When WT1190F struck this atmosphere over the Indian Ocean around 6:20 Universal Time (12:20 a.m. CST) today , it broke apart into multiple fireballs against the blue sky. The object came down around 1:20 p.m. local time. Credit: IAC/UAE Space Agency/NASA/ESA
Clouds hampered observations from the ground in Sri Lanka during the re-entry of WT1190F overnight, but a team of astronomers captured spectacular images of the object from a high-flying plane over the Indian Ocean very close to the predicted time of arrival.
Peter Jenniskens of the SETI Institute and NASA Ames Research Center is shown here before the flight setting up the eleven staring cameras with a wider field of view, including two spectographic cameras, to catch the reentry. Credit: IAC/UAE Space Agency/NASA/ESA
The International Astronomical Center (IAC) and the United Arab Emirates Space Agency hosted a rapid response team to study the re-entry of what was almost certainly a rocket stage from an earlier Apollo moon shot or the more recent Chinese Chang’e 3 mission. In an airplane window high above the clouds, the crew, which included Peter Jenniskens, Mike Koop and Jim Albers of the SETI Institute along with German, UK and United Arab Emirates astronomers, took still images, video and gathered high-resolution spectra of the breakup.
Video and still imagery of WT1190F’s Reentry November 13, 2015
The group of seven astronomers hoped to study WT1190F’s re-entry as a test case for future asteroid entries as well as improve our understanding of space debris behavior. Photos and video show the object breaking up into multiple pieces in a swift but brief fireball. From the spectra, the team should be able to determine the object’s nature — whether natural or manmade.
Wide view of the colorful fireball and breakup when WT1190F struck Earth’s atmosphere. More than 20 cameras were used to record the event. Credit: IAC/UAE Space Agency/NASA/ESAAnimation from photos made on Nov. 12 when WT1190F was still in one piece in orbit about the Earth. Credit: Marco LangbroekFlying observatory. This Gulfstream 450 business jet, sponsored by United Arab Emirates and coordinated by Mohammad Shawkat Odeh from the International Astronomical Center, Abu Dhabi, was used by the team to observe and record the re-entry. Only five windows were available to make observations. Credit: IAC/UAE Space Agency/NASA/ESASETI Institute “staring cameras” used for wide field observations of the re-entry. Credit: IAC/UAE Space Agency/NASA/ESA
a short animation (spanning about 10 minutes) made out of my follow-up images. The first frame was obtained at 08:17UT while the second frame was obtained at 08:27UT of Nov, 12, 2015. (WT1190F is the star-like object at the centre while stars are trailed because the images were stacked on WT1190F motion). Credit: Ernesto Guido
No one’s 100% certain what WT1190F is — asteroid or rocket stage — but we are certain it will light up like a Roman candle when it re-enters Earth’s atmosphere around 6:20 Universal Time (12:20 a.m. CST) tomorrow morning Nov. 13.
Animation by Jost Jahn of WT1190F’s final hours as it races across the sky coming down off the coast of Sri Lanka
As described in an earlier story at Universe Today, an object discovered by the Catalina Sky Survey on Oct 3rd and temporarily designated WT1190F is expected to burn up about 60 miles (100 km) off the southern coast of Sri Lanka overnight. The same team observed it twice in 2013. Based upon the evolution of its orbit, astronomers determined that the object is only about six feet (2-meters) across with a very low density, making it a good fit for a defunct rocket booster, possibly one used to launch either one of the Apollo spacecraft or the Chinese Chang’e 3 lander to the Moon.
Below a plot of the last three orbits of WT1190F. The small red circle is the Earth. For scale, the large green circle is the orbit of the Moon. Notice that its final orbit takes straight into Earth. Credit: Bill Gray / Project Pluto
Additional observations of WT1190F have been made in the past few days confirming its re-entry later tonight. Checking the latest predictions on Bill Gray of Project Pluto’s page, the object will likely be visible from Europe about an hour before “touchdown”. To say it will be moving quickly across the sky is an understatement. Try about 3 arc minutes per second or 3° a minute! Very tricky to find and track something moving that fast.
Three 90-second exposures showing WT1190F zipping across the Rosette Nebula taken on Nov. 11, 2015 at the Konkoly Observatory in Hungary. Credit: Krisztián Sárneczky
58 minutes later, in the minute of time from 6:18 to 6:19 UT, WT1190F will move one full hour of right ascension and plummet 34° in declination while brightening from magnitude +8 to +4.5. If you’d like to attempt to find and follow the object, head over to JPL’s Horizons site for the latest ephemerides and orbital elements. At the site, make sure that WT1190F is in the Target Body line. If not, click Change and search for WT1190F in the Target Body field at the bottom of the window.
WT1190F re-Entry Trajectory. The object is expected to break up and fall harmlessly into the ocean. Credit: Bill Gray, Project Pluto
You’ll find updates at Bill Gray’s site. According to the most recent positions, the object will pass almost exactly in front of the Sun shortly before plunging into the ocean. Sri Lanka’s capital, Colombo, is expected to get the best views.
Because the mystery object’s arrival has been fairly well publicized, I hope to update you with a full report and photos first thing tomorrow morning. Like many of you, I wish I could see the show.
Gerard Kuiper, founder of the Lunar and Planetary Laboratory. Credit: lpl.arizona.edu
In the outer reaches of the Solar System, beyond the orbit of Neptune, lies a region permeated by celestial objects and minor planets. This region is known as the “Kuiper Belt“, and is named in honor of the 20th century astronomer who speculated about the existence of such a disc decades before it was observed. This disc, he reasoned, was the source of the Solar Systems many comets, and the reason there were no large planets beyond Neptune.
Gerard Kuiper is also regarded by many as being the “father of planetary science”. During the 1960s and 70s, he played a crucial role in the development of infrared airborne astronomy, a technology which led to many pivotal discoveries that would have been impossible using ground-based observatories. At the same time, he helped catalog asteroids, surveyed the Moon, Mars and the outer Solar System, and discovered new moons.
Leonid meteor storms. Taurid meteor swarms. Earth is no stranger to meteor showers, that’s for sure. Now, it turns out that the planet Mercury may experience periodic meteor showers as well.
The news of extraterrestrial meteor showers on Mercury came out of the annual Meeting of the Division of Planetary Sciences of the American Astronomical Society currently underway this week in National Harbor, Maryland. The study was carried out by Rosemary Killen of NASA’s Goddard Spaceflight Center, working with Matthew Burger of Morgan State University in Baltimore, Maryland and Apostolos Christou from the Armagh Observatory in Northern Ireland. The study looked at data from the MErcury Surface Space Environment Geochemistry and Ranging (MESSENGER) spacecraft, which orbited Mercury until late April of this year. Astronomers published the results in the September 28th issue of Geophysical Research Letters.
Micrometeoroid debris litters the ecliptic plane, the result of millions of years of passages of comets through the inner solar system. You can see evidence of this in the band of the zodiacal light visible at dawn or dusk from a dark sky site, and the elusive counter-glow of the gegenschein.
The orbit of comet 2P Encke. Image credit: NASA/JPL
Researchers have tagged meteoroid impacts as a previous source of the tenuous exosphere tails exhibited by otherwise airless worlds such as Mercury. The impacts kick up a detectable wind of calcium particles as Mercury plows through the zodiacal cloud of debris.
“We already knew that impacts were important in producing exospheres,” says Killen in a recent NASA Goddard press release. “What we did not know was the relative importance of comet streams over zodiacal dust.”
This calcium peak, however, posed a mystery to researchers. Namely, the peak was occurring just after perihelion—Mercury orbits the Sun once every 88 Earth days, and travels from 0.31 AU from the Sun at perihelion to 0.47 AU at aphelion—versus an expected calcium peak predicted by researchers just before perihelion.
STEREO A catches sight of comet 2P Encke. Image credit: NASA/STEREO
A key suspect in the calcium meteor spike dilemma came in the way of periodic Comet 2P Encke. Orbiting the Sun every 3.3 years—the shortest orbit of any known periodic comet—2P Encke has made many passages through the inner solar system, more than enough to lay down a dense and stable meteoroid debris stream over the millennia.
With an orbit ranging from a perihelion at 0.3 AU interior to Mercury’s to 4 AU, debris from Encke visits Earth as well in the form of the November Taurid Fireballs currently gracing the night skies of the Earth.
