Magnetism and the Lunar Eclipse

Being away from home and in a very difficult environment, I have had the opportunity to be mesmerised by the many loving and genuine young people that I have met, so peaceful and kind with some of the most heartbreaking stories I have ever heard. It is wonderful to see the awe in their eyes when I explained to them some of the upcoming events that our galaxy is offering. On Friday the 27th of July at 8.15pm, we will have the chance to witness the Lunar Eclipse begin, reaching full eclipse by 10.30pm and often known as ‘blood moon’ (it will go a deep burnt red due to refraction of light from our atmosphere much like a sunset) that will be the longest lunar eclipse of the century. In addition, the planet Mars will be at opposition when it will be at its most brightest and nearing its closest to earth in 15 years, accompanied with the International Space Station passing on what will be a clear summer’s evening that I will be spending on the rooftop of this dilapidated building in the heart of the Middle East. While light pollution is a significant issue, everyone will get a chance to witness naked eye these phenomenal galactic events that gives them a glimpse into a series of astronomical narratives that will no doubt provoke questions about our planet, orbits and space. These events arrive at the same time I hear the amazing news that my program working with refugees and asylum seekers back home in Australia will be funded, where I will take disadvantaged girls and young women out on hikes, camping and viewings over my telescope where I will teach them about stargazing. It has given me inspiration on my only afternoon off for the week to write this blog post!

I was asked today, “how does all this happen?” and I attempted – albeit due to language barriers rather awfully! – a brief explanation of the moon crossing the ecliptic where the Earth, Sun and Moon are aligned when the moon orbits through the shadow of Earth. Planets orbit around the sun, the gravity pulling and keeping them in orbit and gravity acts as a powerful force between two objects with a mass. You can read more on the eclipse in a previous blog post that I wrote. Magnetism is an entirely separate force despite similarities and it depends more on particular properties rather than simply mass, such as electrons and can both push and pull. Magnetism is present throughout the universe and we can experience it in many ways; when I am out hiking, my compass explains the pressure of magnetism and direction with the movement of the needle as it is attracted by the force.

There are a number of properties and varieties of magnetic forces that explain invisible fields that applies a force that influence objects or material from the magnetism. There are rules that confirm magnetic fields are dipolar and just like earth has both a north and south magnetic pole and the ‘magnetic flux’ explains how the force and attraction between the poles – usually represented by lines as visible in the image below – that can be averaged by the magnetic field and the perpendicular area the field infiltrates. Measurements of the force is determined by the mathematical formula F= qvB (Lorentz Force Law), which is the magnetic force, the charge, the velocity and the magnetic field and the unit of these field are measured in terms of Standard International (SI) units known as tesla.

Earth’s magnetic field is known as a geomagnetic field and magnetosphere the predominate reason for the magnetic field is the liquid iron core surrounding the solid inner core is the source of this phenomenon, the very ‘magnet’ where the electric currents produced by the flow of iron and other metals including nickel cause convection currents from the inertial force of the Coriolis Effect that ultimately splits the field into a surrounding force that envelops Earth and aligns back into the same direction. The changes in temperature and composition of the liquid core creating the currents that rise or sink matter all play a part in Earths magnetic field, that can be captured visually when solar winds collide with it (usually where the magnetic force is much stronger near the north and south poles) and the charged particles trapped by the magnetic field produce the aurora borealis or the aurora australis.

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The picture explains the rotational poles but that their alignment geographically differs from our north and south poles on earth, whereby the magnetic south poles resides further north of Antarctic’ South Pole and quite close to the south of Australia while the north magnetic pole is closer to northern Canada and thus south of the North Pole. The magnetic lines explain the streamlined flow of the magnetic field that makes it easier to ascertain the process mathematically. Jupiter has a number of powerful toroidal magnetic fields where the intensity is said to have formed from the dynamic movements of the metallic hydrogen within; the field on the surface of the clouds is almost ten times stronger than earth’s. The Milky Way also has magnetic fields as do galaxies and the universe contains some colossal magnetic fields, where observations of galaxy clusters have found magnetic fields extending millions of light years!

The magnetic force is the attraction or the repulsion (as you experience when attempting to connect two magnets with equal poles) occurs from the magnetic field. The properties of electrical fields (pole) with a positive and negative charge differ with that of magnetic fields (dipole) despite a close correlation, because electromagnetism involves a magnetic dipole producing an electric field as it moves and conversely an electric field can produce a magnetic field meaning the difference is an elementary change in the field. A magnet does not have an electric charge as two separate poles, while a dipole interacts as a charge as visualised in the following image. What this means is that the electrical force itself behaves on a charged particle in the direction of the field and does not need motion while a magnetic force requires this motion and acts perpendicular to the magnetic field.

