The constellation Scorpius

Winter is here (in the Southern Hemisphere, at least), and the constellation Scorpius always heralds the southern winter’s icy sting. The image below is based on a vintage astronomical illustration, but I have corrected the star positions of the major stars and indicated their apparent magnitude (brightness) and approximate colour (based on spectral class). It is interesting to compare the image with this quality photograph.

Generations of astronomers have memorised the O–B–A–F–G–K–M stellar classification system developed by Annie Jump Cannon with the mnemonic “Oh, Be A Fine Girl/Guy/Gal/Gentleman, Kiss Me.” Scorpius does not contain any bright O-class stars, but it is easy to see stars ranging from the hot blue-white B class to the cooler orange-red M class (stars which are only “red hot”).

The most obvious star in Scorpius is the enormous red supergiant Antares, which has that name because it is easily confused with the planet Mars (Ares). It is also known as “Cor Scorpii” (the heart of the scorpion). It is easy to recognise the curved tail as well, with the stingers Shaula and Lesath at its tip. It is less obvious which stars are the scorpion’s claws – the artist here has drawn the left claw extended so as to reach the dim white star Psi Scorpii. Other artists draw the scorpion facing more to the right, with the line of blue-white stars being the claws.

Infographic constructed using R (with lm to map true sky coordinates to image coordinates, rasterImage for the background, and the showtext package for fonts).


Eureka! – a book review

Eureka!: The Birth of Science by Andrew Gregory

I recently read Eureka!: The Birth of Science by Andrew Gregory. The book deals with a topic that has long fascinated me – the birth of science. In a previous post I argued that this took place in the 12th century, the age of cathedrals. Gregory takes the view that it happened with the ancient Greeks, and sees Aristotle and Archimedes as among science’s pioneers. He gives a brief defence of this thesis, and provides a quick summary of Greek scientific thought.

Aristotle and Archimedes

I found this book rather short for the subject (177 pages, including bibliography), was disappointed at the lack of endnotes, and found some annoying errors (the Greeks did not consider the universe small, for example – Archimedes took it to be 2 light-years across). But the big unanswered question is: what went wrong? Gregory includes a list of key people at the back of the book, and if you turn that list into a bar chart, you can see that Greek science basically fell off a cliff around 200 BC.

In a brief two-page section towards the end, Gregory suggests that Christianity was somehow responsible for the decline of Greek science, but that simply makes no sense. Was it instead Roman conquest, beginning around 280 BC? Was it the growing separation of aristocratic philosophy from plebeian technology? Was it the replacement of original science by encyclopaedic systematisation (such as that of Pliny)? It would have been nice to have those questions answered.

Goodreads gives this book 3.4 stars; I was rather less enthusiastic.

Eureka!: The Birth of Science by Andrew Gregory: 2 stars

True Stories – a book review

True Stories: And Other Essays by Francis Spufford

I recently finished True Stories: And Other Essays by Francis Spufford – a collection of real gems by a man who can truly write. A selection of essays, book reviews, and other non-fiction works, this book is divided into the thematic sections “Cold,” “Red,” “Sacred,” “Technical,” and “Printed.” The section “Technical,” for example, includes a piece on British engineering, together with a wide-ranging essay on Babbage’s “Difference Engine No. 2,” reconstructed by the Science Museum, London. Babbage never completed this device, of course, and perhaps could not have done so, given the technological limitations of his time. This leads Spufford into a general reflection on counterfactual history, drawing also on the novel The Difference Engine.

The section “Cold” includes several pieces on polar exploration, such as an introduction written for The Worst Journey in the World (a memoir of the 1910–1913 British Antarctic Expedition), and a piece on Ernest Shackleton. I’ve been fascinated by polar exploration since childhood, so I found these particularly interesting.

Grotto in an iceberg, photographed during the 1910–1913 British Antarctic Expedition (image credit)

The section “Red” deals largely with the former Soviet Union. It includes an explanation of Spufford’s fictional documentary book Red Plenty, and the essay “The Soviet Moment,” which is still online at The Guardian: “It was not the revolutionary country people were thinking of, all red flags and fiery speechmaking, pictured through the iconography of Eisenstein movies; not the Stalinesque Soviet Union of mass mobilisation and mass terror and austere totalitarian fervour. This was, all of a sudden, a frowning but managerial kind of a place, a civil and technological kind of a place, all labs and skyscrapers, which was doing the same kind of things as the west but threatened – while the moment lasted – to be doing them better. American colleges worried that they weren’t turning out engineers in the USSR’s amazing numbers. Bouts of anguished soul-searching filled the op-ed pages of European and American newspapers, as columnists asked how a free society could hope to match the steely strategic determination of the prospering, successful Soviet Union. … The loudest and most important lesson of the Soviet experience should always be: don’t ever do this again. Children, don’t try this at home. … Yet we’d better remember to sympathise with the underlying vision that drove this disastrous history, because it is basically our own.

