Full Breakdown
The Physics of a Hypothetical Pole Between England and France
11/28/2025, 2:57:09 AM
Understanding the Core Question
A recent inquiry on Reddit posed an intriguing physics question: if a metal pole stretched from the English coast to the French coast, would pulling one end cause the other end to move instantly? This question challenges our understanding of physical laws, particularly the speed of sound and the speed of light.
The Mechanics of Solid Materials
When one end of a metal pole is pulled, the movement does not propagate instantaneously. Instead, the first layer of atoms in the pole pushes against the next layer, creating a wave that travels through the material. This wave moves at the speed of sound specific to that medium, which is significantly slower than the speed of light. For example, in steel, the speed of sound is approximately 5,130 meters per second.
Experimental Evidence
Material scientist Brian Haidet conducted an experiment to demonstrate this delay. By striking one end of a pole and measuring the time it took for the signal to travel to the other end, he confirmed that the delay matched the expected speed of sound in steel. This empirical evidence illustrates that the movement of the pole's end is not instantaneous but rather takes a measurable amount of time.
Calculating the Delay
To quantify the delay, consider the shortest distance between England and France, which is about 33 kilometers (20 miles). Using the speed of sound in steel, the time it would take for the other end of the pole to respond to a pull is calculated as follows: dividing 33,000 meters by 5,130 meters per second yields approximately 6.43 seconds. This delay, while relatively quick, is still significantly longer than the near-instantaneous travel time of light, which would cover the same distance in just 0.00011 seconds.
Implications of the Findings
These findings highlight a fundamental principle of physics: no information or physical effect can travel faster than the speed of light, which is 299,792,458 meters per second. This principle is crucial in understanding the limitations of physical interactions in solid materials.
Criticism & Opposition
Some may argue that our intuitive understanding of solid objects leads to misconceptions about their behavior under stress. The notion that a solid object can transmit force instantaneously is a common misunderstanding, emphasizing the need for educational outreach in physics.
Verbatim Quotes
- “) guess you might have is that when you yank on one end of the pole, the other end would move at the speed of light.” — Brian Haidet, Material Scientist
- “A little ripple in the density of a piece of steel creates much bigger forces than a similar percentage ripple in the density of some air.” — University of Illinois Urbana-Champaign
Conclusion
The inquiry into the behavior of a hypothetical pole between England and France serves as a fascinating exploration of fundamental physics principles. It illustrates the importance of understanding the mechanics of materials and the limits imposed by the laws of physics on the transmission of force and information.
