Earth’s Magnetic Field

Earth's Magnetic Field
You might say that planet Earth is a very large magnet. We have mentioned before Earth’s magnetic field that is generated by the iron core. The movement of that molten iron generates a magnetic field surrounding our planet. We can see the effect of that field every time we use a compass to find directions.

What you may not realize is that there is also a magnetic field generated by the ocean. Salt water is a good conductor of electricity. Moving electric currents generate magnetic fields. Hans Christian Ørsted discovered that by accident in 1820 when he noticed that placing a compass near a wire carrying an electric current caused deflection of the compass needle.

Salt dissolved in the oceans’ water creates ions, which are electrically charged particles. The movement of ocean tides causes those charged particles to move. Electric current is electrically charged particles in motion. Since electric current generates a magnetic field, the ocean tides generate magnetic fields. Because the movement of ocean currents and tides is complex, the magnetic fields generated by the oceans are more complex than the big magnetic field of the Earth. They are also 20,000 times weaker than Earth’s main magnetic field making them harder to measure.

Today’s satellite technology allows us to map the oceans’ magnetic field. The European Space Agency used three satellites to create a network called “Swarm.” They used the data from those satellites to create a 3-D digital map of this little-known magnetic field. The research shows how the field changes over time. Although the oceans create a relatively small part of Earth’s magnetic field, they play an important role. Mapping this field also give scientists a better picture of how the oceans flow all the way down to the seabeds. That information gives us a better understanding of Earth’s climate.

Combined with the magnetic field produced by the molten core and rocks in Earth’s crust, we are protected by a “cocoon” surrounding our planet. You might say, “Protected from what?” Our Sun frequently erupts in solar storms releasing charged particles that escape into space. Many of those particles travel to the Earth. We call it “solar wind.” Without a protective magnetic shield, those particles would reach Earth’s surface disrupting power grids and aircraft navigation. More basic than that, they would damage human cells causing cancers and other health problems.

We don’t think it’s by chance that we have the protection of Earth’s magnetic field. We see this as one more evidence of the provision of God to make possible life on this planet.
–Roland Earnst © 2018

Earth’s Magnetic Reversals

Earth's Magnetic Reversals and Ancient Pottery
When I took my earth science students on our annual field trip to Lake Michigan, we did a “magnetism and history” exercise showing Earth’s magnetic reversals. We would go to the large sand dune known as “Old Baldy” (no, not named after me), cover a bar magnet with a white handkerchief, and stick it into the sand. The handkerchief would come out completely covered with little black needles of magnetite which is a magnetic iron oxide.

There was a nearby pool where the water was calm and where you could see the magnetic pieces with a pair of binoculars. They pretty much lined up in the same direction, and I showed the students that they were lined up with a compass needle. We would then dig down several feet into the sand to a layer of mud where the magnetite pieces pointed every which way. I would ask my students to tell me why that would be. Most of them said that the Earth must have lost its magnetic field at the time when that mud was deposited. I then told them if we dug down deeper we would find the magnetite pieces lined up again, but in the opposite direction. The point was obvious–the magnetic field of the Earth had flipped.

In reality, there are several other possible causes for the scrambled magnetite pieces, but the magnetic reversal did happen. In the mid-ocean ridge of the Atlantic, lava flows have trapped the magnetite. The process is called “thermoremanent magnetization.” Because the lava flows happened multiple times, they show a picture of the history of the Earth’s magnetic reversals. These lava flows have recorded over a dozen “flips” in the magnetic field of Earth.

Archaeologist Dr. Erez Ben-Yosef of Tel Aviv University has led studies of the history of magnetic changes on the Earth. Ancient pottery has tiny magnetic minerals that were aligned with the Earth’s magnetic field when the pottery was fired in the kiln. The stronger the magnetic field, the greater the alignment of the magnetic particles. From the late eighth to the second century B.C., ceramic jars bearing the impressions of royal stamps were manufactured in and around Jerusalem. Scientists have studied handles from 67 pieces of pottery, and they have found that the magnetic field of the Earth has gone through periodic rises and falls throughout history. The mapping of the magnetic fields gives a record of history, with small changes producing a pattern that improves dating techniques by a huge factor.

What causes the Earth’s magnetic field is still not completely understood, and the magnetic reversals are even more of a mystery. By measuring the magnetic particles in the pottery, scientists can date the pottery very accurately. This dating method can answer many questions about ancient kings and kingdoms including the major figures in the history of Israel.

For more on this go to https://www.haaretz.com/archaeology/1.771427
–John N. Clayton © 2018