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There is a single sock on my windowsill and I have decided not to ask.
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Each of your eyes has a hole your brain paints over
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In each eye there is a patch of the visual field where you see nothing at all, and your brain covers it so smoothly that you have probably never noticed. This is the blind spot, and it corresponds to the optic disc in the retina.
It is surprisingly large. Researchers describe it as roughly 6 by 8 degrees of visual angle, sitting in the outer half of each eye's view, about 15 degrees from wherever you are looking.
Two things hide it. The first is the other eye, which sees the part of the scene that each eye misses, so the two cover for each other. The second is more interesting to me. Even with one eye closed, the brain borrows brightness, colour, texture and even motion from the area around the gap and fills it in, so the hole simply looks like more of whatever surrounds it. My field calls this perceptual filling-in, and it is a neat reminder that part of what you see at any moment is your brain's best estimate of what ought to be there.
You can find yours: close your left eye, look steadily at one point, and slowly move a small object out to the right until it vanishes.
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Monopoly was invented to show why monopolies are bad
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In 1904 Lizzie Magie, a stenographer at the Dead Letter Office in Washington, D.C., patented the Landlord's Game. Players circled a square board buying up railroads, collecting money and paying rent. Magie was also an artist, a writer and an inventor, and she designed the game as a lesson in wealth inequality. The popular story, in which Charles Darrow invented Monopoly during the Great Depression, leaves her out entirely.
It came with two sets of rules, one built around her anti-monopoly ideas. She told a reporter she hoped people would soon discover they were poor because Carnegie and Rockefeller had more than they knew what to do with.
Decades later, Darrow copied a homemade version of the game and sold it to Parker Brothers in 1935. Magie was paid $500 for her patent the same year. By 1940 she was listed in the census as a maker of games, with no income.
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Half of this Australian mining town lives underground
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About half of the 3,500 people in Coober Pedy, an opal-mining town in the Australian outback, live in homes dug into the ground. Locals call them dugouts.
The reason is the heat. In summer it can reach about 45°C in the shade, while underground the temperature stays at a steady 24°C or so all year round.
The town exists because a teenager found opal there roughly a century ago, and Coober Pedy has been estimated to supply about 70 percent of the world's opal. Below ground there are churches, including a Serbian Orthodox one, along with museums, hotels and shops, and residents carve bookshelves straight into the sandstone walls. One has built an underground swimming pool.
The red dust and mining mounds on the surface looked otherworldly enough to stand in for the end of the world in Mad Max Beyond Thunderdome in 1985.
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The US once deliberately made your GPS less accurate
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For years, the GPS signal available to the public was made less accurate on purpose. The US government called it Selective Availability, an intentional degradation of public GPS signals kept for national security reasons.
It ended at midnight on the night of May 1, 2000, on the direction of President Bill Clinton. The White House said civilian users would now be able to pinpoint locations up to ten times more accurately, and the example it chose shows how rough things had been: emergency teams could finally tell which side of the highway they needed to reach, saving what the statement called precious minutes.
The stated aim was to make GPS more useful to civilian and commercial users around the world. In September 2007 the government announced that the next generation of satellites, GPS III, would be built without the feature at all.
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The first spam email was a computer advert sent in 1978
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In May 1978 Gary Thuerk, a marketer at Digital Equipment Corporation, sent a single message to about 400 users of ARPANET. It advertised DEC's new DECSYSTEM-20 computers, the 2020, 2020T, 2060 and 2060T.
His logic made a kind of sense, and the computer museum that now tells the story calls his assumption reasonable: he was advertising machines that could connect to ARPANET to the people already on it. The network, however, was meant for official government business only, and an official at the Defense Communication Agency objected strongly, calling the message a flagrant violation of the use of ARPANET.
I find it oddly reassuring that the very first one already had both ingredients every spam email has had since: something to sell, and someone furious about receiving it. Nearly half a century of filters and blocklists has not managed to separate the two.
The complaint, like the advert, was written in capital letters.
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Tell someone about Lizzie Magie today. She has been owed the credit for a long time.
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