The section “Sacred,” obviously, deals with religion (Spufford is an English Anglican). It includes a critique of Richard Dawkins, a reflection on C. S. Lewis, and a record of travels in Iran. The New Humanist still has online the essay beginning “Allow me to annoy you with the prospect of mutual respect between believers and atheists. … No? No. Because the idea of atheism as an extravagant faith-driven deviation from the null case goes against one of the most cherished elements in the self-image of polemical unbelief: that atheism is somehow scientific, that it is to be adopted as the counterpart in the realm of meaning to the caution and rigour of the scientific method.

Spufford visited the Sheikh Lotfollah Mosque in Isfahan, Iran (image credit)

Finally, the section “Printed” includes miscellaneous introductions and book reviews, including an introduction to The Jungle Book, a review of the Mars trilogy, and an obituary of Iain M. Banks. This last section reflects Spufford’s wide-ranging interests in technology, exploration, and imagination. For me, at least, it established a connection of sorts with the author: we read the same things; we are brothers.

The last section of True Stories includes a review of the Mars trilogy by Kim Stanley Robinson

See The New York Times and the New York Journal of Books for other reviews of True Stories. I’m giving it four stars overall, although several of the individual essays deserve five. This book was a delight to read.

* * * *
True Stories: And Other Essays by Francis Spufford: 4 stars

The first “mixed-race” princess?

Photo: Mark Jones

I see that many Americans are excited by the upcoming royal wedding between Prince Harry and Meghan Markle. I have even heard suggestions that Meghan will be the “first mixed-race princess” in England.

This is, of course, nonsense. Technically, Queen Elizabeth II is herself “mixed-race.” Among other things, she is descended from Zaida of Seville (1070–1100), an Arab princess (daughter to Al-Mu’tamid ibn Abbad). Zaida fled Seville after the savage Almoravid takeover, taking refuge with King Alfonso VI of Castile. Zaida converted to Christianity, took the name Isabella, and became the mistress (and later wife) of King Alfonso. Queen Elizabeth II is her descendant:

The Sand Reckoner

In his short work The Sand Reckoner, Archimedes (c. 287 BC – c. 212 BC) identifies a number larger than what he believed was the number of grains of sand which would fit into the Universe. He was hampered by the fact that the largest number-word he knew was myriad (10,000), so that he had to invent his own notation for large numbers (I will use modern scientific notation instead).

Archimedes’ began with poppyseeds, which he estimated were at least 0.5 mm in diameter (using modern terminology), and which would contain at most 10,000 grains of sand. This makes the volume of a sand-grain at least 6.5×10−15 cubic metres (in fact, even fine sand-grains have a volume at least 10 times that).

Archimedes estimated the diameter of the sphere containing the fixed stars (yellow in the diagram below) as about 2 light-years or 2×1016 metres (we now know that even the closest star is about 4 light-years away). This makes the volume of the sphere 4×1048 cubic metres which means, as Archimedes shows, that less than 1063 grains of sand will fit.

A more modern figure for the diameter of the observable universe is 93 billion light-years, which means that less than 1095 grains of sand would fit. For atoms packed closely together (as in ordinary matter), less than 10110 atoms would fit. For neutrons packed closely together (as in a neutron star), less than 10126 neutrons would fit. But these are still puny numbers compared to, say, 277,232,917 − 1, the largest known prime!

Famous radiation leaks

The chart above shows approximate radiation releases (in becquerels) for some major nuclear disasters. It should be interpreted with caution, since some radioisotopes are more dangerous than others. For example, the releases from Three Mile Island were largely noble gases (mostly xenon), and that incident appears to have had few detectable environmental or health effects. Ticks on the vertical axis of the chart go up logarithmically, in steps of ×1000. For comparison, radium and bananas are also listed.

Chernobyl reactor #4 in 2007, encased in concrete