Earlier this summer, in the name of physics research, I was away in the distant lands of Cornell University. It’s a place that harbors more grass, flowers, trees, and cows than MIT can ever hope to accommodate. However, the natural beauty of Cornell’s campus was not enough to mask a certain flaw in its design: There was no Cornellian analogue to our Infinite Corridor. With few indoor routes to take to work, the weather became a lot easier to notice—and experience.
For some time, it would rain every day at Cornell, and in the most temperamental manner too. I quickly learned to always arm myself with an umbrella when confronting the outdoors. One moment of sunshine could quickly transform into another moment of heavy showers. No chances could ever be taken.
The most memorable weather anomaly occurred on a day that began deceivingly with bright sunshine and oppressing heat. But when late afternoon arrived, the sun retreated behind dark thunderclouds. A storm had arrived. The thunderstorm pounded the area with heavy rain, smashing raindrops relentlessly against the lone window in my lab. At least I brought an umbrella to work, I thought to myself, as the window was illuminated by a flash of lightning, the visual fingerprint of several lightning bolts each carrying over ten billion billion electrons worth of charge across the skies. That day’s storm was fierce and long, and it produced one particularly striking instance of lightning.
It began, like all other lightning, as an electrical discharge from a thundercloud. As it burst through the atmosphere, it heated the air so quickly that the air expanded with extraordinary speed, rapidly enough to break the sound barrier, creating a monstrous thunderclap—BOOM! Most lightning stays within the sky, but this streak was ground-bound.
Lightning does not gamble with where it strikes. Instead, it establishes a path of least resistance. For a ground hit, this tends to end with a tall object. Cornell’s hilly landscape was dotted with numerous towering trees, all prime targets for a lightning strike.
Nature is ironic and cruel. It gives trees enough branches and leaves to be natural umbrellas, but also enough height to be natural lightning rods. In short: trees aren’t exactly your friends during thunderstorms. Lightning can turn trees into wooden bombs. Such was the fate of the tree that I witnessed.
When lightning struck, electrical current swept through the tree to complete the strike, but the current was channeled not through the wood but through a better conductor within the wood: tree sap. The fearsome power of lightning instantaneously boiled the tree sap, which expanded violently and explosively, splitting the tree down its side and expelling chunks of splintered wood with incredible force.
At the time of the strike, I was still tucked away in lab half a mile away, unaware of the dramatic event and the frightening explosion that accompanied it. All I knew was that it was still raining, and therefore I was still very glad that I brought an umbrella since it was almost time to leave work. Shortly, I left the lab with two other interns. As we headed through sheets of rain and down a path towards the destroyed tree, all three of us saw the lightning’s damage and did a double take. We paused, taken aback by the awe-inspiring sight. None of us had ever seen a lightning-struck tree before. However, we had no desire to stick around for too long amidst the downpour. We shuffled forward, through the rain and past the tree.
As we walked away, I resolved to come back later to take pictures. I did, but only after the weather had returned to a sunny state. With my camera, I walked up the hill to the site of the lightning strike. For a moment, I could only stare at the frightening damage that nature afflicted. There stood the tree, slightly charred, horribly splintered, and utterly defeated. The sight was breathtaking.