Pulling Out All the (F)Stops

I remember when I was about five my parents took me to the Denver Natural History Museum, which was doing an exhibit, aimed at kids, based on superheros. One of the set-ups was a screen which showed how quickly various animals– and superheros, of course– could run. When you pushed “start,” you could run along side them, and see how you stacked up. The machine also had a setting for “light,” and after trying it out, I remember being a little skeptical that anything was moving at all. Sure, it was one thing to realize I couldn’t keep up with Flash Gordon, or even a plain old Cheetah. But was the light really travelling? Or was it just showing up instantaneously at the finish as soon as I pressed the button? I was so astonished by the thought that light actually took time to travel that when I got home, I tried to repeat the ‘experiment’ to get my head around it: I stood by the front door with a flashlight, aimed the flashlight at the opposite wall, then turned it on, dropped it, and ran as quickly as I could to see if I could ever “beat” it to the end of the hallway. Sorry, Mom and Dad: I’m pretty sure I broke at least one of our flashlights that way. 

As you can imagine, I never did get my “proof” that photons have to travel at a finite speed just like everything else in the universe. As I grew up, and light became less mysterious, the idea became less difficult to grasp. Still, some small part of me (the part that still likes superheros, I assume) has never quite come to terms with the idea as anything other than a mathematical abstraction. Or, I should say, HADN’T come to terms with it. Until today.

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