Tuesday, July 29, 2008

Vincent Van Gogh

Vincent Van Gogh (30 March 1853 – 29 July 1890), the Dutch painter who cut off his own earlobe, died on this date in 1890, two days after shooting himself in the chest with a pistol. The postimpressionist painter suffered from depression and epileptoid seizures, which caused him to leave home and move to a house in Arles, France. He was joined there for a time by Paul Gauguin. Though he was a prolific artist — he completed nearly 900 paintings, over 1,000 drawings, 150 watercolors, plus letter sketches and graphic designs — Van Gogh succeeded in selling only one painting in his lifetime. Since his death, his paintings have been sold for many millions of dollars, including the Portrait of Dr. Gachet, which went for $82.5 million in 1990.

Grave of Vincent Van Gogh
Quote: "I can't change the fact that my paintings don't sell. But the time will come when people will recognize that they are worth more than the value of the paints used in the picture." — Vincent Van Gogh

Thursday, July 24, 2008

How long would it take Earth's fastest space ship to reach Proxima Centauri?

To date, humans have launched only four space probes that will eventually leave the solar system. These vehicles will likely travel across the depths of space for millions of years to come. NASA launched all four of these remarkable craft during the 1970s to make the first close-up studies of the gas giants in the outer solar system. Following their historic visits to our largest planetary neighbors, the four vehicles followed paths that will carry them beyond the edge of the solar system and into interstellar space.

The first of these space probes was Pioneer 10 that was launched in 1972 and visited Jupiter a year later. Pioneer 10 is currently traversing what we believe to be the edge of the solar system. Unfortunately, the vehicle's power source, a Radioisotope Thermoelectric Generator (RTG), has decayed to the point that it can no longer provide enough electricity to operate the probe. Pioneer 10 stopped transmitting signals to Earth on 23 January 2003 when the craft was over 7.6 billion miles away. The trajectory of Pioneer 10 will bring the vehicle close to the star Aldebaran in the constellation Taurus (The Bull) in about 2 million years.
A twin spacecraft named Pioneer 11 also visited Jupiter in 1974 and continued on to make a flyby of Saturn in 1979. Pioneer 11 too is now on its way into deep space as it heads towards the constellation Aquila (The Eagle). The spacecraft should pass close to one of the stars in that constellation in about 4 million years. Pioneer 11 has also stopped transmitting to Earth, and its final signal was received in November 1995.
Two more NASA probes that built on the successful missions of Pioneer 10 and 11 were the Voyagers. Voyager 1 also visited Jupiter and Saturn and is presently sailing towards the outer limits of the solar system. The craft is headed towards the constellation Camelopardalis (The Giraffe), a star of which it will fly close to in about 300,000 years. Voyager 2 flew past Jupiter, Saturn, Uranus, and Neptune during its Grand Tour of the solar system, but the probe is now headed towards the star Sirius in the constellation Canis Majoris (The Big Dog). Sirius is the brightest star in the night sky, and Voyager 2 will pass close to it in about 160,000 years. Both of the Voyager probes are still transmitting and are expected to continue sending signals to Earth until around 2020 when their power sources decay.
The two Voyagers will be over 10 billion miles from the Sun by then, and it is hoped they will provide the first scientific measurements of the edge of the solar system and the beginnings of interstellar space. The prevailing theory accepted by most researchers says that the edge of the solar system consists of three boundaries called the termination shock, heliopause, and bow shock. The termination shock is believed to mark the transition in the velocity of the solar winds emanating from the Sun from supersonic to subsonic speeds. Even further away is the heliopause, which scientists conjecture is a region where the solar wind ceases to exist. Beyond may lie a bow shock bombarded by galactic cosmic rays. However, these theories of the solar system's outer reaches remain unproven. Only the Voyager probes may be able to provide scientists with any answers about the true nature of this region of space anytime soon.
All four of these distant space probes used the gravitational attraction of the planets they visited to slingshot themselves onto the trajectories they currently follow. These gravitational assists accelerated the vehicles to some of the highest speeds ever reached by manmade objects. Traveling slowest of the foursome is Pioneer 11 at about 26,000 mph (42,000 km/h) with respect to the Sun. Pioneer 10 is currently moving at a rate of over 27,000 mph (44,000 km/h) while Voyager 2 is speeding along at about 36,000 mph (58,000 km/h). The fastest probe, however, is Voyager 1 with a velocity of nearly 39,000 mph (63,000 km/h). Given its greater speed, Voyager 1 currently holds the record as the
fastest interplanetary spacecraft and has passed the Pioneers to become the farthest manmade object from the Sun.
None of these four spacecraft is traveling towards our closest star Proxima Centauri that lies about 4.2 light years away. If Voyager 1 were headed in that direction, however, it would still take the vehicle over 73,000 years to get there!