The Encke connection still presented a problem: the cometary stream is closest to the orbit of Mercury about a week later than the observed calcium peak. It was as if the stream had drifted over time…
Comet 2P Encke, captured by NASA’s MESSENGER spacecraft. Image credit: NASA/Johns Hopkins/APL/SW Research Institute
Enter the Poynting-Robertson effect. This is a drag created by solar radiation pressure over time. The push on cometary dust grains thanks to the Poynting-Robertson effect is tiny, but it does add up over time, modifying and moving meteor streams. We see this happening in our own local meteor stream environment, as once great showers such as the late 19th century Andromedids fade into obscurity. The gravitational influence of the planets also plays a role in the evolution of meteor shower streams as well.
Researchers in the study re-ran the model, using MESSENGER data and accounting for the Poynting-Robertson effect. They found the peak of the calcium emissions seen today are consistent with millimeter-sized grains ejected from Comet Encke about 10,000 to 20,000 years ago. That grain size and distribution is important, as bigger, more massive grains result in a smaller drag force.
This finding shows the role and mechanism that cometary debris plays in exosphere production on worlds like Mercury.
“Finding that we can move the location of stream to match MESSENGER’s observations is gratifying, but the fact that the shift agrees with what we know about Encke and its stream from independent source makes us confident that the cause-and-effect relationship is real, says Christou in this week’s NASA Goddard press release.
Launched in 2004, MESSENGER arrived at Mercury in March 2011 and orbited the world for over four years, the first spacecraft to do so. MESSENGER mapped the entire surface of Mercury for the first time, and became the first human-made artifact to impact Mercury on April 30th, 2015.
The joint JAXA/ESA mission BepiColombo is the next Mercury mission in the pipeline, set to leave Earth on 2017 for insertion into orbit around Mercury on 2024.
An interesting find on the innermost world, and a fascinating connection between Earth and Mercury via comet 2P Encke and the Taurid Fireballs.
Godfrey Kneller's 1689 portrait of Isaac Newton at age 46.
Credit: Isaac Newton Institute
The 17th century was an auspicious time for the sciences, with groundbreaking discoveries being made in astronomy, physics, mechanics, optics, and the natural sciences. At the center of all this was Sir Isaac Newton, the man who is widely recognized as being one of the most influential scientists of all time and as a key figure in the Scientific Revolution.
An English physicist and mathematician, Newton made several seminal contributions to the field of optics, and shares credit with Gottfried Leibniz for the development of calculus. But it was Newton’s publication of Philosophiæ Naturalis Principia Mathematica (“Mathematical Principles of Natural Philosophy”), for which he is most famous. Published in 1687, this treatise laid the foundations for classical mechanics, a tradition which would dominate scientists’ view of the physical universe for the next three centuries.
Early Life:
Isaac Newton was born on January 4th, 1643, – or December 25th, 1642 according to the Julian Calendar (which was in use in England at the time) – in Woolsthorpe-by-Colsterworth, a hamlet in the county of Lincolnshire. His father, for whom he was named, was a prosperous farmer who had died three months before his birth. Having been born prematurely, Newton was small as a child.
His mother, Hannah Ayscough, remarried when he was three to a Reverend, leaving Newton in the care of his maternal grandmother. His mother would go on to have three more children with her new husband, which became Newton’s only siblings. Because of this, Newton apparently had a rocky relationship with his stepfather and mother for some time.
William Blake’s Newton (1795), depicted as a divine geometer. Credit: William Blake Archive/Wikipedia
By the time Newton was 17, his mother was widowed again. Despite her hopes that Newton would become a farmer, like his father, Newton hated farming and sought to become an academic. His interests in engineering, mathematics and astronomy were evident from an early age, and Newton began his studies with an aptitude for learning and inventing that would last for the rest of his life.
Education:
Between the ages of 12 and 21, Newton was educated at The King’s School, Grantham, where he learned Latin. While there, he became the top-ranked student, and received recognition for his building of sundials and models of windmills. By 1661, he was admitted to Trinity College, Cambridge, where he paid his way by performing a valet’s duties (what was known as a subsizar).
During his first three years at Cambridge, Newton was taught the standard curriculum, which was based on Aristotelian theory. But Newton was fascinated with the more advanced science and spent all his spare time reading the works of modern philosophers and astronomers, such as René Descartes, Galileo Galilei, Thomas Street, and Johannes Kepler.
The result was a less-than-stellar performance, but his dual focus would also lead him to make some of his most profound scientific contributions. In 1664, Newton received a scholarship, which guaranteed him four more years until he would get his Masters of Arts degree.
David Loggan’s print of Trinity College, Cambridge, showing Nevile’s Great Court (foreground) and the then-new Wren Library (background). Credit: Cantabrigia Illustrata/Cambridge (1690)
In 1665, shortly after Newton obtained his B.A., the university temporarily closed due to the outbreak of the Great Plague. Using this time to study at home, Newton developed a number of ideas he had which would eventually cement to become his theories on calculus, optics and the law of gravitation (see below).
In 1667, he returned to Cambridge and was elected as a fellow of Trinity, though his performance was still considered less than spectacular. However, in time, his fortunes improved and he gained recognition for his abilities. In 1669, he received his M.A. (before he had turned 27), and published a treatise expounding on his mathematical theories for dealing with infinite series.
By 1669, he succeeded his one-time teacher and mentor Isaac Barrow – a theologian and mathematician who discovered the fundamental theorem of calculus – and became the Lucasian Chair of Mathematics at Cambridge. In 1672, he was elected a Fellow of the Royal Society, which he would remain a part of until the end of his life.
Scientific Achievements:
While studying at Cambridge, Newton maintained a second set of notes which he entitled “Quaestiones Quaedam Philosophicae” (“Certain Philosophical Questions“). These notes, which were the sum total of Newton’s observations about mechanical philosophy, would lead him to discover the generalized binomial theorem in 1665, and allowed him to develop a mathematical theory that would lead to his development of modern calculus.
Newton’s experiment using a prism revealed that light is refracted based on color. Credit: britannica.com
However, Newton’s earliest contributions were in the form of optics, which he delivered during annual lectures while holding the position of Lucasian Chair of Mathematics. In 1666, he observed that light entering a prism as a circular ray exits in the form of an oblong, demonstrating that a prism refracts different colors of light at different angles. This led him to conclude that color is a property intrinsic to light, a point which had been debated in prior years.
In 1668, he designed and constructed a reflecting telescope, which helped him prove his theory. From 1670 to 1672, Newton continued to lecture on optics and investigated the refraction of light, demonstrating that the multicoloured spectrum produced by a prism could be recomposed into white light by a lens and a second prism.
He also demonstrated that colored light does not change its properties, regardless of whether it is reflected, scattered, or transmitted. Thus, he observed that color is the result of objects interacting with already-colored light, rather than objects generating the color themselves. This is known as Newton’s theory of color.
The Royal Society asked for a demonstration of his reflecting telescope in 1671, and the organization’s interest encouraged Newton to publish his theories on light, optics and color. This he did in 1672 in a small treatise entitled Of Colours, which would later be published in a larger volume containing his theories on the “corpuscular” nature of light.
Replica of Newton’s second Reflecting telescope that he presented to the Royal Society in 1672. Credit: Wikipedia Commons
In essence, Newton argued that light was composed of particles (or corpuscles), which he claimed were refracted by accelerating into a denser medium. In 1675, he published this theory in a treatise titled “Hypothesis of Light“, in which he also posited that ordinary matter was composed of larger corpuscles and about the existence of an ether that transmitted forces between particles.
After discussing his ideas with Henry More, an English theosophist and a member of the Cambridge Platonists, Newton’s interest in alchemy was revived. He then replaced his theory of an ether existing between particles in nature with occult forces, based on Hermetic ideas of attraction and repulsion between particles. This reflected Newton’s ongoing interest in both the alchemical and scientific, for which there was no clear distinction at the time.
In 1704, Newton published all of his theories on light, optics and colors into a single volume entitled Opticks: Or, A treatise of the Reflections, Refractions, Inflections and Colours of Light. In it, he speculated that light and matter could converted into one another through a kind of alchemical transmutation, and verged on theories of sound waves in order to explain repeated patterns of reflection and transmission.
While later physicists favored a purely wavelike explanation of light to account for the interference patterns and the general phenomenon of diffraction, their findings owed a great deal to Newton’ theories. Much the same is true of today’s quantum mechanics, photons, and the idea of wave–particle duality, which bear only a small resemblance to Newton’s understanding of light.
