Skulls in the Stars

When I was an undergraduate, one of my professors told the following funny (and probably apocryphal) anecdote (recalled from memory):

A court case was being tried in New Mexico. A group of pornographers were charged with smuggling pornography from Mexico by projecting it across the border to a camera. The defense argued that nothing physical was transported, and in the end the argument boiled down to this: if light moved at a finite speed, the films were being transported; if it moved at infinite speed, the defense was correct. A physicist was brought in to discuss the speed of light but, after a number of figures were presented, the judge interrupted. “When I put my hands over my eyes, the light stops coming immediately, and when I move my hands, it reappears instantly. The speed of light is infinite - the defendants are not guilty!”

The reason I suspect this story is apocryphal is that science has accepted that the speed of light is finite - albeit very large - for centuries. The value, usually denoted c, is approximately meters/second, or 186,282 miles/second. In fact, as we will see in later posts, light is the fastest thing in the universe. The topics we address in this post: a brief history of measuring the speed of light, and how these measurements led inexorably to Einstein’s special theory of relativity.

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In the first post on Einstein’s relativity, we discussed the discoveries and theories which served as the precursors to Einstein’s work. The most significant of these is Newton’s own version of relativity, now dubbed ‘Newtonian relativity’. Before we continue a discussion of the speed of light and how it relates to Einstein’s work, it will be useful to go into a little more detail about Newtonian relativity and conclusions which can be drawn from it.

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I’m planning to do a long-term series of posts on Einstein’s relativity, starting with the special theory and progressing to the general theory (if you don’t know what the difference is, that’s okay, ’cause I’m gonna explain it all, eventually).

Einstein’s theories of relativity are certainly the among most elegant of all of physics. Incredibly deep and counterintuitive consequences can be derived from the statement of a small number of simple postulates, and general features of the special theory of relativity are accessible to anyone who has some familiarity with algebraic manipulation.

But no theory is created ‘in a vacuum’ (pun intended), and Einstein’s is no exception. Relativity has its roots in the very beginnings of what we now call physics, so we begin our discussion with a short introduction to the events and observations that led up to Einstein’s magnificent theories. This post will be pretty much bereft of math; later posts will include algebraic operations as needed.

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