The Helios, which holds the record for fastest manmade object, was a series of two spacecraft launched in the mid-1970s to study the Sun. Both probes were developed through cooperation between the US and West Germany with scientists from both nations providing experiments and NASA providing the launch vehicle and booster. Helios 1 was launched in December 1974 and Helios 2 in January 1976, both reaching the Sun within about three months.

What made the Helios missions so unusual was that the two craft made incredibly close passes to the Sun resulting in very high orbital speeds. These high speeds resulted from the fact that both probes were placed into very elliptical, or eccentric, orbits around the Sun. When a probe is placed into a circular orbit, its speed remains a constant. For example, the Space Shuttle orbits the Earth in a circular or nearly circular orbit at a constant speed of between 17,000 and 18,000 mph (27,355 to 28,960 km/h). When in a highly elliptical orbit, however, a vehicle will reach very high speed when it is close to the body it is orbiting but slow down considerably when it is far away.
The Helios missions both orbited in this manner, with a furthest distance (or aphelion) of nearly 1 Astronomical Unit (AU), which is the distance at which the Earth orbits the Sun. Meanwhile, the closest approach (or perihelion) of the Helios probes was about 0.3 AU. The eccentricity of such an orbit is about 0.54 with a period of about 190 days. The maximum speed of Helios 2, which achieved its perihelion distance of 0.29 AU on 17 April 1976, is quoted as about 150,000 mph (241,350 km/h). By applying some simple equations of orbital mechanics, we can confirm that such an orbit would indeed result in a perihelion velocity of 153,800 mph (247,510 km/h). For comparison, the aphelion speed of Helios 2 turns out to be only 45,360 mph (72,985 km/h) at its farthest distance of 0.983 AU. This massive differential between the vehicle's maximum and minimum speeds graphically illustrates how much an elliptical orbit varies from the circular orbit discussed earlier.
The reason the Helios probes were given such unusual orbits is that they were intended to make various measurements of the interplanetary space between the Sun and Earth. Each probe was equipped with ten experiments including high-energy particle detectors to measure the solar wind, magnetometer readings of the Sun's magnetic field, measurements of variations in electric and magnetic waves, and a micrometeoroid experiments. The two probes completed their primary missions by the early 1980s but were still sending data as late as 1985. Though they are no longer functional, both craft remain in their eccentric orbits around the Sun.

