Category Archives: Relativity

How much does a photon weigh?

A couple of weeks ago, after a glass of wine, I did a twitter “ask me anything” about optics and light which resulted in the question that is the title of this post.  I took a rough twitter stab at it … Continue reading

Posted in Physics, Relativity | 21 Comments

Relativity: Ten minutes to Alpha Centauri?

Einstein’s special theory of relativity is arguably the most amazing physical theory ever conceived.  It utterly transformed our view of the universe, completely eradicating the view that space and time are independent quantities and giving us a new unified fabric … Continue reading

Posted in Physics, Relativity | 11 Comments

Faster than a speeding photon? Precursors test whether light can be faster than light

Over the past two weeks, the biggest physics news has been the apparent observation of neutrinos (nearly undetectable subatomic particles) moving faster than the vacuum speed of light.  At first glance, this would seem to violate Einstein’s special theory of … Continue reading

Posted in Optics, Physics, Relativity | 13 Comments

It’s not shrinkage — it’s relativity! (1889)

The best stories in the history of physics are those in which someone comes from humble origins and, seemingly out of nowhere, makes a brilliant discovery that changes everything.  Such stories, however, can give a very misleading impression of the … Continue reading

Posted in History of science, Physics, Relativity | 17 Comments

Right-wing refutations of relativity really, really wrong!

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 … Continue reading

Posted in ... the Hell?, Relativity | 53 Comments

Lord Rayleigh vs. the Aether! (1902)

(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 … Continue reading

Posted in History of science, Optics, Relativity | 9 Comments

Einstein vs. Whittaker, with Born in the middle

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 … Continue reading

Posted in History of science, Physics, Relativity | 8 Comments