Gravitational fields also acts as force fields for mass and the gravitational force itself depends on the mass and the mass experiences the gravitational force. The gravitational field has a place in every direction and point in space and known by the formula g = F/m where F is the force of gravity. While this may be a brief example of the difference between magnetism and gravitational fields, it will be a wonderful experience with the full lunar eclipse and Mars showcasing the marvels of the universe over a hot, clear night here in Jerusalem!

Further Reading:

Maurizio Gasperini, Theory of Gravitational Interactions, Springer (2016) 115
Stephen Blundell, Magnetism: A Very Short Introduction, Oxford (2012) 106
Anupam Garg, Classical Electromagnetism in a Nutshell, Princeton University Press (2012) 83

A History of the Eclipse: The Birth of Science

A solar eclipse is a clear demonstration of celestial mechanics as the position of the moon and the sun temporarily shadows the sunlight on earth, and indeed for centuries has led to a number of mythologies that attempt to explain the geometry of the unknown universe and where civilisations and formidable historical figures came to greatly influence the study of science and astronomy as we know of it today. The ancient Babylonians, Egyptians and Chinese were so entrenched in these myths that they formed methodical processes aimed at calculating and predicting occurrences and did so with great accuracy that led to the development of the necessary instruments to aid in their observational techniques. For instance, the Babylonians believed that the solar eclipse could potentially be a bad omen that would predict the death of the King and this fear evoked constant study that soon thereafter established the 223 month Saros cycle of eclipses, something that we still use today. Have eclipses prompted astronomers and philosophers to theorise celestial geometry and planetary motion that ultimately enhanced scientific tools prior to the invention of the telescope by Hans Lippershey in 1608 and led to what is known as science?

Several shadows are formed between the earth and the moon that occurs during both lunar and solar eclipses, the latter a result when the moons’ shadow hits the earth, though the sun is four hundred times larger than the moon. During a total solar eclipse, this shadow is called an Umbra,[1] whereby the very center of the shadow’ core is blocked by the moon as it eclipses the sunlight and as this ends, the shadow becomes an Antumbra that forms the lighter section of this shadow. During an annular solar eclipse, when the light source contains a larger diameter due to the distance of the moon during an Apogee (when the moon is at its farthest distance on the elliptical from the earth), the moon appears smaller and thus silhouettes the heat of the outer edge of the sun, forming a visible ‘ring of fire’.[2] When the moon’ distance from the earth is at a Perigree and therefore at its closest range, it enables a total eclipse as the diameter roughly matches and covers the entire sun.[3] It is estimated that a total solar eclipse in a location only occurs once every several hundred years and being an exceedingly rare phenomenon and difficult to predict only added to the mysteries of the heavens.[4]

Prior to the use of the telescope, astronomers recorded their observations using a number of tools, once such being the Armillary Sphere or the Spherical Astrolabe that was used both as a teaching tool and to aid observations. Aristotle, notwithstanding his vast array of knowledge on a number of subjects, included in his curriculum vitae the title of amateur astronomer and authored On the Heavens that observed the material nature of the cosmos through concentric celestial spheres. For Aristotle, the world is both celestial and terrestrial, with the latter sphere composed of changing and chaotic elements of fire, water, earth and air that is surrounded within a perfect and unchanging celestial universe. His theories of motion and cosmology dominated the subject for centuries and remained similar to that of Eudoxus (c 337 BC) who stated that with the earth being the center of the universe, rotating spheres on individual axis moved at various speeds and angles around the earth.[5] As the earth is spherical in shape, it remains stationary as the sun, moon and planets rotated around the earth and the motions of these spheres carried all celestial activity including the fixed stars and ecliptic rotations. As Aristotle’ work survived and being highly influential unlike many of his predecessors, his cosmological views remained dominant until Ptolemy wrote Almagest, a voluminous encyclopedia of astronomy that summarised all knowledge of astronomy available at the time. He also had his own version of a planetary system that was based on the notion of spheres but instead adopted a preference for circular eccentricity or a circular shape of the ellipse (equant) that rotates at various speeds.[6] Accordingly, his system also abandoned Earth’ positon as the center of the system and thus changed the centuries-old influence of Aristotle.