Excerpt from Newton’s “Quaestiones Quaedam Philosophicae”, a collection of observations that would lead to his development of modern calculus. Credit: newtonproject.sussex.ac.uk
Though both he and Leibniz are credited with having developed calculus independently, both men became embroiled in a controversy over who discovered it first. Though Newton’s work in developing modern calculus began in the 1660s, he was reluctant to publish it, fearing controversy and criticism. As such, Newton didn’t publish anything until 1693 and did not give a full account of his work until 1704, whereas Leibniz began publishing a full account of his methods in 1684.
However, Newton earlier works in mechanics and astronomy involved extensive use of calculus in geometric form. This includes methods involving “one or more orders of the infinitesimally small” in his 1684 work, De motu corporum in gyrum (“On the motion of bodies in orbit”), and in Book I of the Principia, which he referred to as “the method of first and last ratios”.
Universal Gravitation:
In 1678, Newton suffered a complete nervous breakdown, most likely due to overwork and an ongoing feud with fellow Royal Society member Robert Hooke (see below). The death of his mother a year later caused him to become increasingly isolated, and for six years he withdrew from correspondence with other scientists, except where they initiated it.
During this hiatus, Newton renewed his interest in mechanics and astronomy. Ironically, it was thanks to a brief exchange of letters in 1679 and 1680 with Robert Hooke that would lead him to make his greatest scientific achievements. His reawakening was also due to the appearance of a comet in the winter of 1680–1681, about which he corresponded with John Flamsteed – England’s Astronomer Royal.
Thereafter, Newton began considering gravitation and its effect on the orbits of planets, specifically with reference to Kepler’s laws of planetary motion. After his exchanges with Hooke, he worked out proof that the elliptical form of planetary orbits would result from a centripetal force inversely proportional to the square of the radius vector.
Newton communicated his results to Edmond Halley (discoverer of “Haley’s Comet”) and to the Royal Society in his De motu corporum in gyrum. This tract, published in 1684, contained the seed that Newton would expand to form his magnum opus, the Principia. This treatise, which was published in July of 1687, contained Newton’s three laws of motion. These laws stated that:
When viewed in an inertial reference frame, an object either remains at rest or continues to move at a constant velocity, unless acted upon by an external force.
The vector sum of the external forces (F) on an object is equal to the mass (m) of that object multiplied by the acceleration vector (a) of the object. In mathematical form, this is expressed as: F=ma
When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body.
Together, these laws described the relationship between any object, the forces acting upon it and the resulting motion, laying the foundation for classical mechanics. The laws also allowed Newton to calculate the mass of each planet, calculate the flattening of the Earth at the poles and the bulge at the equator, and how the gravitational pull of the Sun and Moon create the Earth’s tides.
In the same work, Newton presented a calculus-like method of geometrical analysis using ‘first and last ratios’, worked out the speed of sound in air (based on Boyle’s Law), accounted for the precession of the equinoxes (which he showed were a result of the Moon’s gravitational attraction to the Earth), initiated the gravitational study of the irregularities in the motion of the moon, provided a theory for the determination of the orbits of comets, and much more.
This volume would have a profound effect on the sciences, with its principles remaining canon for the following 200 years. It also informed the concept of universal gravitation, which became the mainstay of modern astronomy, and would not be revised until the 20th century – with the discovery of quantum mechanics and Einstein’s theory of General Relativity.
Newton and the “Apple Incident”:
The story of Newton coming up with his theory of universal gravitation as a result of an apple falling on his head has become a staple of popular culture. And while it has often been argued that the story is apocryphal and Newton did not devise his theory at any one moment, Newton himself told the story many times and claimed that the incident had inspired him.
In addition, the writing’s of William Stukeley – an English clergyman, antiquarian and fellow member of the Royal Society – have confirmed the story. But rather than the comical representation of the apple striking Netwon on the head, Stukeley described in his Memoirs of Sir Isaac Newton’s Life (1752) a conversation in which Newton described pondering the nature of gravity while watching an apple fall.
“…we went into the garden, & drank thea under the shade of some appletrees; only he, & my self. amidst other discourse, he told me, he was just in the same situation, as when formerly, the notion of gravitation came into his mind. “why should that apple always descend perpendicularly to the ground,” thought he to himself; occasion’d by the fall of an apple…”
John Conduitt, Newton’s assistant at the Royal Mint (who eventually married his niece), also described hearing the story in his own account of Newton’s life. According to Conduitt, the incident took place in 1666 when Newton was traveling to meet his mother in Lincolnshire. While meandering in the garden, he contemplated how gravity’s influence extended far beyond Earth, responsible for the falling of apple as well as the Moon’s orbit.
Sapling of the reputed original tree that inspired Sir Isaac Newton to consider gravitation, located on the grounds of Cambridge. Credit: Wikipedia Commons/Loodog
Similarly, Voltaire wrote n his Essay on Epic Poetry (1727) that Newton had first thought of the system of gravitation while walking in his garden and watching an apple fall from a tree. This is consistent with Newton’s notes from the 1660s, which show that he was grappling with the idea of how terrestrial gravity extends, in an inverse-square proportion, to the Moon.
However, it would take him two more decades to fully develop his theories to the point that he was able to offer mathematical proofs, as demonstrated in the Principia. Once that was complete, he deduced that the same force that makes an object fall to the ground was responsible for other orbital motions. Hence, he named it “universal gravitation”.
Various trees are claimed to be “the” apple tree which Newton describes. The King’s School, Grantham, claims their school purchased the original tree, uprooted it, and transported it to the headmaster’s garden some years later. However, the National Trust, which holds the Woolsthorpe Manor (where Newton grew up) in trust, claims that the tree still resides in their garden. A descendant of the original tree can be seen growing outside the main gate of Trinity College, Cambridge, below the room Newton lived in when he studied there.
Feud with Robert Hooke:
With the Principia, Newton became internationally recognized and acquired a circle of admirers. It also led to a feud with Robert Hooke, with whom he had a troubled relationship in the past. With the publication of his theories on color and light in 1671/72, Hooke criticized Newton in a rather condescending way, claiming that light was composed of waves and not colors.
A historical reconstruction of what Robert Hooke looked like. Credit: Wikipedia/Rita Greer/FAL
While other philosophers were critical of Newton’s idea, it was Hooke (a member of the Royal Society who had performed extensive work in optics) that stung Newton the worst. This led to the acrimonious relationship between the two men, and to Newton almost quitting the Royal Society. However, the intervention of his colleagues convinced him to stay on and the matter eventually died down.
However, with the publication of the Principia, matters once again came to a head, with Hooke accusing Newton of plagiarism. The reason for the charge had to do with the fact that earlier in 1684, Hooke had made comments to Edmond Halley and Christopher Wren (also members of the Royal Society) about ellipses and the laws of planetary motion. However, at the time he did not offer a mathematical proof.
Nevertheless, Hooke claimed that he had discovered the theory of inverse squares and that Newton had stolen his work. Other members of the Royal Society believed the charge to be unfounded, and demanded that Hooke release the mathematical proofs to substantiate this claim. In the meantime, Newton removed all reference to Hooke in his notes and threatened to withdraw the Principia from subsequent publishing altogether.
Edmund Halley, who was a friend to both Newton and Hooke, tried to make peace between the two. In time, he was able to convince Newton to insert a joint acknowledgement of Hooke’s work in his discussion of the law of inverse squares. However, this did not placate Hooke, who maintained his charge of plagiarism.
Newton’s own copy of his Principia, with hand-written corrections for the second edition. Credit: Trinity Cambridge/Andrew Dunn
As time moved on, Newton’s fame continued to grow while Hooke’s continued to diminish. This caused Hooke to become increasingly embittered and more protective of what he saw as his work, and he spared no opportunity to lash out at his rival. The feud finally ended in 1703, when Hooke died and Newton succeeded him as president of the Royal Society.
Other Accomplishments:
In addition to his work in astronomy, optics, mechanics, physics and alchemy, Newton also had a keen interest in religion and the Bible. During the 1690’s, he wrote several religious tracts that addressed literal and symbolic interpretations of the Bible. For instance, his tract on the Holy Trinity – sent to the famous political philosopher and social theorist John Locke and unpublished until 1785 – questioned the veracity of 1 John 5:7, the description which the Holy Trinity is based on.
