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"Our ship must seem primitive to you who have been spacefaring for millennia."
"Not at all," the Frinx ambassador said, "we find it very clever. Especially that reality evacuation facility. We have not seen anything like that before."
"Reality evac- Oh! You mean the library?"
#MicroFiction #TootFic #SmallStories

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"Installation: we recommend that you use Docker."

what I'm supposed to see: "hey, it's a simple one-liner! Such clean install, much wow."

what I actually see: "we couldn't figure out how to install this thing on anything but our own machine, but hey, here is a well-compressed image of our entire disk, use this instead so that we can stop trying"

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Interesting fact of the day: While Native Americans never developed the metallurgical knowledge to create steel and iron themselves they did in fact have steel and iron tools long before contact with Europeans.

What happened was drift iron, from asian ship wrecks, due to the current, would often wash ashore along the American north wast. This would take the form of nails or other iron pieces embedded in wood (thus being capable of floating. Native Americans had no idea where this iron was coming from or how it was made, but they did recognize its superior quality as a metal compared to the sorts of metals they typically had access to. As such the Native Americans in the north west would typically harvest this iron and forge it into tools.

To me this is just so extraordinary because they had no contact with outside peoples at this point and had no idea anyone existing out there across the ocean. Yet they kept finding this odd metal they had never seen and must have known it wasnt natural as it was shaped into a nail or a winch or something. So I can only imagine the fantasies they came up with about where it was really coming from, especially considering that it was far stronger and could be made far sharper than any metal they had ever seen. It must have seen magickal to them.

Forgot to ask: Do you have similarly confusing riddles (maybe about something other than physics)? I would love to hear some.

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This whole Internet thing seems to be going peer-shaped.

A colleague mentioned today that the April Fools tradition of pranking unsuspecting people into believing something false can be very unwelcome on the receiving side. That made me think of better ways to observe April Fools and I think I've found a slightly Discordian one that I wish I'd thought of years ago.

Let's share puzzles/riddles that often leave the listener very confused and help them realize that something they might have believed about the world is inaccurate. I think it's much better, because it's educational, there's no temptation not to ask the recipient whether they wish to take part beforehand, and I don't expect recipients to feel like they're being made fun of.

Let me start with a physics puzzle I'm fond of:

Consider a car that travels northward with speed v. Assume there are no losses (no rolling friction, vacuum, etc.) so the car travels at constant speed with engine off. At a point in time, the car engages its engine and speeds up to 2*v northward. How much work did the car engine do?

Well, we can compute the increase of car's kinetic energy: m/2*((2v)^2-v^2)=m/2*3v^2

Alas, let us consider a different (inertial) reference frame: one that moves northward with speed v (note that it's not tied to the car, even though it starts stationary in it). In that reference frame the car sped up from 0 to v, so the increase in car's kinetic energy is m/2*v^2.

What gives? How much energy did the engine actually have to use to speed the car up?

h/t to Ryszard Zapała, my HS physics teacher

I'm trying to design some pretty simple shapes using FreeCAD (using Part Design and Sketcher) and I keep encountering weird issues, including things that look like caching problems (I need to twiddle a value back and forth to see effects of other changes reflected) and outright crashes (tracker.freecadweb.org/view.ph and another that boils down to "this file crashes FreeCAD if I try to edit ~anything in it").

I am most likely using it in a weird way. However, I didn't expect that amount of issues (esp. crashes) even if I was using it completely incorrectly. Is it expected that FreeCAD will be crashy-when-used-weirdly, or maybe is it the fault of my distro (NixOS), or something else?

If only I didn't want chamfers, I would just use solvespace. Unfortunately, chamfers on non-side edges of extrusions are very annoying there.

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How do shops end up with such anti-discounts for volume orders? I don't expect this is intended, so why isn't a sanity check against such cases a common thing?

Court arguments can be hilariously entertaining (because judges are very good at cutting through bullshit) and frustrating (because it's supposed to be pure eristics from both counsels and because many problems are caused by lack of precision in the law) at the same time. I just got entertained by a discussion about differences between kinds of delivery and about excluded middle: youtu.be/cuWVWUaNdqc?t=1486

What are the advantages of through-hole PCBs over wire wrapping?

I can see many advantages of wire wrap (though I've never used it, so I might be mistaken):
- due to wire shape, unwanted capacitances are kept much smaller in wire wrap (compared to e.g. a 2-layer PCB),
- it should be about as labor-intensive to wire wrap through-hole components as it is to solder them (TTBOMK you can't reflow through-hole components, so you need to spend some time per pin),
- no need for explicitly making multi-layer PCBs: the problems of routing, possibly stacking layers (for >2 layer ones), coating vias, etc. just go away.

The only advantage of through-hole PCBs I can see is that they're more durable mechanically and thinner.

Am I missing something obvious?

Let's say that you have two electrodes in vacuum and apply a potential difference to them. This will cause electrons to sometimes be "pulled out" of one of them. How will that impact the temperature of both electrodes?

I would expect the negative electrode to be heated by incoming electrons: after all they've had at least ~0 kinetic energy after leaving the positive electrode, so they bring in extra kinetic energy due to the potential difference.

I'm not sure what should happen to the positive electrode. On one hand, I would intuitively expect ones that have higher kinetic energy of thermal motion to be more likely pulled out, which would decrease the temperature (because we're skimming the top of the kinetic energy distribution, which should decrease the expected value). On the other hand, that would mean that this mechanism is a heat pump that should work regardless of the current temperatures of the electrodes, which is obvious violation of 2nd law of thermodynamics.

Where am I being foolish?

I started thinking about this after reading that one should not apply DC to fluorescent tubes, "because otherwise one filament cools off while the other overheats, evaporates and darkens one end of the tube" (ludens.cl/Electron/Fluolamp/fl).

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