The invisible field that protects our planet | Looking up - Oroville Mercury Register

With our discussion of auroras last week, we also touched on the magnetic field that protects the Earth from the sun’s most punishing particles. Since it always seems like I have more that I want to say than fits into my column each week, let’s take a closer look at our magnetic field and some of its properties.

Scientists believe that the Earth generates a magnetic field thanks to our core, which we think is solid iron but is surrounded by a metalic, liquid outer core that sloshes around it. This movement of molten iron around the solid core creates electrical currents deep within the Earth, which generates our magnetic field.

Related to the magnetic field are our magnetic north and south poles. If you take a compass, our magnetic field is what causes the magnet in that compass to always point north. But over time, our magnetic field has frequently switched polarity, turning 180 degrees and making that compass read south as north and north as south. The last time this happened in a significant event was about 780,000 years ago, though this flip has happened hundreds of times since the formation of our planet, to little fanfare.

Although doomsday theorists often harp on what a dramatic and deadly shift this could be, scientists have studied fossil records from times of great shifts and found no significant effects on the plant and animal life alive at that time. It’s also sometimes said that the change in polarity could strip us of our magnetic field and leave the Earth defenseless against the solar radiation, but there’s no proof that this ever happened in the past reversals either.

Additionally, our poles are already on the move. We were first able to measure the exact location of the magnetic north pole in the early 19th century, and it’s been moving steadily northward ever since. Current estimations have it moving approximately 40 miles a year, much faster than it moved back in the 19th century.

Our magnetic field twists and turns in shape as it is buffeted by those particles from the sun, often leaving it in tight half-circles from the north to south pole. On the sun side, it’s squished tightly against our planet, especially in times of extreme solar activity, and expanded far outward on the night side where it’s not under attack.

Most of the other planets in our solar system also have their own magnetic fields, although Earth’s is the strongest of the terrestrial (rocky surface) worlds. It may be no coincidence that life evolved on this particular planet; scientists believe that the magnetic field plays a large part in protecting us from radiation from the sun and other cosmic particles, and it also stops the solar wind from blowing away our atmosphere. This is pretty much exactly what happened to the smaller planet Mars, whose core may have solidified over time, leaving it with a very weak magnetic field and little protection.

This also means that other planets in our solar system can also have auroras in their upper atmospheres when the timing is right, thanks to those magnetic fields. The next generations of astronauts may be seeing auroras on Jupiter before they see any Earth-bound beauties!

LOOKING UP THIS WEEK: In the predawn mornings, you’ll find a bright Venus low in the east. Saturn and Jupiter will be in the south each morning, with a brighter Jupiter slightly to the right. Mars still graces the evening sky in the west. The moon is currently a waning gibbous and will be third quarter on Sunday.

Marisa Stoller can be reached at mcorley@norcaldesigncenter.com or on Twitter @MarisaStoller

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