A hundred years ago this month, the October 1921 issue of Popular Science showed this signaling device for use by the military. It provided a level of security, because its light beam was visible only over a small area. It’s a very simple idea–it consists of a telescope with a flashlight bulb mounted inside at the focal point. It was easily aimed by looking through the telescope. The bulb’s filament was visible, and it was simply a matter of lining it up so that was visible over the spot where you wanted your signal seen.

Students looking for a science fair project could easily recreate this.  All that’s needed is a toy telescope like the one shown here.  It can be carefully disassembled and the bulb place inside.  You can use the bulb from an old flashlight, or buy the bulb separately.  For this project an old-fashioned incandescent bulb will work better than an LED.

You’ll also need some hookup wire and batteries.  While not absolutely necessary, a battery holder will make the job a lot easier.  Normally, for a science project involving light bulbs, it’s most convenient to get a socket for the bulb.  However, in this case, the socket might not fit.  Therefore, the best option would be to solder the wires directly to the bulb.  A soldering iron, complete with solder and everything else you need, is surprisingly inexpensive.

To send Morse code, you’ll also need a small pushbutton switch.

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If Junior likes playing with matches, and the due date for the science fair project is rapidly approaching, then the perfect project can be found in the September 1941 issue of Popular Science. This experiment answers the question, “which surface provides the least wind resistance,” and it turns out the answer is the airfoil.

Junior can easily demonstrate this with the self-explanatory experiment shown here. With the piece of cardboard flat, drag is produced, and when you blow toward the flame, it actually moves back toward you. But when the card is bent into a teardrop shape, scientifically known as an airfoil, then the air blows the flame away.

If Junior just remembered that the science fair project is due tomorrow, and it hasn’t even been started, you’ve come to the right place. This last-minute experiment from 80 years ago will prove an important scientific principle, you have everything you need around the house, and the teacher will be suitably impressed at Junior’s ingenuity. The teacher needn’t suspect that the project was put off until the last minute.

This project answers the simple question, “what kind of clothing keeps you cooler?” It turns out that it’s light colored clothing. All you need is a couple of pieces of cardboard, a table lamp, and a little bit of wax. If you can’t find any wax around the house, you can always go to the closest all-night supermarket and buy a package of birthday candles.

While you are out buying the wax, Junior should cut out the two small human figures, one from a piece of white cardboard, and one from a piece of black cardboard. If you can’t find any black cardboard, just make the both out of white cardboard and color one with a black magic marker. The arms should be made separately, and the arm is attached with a small drop of wax. If Junior is not old enough to play with matches, then an adult should light the candle and place a drop of wax in the correct spot.

Then, you stand up both of the figures and shine a lamp on them. You want the hottest lamp you can find, so don’t mess around with energy-efficient bulbs.

Eventually, one of the figures will get hot enough that its arm will fall off. Unless the laws of physics have changed in the last 80 years (hint: they haven’t), it will be the one in dark clothing. Junior has proven that you will be cooler if you wear light clothing on a hot day.

The experiment appeared in the August 1941 issue of Popular Science.

If Junior just announced that the science fair project is due tomorrow, but the project hasn’t even been started, there’s no need to panic. Thanks to these simple projects from 85 years ago, it’s still possible to get an A on the assignment, and the teacher will assume that many weeks of planning went into the project.

Shown above is a simple method of determining the center of gravity (or, since the teacher will prefer the more scientifically accurate term, the center of mass) of an object. Cardboard is used, but any similar substance of uniform thickness will work fine. After the pattern is cut out, the design is hung by one edge. A plum line (which is just a piece of string, with a weight on one end) is hung from the same point, and it is traced on the item. Then, it’s hung from another edge. Where the two lines intersect, that is the center of mass.

The other project, shown below, gives a visual indication of sound waves. All that’s needed is a couple of cardboard tubes, a balloon, and some sand. Both projects appeared in the August 1936 issue of Popular Science.

110 years ago, a young John Long of Leechburg, PA, sent in this self-explanatory idea for building an alarm clock to the “Young Edisons” department of Popular Electricity magazine.

The magazine carried the feature of letters from readers of its Junior Department. Letters were to accurately and briefly describe experiences in the making and operation of electrical devices and the performance of electrical experiments. The magazine asked readers, “see how good an ‘engineering report’ you can make of your investigations.”

Young Mr. Long constructed this alarm switch with a battery, door bell, and pocket watch.

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If Junior is looking for an interesting demonstration for the first post-COVID science fair, he or she can’t go wrong with this illustration of how human reflexes work.  If you touch a hot stove, your body needs to react before the brain kicks in.  Therefore, you are hardwired to jerk your hand away.

This demonstration illustrates the principle.  A flame is brought close to a simulated human hand, but as soon as it comes into contact with the simulated nerve, the solenoid energizes and jerks the hand away.

The idea appeared 80 years ago this month in the June 1941 issue of Popular Science.  For the young scientist wishing to duplicate the project, all of the parts are readily available on Amazon:  This switch will kick in at 40 degrees Celsius, an uncomfortably warm, but not dangerous temperature.  This 3-volt solenoid will reliably move the hand.  And there’s no need for the old-school dry cell batteries shown above.  Alkaline D cells will work very well, especially if you have a battery holder for them.   And while Junior can make the hand out of cardboard, he or she will be virtually guaranteed the blue ribbon with a realistic looking plastic hand.

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