Monday Links from the Lockdown vol. DXLVII

[NickFitz]

If you want to search some of the old OS maps, they are free here:
Ordnance Survey Maps - National Library of Scotland

A site on which I spend far too much time

The various slippy map interfaces are good for exploring particular regions through time. Here's a side-by-side view of the area around Aldwych before and after there was an Aldwych

[WTFH]

If you want to search some of the old OS maps, they are free here:
Ordnance Survey Maps - National Library of Scotland

[NickFitz]

While everybody else is out there getting the second wave started, do the smart thing and stay safely inside and online instead

• Lost in the Waves - Walt Marino took his autistic son Christopher swimming at a Florida beach, but they were caught by a powerful current: ”The current grabbed father and son almost immediately. They floated past the glistening rocks, and then it pulled them faster, the sand disappearing beneath their toes… After 20 minutes, they were about a mile out, at the mouth of the open sea. A green navigational buoy bobbed there, tall and round, with a rusted bell clanging back and forth. Walt reached out to try and grab onto the buoy but struggled against the current. Christopher just kept laughing, unaware of the danger, of the situation, of the fading shore and the strength of the current, of the ocean ahead. ”
  
  
• This Is Why The Speed Of Gravity Must Equal The Speed Of Light - HT to wattaj for this cogent explanation of one of the fundamental aspects of relativity: ”If the Sun were spontaneously (somehow) removed from existence, how long would Earth remain in its elliptical orbit before flying off in a straight line? Believe it or not, the answer to this must be exactly the same amount of time as it was for light: 8 minutes and 20 seconds. The speed of gravity not only equals the speed of light to an incredibly precise degree observationally, but these two constants must be exactly equal theoretically, or General Relativity would fall apart. Here's the science behind why.”
  
  
• Mapping the nation: the early years of the Ordnance Survey - Yesterday was the OS's birthday: ”On 21 June 1791 Charles Lennox, the Master-General of the Board of Ordnance, purchased an impressive three-foot theodolite. This instrument, now on display in Science City 1550-1800: The Linbury Gallery, became recognised as the founding act and was central to the survey’s activities for the next 70 years.” This is the theodolite in question
  
  
  
  
  
• Dead Reckoning - ”In the Earth’s extreme southern latitudes, where the Pacific and Atlantic oceans meet, there is a rocky gap of sea between Antarctica and South America known as the Drake Passage. Among 18th century seafarers, this corridor was also known by a more ghoulish nickname: The sailors’ graveyard… Sensible sailors avoided the corridor except in the relatively calm summer, yet on 12 April 1741⁠—deep into blustery autumn⁠—the British Royal Navy ship HMS Wager was at full sail in the dead center of the Drake Passage.” The mission of the Wager descended into shambolic tragedy, though the various tales of how some survived are each quite remarkable.
  
  
• Dark Matter Experiment Finds Unexplained Signal - ”Researchers say there are three possible explanations for the anomalous data. One is mundane. Two would revolutionize physics.” It'll probably turn out to be the boring one, but you never know
  
  
• Coal-burning in Siberia led to climate change 250 million years ago - ”A team of researchers led by Arizona State University School of Earth and Space Exploration Professor Lindy Elkins-Tanton has provided the first ever direct evidence that extensive coal burning in Siberia is a cause of the Permo-Triassic Extinction, the Earth’s most severe extinction event… Calculations of sea water temperature indicate that at the peak of the extinction, the Earth underwent lethally hot global warming, in which equatorial ocean temperatures exceeded 104 degrees Fahrenheit. It took millions of years for ecosystems to be re-established and for species to recover.” The full paper is available at the journal Geology as a PDF.
  
  
  
  
  
• My dad launched the quest to find alien intelligence. It changed astronomy. - Nadia Drake on her father Frank's Project Ozma sixty years ago, and the subsequent, better-known SETI: ”Astronomers knew of no worlds beyond our solar system back in the 1960s, but Drake reasoned that if planets like Earth orbited stars like the sun, then those worlds might be populated by civilizations advanced enough to broadcast their presence to the cosmos… So he designed an experiment to search for signals coming from worlds that could be orbiting the nearby stars Epsilon Eridani and Tau Ceti. He named the experiment Project Ozma, after the princess in L. Frank Baum’s Oz series—an homage to an adventure tale populated by exotic and unearthly beings.”
  
  
• Running a bakery on Emacs and PostgreSQL - This is what happens when a programmer, in this case Piers Cawley, becomes a baker: ”The key insight is that a bakery formula is so cliched that it can be represented as data… I did consider reaching for the object oriented hammer at this point, but thought that I might be able to do everything I needed without leaving SQL.” For more details on representing recipes in a relational database, read the followup article A recipe is just a directed acyclic graph…
  
  
• A look at the die of the 8086 processor - ”The Intel 8086 microprocessor was introduced 42 years ago this month, so I made some high-res die photos of the chip to celebrate. The 8086 is one of the most influential chips ever created; it started the x86 architecture that still dominates desktop and server computing today. By looking at the chip's silicon, we can see the internal features of this chip.” Ken Shirriff explores the venerable microprocessor; he'll be going into more depth in future articles, but as he explains in footnote 8: ”The main reason I haven't done more analysis of the 8086 is that I etched the chip for too long while removing the metal and removed the polysilicon as well, so I couldn't photograph and study the polysilicon layer. Thus, I can't determine how the 8086 circuitry is wired together. I've ordered another 8086 chip to try again.”
  
  
• A Photo Trip to the Abandoned Village of Houtouwan - Another of those amazing abandoned Oriental places that'll probably turn up as a villain's lair in a Bond film: ”In the Pacific Ocean, east of Shanghai, China, lies tiny Shengshan Island, which is less than three miles across. The hilly island is home to several fishing villages, including Houtouwan, which was abandoned in the 1990s. Once a thriving community, the now-empty brick houses of Houtouwan stand completely covered by blankets of vegetation.”
  
  
  

Happy invoicing!