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mohn

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Interesting question, a lot of search engine results claim that John Von Neumann was presented with the problem and quickly solved it by summing the infinite series instead reframing it as a constant speed for an easily calculated duration. Plausible, but sounds apocryphal. Here's the oldest reference I've found and verified by reading scans[0] of the source book:

Initiation Mathématique (1906) by Charles-Ange Laisant (1841--1920), number 53. Le chien et les deux voyageurs.

The setup here has two pedestrians walking in the same direction with a dog running back and forth between them. One of them starts out some distance ahead of the other but, because the one behind walks faster, they eventually intersect. It briefly mentions a variation where they are walking toward one another, as in the typical trains & fly version of the problem. Best of luck finding older, I wouldn't be surprised if it's out there!

[0] https://i.imgur.com/vCCFgAQ.png

I'd like to read the accounts of contemporary curmudgeons bemoaning the way young Greeks are clamoring for mom's mirror, and how you should limit your kids to no more than one twelfth of a day of mirror time, setting the clepsydra if necessary.

I don't think Google can fix it

Can they eventually throw away Android and replace it with Fuchsia? In the reporting about Fuchsia that I read ages ago, it sounded like it was intended to be an Android replacement but, looking into it again just now, it seems more like an embedded OS for other non-smartphone hardware -- maybe with some (aspirational?) claims of utility on smartphones and tablets.

It sounds like GP would benefit from satellite internet bypassing the firewall, but I don't know how hard the Chinese government works to crack down on that loophole.

Cool project! I'm very interested in accurate preservation of the behavior of these old systems (chip decapping and scanning, FPGA reimplementation, accuracy-focused emulators) and using Ghidra to reverse engineer old games, especially on the 6502 and m68k architectures. Just an enthusiastic spectator at this point, but I hope to contribute something to the field eventually.

A sidenote: the action at 0:19 in the 50x-speed demo is intriguing. I've played many hours of Super Mario Brothers and watched various tool-assisted speedruns of it, but I don't recall seeing a Goomba reverse direction like that instead of just plowing into Mario. Is that a game glitch that you intended to show off with your recorded keyboard inputs? I haven't played in a long time, so I also wouldn't be surprised to hear that such behavior is common. I didn't find an obvious reference to it in the TAS info here [0].

Edit: there is precedent for that Goomba behavior [1].

[0] https://tasvideos.org/GameResources/NES/SuperMarioBros

[1] https://www.reddit.com/r/Mario/comments/add1fx/changing_goom...

I was researching the Armatron last weekend and was surprised to learn then about the single-motor operation. It's quite a complex system of linkages and transmissions [0] to enable the six degrees of freedom. I suppose that explains why the toy is so noisy. I had no idea that was how it worked, must not have taken mine apart when it broke or I outgrew it or whatever happened.

[0] http://www.jeff-z.com/pinball/toys/armatron/armatron.html

Estimates of:

1000000 space debris objects from greater than 1 cm to 10 cm

130 million space debris objects from greater than 1 mm to 1 cm

For high aspect ratio debris, it's not clear whether the given size ranges refer to the long or short axis. I wonder how the Project West Ford[0] artificial ionosphere needles contribute to these estimates. Apparently the remaining needles are mostly in clumps, so they might not be estimated at the individual level.

I hope we can develop a good method for space debris cleanup. It would be a shame if humanity ends up suffering from Kessler Syndrome[1]. Time to brush up on how to use a map and compass, I guess.

[0] https://en.wikipedia.org/wiki/Project_West_Ford

[1] https://en.wikipedia.org/wiki/Kessler_syndrome

Adding on in this vein: I'm curious if the late Presidential hopeful Ross Perot wrote any noteworthy software, or if his role in tech was only that of a salesman. He's another case of not winning the races for elected office, but 18.9% of the popular vote in 1992 and a fortune of approximately $4 billion in 2019 is nothing to sneeze at.

Hounsfield pondered whether it was possible to detect hidden areas in Egyptian pyramids by capturing cosmic rays that passed through unseen voids.

I also wondered about this possibility a few years ago and when I searched online, I found an example of muon tomography of the volcanic dome of La Soufrière on the island of Guadeloupe[1]. Cool non-seismic approach to a difficult imaging problem.

Specifically, I was wondering about neutrino tomography of the entire earth, but the low probability of neutrino collisions would seem to make that infeasible.

[1] https://www.youtube.com/watch?v=CPYhqJ3e-2o

When I first read this comment I was picturing a hot water radiator behind you, so it sounded unlikely based on the blackbody radiation curve for ~320 K.

But now I realize you're probably talking about an electric heater. Given that their heating elements get so hot that they're putting out visible red/orange light, it seems very plausible that an electric heater could produce enough ~940 nm IR to drown out the signal from the remote.

Thanks for sharing! I will try to keep this in mind when I'm troubleshooting IR remotes in the future.

Your source says its numbers are "generated with the unix command line tool ping", which reports round trip time.

In fiber, with light traveling at about (2/3) * c, the minimum latency from SF to Tokyo would be about 42 ms.

It is cool, but having fiber optics poking out of your head is pretty conspicuous.

Chemogenetics (RASSLs/DREADDs)[0] and magnetogenetics[1] allow for more subtle activation. The interesting magnetogenetics results from the mid 2010s were not well-reproduced in the late 2010s, but the physical principle seems sound to me. I'm still hopeful that the technique will see successful application in mammals. Being able to turn the effect off quickly by stopping the external stimulation (vs. having to wait for drug metabolism/excretion in the case of chemogenetics) seems very useful.

Edit: the magnetoreceptors I read about in 2018 were naturally occurring in some turbid-water-dwelling fish. If they don't work well outside the chemical environment of the fish brain, it may be a while before a suitable alternative receptor can be discovered/engineered and used effectively in mammals.

Skepticism about the utility of magnetogenetics is definitely warranted, given how much RF pollution there is in our environment. If your patients have to live the rest of their lives in a shielded room (or wearing a helmet) to prevent unintentional stimulation, then it's not a very good therapy. It could still be useful for preclinical research where you have more control over your subjects' environment, though.

[0] https://en.wikipedia.org/wiki/Receptor_activated_solely_by_a...

[1] https://en.wikipedia.org/wiki/Magnetogenetics