Wednesday, July 23, 2008

Today in History

Comet Hale-Bopp (formally designated C/1995 O1) was probably the most widely observed comet of the twentieth century, and one of the brightest seen for many decades. It was visible to the naked eye for a record 18 months, twice as long as the previous record holder, the Great Comet of 1811.
Hale-Bopp was discovered on 23 July 1995 at a very large distance from the Sun, raising expectations that the comet could become very bright when it passed close to the Sun. Although comet brightnesses are very difficult to predict with any degree of accuracy, Hale-Bopp met or exceeded most predictions for its brightness when it passed perihelion on April 1 1997. The comet was dubbed the Great Comet of 1997.
The passage of Hale-Bopp was notable also for inciting a degree of panic about comets not seen for decades. Rumours that the comet was being followed by an alien spacecraft gained remarkable currency, and inspired a mass suicide among followers of a cult named Heaven's Gate.
The comet was discovered by two independent observers, Alan Hale and Thomas Bopp, both in the United States. Hale had spent many hundreds of hours searching for comets without finding one, and was tracking known comets from his driveway in New Mexico when he chanced upon Hale-Bopp, with an apparent magnitude of 10.5, near the globular cluster M70, in the constellation of Sagittarius, just after midnight. Hale first established that there was no other deep-sky object near M70, and then consulted a directory of known comets, finding that no known objects were in this area of the sky. Once he had established that the object was moving relative to the background stars, he emailed the Central Bureau for Astronomical Telegrams, the clearing house for astronomical discoveries.
Bopp did not own a telescope. He was out with friends near Stanfield, Arizona observing star clusters and galaxies when he chanced across the comet(Mikkel) while at the eyepiece of his friend's telescope. He realised he might have spotted something new when he checked his star atlases to find out what other deep-sky objects were near M70, and found that there were none. He contacted the Central Bureau of Astronomical Telegrams via telegram. The following morning, it was confirmed that this was a new comet, and it was named Comet Hale-Bopp, with the designation C/1995 O1. The discovery was announced in International Astronomical Union circular 6187.

Friday, July 18, 2008

Is anyone looking for extraterrestrial life?

Despite the fact that alien life forms have never been discovered, the search for extraterrestrial intelligence (or SETI, as it is called) remains a popular pursuit. Astronomers (scientists specializing in the study of matter in outer space) believe that if life does exist on other planets, we now possess the technological capability of finding it and perhaps even communicating with it.
Most modern SETI missions use radio telescopes—instruments consisting of a large concave dish with an antenna at the center, tuned to a certain wavelength, that receive and process radio waves. The radio telescopes, tuned to nearby stars, listen for signals that may have been sent by alien civilizations.
The first large-scale SETI experiment, called Project Ozma, was begun by astronomer Frank Drake (1930-) in 1960. Drake conducted Project Ozma at the National Radio
Astronomy Observatory at Green Bank, West Virginia. The object of the experiment was to search for signs of life in distant solar systems through intergalactic radio waves.

Unidentified flying object (UFO) expert J. Allen Hynek (1910-1986) developed the following scale to describe encounters with extraterrestrial beings or vessels:
Close Encounter of the First Kind— sighting of a UFO at close range with no other physical evidence.
Close Encounter of the Second Kind—sighting of a UFO at close range, but with some kind of proof, such as a photograph, or an artifact from a UFO.
Close Encounter of the Third Kind— sighting of an actual extraterrestrial being.
Close Encounter of the Fourth Kind— abduction by an extraterrestrial spacecraft.

Thursday, July 17, 2008

Who invented the telescope?

Hans Lippershey (ca. 1570-1619), a German-Dutch lens grinder and spectacle (glasses) maker, is generally credited with inventing the telescope. This is because in 1608 Lippsershey became the first scientist to apply for a patent for the telescope. (A patent is a grant made by a government that allows the creator of invention the sole right to make, use, and sell that invention for a set period of time.) Two other inventors, Zacharias Janssen and Jacob Metius, also developed telescopes around this time. Modern historians consider both Lippershey and Janssen to be likely candidates for the title of "inventor of the telescope," with Lippershey possessing the strongest claim.

Georges Lemaître

Scientific research shows that the universe has been expanding at an accelerating rate; this is said to be due to the dark energy that makes up some 70 percent of the total energy density of today's universe. This discovery further bears out the big bang theory, which had been first proposed by astrophysicist and cosmologist Georges Lemaître in 1927. LeMaître, who was born on this date in 1894, stated that the universe began some 20 billion years ago with the violent explosion of a small mass of matter at extremely high density and temperature.

