It's essentially linkbait spam. Just google 'ladder paradox' or 'barn-pole paradox' for a zillion detailed, often illustrated explanations. "Relativity's greate

It's essentially linkbait spam. Just google 'ladder paradox' or 'barn-pole paradox' for a zillion detailed, often illustrated explanations. "Relativity's greatest thought experiment" itself is a tip off. Says who? Einstein and popularizers like, say, Carl Sagan were fond of "[...] a paradox upon which I had already hit at the age of sixteen: If I pursue a beam of light with the velocity c (velocity of light in a vacuum), I should observe such a beam of light as an electromagnetic field at rest though spatially oscillating. There seems to be no such thing, however, neither on the basis of experience nor according to Maxwell's equations. [...]" You can also make a reasonable argument that this is relativity's greatest thought experiment: http://physics.syr.edu/courses/modules/LIGHTCONE/galileo.html http://physics.syr.edu/courses/modules/LIGHTCONE/galileo.htm... Edit: In an internet long past, when it was small enough to have such a thing as a physics FAQ, this was among them. http://www.faqs.org/faqs/physics-faq/part4/ http://www.faqs.org/faqs/physics-faq/part4/ The first chapter of the referenced Taylor & Wheeler 'Spacetime Physics' can be found here: http://www.eftaylor.com/download.html http://www.eftaylor.com/download.html