Monday, October 07, 2013

Turtles are more closely related to Crocodiles than Lizards!

The orange line shows where turtles actually belong in this part of the tree of life, the dashed lines indicate previous suggestions.
New DNA techniques have recently been developed to more easily determine where species belong in the tree of life. See Large-Scale Gene Comparisons Boost Tree of Life Studies in Science. As you may have heard, birds and dinosaurs are closely related. Moving further up the tree, Archosaurs are a group that contain birds, dinosaurs and crocodiles as well as the extinct flying reptiles, the Pterosaurs. Thanks to this new research, turtles are now known to be the sister group to the archosaurs.
A red-eared slider.

Sunday, September 15, 2013

Harriet Dark Art

Harriet Dark is an art student here in Boston. You can see more of her haunting work at Harriet Dark Art.

Monday, August 12, 2013


Steven Pinker, a linguistics professor at Harvard and prolific author, has a provocative article at The New Republic web site, Science Is Not Your Enemy An impassioned plea to neglected novelists, embattled professors, and tenure-less historians (August 2013). Pinker says that science is now encroaching on matters traditionally in the realm of the humanities, for example human emotion and human values, and that has generated a backlash in various quarters: the humanities, religion and public policy. Scientism is a term - new to me - used by critics who believe that science is often misapplied when it address some of the traditional concerns of the humanities, religion and public policy. I have found many other things Pinker has written very interesting, especially when they are focused on his specialty, linguistics. However, this article seems to me yet another example of someone who knows a lot of science and feels like their scientific knowledge supports some of their other values and opinions, but their attempt to make their case unfortunately comes off very weak. I suspect that Pinker's article will often have the exact opposite effect of what he says he intends. Instead of reassuring people who think science overreaches, it will just seem like yet another attempt that misuses science to support someone's personal opinions. See The Scientism of Steven Pinker by Ross Douthat in the New York Times, for someone who didn't find Pinker at all convincing.
Faulty 'scientific' results have, of course, repeatedly been used to support personal biases, The Mismeasure of Man, by Steven Jay Gould is a collection of interesting historical examples. In some cases the errors and misinterpretations were really rather subtle, but invariably the errors somehow ended up supporting the preconceived notions of the investigators.

Tuesday, August 06, 2013

Bunker Hill

Bunker Hill: A City, a Siege, a Revolution is a 2013 book by Nathaniel Philbrick. It focuses heavily on Joseph Warren, a physician, politician and patriot general killed during the 1775 battle of Bunker Hill. The detailed accounts of the years leading up to and following the battle were quite interesting, especially since I've been a resident of the Boston area for most of my life. The Bunker Hill monument is easily visible from my windows. My favorite quotes from the book were from the loyalist pastor Mather Byles. When asked how he could be a "brainless Tory", Byles replied, "Tell me, which is better, to be ruled by one tyrant 3,000 miles away, or by 3,000 tyrants not a mile away?" He called the sentry stationed outside his house his "Observe-a-Tory". The Death of General Warren at the Battle of Bunker's Hill, June 17,1775 by John Trumbull

A Quantum Critique

Many reputable thinkers have had issues with quantum mechanics, notably Einstein, who said "God does not play dice with the universe", referring to the probabilistic outcomes predicted by standard quantum theory. The EPR Paradox (the 'E' stands for Einstein) and Bell's Theorem are two well-known examples of the somewhat peculiar predictions of quantum mechanics. John Bell is quoted saying about quantum mechanics
I did not dare to think that it was false, but I knew it was rotten!
The Fate of the Quantum by Nobel prize winner Gerard 't Hooft is a sophisticated critique of quantum mechanics which also touches upon philosophical issues such as Free Will. The standard interpretations of quantum theory often invoke the free will of experimenters to make independent decisions at the last second. 't Hooft complains that alternative interpretations are sometimes dismissed, on grounds more philosophical than scientific:
This explanation is usually also dismissed. It is called a ‘conspiracy theory’, and that is considered to be disgusting. But are ‘disgusting’, or ‘ridiculous’, valid arguments in a mathematical proof? We have reasons to doubt that.
More concretely the paper mentions the concept of Superdeterminism, which probably eliminates the possibility of free will and also evades the assumptions behind Bell's Theorem.
For what it's worth - probably not that much haha - I'm with 't Hooft on this one. Over the years I've bored my friends and even written an outline of a paper along these lines, but haven't polished my arguments into publishable form, so it's nice to see that someone as distinguished as 't Hooft has basically saved me the trouble. 't Hooft doesn't, at the moment, have a completely fleshed out proposal to compete with quantum mechanics and, alas I don't either. He finds Quantum cellular automata interesting in this context and so did I at one point, but he also mentions the same problem that caused me to give up on that - issues of compatibility with relativity.

Friday, August 02, 2013

The Invisible Gorilla Strikes Again!

This video is a test of selective attention, count how many times the players in white pass the basketball.

Casual observers may miss the gorilla, but what about expert observers? The following study tested radiologists looking for lung nodules in CT scans. A picture of a gorilla was inserted into some of the images. A majority of the radiologists did not notice! See The invisible gorilla strikes again: Sustained attentional blindness in expert observers by Trafton Drew, Melissa Võ, Jeremy Wolfe for a poster and here for a link to the full paper.

