Joan Feynman is an American astrophysicist who is best known for developing an understanding of auroras (what we call the northern lights). Feynman has spent her life studying the physics of the earth’s magnetic field and how it interacts with the sun’s energy. Through the story of Joan Feynman, we’ll explore the physics of magnetism.
Joan Feynman was born in 1927, in New York, USA. Joan was an inquisitive child, and she exhibited an interest in understanding the natural world from an early age. However, her mother and grandmother both dissuaded her from pursuing science, since they believed that women’s brains were not physically capable of understanding complex scientific concepts in the way that men’s brains could. Despite this, her brother Richard Feynman (who is also a famous physicist) always encouraged her to be curious about the universe. It was he who originally introduced young Joan to auroras when, one night, he coaxed her out of bed to witness the northern lights flickering above an empty golf course near their home. Later, Feynman would find comfort in an astronomy book given to her by her brother. One day, she came across the research of noted astronomer Cecilia Payne-Gaposchkin which made her realise that women could, in fact, study science.
Joan Feynman spent the bulk of her career studying the interactions between the solar wind and the Earth’s magnetic field. While working at the NASA Ames Research Center in 1971, Feynman discovered that the periodic spouting of solar material known as a solar coronal mass ejection (CME) could be identified by the presence of helium in the solar wind. This was an important find because, although CME’s were known at the time, they had until then been difficult to detect. She spent her career investigating and understanding the earth’s magnetic field and how it interacts with the sun’s radiation to produce those amazing green lights in the sky.
What is magnetism?
Magnetism is the force of attraction or repulsion between two magnetic objects. It is also a form of energy and can be very useful for technology and in our everyday lives. A magnet is made up of an iron core, or cobalt, nickel and lodestone. These metals are special because they can attract or repel other metals. You may ask why sometime magnets repel, and sometimes they attract? This is all to do with the poles of the magnet. Every magnet has a north and a south pole (Just like the Earth). When two north poles are brought together, they will repel each other. If a north and a south pole are brought together, they will attract.
Just like a magnet, the planet earth itself has a magnetic energy associated with it. If you hang a bar magnet from a retort stand on a piece of string, it will rotate and line up in a certain direction – this is the earth’s magnetic north pole. The same physics is used in a compass, which sailors and hikers use to know which direction they are going in.
How is the earth magnetic?
The best explanation we have for the earth’s magnetic field is that there is a very hot, liquid iron core at the very centre of our planet. As the planet rotates, current is generated in the molten core which produces electricity – which in turn produces a magnetic field. The magnetic field of the earth is relatively weak, the magnets on your fridge are stronger! But the earth’s magnetic field is still strong enough to interact with cosmic rays coming from the Sun, which produce the amazing colours in the sky we call auroras.