Later religious works – like The Chronology of Ancient Kingdoms Amended (1728) and Observations Upon the Prophecies of Daniel and the Apocalypse of St. John (1733) – also remained unpublished until after his death. In Kingdoms, he dealt with the chronology of various ancient kingdoms – the First Ages of the Greeks, ancient Egyptians, Babylonians, Medeans and Persians – and offered a description of the Temple of Solomon.
In Prophecies, he addressed the Apocalypse, as foretold within the Book of Daniel and Revelations, and espoused his belief that it would take place in 2060 CE (though other possible dates included 2034 CE). In his textual criticism titled An Historical Account of Two Notable Corruptions of Scripture(1754), he placed the crucifixion of Jesus Christ on April 3rd, AD 33, which agrees with a traditionally accepted date.
Portrait of Newton in 1702, painted by Godfrey Kneller. Credit: National Portrait Gallery, London
In 1696, he moved to London to take up the post of warden of the Royal Mint, where he took charge of England’s great recoining. Newton would remain in this post for 30 years, and was perhaps the best-known Master of the Mint. So serious was his commitment to the role that he retired from Cambridge in 1701 to oversee the reform of England’s currency and the punishment of counterfeiters.
As Warden, and afterwards Master, of the Royal Mint, Newton estimated that 20 percent of the coins taken in during the Great Recoinage of 1696 were counterfeit. Conducting many investigations personally, Newton traveled to taverns and bars in disguise to gather evidence, and conducted more than 100 cross-examinations of witnesses, informers, and suspects – which led to the successful prosecution of 28 counterfeit coiners.
Newton was a member of the Parliament of England for Cambridge University in 1689–90 and 1701–2. In addition to being President of the Royal Society in 1703, he was an associate of the French Académie des Sciences. In April 1705, Queen Anne knighted Newton during a royal visit to Trinity College, Cambridge, making him the second scientist to be knighted (after Sir Francis Bacon).
Death and Legacy:
Towards the end of his life, Newton took up residence at Cranbury Park near Winchester with his niece and her husband, where he would stay until his death. By this time, Newton had become one of the most famous men in Europe and his scientific discoveries were unchallenged. He also had become wealthy, investing his sizable income wisely and bestowing sizable gifts to charity.
Newton’s tomb in Westminster Abbey. Credit: Wikipedia Commons/Klaus-Dieter Keller
At the same time, Newton’s physical and mental health began to decline. By the time he reached 80 years of age, he began experiencing digestive problems and had to drastically change his diet and lifestyle. His family and friends also began to worry about his mental stability, as his behavior became increasingly erratic.
Then, in 1727, Newton experienced severe pain in his abdomen and lost consciousness. He died in his sleep on the next day, on March 2oth, 1727 (Julian Calendar; or March 31st, 1727, Gregorian Calendar) at the age of 84. He was buried in tomb at Westminster Abbey. And as a bachelor, he had divested much of his estate to relatives and charities during his final years.
After his death, Newton’s hair was examined and found to contain mercury, probably resulting from his alchemical pursuits. Mercury poisoning has been cited as a reason for Newton’s eccentricity in later life, as well as the nervous breakdown he experienced in 1693. Isaac Newton’s fame grew even more after his death, as many of his contemporaries proclaimed him to be the greatest genius who ever lived.
These claims were not without merit, as his laws of motion and theory of universal gravitation were unparalleled in his the time. In addition to being able to bring the orbits of the planets, the Moon, and even comets into one coherent and predictable system, he also invented modern calculus, revolutionized our understanding of light and optics, and established scientific principles that would remain in use for the following 200 years.
Albert Einstein was one of Newton’s many admirers, claiming that to Newton, nature was “an open book, whose letters he could read without effort”. Credit: Ferdinand Schmutzer/Public Domain
In time, much of what Newton espoused would be proven wrong, thanks largely to Albert Einstein. With his General Theory of Relativity, Einstein would prove that time, distance and motion were not absolutes, but dependent on the observer. In so doing, he overturned one of the fundamental precepts of universal gravitation. Nevertheless, Einstein was one of Newton’s greatest admirers and acknowledged a great debt to his predecessor.
In addition to calling Newton a “shining spirit” (in a eulogy delivered in 1927 on the 200th anniversary of Newton’s death), Einstein also remarked that “Nature to him was an open book, whose letters he could read without effort.” On his study wall, Albert Einstein is said to have kept a picture of Newton, alongside pictures of Michael Faraday and James Clerk Maxwell.
A survey of Britain’s Royal Society was also conducted in 2005, where members were asked who had the greater effect on the history of science: Newton or Einstein. The majority of the Royal Society’s members agreed that overall, Newton had a greater impact on the sciences. Other polls conducted in recent decades have produced similar results, with Einstein and Newton vying for first and second place.
It is not easy thing to be living during one of the most auspicious times in history. Moreover, it is not easy in the midst of all of that to be blessed with an insight that will lead one to comes up with ideas that will revolutionize the sciences and forever alter the course of history. But throughout it all, Newton maintained a humble attitude, and summarized his accomplishments best with the famous words: “If I have seen further it is by standing on the shoulders of giants.“
A November rain hails from the Sickle of the Lion.
Hot on the heels of the October Orionids and the Halloween fireballs of the Taurid meteors comes the Leonid meteor shower. On most years, the Leonids are a moderate shower, with hourly local rates reaching around 20. Once every 33 years, however, the Leonids are responsible for putting on one of the greatest astronomical shows ever witnessed, producing a grand storm with a zenithal hourly rate topping thousands per hour.
The orientation of the Earth and the relative positions of the Sun, Moon and the Leonid meteor radiant on November 17th at 4:00 UT. Image credit: Stellarium
Prospects for 2015
First, the bad news. 2015 isn’t forecast to be a ‘storm year’ for the Leonids, though that shouldn’t stop a vigilant observer from watching. The good news is, we’re just about midway betwixt the storm years of 1998-99 and 2031-32. The Leonids intensify once every 33 years, and if the increased activity seen in the late 1990s was any indication, we’d bet we’ll start seeing a pickup in rates from the Leonids in the late 2020’s or so. The good news for 2015, however, is that the peak for the Leonids occur on November 18th at around 4:00 Universal Time (UT)/ (11:00 PM EST on November 17th). This places the waxing crescent Moon out of the picture, just a day before reaching First Quarter phase. New Moon for November 2015 occurs on November 11th at 17:47 UT/12:47 PM EST.
A composite of the 2014 Leonids. Image credit: Alan Dyer/Amazing Sky Photography
Fun fact: the August Perseids, November Leonids and the December Geminid meteor showers are spaced out on the calendar in such a way that, when the Moon phase is favorable for one shower on a particular year, it is nearly always favorable across all of them.
The Leonids are mildly active from November 6th through November 30th, and though the above prediction for activity in 2015 favors European longitudes at dawn, some predictions have the peak arriving up to seven hours early this year.
A simulated ‘Leonid storm.’ Note the true position of the radiant in the center of the backwards ‘?’ asterism is slightly offset. Image credit: Stellarium
The Leonids are the dusty remnants laid down by periodic comet 55P Tempel-Tuttle on its 33-year path through the inner solar system. The Leonids are fast-movers, hitting the Earth nearly head-on in the dawn. You can see this in the relative position of the radiant, which rises in mid-November around 11PM local, and reaches the zenith around 6AM local time.
A late season Leonid meteor from 2014. Image credit: The UK Monitoring network (UKMON)
Often bluish in color, the Leonids hit the Earth’s atmosphere at over 70 km/sec… almost the fastest theoretical speed possible. For best results, watch for Leonids to spike in activity close to local dawn.
A 1799 woodcut depicting the Leonids at sea. Image credit: Public Domain
The Leonids have a storied history, going back 902 AD report from Arabic annals of the ‘Year of Stars.’ The Great Meteor Storm of 1833 dazzled (and terrified) residents of the eastern seaboard of the United States, and the spectacle not only inspired astronomer Denison Olmsted to pioneer studies into the fledgling field of meteor shower science, but has been attributed to adding fervor to many of the religious revivalist movements that sprang up in the 1830s in the United States as well.
The last outburst from the Leonids that reached such an apocalyptic scale was in 1966, when observers across the southwestern United States reported hourly rates approaching an amazing ZHR=144,000. Witnesses that remember this spectacle say it produced an illusion reminiscent of the Star Trek ‘warp speed’ effect, as Earth rammed headlong into the dense Leonid meteor stream.
