This Day in History (18-Feb-1930) – Clyde Tombaugh Discovers Pluto

Looking over some photographic plates from the month before as part of his research into asteroids, astronomer Clyde Tombaugh noticed a peculiar object on February 18, 1930: the ‘Planet X’. Part of a larger cloud of debris called the Kuiper belt, the small orb 4.6 billion miles from the sun has become a controversial figure in the scientific community. Lurking among the distant rocks sprayed across space beyond the orbits of Uranus and Neptune, Percival Lowell — the founder of the observatory Tombaugh worked at — first theorized the presence of a “Planet X” affecting the two outermost planets and predicted its location in 1909. Tombaugh carried on the research after Lowell’s death and diligently spent each day taking photographs of the night sky and looking them over with a blink comparator, an optical device that allows the researcher to quickly flip back and forth between two images.

The news shocked the public, resulting in a flood of more than a thousand letters arriving at the Lowell Observatory with ideas for naming the planet. Venetia Burnley, an 11-year-old girl from the English city of Oxford, suggested Pluto, Roman name for the Greek god of the underworld, Hades (world of deads). Taking 248 Earth years to make one pass around the sun, Pluto’s orbit does not fit the regular pattern exhibited by the other eight planets. At times, it is within the path trotted by Neptune, a factor in debates about the true status of the object.

Following more than 75 years of being regarded as a planet, the International Astronomical Union announced Pluto no longer fit the bill in August 2006. Citing the shape of its orbit and the various asteroids it shares the Kuiper belt with, experts decided to downgrade it to a dwarf planet. (True planets have to “own” their path around the sun.)

There are now officially only eight planets in our solar system. Pluto  is much smaller than any of the official planets. It is smaller than seven of the solar system’s moons including moon of the earth. Pluto has not yet been visited by a spacecraft. Even the Hubble Space Telescope can resolve only the largest features on its surface (left and above). A spacecraft called New Horizons was launched in January 2006. If all goes well it should reach Pluto in 2015.


This Day in History (13-Feb-1633) – Galileo Galilei arrives in Rome for trial after publishing his thoughts on heliocentrism

Galileo used his mathematics knowledge and technical skills to  build a telescope in 1609.  Galileo’s observations strengthened his belief in Copernicus’ theory (published in 1514)that Earth and all other planets revolve around the Sun. Galileo expected the telescope to quickly make believers in the Copernican system out of all educated persons, but he was disappointed. The Catholic Church, which was very powerful and influential in Galileo’s day, strongly supported the theory of a geocentric, or Earth-centered, universe. In 1616, on orders of the Pope Paul V, Cardinal Bellarmine called Galileo to his residence and administered a warning not to hold or defend the Copernican theory; Galileo was also forbidden to discuss the theory orally or in writing. After repeated convincing attempts by Galileo, Pope Urban VIII allowed him to write about the Copernican theory as long as he treated it as a mathematical hypothesis.

In 1630 he completed his book Dialogue Concerning the Two Chief World Systems in which the Ptolemaic and Copernican models were discussed and compared. Vatican cleared (conditionally) to publish the book. The book was printed in 1632 which was quickly sold out and soon became the talk of the literary public. Enemies of Galileo had convinced the Pope that the Dialogue was nothing but a thinly-veiled brief for the Copernican model. Pope Urban VIII, convinced by the arguments of various Church officials, stopped its distribution; the case was referred to the Inquisition and Galileo was summoned to Rome despite his infirmities, to answer the charges in February 1633. Old Galileo travelled for twenty-three days in cold winter from Florence to Rome.

He was formally interrogated for 18 days and on April 30 Galileo confessed that he may have made the Copernican case in the Dialogue too strong and offered to refute it in his next book.  Galileo was sentenced to life imprisonment. Because of his age and poor health, he was allowed to serve his imprisonment under house arrest until his death in 1642. The Church finally accepted that Galileo might be right in 1983.



This Day in History (17-May-1902) – Greek archaeologist Valerios Stais discovers the Antikythera mechanism, an ancient mechanical analog computer

Pieces of the ancient calculating machine were discovered by sponge divers exploring the remains of an ancient shipwreck off the tiny island of Antikythera in 1900. For decades, scientists have been trying to figure out how the device’s 80 fragmented pieces fit together and unlock its workings. The team was able to pin down the device’s construction date more precisely. Radiocarbon dating suggested it was built around 65 BC, but newly revealed lettering on the machine indicate a slightly older construction date of 150 to 100 BC. The team’s reconstruction also involves 37 gear wheels, seven of which are hypothetical.

