Simple setup answers complex questions about the physics of solids

Thought experiments can be extremely powerful; after all, pretty much all that [Einstein] came to was based on thought experiments. But when a thought experiment turns into a real experiment, it’s when things can get really interesting and where unexpected insights emerge.

take [AlphaPhoenix]’s simple question: “Are solid objects really solid?” At first glance, this seems like a silly and trivial question, but the thought experiment he presents reveals more. He claims that pushing on one end of a solid metal rod a meter or so in length will result in movement at the other end of the rod virtually instantaneously. But what if we scale that bar significantly up – for example, to a light second in length. Is a displacement at one end of the robbery immediately visible at the other end? It’s a bit of an insanity.

To answer the question, [AlphaPhoneix] set up a simple experiment with the aforementioned steel bar – the shorter one, of course. The test setup was pretty smart: a piezoelectric sensor at one end of the rod and a hammer coupled to a battery at the other end to sense when the hammer came in contact with the rod. Both sensors were connected to an oscilloscope to set up to capture the pulses and measure the time. It turned out that the test setup was quite a challenge to get right, and troubleshooting the rig took him down into a rabbit hole that was as interesting as answering the original question. We do not want to ruin the ending, but suffice it to say that we were glad that our first instinct proved to be correct, even if it was for the wrong reasons.

If you have not checked out [AlphaPhoenix] anyway you really should. With a doctorate in materials science, he has an interesting view on things like calculating pi using raindrops or keeping “ultra” in ultra-high vacuum.

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