Our own personal encounter with a Leonid meteor storm in 1998 from the dark desert skies of Kuwait wasn’t quite that intense, but thrilling to see nonetheless. Rates neared one every few seconds towards sunrise, with several fireballs punctuating the action, lighting up the desert floor. Here, as US coalition forces were on the verge of unleashing what would become Operation: Desert Fox over Iraq, the Universe was putting on a fireworks show of its own.
The Leonid meteor storms are the stuff of astronomical legend, a once in a lifetime event. Ever since we witnessed just what the Leonids are capable of, we never miss this annual shower, as we remember one night back in 1998, and look forward to the storms of 2032.
Here’s what the Leonids have been doing on previous recent years:
Radio observations were carried out from the Allen Telescope Array of the reputed megastructure-encompassed star KIC 8462852.
Astronomers at the SETI institute (search for extraterrestrial intelligence) have reported their findings after monitoring the reputedmegastructure-encompassed star KIC 8462852. No significant radio signals were detected in observations carried out from the Allen Telescope Array between October 15-30th (nearly 12 hours each day). However, there are caveats, namely that the sensitivity and frequency range were limited, and gaps existed in the coverage (e.g., between 6-7 Ghz).
Lead author Gerald Harp and the SETI team discussed the various ideas proposed to explain the anomalous Kepler brightness measurements of KIC 8462852, “The unusual star KIC 8462852 studied by the Kepler space telescope appears to have a large quantity of matter orbiting quickly about it. In transit, this material can obscure more than 20% of the light from that star. However, the dimming does not exhibit the periodicity expected of an accompanying exoplanet.” The team went on to add that, “Although natural explanations should be favored; e.g., a constellation of comets disrupted by a passing star (Boyajian et al. 2015), or gravitational darkening of an oblate star (Galasyn 2015), it is interesting to speculate that the occluding matter might signal the presence of massive astroengineering projects constructed in the vicinity of KIC 8462582 (Wright, Cartier et al. 2015).”
One such megastructure was discussed in a famous paper by Freeman Dyson (1960), and subsequently designated a ‘Dyson Sphere‘. In order to accommodate an advanced civilisation’s increasing energy demands, Dyson remarked that, “pressures will ultimately drive an intelligent species to adopt some such efficient exploitation of its available resources. One should expect that, within a few thousand years of its entering the stage of industrial development, any intelligent species should be found occupying an artificial biosphere which completely surrounds its parent star.” Dyson further proposed that a search be potentially conducted for artificial radio emissions stemming from the vicinity of a target star.
The SETI team summarized Dyson’s idea by noting that Solar panels could serve to capture starlight as a source of sustainable energy, and likewise highlighted that other, “large-scale structures might be built to serve as possible habitats (e.g., “ring worlds”), or as long-lived beacons to signal the existence of such civilizations to technologically advanced life in other star systems by occluding starlight in a manner not characteristic of natural orbiting bodies (Arnold 2013).” Indeed, bright variable stars such as the famed Cepheid stars have been cited as potential beacons.
The Universe Today’s Fraser Cain discusses a ‘Dyson Sphere‘.
If a Dyson Sphere encompassed the Kepler catalogued star, the SETI team were seeking in part to identify spacecraft that may service a large structure and could be revealed by a powerful wide bandwidth signal. The team concluded that their radio observations did not reveal any significant signal stemming from the star (e.g., Fig 1 below). Yet as noted above, the sensitivity was limited to above 100 Jy and the frequency range was restricted to 1-10 Ghz, and gaps existed in that coverage.
Fig 1 from Harp et al. (2015) conveys the lack of radio waves emerging from the star KIC 8462852 (black symbols), however there were sensitivity and coverage limitations (see text). The signal emerging from the quasar 3c84 is shown via blue symbols.
What is causing the odd brightness variations seen in the Kepler star KIC 8462852? Were those anomalous variations a result of an unknown spurious artefact from the telescope itself, a swath of comets temporarily blocking the star’s light, or perhaps something more extravagant. The latter should not be hailed as the de facto source simply because an explanation is not readily available. However, the intellectual exercise of contemplating the technology advanced civilisations could construct to address certain needs (e.g., energy) is certainly a worthy venture.
Portrait of Galileo Galilei by Giusto Sustermans (1636). Credit: nmm.ac.uk
When it comes to scientists who revolutionized the way we think of the universe, few names stand out like Galileo Galilei. A noted inventor, physicist, engineer and astronomer, Galileo was one of the greatest contributors to the Scientific Revolution. He build telescopes, designed a compass for surveying and military use, created a revolutionary pumping system, and developed physical laws that were the precursors of Newton’s law of Universal Gravitation and Einstein’s Theory of Relativity.
But it was within the field of astronomy that Galileo made his most enduring impact. Using telescopes of his own design, he discovered Sunspots, the largest moons of Jupiter, surveyed The Moon, and demonstrated the validity of Copernicus’ heliocentric model of the universe. In so doing, he helped to revolutionize our understanding of the cosmos, our place in it, and helped to usher in an age where scientific reasoning trumped religious dogma.
Early Life:
Galileo was born in Pisa, Italy, in 1564, into a noble but poor family. He was the first of six children of Vincenzo Galilei and Giulia Ammannati, who’s father also had three children out of wedlock. Galileo was named after an ancestor, Galileo Bonaiuti (1370 – 1450), a noted physician, university teacher and politician who lived in Florence.
His father, a famous lutenist, composer and music theorist, had a great impact on Galileo; transmitting not only his talent for music, but skepticism of authority, the value of experimentation, and the value of measures of time and rhythm to achieve success.
The Camaldolese Monastery at Vallombrosa, 35 km southeast of Florence, where Galileo was educated until 1581. Credit: nobility.org
In 1572, when Galileo Galilei was eight, his family moved to Florence, leaving Galileo with his uncle Muzio Tedaldi (related to his mother through marriage) for two years.When he reached the age of ten, Galileo left Pisa to join his family in Florence and was tutored by Jacopo Borghini -a mathematician and professor from the university of Pisa.
Once he was old enough to be educated in a monastery, his parents sent him to the Camaldolese Monastery at Vallombrosa, located 35 km southeast of Florence. The Order was independent from the Benedictines, and combined the solitary life of the hermit with the strict life of a monk. Galileo apparently found this life attractive and intending to join the Order, but his father insisted that he study at the University of Pisa to become a doctor.
Education:
While at Pisa, Galileo began studying medicine, but his interest in the sciences quickly became evident. In 1581, he noticed a swinging chandelier, and became fascinated by the timing of its movements. To him, it became clear that the amount of time, regardless of how far it was swinging, was comparable to the beating of his heart.
When he returned home, he set up two pendulums of equal length, swinging one with a large sweep and the other with a small sweep, and found that they kept time together. These observations became the basis of his later work with pendulums to keep time – work which would also be picked up almost a century later when Christiaan Huygens designed the first officially-recognized pendulum clock.
Galileo Demonstrating the New Astronomical Theories at the University of Padua, by Félix Parra (1873). Credit: munal.gob.mx
Shortly thereafter, Galileo accidentally attended a lecture on geometry, and talked his reluctant father into letting his study mathematics and natural philosophy instead of medicine. From that point onward, he began a steady processes of inventing, largely for the sake of appeasing his father’s desire for him to make money to pay off his siblings expenses (particularly those of his younger brother, Michelagnolo).
In 1589, Galileo was appointed to the chair of mathematics at the University of Pisa. In 1591, his father died, and he was entrusted with the care of his younger siblings. Being Professor of Mathematics at Pisa was not well paid, so Galileo lobbied for a more lucrative post. In 1592, this led to his appointment to the position of Professor of Mathematics at the University of Padua, where he taught Euclid’s geometry, mechanics, and astronomy until 1610.
During this period, Galileo made significant discoveries in both pure fundamental science as well as practical applied science. His multiple interests included the study of astrology, which at the time was a discipline tied to the studies of mathematics and astronomy. It was also while teaching the standard (geocentric) model of the universe that his interest in astronomy and the Copernican theory began to take off.
Telescopes:
In 1609, Galileo received a letter telling him about a spyglass that a Dutchman had shown in Venice. Using his own technical skills as a mathematician and as a craftsman, Galileo began to make a series of telescopes whose optical performance was much better than that of the Dutch instrument.