The new analysis reveals that the device’s front dials had pointers for the sun and Moon—called the “golden little sphere” and “little sphere,” respectively—and markings which coincided with the zodiac and solar calendars. The back dials, meanwhile, appear to have been used for predicting solar and lunar eclipses. There is a dial dedicated to the four-year Olympiad Cycle of athletic games in ancient Greece. The researchers also show that the device could mechanically replicate the irregular motions of the Moon, caused by its elliptical orbit around the Earth, using a clever design involving two superimposed gear-wheels, one slightly off-center, that are connected by a pin-and-slot device. The research team has also deciphered all the months on the Mechanism’s 19-year calendar, revealing month names that are of Corinthian origin, probably from a Corinthian colony of the western Hellenic world.

The Antikythera mechanism seems to be an arithmetical counterpart of the much more familiar geometrical models of the solar system which were known to Plato and Archimedes and evolved into the orrery and the planetarium.



This Day in History (10-Apr-1815) – Mount Tambora in Indonesia Begins Erupting

Six hundred miles east of Jakarta, the capital of Indonesia, Mount Tambora stretches nearly 9,000 feet above the Java Sea on the island of Sumbawa. The volcano originally grew to about 12,000 feet elevation before a major explosion destroyed its summit and left a pre-1815 caldera more than 43,000 years ago. On April 10, 1815 evening, the towering peak exploded violently, killing more than 100,000 people, directly and indirectly, as it spewed rock and ash high into the atmosphere. The eruption, lasting more than three months, is the largest in past 10,000 years and, arguably, the most influential on a global scale.

The eruption emptied about 50-150 cubic km of magma and measures 7 on the VEI scale. It produced a giant plinian eruption column, which is estimated to have reached more 40-50 km altitude, ejecting large amounts of ash and aerosols into the stratosphere. With the cataclysmic eruption, the entire shape of the mountain changed. The caldera — the central peak — collapsed into the magma chamber below, decreasing the height of Mount Tambora by more than 5,000 feet as ash and rock shot up from below. Caldera collapse destroyed 30 km3 of the mountain and formed a 6 km wide and 1250 m deep caldera. Floating islands of pumice 3 miles long were observed in April 1815, and even 4 years later, these islands still hindered navigation.  As the intense heat escaped through the vent, the explosion was heard some 1,600 miles away in western Indonesia.

Up until the summer of 1816, with ash still in the upper atmosphere, the long-term consequences of the eruption finally began to take shape, causing the “Year Without a Summer” and wreaking havoc on weather patterns. The reason for the climatic changes was increased absorption of sunlight due to a veil of aerosols (consisting mostly of tiny droplets of H2SO3 acid, formed by SO2 release) that were dispersed around both hemispheres by stratospheric currents from the tall eruption column.  Global temperatures dropped by as much as 3 deg C in 1816 and recovered during the following years.


This Day in History (2-Apr-1845) – H L Fizeau & J Leon Foucault take 1st photo of Sun

Louis-Jacques Daguerre, inventor of the daguerreotype process of photography, put on a free course on his new photographic techniques in Paris, which was attended by the two college student friends Louis Fizeau and Lion Foucault. They watched Daguerre expose a plate in a camera pointing out the window, then after talking about his process for about 30 minutes, he developed the plate using a variety of chemicals to reveal the picture. Although Fizeau and Foucault were impressed they also realised the limitations of the process – it would be wonderful to be able to take portraits, they thought, but the subject could not be expected to remain motionless for 30 minutes. After the course ended they began to experiment to try to speed up the process, and Fizeau had the idea of sensitizing the plate using bromine. Experimentation led to them reducing the exposure time from 30 minutes to 20 seconds. The discovery did not have the impact that it might, however, for other photographic methods were coming into use.

François Arago, a French mathematician, was aware of the great scientific potential of the new methods of photography and, in particular, he was aware of the advances made by Fizeau and Foucault. He approached the two friends in 1845 and suggest that they might attempt to make photographs of an image of the sun produced by a telescope. After multiple attempt, on 2nd April, 1845, the first surviving daguerrotype photograph of the sun was taken by Fizeau and Foucault. The 5-inch image showed many details including a few sunspots.

Berkowski, a local daguerrotypist whose first name was never published, later made the first solar eclipse photograph on July 28, 1851, also using the daguerrotype process, at the Royal Observatory in Königsberg, Prussia (now Kalinigrad in Russia). A small 6-cm refracting telescope was attached to the 15.8-cm Fraunhofer heliometer and a 84-second exposure was taken shortly after the beginning of totality. By 1858, daily photographic records of the solar surface were taken by Warren de la Rue at the Kew Observatory in England, and by Jules Janssen at the Meudon Observatory near Paris. For the next 14 years, de la Rue record the complete 11 year solar cycle in a series of almost 3000 images that clearly showed sunspots and other features.