When I was a little kid about 7 years old, I read an article in a science fiction magazine that showed how to build your own UFO detector. The device is a crude but fairly sensitive magnetometer, it looked interesting so I built one. The theory is that an alien UFO would travel with some sort of advanced electromagnetic propulsion, it would disturb the magnetic field and the sensor would detect it. It’s a simple trembler switch, you can make it yourself with some wire, a magnet, and an doorbell. I was surprised to discover it really works!
The entire switch is about 6 inches tall, made from 3 pieces of uninsulated solid copper wire. The illustration shows the general layout of the switch, with the two sides of the circuit indicated in blue and red. It’s a simple pendulum hanging from a hook, and down through an open loop. When the pendulum swings, it will hit the loop and complete the circuit. The pendulum’s counterweight is a small magnet, I used a cylindrical refrigerator magnet and wrapped the end of the copper wire around it. The magnet isn’t part of the electrical circuit, but when a large magnetic field moves by, it will attract the counterweight and cause the pendulum to swing. You can verify this by waving a magnet near the sensor, the pendulum will swing wildly, and will be influenced by a moving magnet even at a fair distance.
I made the hook about 6 inches high and the lower loop about 1/2 inch in diameter, and put it under a glass jar so it wouldn’t be triggered by drafts. Connect the bottom end of the loop to one wire of the doorbell, connect bottom of the hook to the other wire, hang the pendulum on the hook, and your UFO detector is ready for action.
You can increase the sensitivity of the switch in two ways; you can increase the length of the pendulum, or decrease the size of the loop. You could actually make this several feet tall, and it would be so sensitive it could detect nearby electric motors and TVs, and it would be very sensitive to vibration. But we’re trying to detect huge metal spaceships so we should start fairly small. And it turns out that even a small detector is very sensitive.
I left my detector running in my bedroom at night, of course aliens would come under cover of darkness. I waited for the alarm signal night after night. I decided to decrease the size of the loop a bit. I also improved the pendulum by substituting a little bar magnet, and aligning it with magnetic north. Then one night as I was sleeping, the UFO detector rang!
I rushed to my window but I could see nothing. I ran barefoot out into the yard and searched the sky. I could hear the motors approaching, it was a small aircraft flying at low altitude, a propeller aircraft from the local airport, darn it! I was disappointed, but I’d successfully detected a flying object, even if if it wasn’t unidentified.
I decided to make the device a little more sensitive so I could detect more distant UFOs. As I tuned the sensor, it became so sensitive I could detect high altitude jet airliners, and even large trucks driving down the street! It appears that any large mass of metal moving through earth’s magnetic field can trigger the alarm. I got a quite a few aircraft detections, but I never saw any alien spaceships. Eventually my Dad got mad at me for constantly waking up in the middle of the night and running through the house, so he made me turn off my UFO detector forever.
Update: I poked around the web and found other descriptions of the UFO detector. Apparently it was a popular device during the 1960s, and quite a few people made these sensors in various designs. I wonder who invented it?