Sunday, 27 September 2020
Thursday, 17 September 2020
Saturday, 12 September 2020
This does not ring true: perhaps it was put about by somebody annoyed by the challenge of trying to pass crinolined ladies on a narrow street, or to fit them into a pew, a doorway, an omnibus, or a carriage.
Saturday, 5 September 2020
1859 was the year that Charles Darwin and Abraham Lincoln turned 50 (they were born on the same day in 1809) and by the end of the year, their names were becoming known, all over the civilised world. It was the year of the first oil well, the invention of the slide rule and spectroscopy (rapidly giving us enough extra chemical elements to make the Periodic Table mean something). It was also the year in which Mendel started investigating the genetics of peas, the Suez canal was started, key evidence for the germ theory of disease was being assembled, and tobacco-smoking was first identified as a cause of cancer—and that's just for starters!
Railways, telegraphs under the sea, steamships and internal combustion were all tying the world together in amazing ways.
The end result was a work entitled Mr Darwin's Incredible Shrinking World, which saw the light of day in 2008 as a print book which you may or may not be able to pick up somewhere: here's a quick outline.
The work is certainly available from Amazon as a Kindle e-book, and also from Booktopia, or you can listen to me talking about it here.
Anyhow, my next few entries are drawn from chapter 7 of that book, and they serve to describe life in that era. If you want to see the others, use the tag 1859, which appears at the end of each entry. I will begin with fashions.
And in Britain, the poor were still being banged up in workhouses. I may or may not get back to discuss the fate of Thomas Drewery's orphans in Victoria, not long after that, but I have already described the fate of Australian poet, Jennings Carmichael, who died in an English poorhouse.
|Is it all about equipment? This is|
Tycho Brahe's Uraniborg.
|Dolly Pentreath memorial, Mousehole, Cornwall.|
Sunday, 23 August 2020
|Did you know that I collect volcanoes?|
One of the hallmarks of popular science is the disaster scenario, because it sells well. Sometime, though, the scenarios are popular, but not science. Let us consider the view that asteroid strikes cause volcanoes to erupt.
Wednesday, 19 August 2020
With the exception of the Flat-Earthers (and even climate clowns hate it when they are treated as latterday Flat-Earthers!), we all believe that the Earth is pretty much a sphere, but pretty much leaves wiggle room, and strange as it may seem, it was an upgraded version of a playground swing that revealed the precise shape of our globe, which some people likened to a watermelon stood on end, while others thought was more like a pumpkin.
This is the story of how they did it, almost three centuries ago.
When he returned to Europe, La Condamine brought with him what the locals called cauchu, and the French still call caoutchouc. Thanks to Joseph Priestley, we still call it ‘rubber’, because it can be used to rub out pencil marks, and what is an eraser in some English-speaking countries is still called a rubber in others.
Friday, 14 August 2020
Charles E. Benham (1860-1929) was a journalist and inventor, and he deserves more than this, or what his Wikipedia entry, offers. I was triggered to go here this morning because of a comment Stew made about my last entry: there may be more, later.
When I first discovered the Benham disc, I was delighted, because I am colour-blind. The Benham disc is a black and white patterned circle, which looks coloured when it is spun around. I had heard of these things but I had never tried them, and I thought it would be interesting to see whether they had the same effect on a colour-blind viewer. Being colour-blind does not mean that you “see everything in black and white”, as David Brewster said. It simply means you see colours differently. It occurred to me to wonder if maybe I would see different colours in the disc from those other people see.
Benham described his illusion in an article published in Nature back in 1894. In those days, if you wanted to see the disc, you would look for the design on a children’s top, known, predictably, as ‘Benham’s top’. The first account was a brief and anonymous one, noting that the ‘disc’ on the top was a black semi-circle, with the white half of the circle divided in four, and with black arcs painted in.
As the disc is rotated, people see different colours from the different black arcs. And, as the reporter noted, if “. . the direction of rotation is reversed, the order of these tints is also reversed. The cause of these appearances does not appear to have been exactly worked out.”
An ‘Artificial Spectrum Top’, devised by Mr. C. E. Benham, and sold by Messrs Newton and Co., furnishes an interesting phenomenon to students of physiological optics. The top consist of a disc, one half of which is black, while the other half has twelve concentric circles drawn upon it. Each arc subtends an angle of forty-five degrees. In the first quadrant there are three such concentric arcs, in the next three more, and so on; the only difference being that the arcs are parts of circles of which the radii increase in arithmetic progression. Each quadrant thus contains a group of arcs differing in length from those of the other quadrants. The curious point is that when this disc is revolved, the impression of different colours is produced upon the retina.
(Nature , 51 (1309), November 29, 1894, 113–114.)
There followed an animated correspondence, during which Benham stepped in. Illuminate the top with a bright sodium flame, he said, and you will see a very clear blue, and a very clear red. And now the controversy heats up: immediately underneath, in the same issue, Professor Liveing retorts that he has seen no such colours: the phenomenon is obviously a subjective one. Clearly there is room for more research here.
It is unclear whether Nature thought so too, for they go on in the same column to publish next a letter from F. G. Donnan in Leipzig, suggesting that we need a new word in chemistry: ‘solute’, and the discussion seems to have died there. Well, as far as I can judge, I see the same colour effects as other people, which means we won’t learn anything about colour blindness from the Benham disc. But how about trying to learn about colour vision? What causes the colour effect as the disc slows down?
Most explanations seem to speculate rather than to explain, but here is the official version as found in psychology text-books. We have three kinds of light receptor in our eyes, in the same way there are three kinds of phosphor in a colour TV. Speaking crudely, these receptors, the cone cells, are all sensitive to just one of red, green and blue.
According to the theory, you need all three kinds of cone in the retina of your eye to see colours normally. Somehow, the cones which pick up one of the colours (red, for example) must react differently to flashing lights of a particular frequency. So with different size black bits on the disc, we get different frequency effects, and so our eyes are stimulated to ‘see’ different colours.
Well, that’s what the theory says. Some time in the future, a careful and critical look at it, will reveal once and for all whether and how this official explanation operates, and where it breaks down. There is probably a Nobel Prize in this for somebody, though they will need to acknowledge Gustav Fechner, and that's a hint.
Thursday, 13 August 2020
Friday, 31 July 2020
|Logicians with a smattering of Greek will|
share my delight in this Athenian street sign.
“Not so fast”, says the young lawyer. “If I lose the case, I have yet to win a case and need not pay you. But if I win, then by the court’s judgement, I do not have to pay you.” Does the lawyer have to pay?
But what about the word “heterological” — does it describe itself or not? If “heterological” is heterological, then it describes itself, and so it is autological. But if the word is autological, then that means it is a word that does not describe itself … or something.
Let's get back to more practical stuff!
Tuesday, 28 July 2020
As the man sprints desperately across that metre, the tortoise sneaks a further tenth of a metre, and while Achilles is lunging across that tenth of a metre, the tortoise drifts another centimetre, and so the human can never catch the tortoise. The same argument can be used to show that a thrown spear can never reach its target!
Monday, 20 July 2020
Sunday, 19 July 2020
|A bumblebee, coming in to land (or fall?)|
Curiously, the pursuit of novel sources for saltpetre during the Napoleonic wars led a French chemist, Bernard Courtois, to discover iodine, but that's another story...the next story, in fact.
Friday, 17 July 2020
In case you don't look out for details, the hole that the fly was caught in (or poked into) was actually made by a projectile coming from the other side, so the accompanying question about the fly's speed is, at the very least, just a bit misleading, but somebody is going to cite a legend.