My wife and I watched an amazing 2004 NOVA special from NetFlix last night called “Magnetic Storm.” We love watching these types of science specials from time to time. I knew a few things about magnetic fields as they apply to earth science, but learned several new things in this special too that are amazing. Prior to watching this, I understood:
- The earth’s molten core is responsible for the magnetic field that surrounds the earth.
- The interaction of our planet’s magnetic field with the solar wind gives rise to the aurora borealis / northern lights.
- Other planets, like Mars, have a colder core than the earth and therefore don’t have a magnetic field.
- The polarity of the earth’s magnetic field has “flipped” or reversed many times over the past millenia.
I learned in this episode, among other things, that:
- Scientists do not completely understand the process which gives rise to a planet’s magnetic field. They believe in addition to the hot molten core, the movement of the iron within the core is essential to the emergence of the “dynamo” which creates our planetary magnetic field.
- The magnetic field of the earth has been weakening precipitously in the past 300 years. Some scientists believe we are in the midst of another magnetic field polarity reversal, which is long overdue according to the geologic record.
- Evidence of past magnetic field reversals is found not only in volcanic rock from past lava flows, but also in ancient pottery which contains magnesium. When magnesium and other metals are liquified and then solidify again, their crystals align with the prevailing magnetic field of the earth and reveal both it’s direction and strength at that specific time.
- Scientists only recently discovered that Mars does not have a magnetic field. Meteor crater impact regions on Mars do NOT show expected levels of magnetism. If Mars had a magnetic field at the time the meteor crater impacts in question took place, some of the rock melted during the collision should have taken on magnetic properties during the cooling process. The rocks in these areas did NOT, which show that Mars didn’t have a magnetic field at that time.
- The discovery of past magnetic field pole reversals was quite controversial in the scientific community, and it took about fifty years before it was generally accepted that these reversals had happened many times and would recur in the future.
One of the reasons I love watching these types of NOVA specials so much is that the scientists who are interviewed are not hesitant to discuss the LIMITS of their own knowledge, and the limits of other scientists in their fields. They openly discuss their personal and professional knowledge boundaries. It is humbling to understand how many BIG issues we still don’t fully understand in science, According to this 2004 video, scientists have still not successfully created a dynamo in the lab which creates and sustains a magnetic field like our planet does. For more on this, read the relatively short WikiPedia article on “Dynamo Theory.”
Part of redefining education in the 21st century involves changing the perceived identity of the teacher and professor in the classroom, from being the sole fount or source of knowledge, to being an expert learner along with students who is a professional facilitator and knowledge architect. Educators must learn to structure and facilitate learning activities which permit learners (who are both “novices” and “experts” in their own right in different contexts) to access expert knowledge and resources via print as well as electronic tools as they build their own understandings and skills in different academic domains.
Check out the fantastic website for “Magnetic Storm” which accompanies this NOVA special. The gallery of auroras is one of many features worth exploring!
One of the predicted consequences of a magnetic field reversal on earth and a polarity reversal of our planet’s magnetosphere is the appearance of auroras in lower latitudes with greater frequency. I have only seen the northern lights once or twice when I was in Minnesota in the mid-1980s, and at that time they were pretty faint. I would love to see auroras at some point in my life, especially some which are as dramatic as those featured on this website. For more amazing photos of auroras, check out the Flickr group “Aurora (Borealis and Australis),” which has over 1000 contributed images from people all over the world.
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