Monthly Archives: July 2016

Lightning Electricity in the Palm of Your Hand

During a thunderstorm, lightning often appears to flash instantaneously from cloud to ground, but there’s much more going on than meets the eye! Friction between air currents causes a buildup of negative charge in the lower parts of the clouds. Like charges repel each other, so the excess negatives begin developing an escape route. Strong, invisible electric “feelers”, called stepped leaders, branch downwards through the air.


Lightning over Norman, Oklahoma, 1978. Image credit: C. Clark, NOAA

As stepped leaders inch closer to Earth’s surface, they leave a conducting path in their wake. Their electromagnetic field also NOAAlightning2begins affecting electrical phenomena on the ground. Positive streamers of charge reach up towards the negative stepped leaders. When streamers and stepped leaders meet, an ionized bridge is completed from clouds to ground.

Given an unbroken conducting path to follow, the negative charges built up along the stepped leader flow rapidly into the ground. The lowest charges are the first to dissipate, clearing the way for charges higher up to follow downwards along the same channel. This upward propagation of charge movement emits visible light, as shown in the NOAA gif at left. Stepped leaders emit light, too, but very faintly. Since the whole process happens incredibly quickly, our view is dominated by the brighter return stroke.


Ever been told not to go swimming in a thunderstorm? That’s because water is a great conductor! If lightning struck the water you were swimming in, a massive shock would be efficiently transferred to your body. In this video, the Oudin coil generates a buildup of negative charge (concentrated on the metal tip of the device). When we bring the excess charge near water, artificial lightning arcs both to and through the puddles!

Written By: Caela Barry

Geometric Bubbles

Bubble formation is governed by one simple rule: minimize surface area. Free-floating bubbles are spherical because that’s the most efficient way to enclose a given volume of air. Give a soap film edges to stretch between, and its behavior gets interesting!


Try building geometric bubble frames out of drinking straws and pipe cleaners. Create corner connections by bending pipe cleaners into small star shapes. A star connector should have one point for each edge you’d like to attach to it. Insert the points of the stars into the ends of drinking straw segments to assemble your apparatus. This method is great for outlining prisms and platonic solids.


Curved shapes are fun to experiment with, too! Bend wire into a helix, cylinder, or drum shape for a different take on bubble geometry. How many kinds of frames can you come up with?

Written By: Caela Barry


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