 days due to the errors that had accumulated in the pre-Julian calendar.

628 - Brahmagupta, the head of the astronomical observatory at Ujjain, writes a text on astronomy, Brahmasphutasiddhanta (The Opening of the Universe).

990 - Abu-Mahmud al-Khujandi builds a huge observatory near Tehran, Iran, and observes a series of meridian transits of the Sun, which allowed him to calculate the tilt of the Earth's axis relative to the Sun.

1054 - Crab Supernova (SN 1054) is observed on Earth by Chinese, Japanese, Arab, and American Indian astronomers. It was bright enough to see in daylight for 23 days.


Crab Nebula (NASA); ........................... Nicolaus Copernicus; ............................... De Revolutionibus

1543 - Nicolaus Copernicus' epochal book, De revolutionibus orbium coelestium, is published just before he died. This is often regarded as the starting point of modern astronomy.

1577 - Danish astronomer Tycho Brahe uses parallax to prove that comets are distant objects and not atmospheric phenomena. Tycho is credited with the most accurate astronomical observations of his time.

1609 - Johannes Kepler states his first two laws of planetary motion: 1. The orbit of every planet is an ellipse with the sun at a focus; 2. A line joining a planet and the sun sweeps out equal areas during equal intervals of time.


Tycho Brahe; ................... Johannes Kepler (Aldaron); .................... Galileo facing Inquisition

1610 - Galileo Galilei uses a small telescope to make the greatest astronomical discoveries of all time: the discovery of the four largest satellites of Jupiter, lunar mountains and craters, the phases of Venus, the Milky Way as a multitude of densely packed stars, and the observation and analysis of sunspots.

1687 - The Philosophiae Naturalis Principia Mathematica, mathematical principles of natural philosophy, a three-volume work by Isaac Newton, is published on 5 July 1687. It contains the foundation of classical mechanics, as well as the law of universal gravitation and a derivation of Kepler's laws for the motion of the planets.

1705 - Edmund Halley predicts the periodicity of Halley's comet and computes its expected path of return. In 1718, he discovers stellar proper motions by comparing his astrometric measurements with those of the Greeks.


Newton's telescope (Andrew Dunn); ........... Comet Halley (NASA); ....................... Charles Messier

1771 - Charles Messier publishes his first list of nebulae. The purpose of the catalog was to help comet hunters to distinguish between permanent and transient objects in the sky.

1781 - William Herschel discovers Uranus. He constructed more than 400 telescopes, discovered two moons of Saturn and two moons of Uranus, created extensive catalogs of nebulae and double stars, and concluded that the Milky Way is in the shape of a disk.

1814 - Joseph von Fraunhofer invents the spectroscope, and discovered 574 dark absorption lines appearing in the Sun's spectrum.

1838 - Friedrich Bessel, Friedrich Georg Wilhelm Struve, and Thomas Henderson measure stellar parallaxes, providing the first accurate measurements of interstellar distances.


Planet Uranus (NASA); ......................................... Herschel's 40 foot telescope; ................ Kirchhoff's first spectroscope

1860 - Gustav Kirchoff and Robert Bunsen discover that each element has its own distinct set of spectral lines and use this fact to explain the solar dark lines.

1908 - Henrietta Swan Leavitt discovers the Cepheid period-luminosity relation, providing an important yardstick for measuring distances in the Universe.

1910 - Ejnar Hertzsprung and Henry Russell study the relation between magnitudes and spectral types of stars. The Hertzsprung-Russell diagram represented a huge leap forward in understanding stellar evolution.

1915 - Albert Einstein completes his theory of general relativity. 'Matter tells space how to curve, space tells matter how to move'.

1922 - Alexander Friedmann finds a solution to the general relativity field equations which suggests a general expansion of space.

1923 - Edwin Powell Hubble profoundly changes our understanding of the universe by demonstrating the existence of other galaxies besides the Milky Way. Hubble also devises a system for classifying galaxies, according to their appearance in photographic images.


Andromeda Galaxy (John Lanoue); ........... Hubble's law (Brews Ohare); ............ George Gamow

1929 - Edwin Hubble and Milton Humason formulate the empirical Hubble's law -- the linear redshift-distance relation, thus showing the expansion of the universe.

1929 - George Gamow, a Russian-born physicist and cosmologist, proposes hydrogen fusion as the energy source for stars. He discovered alpha decay via quantum tunneling and worked on star formation, stellar nucleosynthesis, big bang nucleosynthesis, etc.

1930 - Clyde Tombaugh discovers the dwarf planet Pluto.

1930 - Subrahmanyan Chandrasekhar discovers the white dwarf maximum mass limit. The limit describes the maximum mass of a white dwarf star, above which a star will ultimately collapse into a neutron star or black hole.

1931 - Karl Guthe Jansky, American physicist and radio engineer, discovers radio waves emanating from the Milky Way. He is considered one of the founding figures of radio astronomy.

1931 - Roman Catholic priest Georges Lemaître proposes his 'hypothesis of the primeval atom', what became known as the Big Bang theory.

1933 - Fritz Zwicky applies the virial theorem to the Coma galaxy cluster and obtains evidence for unseen matter, what is now called dark matter. Zwicky was an original thinker, with many important contributions in astronomy.


Subrahmanyan Chandrasekhar; ... Cosmic Microwave Background (NASA); ... The Horn Antenna in Holmdel Township

1965 - Arno Penzias and Robert Wilson discover the cosmic microwave background radiation, predicted in 1948 by Ralph Alpher, George Gamow and Robert Herman.

1967 - Jocelyn Bell and Anthony Hewish discover the first radio pulsars, the greatest astronomical discovery of the twentieth century.

1971 - Cygnus X-1, a galactic X-ray source in the constellation Cygnus, is identified as a binary black hole candidate system.

1980 - Alan Guth, a theoretical physicist and cosmologist, proposes the inflationary Big Bang universe as a possible solution to the horizon and flatness problems.

1998 - Published observations of Type Ia supernovae by the High-z Supernova Search Team, followed in 1999 by the Supernova Cosmology Project, suggest that the expansion of the universe is accelerating.



Further reading:

Archaeoastronomy and Stonehenge
Astronomiae Historia
C41/ICHA website
Society for the History of Astronomy
Wikipedia History of astronomy

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