Question

If you have a very long and rigid pole and have an observer on each end, if one of them pushes the pole how soon will the other one feel it? Can this response time be shorter the time it would take light to travel the length of the pole?

Asked by: Dmitry Meerson

 Answer

The rigidity of any pole depends on the material from which it is made, but there is no material that is infinitely rigid. A push on one end of a pole only appears to be transmitted instantaneously to the other end because of its relatively short length compared to the speed of transmission. Each atom must influence its neighbor along the pole via electromagnetic force, which in turn is carried by (guess what?) 'light' photons!

So yes, the speed at which a push on one end of the rod travels to the other end is subject to the same universal speed limit, the speed of light, as any other physical phenomenon. Therefore, you could NOT use a 'rigid' pole to transmit signals faster than light to another observer.

Answered by: Paul Walorski, B.A. Physics, Part-time Physics Instructor

Search

Loading



Sponsors

USC University of Southern California Dornsife College Physics and Astronomy Department McMaster University Physics and Astronomy Department

Science Quote

'For the sake of persons of ... different types, scientific truth should be presented in different forms, and should be regarded as equally scientific, whether it appears in the robust form and the vivid coloring of a physical illustration, or in the tenuity and paleness of a symbolic expression.'

James Clerk Maxwell
(1831-1879)

Deal of the Day

Image of Shark Tooth Fossil in Matrix. Click on this image for more info. Shark Tooth Fossil in Matrix
Regular Price: $39.95
Today's Price: $15.00
Superb shark fossil specimen for the science classroom! Buy it now! Deal ends at midnight!

Top Selling

Here are our physics & astronomy bestsellers:
Mini Plasma Ball
Slide Making Kit
Top Secret - Spinning Top
Wood Grain Newtons Cradle
Deluxe 3D Mirascope
Solar Radiometer
Periscope
Solar Science 4M Kit
Ultimate Chemistry Set CHEM C3000
3D Magnetic Field Tube