Georges Henri Joseph Éduard Lemaître (July 17, 1894 – June 20, 1966) was a Belgian Roman Catholic priest, honorary prelate, professor of physics and astronomer at the Université catholique de Louvain.
Lemaître proposed what became known as the Big Bang theory of the origin of the Universe, which he called his 'hypothesis of the primeval atom'.

After studying humanities at a Jesuit school (Collège du Sacré-Coeur, Charleroi), Lemaître entered the civil engineering school of the Catholic University of Leuven at the age of seventeen. In 1914, at the beginning of World War I, he paused his studies to engage as a volunteer in the Belgian army. At the end of hostilities, he received the Military Cross with palms.
After the war, he undertook studies in physics and mathematics and began to prepare for priesthood. He obtained his doctorate in 1920 with a thesis entitled l'Approximation des fonctions de plusieurs variables réelles (Approximation of functions of several real variables), written under the direction of Charles de la Vallée-Poussin. He was ordained a priest in 1923.
In 1923, he became a graduate student in astronomy at the University of Cambridge, spending one year at St Edmund's House (now St Edmund's College, Cambridge). He worked with the astronomer Arthur Eddington who initiated him into modern cosmology, stellar astronomy and numerical analysis. He spent the following year at Harvard College Observatory in Cambridge, Massachusetts with Harlow Shapley, who had just gained a name for his work on nebulae, and at the Massachusetts Institute of Technology, where he registered for the doctorate in sciences.

On March 17, 1934, Lemaître received the Francqui Prize, the highest Belgian scientific distinction, from King Léopold III. His proposers were Albert Einstein, Charles de la Vallée-Poussin and Alexandre de Hemptinne. The members of the international jury were Eddington, Langevin and Théophile de Donder. Another distinction that the Belgian government reserves for exceptional scientists was allotted to him in 1950: the decennial prize for applied sciences for the period 1933-1942.

In 1936, he was elected member of the Pontifical Academy of Sciences.
In 1941, he was elected member of the Royal Academy of Sciences and Arts of Belgium.
In 1946, he published his book on L'Hypothèse de l'Atome Primitif (The Primeval Atom Hypothesis), a book which would be translated into Spanish in the same year and into English in 1950.
In 1953 he was given the very first Eddington Medal award of the Royal Astronomical Society.
During the 1950s, he gradually gave up part of his teaching workload, ending it completely with his éméritat in 1964.
At the end of his life, he was devoted more and more to numerical calculation. He was in fact a remarkable algebraicist and arithmetical calculator. Since 1930, he used the most powerful calculating machines of the time like the Mercedes. In 1958, he introduced at the University a Burroughs E 101, the University's first electronic computer. Lemaître kept a strong interest in the development of computers and, even more, in the problems of language and programming. With age, this interest grew until it absorbed him almost completely.
He died on June 20, 1966 shortly after having learned of the discovery of cosmic microwave background radiation, proof of his intuitions about the birth of the Universe.

Friday, July 11, 2008

Three Great Space Telescopes

The Spitzer Space Telescope (formerly the Space Infrared Telescope Facility or SIRTF) The name chosen was that of Dr. Lyman Spitzer, Jr., the first to propose placing telescopes in space, in the mid-1940s. The US$ 800 million Spitzer was launched on Monday 25 August 2003 at 1:35:39 (EDT) from Cape Canaveral Air Force Station, Florida.
Launch vehicle: Delta II 7920H ELV
Mission length: 2.5-5+ years
Mass: 950 kg (2090 lb)
Orbit Location: the Sun

