Barber's pole - appear faster than light?

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SUMMARY

The discussion centers on the theoretical concept of a massless barber's pole and whether the line appearing to travel up its side can exceed the speed of light. Participants agree that while the line's apparent speed can exceed the speed of light, no physical part of the pole or any information is transmitted faster than light, adhering to the laws of relativity. The analogy of a searchlight sweeping across a distance and the beam of a flashlight pointing from the Moon to Ceres illustrates this phenomenon, emphasizing that these are not real objects moving faster than light but rather perceived motions.

PREREQUISITES
  • Understanding of Einstein's theory of relativity
  • Familiarity with the concept of superluminal speed
  • Basic knowledge of light propagation and its limitations
  • Concept of massless objects in theoretical physics
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  • Explore Einstein's theory of relativity and its implications on speed limits
  • Research the concept of superluminal motion in theoretical physics
  • Investigate the properties of massless particles and their behavior
  • Learn about the effects of light speed in various mediums and contexts
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The discussion is beneficial for physicists, students of theoretical physics, and anyone interested in the implications of relativity and the nature of light speed in various scenarios.

kyle1320
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Hi, so imagine this: You have (for this theoretical situation) an entirely massless barber's pole. When it spins, the speed of the of the circumference of the pole is less than the speed the line appears to travel up (or down) the side of the barber's pole. If you were to spin the pole, could the line traveling up the pole appear to go faster than light, even though no physical part of the pole is traveling faster? Disregarding red / blue shift.
 
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Welcome to PF, Kyle. Nothing physical is moving faster than c. It's the same idea as the spot of a searchlight sweeping at superluminal speed. The law of relativity states that no information can be transmitted at or above c; that is not violated by the circumstance in question.
 
kyle1320 said:
could the line traveling up the pole appear to go faster than light, even though no physical part of the pole is traveling faster?
It could. Just as if I pointed a flashlight at the Moon, then whipped it around to point it at Ceres.

The "beam" gets from Moon to Ceres - a distance of hunderds of millions of miles - in a fraction of a second.

Of course, the beam is no more a real thing than the imaginary line you attribute to points on the barber pole.
 

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