Archive for the 'Relativity' category

Right-wing refutations of relativity really, really wrong!

Aug 09 2010 Published by under ... the Hell?, Relativity

Back when I first started my blog, I spent a lot more time dealing with crazy people who are convinced that Einstein's theories of relativity are wrong (see here, here and here).  More recently, I haven't spent a lot of time on the crazy train, but I have been meaning to get back to my long-neglected series of posts explaining relativity.

Enter Conservapedia, the right-wing version of Wikipedia intended to combat the liberal bias in reality!  Over the past day, Twitter has been abuzz with tweets¹ on the Conservapedia page on "Counterexamples to relativity", provides a list of 24 "points" that attempt to show the weakness of Einstein's crazy ideas!

In my mind, perhaps the most despicable sort of denialism or crankery, however, is that which is based on some sort of political or religious ideology.  This is clearly what is going on here, and the author relies on a familiar form of rhetorical trickery known as the "Gish Gallop": throw as many claims out there as possible, regardless of their validity, with the realization that most people will be swayed by the amount of "evidence", and not look too closely at the details.

Looking at the "evidence", it is clear that there isn't a single point made that isn't misleading, incoherent, or simply dishonest.  A person reading the Conservapedia post will be measurably more ignorant afterwards, and I get the distinct impression that this is what the author intended.

But never fear, dear reader!  I'm here to go through the list of some of the most entertaining assertions, and explain why they're nonsense. Why bother, you ask?  For one thing, entertainment.  For another, there's always a chance that someone may come across the Conservapedia entry and look for some sort of counterbalance... someone should write one!

One caveat: I can't guarantee that the list I present will match the list on the Conservapedia page.  I saved the tweeted list, but after all the internet attention, it was reduced to four points.  Soon afterwards,  it reverted to the original list again.  There's no guarantee that it will remain in its current form, though...

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Lord Rayleigh vs. the Aether! (1902)

Jul 09 2009 Published by under History of science, Optics, Relativity

(Note: This is an attempt to get myself rolling on my long-ignored series of posts explaining Einstein's theories of relativity.  It's also a really cool experiment in the history of science.)

One of the most fascinating aspects of 19th century physics is that many remarkable ideas and ingenious experiments were motivated by a physical hypothesis which we now know to be incorrect: namely, the aether.   When light was demonstrated to have wavelike properties in the early 1800s, it was natural to reason that, like other types of waves, light must result from the excitation of some medium:  after all, water waves arise from the oscillations of water, sound waves arise from the oscillation of air, and string vibrations are of course the oscillations of string.  The hypothetical medium which carries light vibrations was dubbed the "aether", due to its unknown, "aetherial" nature.

A lot of scientists speculated on the physical properties of the aether, and sometimes this speculation produced lasting results in other fields; for instance, Earnshaw's theorem was originally conceived to try and describe the forces involved in the aether's oscillation.

By the late 1800s, however, more and more research cast doubt on the very existence of the aether, notably the Michelson-Morley experiment (to be discussed below).  In response, theoreticians produced more and more "patches" to the aether theory, until at last Einstein published his special theory of relativity, which eliminated the need for an aether and in fact suggested that the idea of an aether was incompatible with the experimental evidence.

Before this happened, however, at least one brilliant researcher took up the challenge of testing one of the "patches" to the aether.  Lord Rayleigh (1842-1919), distinguished physicist and eventual Nobel Prize winner, conceived of and carried out a very clever optical experiment to see whether objects shrink in the direction of motion, a phenomenon known as length contraction.

As is often the case, even though the experiment was unsuccessful, we can still learn many useful lessons about the workings of science from it!

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Einstein vs. Whittaker, with Born in the middle

Jul 15 2008 Published by under History of science, Physics, Relativity

My former thesis advisor is the greatest! I recently helped him update an electronic compilation of his collected papers, but refused any payment for my services. He ignored me and sent me a copy of The Born-Einstein Letters, a compilation of correspondence between Albert Einstein and Max Born between 1916 and 1955.

This gives me an opportunity/excuse to discuss one of my favorite exchanges between the pair, concerning Sir Edmund Whittaker's book A History of the Theories of Aether and Electricity.

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What a drag: Arago's Experiment (1810)

Jul 05 2008 Published by under History of science, Optics, Physics, Relativity

Note: This post is my contribution to the first-ever edition of The Giant's Shoulders, a new blog event compiling posts concerning classic science papers.

I've been meaning to get back to my series of posts on relativity, but things have gone slower than I expected because of my obsessive desire to truly understand the historical scientific issues that were prevalent at the time.

In the meantime, I've been thinking about an interesting, infrequently-discussed topic in special relativity: the behavior of light on propagation through moving matter. This question was inspired by a comment on Uncertain Principles some time ago. In fact, one of the earliest hints of special relativity came from an experiment performed by François Arago in 1810 on 'stellar aberration', nearly 100 years before Einstein's landmark 1905 paper! In this post I'll discuss Arago's experiment, its historical context, and the conclusions that were drawn from it.

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Relativity: Measuring the speed of light

Mar 21 2008 Published by under Optics, Physics, Relativity

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 \(c = 3\times 10^8 \) 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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Relativity: Newtonian relativity

Feb 19 2008 Published by under Physics, Relativity

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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The pre-history of Einstein's relativity

Feb 12 2008 Published by under Physics, Relativity

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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