Galileo Galilei’s telescope with his handwritten note specifying the magnifying power of the lens, at an exhibition at The Franklin Institute in Philadelphia. Credit: AP Photo/Matt Rourke
As he would later write in his 1610 tract Sidereus Nuncius (“The Starry Messenger”):
“About ten months ago a report reached my ears that a certain Fleming had constructed a spyglass by means of which visible objects, though very distant from the eye of the observer, were distinctly seen as if nearby. Of this truly remarkable effect several experiences were related, to which some persons believed while other denied them. A few days later the report was confirmed by a letter I received from a Frenchman in Paris, Jacques Badovere, which caused me to apply myself wholeheartedly to investigate means by which I might arrive at the invention of a similar instrument. This I did soon afterwards, my basis being the doctrine of refraction.”
His first telescope – which he constructed between June and July of 1609 – was made from available lenses and had a three-powered spyglass. To improve upon this, Galileo learned how to grind and polish his own lenses. By August, he had created an eight-powered telescope, which he presented to the Venetian Senate.
By the following October or November, he managed to improve upon this with the creation a twenty-powered telescope. Galileo saw a great deal of commercial and military applications of his instrument(which he called a perspicillum) for ships at sea. However, in 1610, he began turning his telescope to the heavens and made his most profound discoveries.
Galileo Galilei showing the Doge of Venice how to use the telescope, by Giuseppe Bertini (1858). Credit: gabrielevanin.it
Achievements in Astronomy:
Using his telescope, Galileo began his career in astronomy by gazing at the Moon, where he discerned patterns of uneven and waning light. While not the first astronomer to do this, Galileo artistic’s training and knowledge of chiaroscuro – the use of strong contrasts between light and dark – allowed him to correctly deduce that these light patterns were the result of changes in elevation. Hence, Galileo was the first astronomer to discover lunar mountains and craters.
In The Starry Messenger, he also made topographical charts, estimating the heights of these mountains. In so doing, he challenged centuries of Aristotelian dogma that claimed that Moon, like the other planets, was a perfect, translucent sphere. By identifying that it had imperfections, in the forms of surface features, he began advancing the notion that the planets were similar to Earth.
Galileo also recorded his observations about the Milky Way in the Starry Messenger, which was previously believed to be nebulous. Instead, Galileo found that it was a multitude of stars packed so densely together that it appeared from a distance to look like clouds. He also reported that whereas the telescope resolved the planets into discs, the stars appeared as mere blazes of light, essentially unaltered in appearance by the telescope – thus suggesting that they were much farther away than previously thought.
Using his telescopes, Galileo also became one the first European astronomer to observe and study sunspots. Though there are records of previous instances of naked eye observations – such as in China (ca. 28 BCE), Anaxagoras in 467 BCE, and by Kepler in 1607 – they were not identifies as being imperfections on the surface of the Sun. In many cases, such as Kepler’s, it was thought that the spots were transits of Mercury.
In addition, there is also controversy over who was the first to observe sunspots during the 17th century using a telescope. Whereas Galileo is believed to have observed them in 1610, he did not publish about them and only began speaking to astronomers in Rome about them by the following year. In that time, German astronomer Christoph Scheiner had been reportedly observing them using a helioscope of his own design.
At around the same time, the Frisian astronomers Johannes and David Fabricius published a description of sunspots in June 1611. Johannes book, De Maculis in Sole Observatis (“On the Spots Observed in the Sun”) was published in autumn of 1611, thus securing credit for him and his father.
In any case, it was Galileo who properly identified sunspots as imperfections on the surface of the Sun, rather than being satellites of the Sun – an explanation that Scheiner, a Jesuit missionary, advanced in order to preserve his beliefs in the perfection of the Sun.
Using a technique of projecting the Sun’s image through the telescope onto a piece of paper, Galileo deduced that sunspots were, in fact, on the surface of the Sun or in its atmosphere. This presented another challenge to the Aristotelian and Ptolemaic view of the heavens, since it demonstrated that the Sun itself had imperfections.
On January 7th, 1610, Galileo pointed his telescope towards Jupiter and observed what he described in Nuncius as “three fixed stars, totally invisible by their smallness” that were all close to Jupiter and in line with its equator. Observations on subsequent nights showed that the positions of these “stars” had changed relative to Jupiter, and in a way that was not consistent with them being part of the background stars.
The Galilean moons, shown to scale – Io (top right), Europa (upper left), Ganymede (right) and Callisto (bottom left). Credit: NASA/JPL
By January 10th, he noted that one had disappeared, which he attributed to it being hidden behind Jupiter. From this, he concluded that the stars were in fact orbiting Jupiter, and they were satellites of it. By January 13th, he discovered a fourth, and named them the Medicean stars, in honor of his future patron, Cosimo II de’ Medici, Grand Duke of Tuscany, and his three brothers.
Later astronomers, however, renamed them the Galilean Moons in honour of their discoverer. By the 20th century, these satellites would come to be known by their current names – Io, Europa, Ganymede, and Callisto – which had been suggested by 17th century German astronomer Simon Marius, apparently at the behest of Johannes Kepler.
Galileo’s observations of these satellites proved to be another major controversy. For the first time, a planet other than Earth was shown to have satellites orbiting it, which constituted yet another nail in the coffin of the geocentric model of the universe. His observations were independently confirmed afterwards, and Galileo continued to observe the satellites them and even obtained remarkably accurate estimates for their periods by 1611.
Heliocentrism:
Galileo’s greatest contribution to astronomy came in the form of his advancement of the Copernican model of the universe (i.e. heliocentrism). This began in 1610 with his publication of Sidereus Nuncius, which brought the issue of celestial imperfections before a wider audience. His work on sunspots and his observation of the Galilean Moons furthered this, revealing yet more inconsistencies in the currently accepted view of the heavens.
Galileo’s Sidereus Nuncius (“Starry Messenger”), published in 1610, laid out his observations of the moon’s surface, which included mountains and impact craters. Credit: brunelleschi.imss.fi.it
Other astronomical observations also led Galileo to champion the Copernican model over the traditional Aristotelian-Ptolemaic (aka. geocentric) view. From September 1610 onward, Galileo began observing Venus, noting that it exhibited a full set of phases similar to that of the Moon. The only explanation for this was that Venus was periodically between the Sun and Earth; while at other times, it was on the opposite side of the Sun.
According to the geocentric model of the universe, this should have been impossible, as Venus’ orbit placed it closer to Earth than the Sun – where it could only exhibit crescent and new phases. However, Galileo’s observations of it going through crescent, gibbous, full and new phases was consistent with the Copernican model, which established that Venus orbited the Sun within the Earth’s orbit.
These and other observations made the Ptolemaic model of the universe untenable. Thus, by the early 17th century, the great majority of astronomers began to convert to one of the various geo-heliocentric planetary models – such as the Tychonic, Capellan and Extended Capellan models. These all had the virtue of explaining problems in the geocentric model without engaging in the “heretical” notion that Earth revolved around the Sun.
In 1632, Galileo addressed the “Great Debate” in his treatise Dialogo sopra i due massimi sistemi del mondo (Dialogue Concerning the Two Chief World Systems), in which he advocated the heliocentric model over the geocentric. Using his own telescopic observations, modern physics and rigorous logic, Galileo’s arguments effectively undermined the basis of Aristotle and Ptolemy’s system for a growing and receptive audience.
Frontispiece and title page of the Dialogue, 1632. Credit: moro.imss.fi.it
In the meantime, Johannes Kepler correctly identified the sources of tides on Earth – something which Galileo had become interesting in himself. But whereas Galileo attributed the ebb and flow of tides to the rotation of the Earth, Kepler ascribed this behavior to the influence of the Moon.
Combined with his accurate tables on the elliptical orbits of the planets (something Galileo rejected), the Copernican model was effectively proven. From the middle of the seventeenth century onward, there were few astronomers who were not Copernicans.