However, prior to Aristotle’ astronomical accounts the Ionian philosophers perhaps beginning with Thales of Miletus (c624 BC) who is said to have predicted the solar eclipse of the 585 BC[7] became highly influential in the development of natural philosophy. According to Herodotus, this solar eclipse had such a powerful influence that the war between the Lydians and the Medes came to an end when they viewed the eclipse as a sign and a warning from the gods.[8] While the Egyptians and Babylonians had already formed extensive observations of the night sky, the latter in particular employing the Saros that determines periodicity of eclipses governed by a repetitive cycle spanning 18 years, 11 days and 8 hours and enabled them with the skill to predict eclipses,[9] they were restricted by the superstitions and myths formed in their pagan rituals that viewed these eclipses as bad omens, particularly for the ruling class. The Greek philosophers were empowered with more intellectual maneuverability that established a better scientific approach to astronomy that was instead viewed to be governed by natural laws; what made up the universe was material rather than supernatural and the Armillary Sphere exemplified this as a teaching tool. Thales studied geometry in Egypt and this mathematical knowledge was brought back to Greece as he soon thereafter became credited to developing a number of advancements in the subject that attempted to explain unknown astronomical concepts. The earth, for instance, was a large mass floating on water and earthquakes were evidence of oceanic turbulence. Thales stated that the material that formed the universe was water (our dark matter) and is the fundamental element that all the material world. Cosmological theories continued with his followers such as Anaximander and Anaximenes that questioned the origin of the universe. Anaximenes took it one step further, purporting that the element that forms water – air – is the building block of all material things and water is merely the compressed form of this element.

Anaximander was far more interesting as he purported that the universe was formed by a chaos of infinite opposites (such as hot and cold) and his cosmological model of the universe was intriguing to say the least, suggesting a cylindrical earth surrounded by wheels of fire from the sun that we are able to see through holes that rotate past us. This period is clearly marked a great many discussions on the physics of the universe that attempted to explain the appearances of celestial objects, when things are static or dynamic, constant or eternal. Hipparchus (c190 BC) discovered the precession of the equinoxes by using the solar eclipse by estimating the distance of the moon from the earth.[10] The Armillary Sphere were devices that enabled a demonstration of the rings that represented the celestial spheres and attached to them were fixed globes set to an elliptical axis and were “sometimes mounted on handles, but often were set like globes into cradles so that the sphere could be adjusted to represent the heavens as seen from any latitude.”[11] A number of spheres continued to be developed and adjusted from Ptolemy to Copernicus as an instrument to explain and observe equatorial coordinates and through Aristotle moved into the Islamic world.

The cosmological and astronomical theories during this period nevertheless contained the practice of supernatural and mystical influences that viewed the heavens as practical tools for predicting events throughout the passage of time. While methods of observations and the tools that strengthened how they recorded data steadily advanced, the observations continued to be shrouded by such celestial mysteries that evoked a sense of fear and awe. In China, for instance, the Emperor had control of the heavens and therefore predicting eclipses and other activities (lifa) along with the study of astronomical phenomena (tianwen) played a powerful role in his position as supreme leader.[12] Without an orderly understanding of astronomical event, it was viewed as a bad omen and a sign of problems ahead. China is attributed as having the first record of a solar eclipse (c. 2134 BC).[13] Like the ancient Hellenistic astronomers, China also used their own version of an ancillary sphere and took it even one step further by developing a mechanically powered globe using a sophisticated haudralic system during the Han Dynasty.[14] However, Shen Kuo (c1095) who is said to have developed the magnetic-needle compass did so following his observations of planetary motions and by using the models of solar eclipses was able to verify that celestial objects were in fact round.[15]

