By Scott Hamilton

Did you ever wonder why a magnetic compass works? They are actually a very simple design and you can actually make one with a needle, a magnet, a fork and a bowl of water. The tricky part is getting the needle to float on the water. First lay the needle on the magnet; this will magnetize the needle. If your magnet happens to be labeled, you should set the point of the needle on the north end of the magnet. After a few minutes, set the needle on the fork and slowly lower the fork into the bowl of water. If you do this just right you will leave the needle floating on the water. The needle will then align itself with the Earth’s magnetic field, pointing North or South, depending on which way the needle was magnetized.

Now that you know how to make a simple compass, you need to learn why it works. The earth contains a very large amount of iron in the core, and this iron has become magnetized over thousands of years of exposure to electromagnetic waves from the Sun. The magnetic field of the Earth that makes the compass work is not as constant as we might believe, in fact a magnetic compass can be off by as much as 1200 miles from pointing at true North at any given time of the year. On average it is about 300 miles off of true North.

Magnetic North moves because of the interaction of Earth’s magnetic field with the magnetic fields of the Sun and other planets in the solar system. Just like if you place two magnets near each other on a table they change the shape of each other’s magnetic field, the planets and Sun impact each other in the same way. If you want to see this in action, you can use a compass and a set of magnets; the compass needle will align to the magnetic field of the magnets. As you add more magnets to the table pointing in different directions around the compass, the needle will change directions.

There is one other thing most people don’t know about the Earth’s magnetic field, and that is the fact that it is constantly changing in strength. A recent archaeological discovery in Mesopotamia helped to not only confirm this fluctuation, but pinpoint the time frame of one of the strongest fields in history. We have known from studying natural rock formations that a surge in electromagnetic energy occurred sometime between 1050 and 550 BC from clues found in artifacts from Azores, Bulgaria and China. This event is known as the “Levantine Iron Age geomagnetic Anomaly.” However this latest discovery allowed scientists to pinpoint this 500-year range down to the time of King Iakun-Diri (610-590 BC).

The same group of scientist decided to also study some of the bricks baked during the reign of King Nebuchadnezzar II, also from 604-562 BC, and form a sampling of 32 stones, five of which bore the mark of King Nebuchadnezzar. Proving a date that they were placed resulted in showing the same high strength magnetic field to be present when the bricks were formed, allowing them to narrow the date of the anomaly. What to me is a little more interesting is that we can use the measurement of the magnetic properties of man-made materials to pinpoint the dates of other artifacts from the same time period, and it appears to be more accurate than current carbon dating methods.

So exactly how this method works gets a little complicated to explain, but basically when material containing even small traces of iron is heated, the iron particles align with the earth’s magnetic field. The stronger the magnetic field, the tighter the alignment of the particles becomes. There are a lot of other factors involved, like the amount of time the brick, or other clay object was exposed to heat, and the level of the heat exposure, but all of that is easy to determine because we know how those factors impact the strength of the final clay product. It is the difference between having extremely hard clay objects like porcelain and more fragile objects like clay pots and bricks. The exciting finding was that it was easy to spot a tighter alignment in all the clay artifacts that were studied from the period of the “Levantine Iron Age” as compared to other periods of time.

Interestingly enough we can utilize this method to both create a history of the Earth’s magnetic field strength over time and accurately date artifacts from unknown time periods based on the data gathered from artifacts with known dates. This makes the magnetic dating process valuable to both science and archaeology and creates a tight link between the science and the history, but it also makes me wonder if there is a connection between man’s first use of Iron in the Levantine Iron Age and the increase in the magnetic field in artifacts. Is it possible that people in the Levantine Iron age were producing electricity and utilizing it in the brick making process, creating these strong magnetic fields in the bricks and not from natural sources? It’s definitely an interesting theory.

Until next week, stay safe and learn something new.

Scott Hamilton is an Expert in Emerging Technologies at ATOS and can be reached with questions and comments via email to shamilton@techshepherd.org or through his website at https://www.techshepherd.org.

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