The Inquisition and House Arrest:
As a devout Catholic, Galileo often defended the heliocentric model of the universe using Scripture. In 1616, he wrote a letter to the Grand Duchess Christina, in which he argued for a non-literal interpretation of the Bible and espoused his belief in the heliocentric universe as a physical reality:
“I hold that the Sun is located at the center of the revolutions of the heavenly orbs and does not change place, and that the Earth rotates on itself and moves around it. Moreover … I confirm this view not only by refuting Ptolemy’s and Aristotle’s arguments, but also by producing many for the other side, especially some pertaining to physical effects whose causes perhaps cannot be determined in any other way, and other astronomical discoveries; these discoveries clearly confute the Ptolemaic system, and they agree admirably with this other position and confirm it.“
More importantly, he argued that the Bible is written in the language of the common person who is not an expert in astronomy. Scripture, he argued, teaches us how to go to heaven, not how the heavens go.
Galileo facing the Roman Inquisition. by Cristiano Banti’s (1857). Credit: law.umkc.edu
Initially, the Copernican model of the universe was not seen as an issue by the Roman Catholic Church or it’s most important interpreter of Scripture at the time – Cardinal Robert Bellarmine. However, in the wake of the Counter-Reformation, which began in 1545 in response to the Reformation, a more stringent attitude began to emerge towards anything seen as a challenge to papal authority.
Eventually, matters came to a head in 1615 when Pope Paul V (1552 – 1621) ordered that the Sacred Congregation of the Index (an Inquisition body charged with banning writings deemed “heretical”) make a ruling on Copernicanism. They condemned the teachings of Copernicus, and Galileo (who had not been personally involved in the trial) was forbidden to hold Copernican views.
However, things changed with the election of Cardinal Maffeo Barberini (Pope Urban VIII) in 1623. As a friend and admirer of Galileo’s, Barberini opposed the condemnation of Galileo, and gave formal authorization and papal permission for the publication of Dialogue Concerning the Two Chief World Systems.
However, Barberini stipulated that Galileo provide arguments for and against heliocentrism in the book, that he be careful not to advocate heliocentrism, and that his own views on the matter be included in Galileo’s book. Unfortunately, Galileo’s book proved to be a solid endorsement of heliocentrism and offended the Pope personally.
Portrait of Galileo gazing at the words “E pur si muove” scratched on the wall of his prison cell, attributed to Bartolomé Esteban Murillo (1618-1682). Credit: Wikipedia Commons
In it, the character of Simplicio, the defender of the Aristotelian geocentric view, is portrayed as an error-prone simpleton. To make matter worse, Galileo had the character Simplicio enunciate the views of Barberini at the close of the book, making it appear as though Pope Urban VIII himself was a simpleton and hence the subject of ridicule.
As a result, Galileo was brought before the Inquisition in February of 1633 and ordered to renounce his views. Whereas Galileo steadfastly defended his position and insisted on his innocence, he was eventually threatened with torture and declared guilty. The sentence of the Inquisition, delivered on June 22nd, contained three parts – that Galileo renounce Copernicanism, that he be placed under house arrest, and that the Dialogue be banned.
According to popular legend, after recanting his theory publicly that the Earth moved around the Sun, Galileo allegedly muttered the rebellious phrase: “E pur si muove” (“And yet it moves” in Latin). After a period of living with his friend, the Archbishop of Siena, Galileo returned to his villa at Arcetri (near Florence in 1634), where he spent the remainder of his life under house arrest.
Other Accomplishments:
In addition to his revolutionary work in astronomy and optics, Galileo is also credited with the invention of many scientific instruments and theories. Much of the devices he created were for the specific purpose of earning money to pay for his sibling’s expenses. However, they would also prove to have a profound impact in the fields of mechanics, engineering, navigation, surveying, and warfare.
Galileo’s La Billancetta, in which he describes a method for hydrostatic balance. Credit: Museo Galileo
In 1586, at the age of 22, Galileo made his first groundbreaking invention. Inspired by the story of Archimedes and his “Eureka” moment, Galileo began looking into how jewelers weighed precious metals in air and then by displacement to determine their specific gravity. Working from this, he eventually theorized of a better method, which he described in a treatise entitled La Bilancetta (“The Little Balance”).
In this tract, he described an accurate balance for weighing things in air and water, in which the part of the arm on which the counter weight was hung was wrapped with metal wire. The amount by which the counterweight had to be moved when weighing in water could then be determined very accurately by counting the number of turns of the wire. In so doing, the proportion of metals like gold to silver in the object could be read off directly.
In 1592, when Galileo was a professor of mathematics at the University of Padua, he made frequent trips to the Arsenal – the inner harbor where Venetian ships were outfitted. The Arsenal had been a place of practical invention and innovation for centuries, and Galileo used the opportunity to study mechanical devices in detail.
In 1593, he was consulted on the placement of oars in galleys and submitted a report in which he treated the oar as a lever and correctly made the water the fulcrum. A year later the Venetian Senate awarded him a patent for a device for raising water that relied on a single horse for the operation. This became the basis of modern pumps.
A replica of the earliest surviving telescope attributed to Galileo Galilei, on display at the Griffith Observatory. Credit: Wikipedia Commons/Mike Dunn
To some, Galileo’s Pump was a merely an improvement on the Archimedes Screw, which was first developed in the third century BCE and patented in the Venetian Republic in 1567. However, there is no apparent evidence connecting Galileo’s invention to Archimedes’ earlier and less sophisticated design.
In ca. 1593, Galileo constructed his own version of a thermoscope, a forerunner of the thermometer, that relied on the expansion and contraction of air in a bulb to move water in an attached tube. Over time, he and his colleagues worked to develop a numerical scale that would measure the heat based on the expansion of the water inside the tube.
The cannon, which was first introduced to Europe in 1325, had become a mainstay of war by Galileo’s time. Having become more sophisticated and mobile, gunners needed instruments to help them coordinate and calculate their fire. As such, between 1595 and 1598, Galileo devised an improved geometric and military compass for use by gunners and surveyors.
During the 16th century, Aristotelian physics was still the predominant way of explaining the behavior of bodies near the Earth. For example, it was believed that heavy bodies sought their natural place of rest – i.e at the center of things. As a result, no means existed to explain the behavior of pendulums, where a heavy body suspended from a rope would swing back and forth and not seek rest in the middle.
The Sector, a military/geometric compass designed by Galileo Galilei. Credit: chsi.harvard.edu
Already, Galileo had conducted experiments that demonstrated that heavier bodies did not fall faster than lighter ones – another belief consistent with Aristotelian theory. In addition, he also demonstrated that objects thrown into the air travel in parabolic arcs. Based on this and his fascination with the back and forth motion of a suspended weight, he began to research pendulums in 1588.
In 1602, he explained his observations in a letter to a friend, in which he described the principle of isochronism. According to Galileo, this principle asserted that the time it takes for the pendulum to swing is not linked to the arc of the pendulum, but rather the pendulum’s length. Comparing two pendulum’s of similar length, Galileo demonstrated that they would swing at the same speed, despite being pulled at different lengths.
According to Vincenzo Vivian, one of Galileo’s contemporaries, it was in 1641 while under house arrest that Galileo created a design for a pendulum clock. Unfortunately, being blind at the time, he was unable to complete it before his death in 1642. As a result, Christiaan Huygens’ publication of Horologrium Oscillatoriumin 1657 is recognized as the first recorded proposal for a pendulum clock.
Death and Legacy:
Galileo died on January 8th, 1642, at the age of 77, due to fever and heart palpitations that had taken a toll on his health. The Grand Duke of Tuscany, Ferdinando II, wished to bury him in the main body of the Basilica of Santa Croce, next to the tombs of his father and other ancestors, and to erect a marble mausoleum in his honor.
Tomb of Galileo Galilei in the Santa Croce Basilica in Florence, Italy. Credit: Wikipedia Commons/stanthejeep
However, Pope Urban VIII objected on the basis that Galileo had been condemned by the Church, and his body was instead buried in a small room next to the novice’s chapel in the Basilica. However, after his death, the controversy surrounding his works and heliocentricm subsided, and the Inquisitions ban on his writing’s was lifted in 1718.
In 1737, his body was exhumed and reburied in the main body of the Basilica after a monument had been erected in his honor. During the exhumation, three fingers and a tooth were removed from his remains. One of these fingers, the middle finger from Galileo’s right hand, is currently on exhibition at the Museo Galileo in Florence, Italy.
In 1741, Pope Benedict XIV authorized the publication of an edition of Galileo’s complete scientific works which included a mildly censored version of the Dialogue. In 1758, the general prohibition against works advocating heliocentrism was removed from the Index of prohibited books, although the specific ban on uncensored versions of the Dialogue and Copernicus’s De Revolutionibusorbium coelestium (“On the Revolutions of the Heavenly Spheres“) remained.