Wednesday, July 17, 2013

Cosmography of the Local Universe

At Cosmography of the Local Universe there is a video showing the distribution and motion of the galaxies in our neighborhood. There is also an accompanying paper by Courtois, Pomar, Tully, Hoffman and Courtois. In the video "distances" are represented by velocities in km/s. It's difficult to figure out distances to galaxies directly, what we can actually measure is the "redshift" of spectral lines, which can be interpreted as a velocity, which is then assumed to also indicate distances, due to the fairly uniform expansion of our local universe. Another term appearing in the video is the 'Zone of Avoidance' or ZOA. Our own galaxy, the Milky Way, blocks our view of the galaxies, due to the the dust and stars of the Milky Way being concentrated around the plane of the Milky Way's disk. So we really don't have much information about the galaxies laying in those directions.
One of the characteristic features of the distribution of galaxies is the presence of voids: huge, roughly spherical regions in which galaxies are very sparse. I have a collection of interesting links to the literature about voids here.

Friday, July 05, 2013

“On the quantum theory of radiation” by Albert Einstein

In Einstein's 1917 paper “On the quantum theory of radiation” he introduced the concepts of stimulated and spontaneous emission of radiation, the effects that make possible lasers and many other fascinating devices. He accomplished this in masterful fashion by starting with the simplest of assumptions, all but one of which were traditional classical physics. Using just one basic quantum notion - Bohr's idea of quantized molecular energy levels - his amazing powers of deduction led him to hypothesize new observable physical phenomenon as well as rederiving Planck's radiation law in a very neat way. This was apparently also the first time that anyone realized that photons should carry momentum as well as energy. This English translation of the original paper is beautifully written. Here are two nice retrospectives: Einstein as armchair detective: The case of stimulated radiation by Vasant Natarajan; Rereading Einstein on Radiation by Daniel Kleppner.
A dim recollection of freshman physics is probably enough to follow much of Einstein's train of logic.
"A Theory Should be as Simple as Possible - but not Simpler"

Saturday, June 15, 2013

I would have liked to have written a shorter title, but I did not have the time

I would have written a shorter letter, but I did not have the time. Blaise Pascal in Provincial Letters: Letter XVI; similar statements have been attributed to Mark Twain, T.S. Eliot, Cicero, and others besides. From Simplicity - Wikiquote.

Wednesday, May 22, 2013

Richard Holmes at the Radcliffe Institute

I attended a talk by biographer Richard Holmes at the Radcliffe Institute here in Cambridge yesterday (5/22/2013): The Scientist Within: Scientific Biography and The Creative Moment. I had read his book, The Age of Wonder: How the Romantic Generation Discovered the Beauty and Terror of Science which I found fascinating. I've found attending talks by authors of favorite books to be highly uneven, sometimes they are great and sometimes they are very disappointing. Sometimes the author is just how you pictured them, sometimes they are not all what you expected. In this case, happily, I was smiling appreciatively throughout his talk. In one gem from the talk, Holmes read a passage from Byron's Don Juan, Canto the tenth:
When Newton saw an apple fall, he found
In that slight startle from his contemplation --
'T is said (for I'll not answer above ground
For any sage's creed or calculation) --
A mode of proving that the earth turn'd round
In a most natural whirl, called "gravitation;"
And this is the sole mortal who could grapple,
Since Adam, with a fall or with an apple.
In contrast, William Blake found Newton's work deeply offensive. I had of course seen reproductions of the Blake monotype many times and had always thought of it as a rather heroic depiction, until Holmes pointed out Blake's actual opinion of Newton. He showed a slide of Blake's image along with a photo of the Eduardo Paolozzi bronze at the British museum.

Tuesday, April 23, 2013

Alternative History

I recently read A Palette of Particles, another fine book by the writer and physicist Jeremy Bernstein about the history of particle physics up to the Higgs boson. Bernstein mentions one chilling near miss in physics. In Rome in 1934 an Italian team led by Enrico Fermi actually observed nuclear fission. But they misinterpreted what they saw. Bernstein asks us to imagine how world history might have been different if fission was discovered in Fascist Italy in 1934 instead of four years later in Berlin 1938. Even though fission was discovered in Germany, by that time, the fascist powers were rapidly becoming very isolated from the rest of the scientific community. Lack of scientific knowledge might have been only part of the reason the Nazis weren't able to build a bomb, but it was probably a factor. After WWII several distinguished German scientists were held together by the Allies in England (Operation Epsilon) and their conversations were secretly recorded. Several of them, including Heisenberg, seemed surprised when they learned of the atomic bomb and may have mistakenly believed that an explosion would require tons of uranium, not kilograms.

Saturday, April 06, 2013

The Variational Principles of Mechanics

I'm currently reading The Variational Principles of Mechanics by Cornelius Lanczos, the fourth edition published in 1970. From the preface to the first edition (1949):
The variational principles of mechanics are firmly rooted in the soil of that great century of Liberalism which starts with Descartes and ends with the French Revolution and which has witnessed the lives of Leibniz, Spinoza, Goethe, and Johann Sebastian Bach. It is the only period of cosmic thinking in the entire history of Europe since the time of the Greeks
The Action Principle may be the most profound principle in all of nature. The 18th century origins of the principle were colorful and controversial. Characters who were deeply involved included Émilie du Châtelet, an aristocratic lady; her lover, the writer Voltaire; and Fredrick the Great, King of Prussia! See The Berlin Academy and forgery.
Du Châtelet was a remarkable woman, her French translation of Isaac Newton's great work Principia Mathematica is still considered definitive. Café Gradot was the meeting place for intellectuals in Paris at the time, many of them her friends. When she tried to join her friends at their table, the management threw her out - women were not allowed in the cafés at the time. Undeterred, on later occasions she arrived attired as a man, and was able to participate in the discussions at the cafe without further incident.

Friday, February 01, 2013