While such celestial activity was during the time of the Egyptians and Babylonians shrouded with pagan mysticism, astronomy soon thereafter through Saint Thomas Aquinas enabled the world to view Aristotelian cosmology through a Christian lens, one clearly visible when Copernicus’ model that the earth revolves around the sun was met with denunciation by the dominant Catholic influences of the time. Scholastic astronomy was introduced to medieval Europe from the Islamic Golden Age following the decline of the Roman Empire and the new Ottoman Empire steadily controlling the Middle East and North Africa attained access to the library of Alexandria and thus the work of the ancient Greeks, translating them into Arabic and improving a number of astronomical models that advanced an understanding of the elliptical movements of planets and the moon. Translations of the Arabic to Latin enabled Aristotelian and all scientific writing to move into Europe when the Christians conquered the Moors in Spain and Aquinas successfully incorporated Aristotelian philosophy into Christendom. Thinkers such as Casanus began to combine theological influences to cosmological theories, purporting that the universe is infinite and that there was no specific location of space, instead space was everywhere. The subject of eclipses developed intense interest during the Islamic Golden Age as Islam required a sophisticated approach to prayer that required the correct direction toward Mecca during important periods of sunrise and sunset together with the calendrical system of the moon that inevitably enhanced the study and the equipment thereof including sundials and quadrants.[16] However, it is the Equatorium that was developed by Ibn al-Samh and al-Zarqali and translated in Castille under the patronage of King Alfonso X[17] in the book Libros Del Saber De Astronomia (Books of the knowledge of astronomy)[18] that assisted with astronomical calculations.

It is clear that studies of the solar eclipse prior to the development of the telescope have led to a great many developments in the study of astronomy and science as a whole. As the ancient Hellenistic community of philosophers approached the subject with more freedom of religious constraint, natural philosophy contributed vastly to the subject that even included mathematical advancements, such as the Pythagorean Theorem where the square of the hypotenuse is equal to the sum of the square of the remaining sides of a triangle. Pythagoras himself believed that reality is formed through numbers or that the material world can be reduced to simple numbers and by bringing with him the knowledge from the Babylonians that the earth is spherical in shape, visible during a curved shadow on the moon during eclipses, changed the study of astronomy and ultimately influenced the development of the study of science as we know today.

When I first heard of the eclipse in the United States in 2017 as I was in Hawaii, I never really thought that this celestial phenomenon could have had such a profound historical influence on the study of science. While the subject evoked many mythologies, mythologies even present today with theories of biblical Armageddon that the eclipse has stirred, there is no doubt that the motion of the moon around the earth, the sun and planetary models that attempted to explain geometric orbits from spheres to water, mathematical to theological, changed the face of history and enabled the beginning of the study of western science. While the origin of the universe continues to remain impossible to answer – I myself am controversially of the opinion that the origin of the universe is in God – the material world that we experience nevertheless can be scientifically explained without it being shrouded by theological superstition and bad omens. I think we can use science to quite easily predict that if Armageddon were coming, it is likely because of the United States along with many other countries that are ruining the earth without needing the book of revelations to tell us that.

 

[1] Martin Mobberley, Total Solar Eclipses and How to Observe Them, Springer Science & Business Media (2007) 38
[2] Nicholas Nigro, Knack Night Sky: Decoding the Solar System, from Constellations to Black Holes, Rowman & Littlefield (2010) 206
[3] Op. Cit., Mobberley, 39
[4] Michael Borgia, Human Vision and The Night Sky: How to Improve Your Observing Skills, Springer Science & Business Media (2006) 112. It is good to note that total solar eclipses occur regularly (every 18 months) but in one given location will span over 300 years.
[5] Richard Jones, The Medieval Natural World, Routledge (2013) 30
[6] Michael Zeilik, Astronomy: The Evolving Universe, Cambridge University Press (2002) 34
[7] Lisa Rezende, Chronology of Science, Infobase Publishing (2006) 21
[8] William Hales, Chronology and Geography, C.J.G. & F. Rivington, (1830) 71
[9] https://eclipse.gsfc.nasa.gov/SEsaros/SEsaros.html
[10] Lloyd Motz and Jefferson Hane Weaver, The Story of Astronomy, Springer (2013) 45
[11] John Lankford, History of Astronomy: An Encyclopedia, Taylor & Francis (1997) 34
[12] Frances Wood, Great Books of China (2017) in Almanac or Tongshu (c 1000 – c 600 BCE)
[13] Aaron Millar, The 50 Greatest Wonders of the World, Icon Books (2016)
[14] Joseph Needham, Science and Civilisation in China: Volume 3, Mathematics and the Sciences of the Heavens and the Earth, Cambridge University Press (1959) 458
[15] Ancient China’s Technology and Science: Compiled by the Institute of the History of Natural Sciences, Chinese Academy of Sciences. Foreign Languages Press (1983) 153
[16] Ludwig W. Adamec, Historical Dictionary of Islam, Rowman & Littlefield (2016) 393
[17] Roshdi Rashed, Encyclopedia of the History of Arabic Science, Routledge (2002) 256
[18] Belén Bistué, Collaborative Translation and Multi-Version Texts in Early Modern Europe, Routledge (2016) 65