All traces of official opposition to heliocentrism by the church disappeared in 1835 when works that espoused this view were finally dropped from the Index. And in 1939, Pope Pius XII described Galileo as being among the “most audacious heroes of research… not afraid of the stumbling blocks and the risks on the way, nor fearful of the funereal monuments”.
A bust of Galileo at the Museo Galileo in Florence, Italy, where recovered parts of his body and many of his possessions are on display. Credit: NYT/Kathryn Cook
On October 31st, 1992, Pope John Paul II expressed regret for how the Galileo affair was handled, and issued a declaration acknowledging the errors committed by the Catholic Church tribunal. The affair had finally been put to rest and Galileo exonerated, though certain unclear statements issued by Pope Benedict XVI have led to renewed controversy and interest in recent years.
Alas, when it comes to the birth of modern science and those who helped create it, Galileo’s contributions are arguably unmatched. According to Stephen Hawking and Albert Einstein, Galileo was the father of modern science, his discoveries and investigations doing more to dispel the prevailing mood of superstition and dogma than anyone else in his time.
These include the discovery of craters and mountains on the Moon, the discovery of the four largest moons of Jupiter (Io, Europa, Ganymede and Callisto), the existence and nature of Sunspots, and the phases of Venus. These discoveries, combined with his logical and energetic defense of the Copernican model, made a lasting impact on astronomy and forever changed the way people look at the universe.
Galileo’s theoretical and experimental work on the motions of bodies, along with the largely independent work of Kepler and René Descartes, was a precursor of the classical mechanics developed by Sir Isaac Newton. His work with pendulums and time-keeping also previewed the work of Christiaan Huygens and the development of the pendulum clock, the most accurate timepiece of its day.
The €25 coin minted for the 2009 International Year of Astronomy, showing Galileo on the obverse. Credit: coinnews.net
Galileo also put forward the basic principle of relativity, which states that the laws of physics are the same in any system that is moving at a constant speed in a straight line. This remains true, regardless of the system’s particular speed or direction, thus proving that there is no absolute motion or absolute rest. This principle provided the basic framework for Newton’s laws of motion and is central to Einstein’s special theory of relativity.
The United Nations chose 2009 to be the International Year of Astronomy, a global celebration of astronomy and its contributions to society and culture. The year 2009 was selected in part because it was the four-hundredth anniversary of Galileo first viewing the heavens with his a telescope he built himself.
A commemorative €25 coin was minted for the occasion, with the inset on the obverse side showing Galileo’s portrait and telescope, as well as one of his first drawings of the surface of the moon. In the silver circle that surrounds it, pictures of other telescopes – Isaac Newton’s Telescope, the observatory in Kremsmünster Abbey, a modern telescope, a radio telescope and a space telescope – are also shown.
Other scientific endeavors and principles are named after Galileo, including the NASA Galileo spacecraft, which was the first spacecraft to enter orbit around Jupiter. Operating from 1989 to 2003, the mission consisted of an orbiter that observed the Jovian system, and an atmospheric probe that made the first measurements of Jupiter’s atmosphere.
This mission found evidence of subsurface oceans on Europa, Ganymede and Callisto, and revealed the intensity of volcanic activity on Io. In 2003, the spacecraft was crashed into Jupiter’s atmosphere to avoid contamination of any of Jupiter’s moons.
The European Space Agency (ESA) is also developing a global satellite navigation system named Galileo. And in classical mechanics, the transformation between inertial systems is known as “Galilean Transformation“, which is denoted by the non-SI unit of acceleration Gal (sometimes known as the Galileo). Asteroid 697 Galilea is also named in his honor.
Yes, the sciences and humanity as a whole owes a great dept to Galileo. And as time goes on, and space exploration continues, it is likely we will continue to repay that debt by naming future missions – and perhaps even features on the Galilean Moons, should we ever settle there – after him. Seems like a small recompense for ushering in the age of modern science, no?
Portrait of Christiaan Huygens, painted by von Bernard Vaillant in 1686. Credit: Hofwijck Museum, Voorburg/Public Domain
The 17th century was a very auspicious time for the sciences, with advancements being made in the fields of physics, mathematics, chemistry, and the natural sciences. But it was perhaps in the field of astronomy that the greatest achievements were made. In the space of a century, several planets and moons were observed for the first time, accurate models were made to predict the motions of the planets, and the law of universal gravitation was conceived.
In the midst of this, the name of Christiaan Huygens stands out among the rest. As one of the preeminent scientists of his time, he was pivotal in the development of clocks, mechanics and optics. And in the field of astronomy, he discovered Saturn’s Rings and its largest moon – Titan. Thanks to Huygens, subsequent generations of astronomers were inspired to explore the outer Solar System, leading to the discovery of other Cronian moons, Uranus, and Neptune in the following century.
The comforting blue glow of an ion drive. Image Credit: NASA
When we think of space travel, we tend to picture a massive rocket blasting off from Earth, with huge blast streams of fire and smoke coming out the bottom, as the enormous machine struggles to escape Earth’s gravity. Rockets are our only option for escaping Earth’s gravity well—for now. But once a spacecraft has broken its gravitational bond with Earth, we have other options for powering them. Ion propulsion, long dreamed of in science fiction, is now used to send probes and spacecraft on long journeys through space.
NASA first began researching ion propulsion in the 1950’s. In 1998, ion propulsion was successfully used as the main propulsion system on a spacecraft, powering the Deep Space 1 (DS1) on its mission to the asteroid 9969 Braille and Comet Borrelly. DS1 was designed not only to visit an asteroid and a comet, but to test twelve advanced, high-risk technologies, chief among them the ion propulsion system itself.
Ion propulsion systems generate a tiny amount of thrust. Hold nine quarters in your hand, feel Earth’s gravity pull on them, and you have an idea how little thrust they generate. They can’t be used for launching spacecraft from bodies with strong gravity. Their strength lies in continuing to generate thrust over time. This means that they can achieve very high top speeds. Ion thrusters can propel spacecraft to speeds over 320,000 kp/h (200,000 mph), but they must be in operation for a long time to achieve that speed.
An ion is an atom or a molecule that has either lost or gained an electron, and therefore has an electrical charge. So ionization is the process of giving a charge to an atom or a molecule, by adding or removing electrons. Once charged, an ion will want to move in relation to a magnetic field. That’s at the heart of ion drives. But certain atoms are better suited for this. NASA’s ion drives typically use xenon, an inert gas, because there’s no risk of explosion.
Detail of an ion drive. Image: NASA Glenn Research Center. Vectorization by Chabacano
In an ion drive, the xenon isn’t a fuel. It isn’t combusted, and it has no inherent properties that make it useful as a fuel. The energy source for an ion drive has to come from somewhere else. This source can be electricity from solar cells, or electricity generated from decay heat from a nuclear material.
Ions are created by bombarding the xenon gas with high energy electrons. Once charged, these ions are drawn through a pair of electrostatic grids—called lenses—by their charges, and are expelled out of the chamber, producing thrust. This discharge is called the ion beam, and it is again injected with electrons, to neutralize its charge. Here’s a short video showing how ion drives work:
Unlike a traditional chemical rocket, where its thrust is limited by how much fuel it can carry and burn, the thrust generated by an ion drive is only limited by the strength of its electrical source. The amount of propellant a craft can carry, in this case xenon, is a secondary concern. NASA’s Dawn spacecraft used only 10 ounces of xenon propellant—that’s less than a soda can—for 27 hours of operation.
NASA Evolutionary Xenon Thruster. Image Credit: NASA
In theory, there is no limit to the strength of the electrical source powering the drive, and work is being done to develop even more powerful ion thrusters than we currently have. In 2012, NASA’s Evolutionary Xenon Thruster (NEXT) operated at 7000w for over 43,000 hours, in comparison to the ion drive on DS1 that used only 2100w. NEXT, and designs that will surpass it in the future, will allow spacecraft to go on extended missions to multiple asteroids, comets, the outer planets, and their moons.
Missions using ion propulsion include NASA’s Dawn mission, the Japanese Hayabusa mission to asteroid 25143 Itokawa, and the upcoming ESA missions Bepicolombo, which will head to Mercury in 2017, and LISA Pathfinder, which will study low frequency gravitational waves.
With the constant improvement in ion propulsion systems, this list will only grow.