Orbit period: 1 year
Diameter: 0.8 m
Focal Lenght: 10.2 m

The Chandra X-ray Observatory is a satellite launched on STS-93 by NASA on July 23, 1999. It was named in honor of Indian-American physicist Subrahmanyan Chandrasekhar who is known for determining the mass limit for white dwarf stars to become neutron stars. "Chandra" also means "moon" or "luminous" in Sanskrit.
Launch vehicle: Space Shuttle Columbia STS-93
Mission length: 4 days, 22 hours, 50 minutes, 18 seconds
Mass: 4,790 kg (10,600 lb)

Orbit period: 64.2 hours
Diameter: 1.2 m (3.9 ft)
Focal Lenght: 10 m (33 ft)

The Hubble Space Telescope (HST; also known colloquially as "the Hubble" or just "Hubble") is a space telescope that was carried into orbit by a Space Shuttle in April 24 1990. It was named in honor of the American astronomer, Edwin Hubble. Although not the first space telescope, the Hubble is one of the largest and most versatile, and is well known as both a vital research tool and a public relations boon for astronomy. The HST is a collaboration between NASA and the European Space Agency, and is one of NASA's Great Observatories, along with the Compton Gamma Ray Observatory, the Chandra X-ray Observatory, and the Spitzer Space Telescope
Mass: 11,110 kg (24,250 lb)
Orbit period: 96–97 minnutes
Diameter: 2.4 m
Focal Lenght: 57.6 m
Orbit location: low Earth orbit

Hubble Deep Field

Hubble Ultra Deep Field is the most important image ever taken by humanity.
In late September 2003 Hubble Space Telescope took this picture about 47 billion light years away.

In this NASA handout, a view of deepest view of the visible universe ever achieved are seen in a Hubble Telescope composite photograph released March 9, 2004. The Hubble Ultra Deep Field (HUDF) photograph is a composite of a million one-second exposures and reveals galaxies from the time shortly after the big bang.

Thursday, July 10, 2008

Dark Energy, Dark Matter

What is dark energy? More is unknown than is known — we know how much there is, and we know some of its properties; other than that, dark energy is a mystery — but an important one. Roughly 70% of the Universe is made of dark energy. Dark matter makes up about 25%. The rest - everything on Earth, everything ever observed with all of our instruments, all normal matter adds up to less than 5% of the Universe. Then again, maybe it shouldn't be called "normal" matter since it is a small fraction of the Universe!

Ocean and Earth System

Just by looking at images of Earth from space, it's clear that the ocean is a significant piece of the Earth's story. In fact, the ocean represents over 70% of the Earth's surface and contains 97% of all water on Earth. The ocean stores heat like a "fly wheel" for climate. Its huge capacity as a heat and water reservoir moderates the climate of Earth. Within this Earth system, both the physical and biological processes of the ocean play a key role in the water cycle, the carbon cycle, and climate variability.

Even if you live nowhere near the ocean, you will still experience the ocean's influence in our Earth system. Most of the rain that falls on landcomes from the tropical ocean. The ocean is the primary driver of weather and climate and can give us clues to global phenomenon such as El Niño. The phytoplankton (microscopic plants) that live in the ocean are responsible for almost half the oxygen you inhale and play a vital role in the carbon cycle. Far inland from the ocean, fields of crops enjoy rainwater that traveled through the water cycle and spent a few days or perhaps thousands of years cycling through the ocean.


Try this: your "point of view" makes a difference!Hold up your thumb at arm's length. With one eye closed, line up your thumb with an object in the distance. Now switch eyes so that only the other eye is open. Does your thumb suddenly change position? Move your thumb closer to your nose and try again. Can you see your thumb jump even more?
Astronomers call this effect "parallax." The closer an object, the more it appears to shift against the distant background, when viewed from two different spots

