The Cable to the Moon: Veritasium's Light Bulb Experiment in Low-Cost Miniature Form

TL;DR

This paper explores the delay in lighting a bulb in an extremely long circuit, using a miniature model to experimentally demonstrate the effects of signal propagation time over long wires.

Contribution

It provides an experimental setup and results for understanding signal delay in circuits with extremely long wires, illustrating the physics of light propagation in practical terms.

Findings

Signal delay matches the light travel time in the wires

Experimental results confirm theoretical predictions of delay

Educational demonstration of physics principles in circuit design

Abstract

In a popular YouTube video by the channel Veritasium, the following question is posed: Imagine you have a giant circuit consisting of a battery, a switch, a light bulb, and two wires which are each 300,000 km long. That is the distance that light travels in one second. So, they [the wires] would reach out halfway to the Moon and then come back to be connected to the light bulb, which is one meter away. Now the question is: After I close this switch, how long would it take for the light bulb to light up: Is it half a second, one second, two seconds, 1m/c or none of the above? As part of the Physics Specialist Camp 2022 in Seifhennersdorf -- a final event of the Saxon Physics Olympiad -- students from grades 9 and 10 built a miniature model consisting of a printed circuit board and two 10-meter cables to experimentally study the question. This article describes the experimental setup, presents some exemplary results, and explains them in detail. To enable reconstruction for educational purposes, the final PCB layout, as well as the supply sources and design considerations, are provided.