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