Tuesday, July 8, 2008

The Moon

Did you ever notice that the Moon always looks the same? Sure, it waxes and wanes from a new moon to a full moon, but the bright and dark patches on the Moon always look the same. In fact, these features are so familiar that people call it the Man in the Moon.
This is because the Moon always points the same face towards the
Earth. The Moon does actually rotate on its axis, it's just that the amount of time it takes to make a complete orbit around the Earth matches the amount of time it takes to complete one rotation. In both cases, this is 27.3 days.
So, when you hear people refer to the far side of the Moon, they're talking about the part of the Moon that always faces away from the Earth. Until we sent spacecraft into orbit around the Moon to take pictures, nobody on Earth had ever seen what the far side of the Moon looks like.
But why does this happen? Over the few billions years since its formation, the Moon has become tidally locked with the Earth. In the distant past, the Moon had different rotation and orbital speeds, and it showed all of its sides to our planet. But the gravity of the Earth tugged at the irregular shapes on the Moon, causing it to slow its rotation down until it was exactly the same length as its orbit.
The Earth, on the other hand, has so much mass that the force of gravity from the Moon pulling on Earth can't overcome its rotational speed. The Moon does create the tides, though, and causes the ground to rise and fall - it's just such a small amount that you can't feel it.
Sometimes people mistakenly call this the dark side of the Moon. But there is no dark side of the Moon. Think about it, when we're seeing a new moon, that's because the familiar part that we can always see is in shadow. But at that point, the far side will be bathed in sunlight.

How Does the Earth Protect Us From Space?

Answer: Our Earth keeps us very safe from a dangerous Universe that's always trying to kill us in new and interesting ways.
Risk: Cosmic rays are high energy particles fired at nearly the speed of light by the Sun, supermassive black holes and supernovae. They have the ability to blast right through your body, damaging DNA as they go. Long term exposure to cosmic rays increases your chances of getting cancer. Fortunately, we have our atmosphere to protect us. As cosmic rays crash into the atmosphere, they collide with the oxygen and nitrogen molecules in the air.
Risk: Gamma rays and X-rays. As you know, radiation can damage the body. Just a single high-energy photon of gamma rays can cause significant damage to a living cell. Once again, though, the Earth's atmosphere is there to protect us. The molecules in the atmosphere absorb the high-energy photons preventing any from reaching us on the ground. In fact, X-ray and gamma ray observatories need to be built in space because there's no way we can see them from the ground.
Risk: Ultraviolet radiation. The Sun is bathing the Earth in ultraviolet radiation; that's why you get a sunburn. But the ozone layer is a special region of the atmosphere that absorbs much of this radiation. Without the ozone layer we would be much more exposed here on the surface of the Earth to UV rays, leading to eye damage and greater incidence of skin cancer.
Risk: Solar flares. Violent explosions on the surface of the Sun release a huge amount of energy as flares. In addition to a blast of radiation, it often sends out a burst of plasma traveling at nearly the speed of light. The Earth's magnetosphere protects us here on Earth from the effects of the plasma, keeping it safely way from the surface of the planet. And our atmosphere keeps the X-ray/gamma ray radiation out.
Risk: Cold temperatures. Space itself is just a few degrees above absolute zero, but our atmosphere acts like a blanket, keeping warm temperatures in. Without the atmosphere, we'd freeze almost instantly.
Risk: Vacuum. Space is airless. Without the Earth, there'd be no air to breath, and the lack of pressure damages cells and lets water evaporate out into space. Vacuum would be very, very bad.

Friday, July 4, 2008

Q & A

Q: What element is most plentiful on the Sun?
A: Hydrogen. The Sun is made up of about 75% hydrogen and 25% helium. About 0.1% is metals (made from hydrogen via nuclear fusion). This ratio is changing over time (very slowly), as the nuclear reactions continue, converting smaller atoms into more massive ones.

Q & A

Q: Why can't we see gravity?
A: First of all, we can only see the light that is reflected from things (we don't see the thing itself), and gravity doesn't reflect light. Gravitational lensing, however, is the displacement of light due to the warping of space by a gravitational lens (a massive object in space that bends light that passes by it, due to the gravitational forces). This is a way that gravity can be "seen."