Well, somebody better stop them if they're not supposed to be doing that? Or should I put my glasses on and reread the post title?

Give it a look-see in Google maps, satellite view. Only the west part has green stuff (except for a weeks between grey snow slush and brown dead grass).

Like others have alluded to, the angle your sister is coming from only makes any sense because of how different related conditions are referred to, because of specific quirks in how and when each part was figured out.

It's kind of like saying 'diabetic ketoacidosis is a symptom of diabetes, so there should be other conditions which cause it.' Except, 'diabetic' is in the name, while 'HIV' isn't in the name that stuck for the condition it can cause, AIDS.

Man, I forgot about that one. Switching off the body's firewall settings sure does cause weird and awful things to happen sometimes...

It's like having a house infested with ants that ant-poison won't kill anymore because you haphazardly used several kinds sequentially over time without successfully killing all of the ants ever, resulting in resistance to a variety of pesticides and unique behavioral responses to past agents, versus a house that ant poison has stopped functioning inside of. You've created a 'special ants' problem, not a 'special house' problem.

How is that chitin resisting the 4000 Newtons, in terms of the orientation of the forces being exerted on the material? Tensile strength? Compressive? Resistance to buckling? Stiffness?

I sincerely doubt that value is a fair or meaningful comparison to a human spine any more than, for example, me letting everyone know that chicken eggs have an ultimate strength of 14,000 Newtons if you apply the load properly.

I'm perfectly willing to believe that the rest of what you say is true, but that specific bit really stuck out and cast doubt on all what you said, for me. A solid block of calcium carbonate would be impossible to crush with your hands, but, well, eggs are like eggs are, because of how thin that incredibly hard shell is.

If those paleoarthropods had thicker exoskeletons relative to their other proportions, or if we had some numbers backing up that chitin with less protein in its matrix has a higher tensile/compressive strength, I think maybe some of these 2.5m creatures could resist a guy with reasonably good boots on, but I don't think you've shown any of that to be true yet.

So, a little googling got me this: https://astronomy.com/magazine/ask-astro/2006/01/how-close-can-stars-get-to-each-other-in-galaxy-cores

TLDR; stars only 860 AU (Earth-Sun distances) apart instead of 5 lightyears (360 times further) means probably no planets in the first place, but pretending there were, the night sky would ABSOLUTELY be brighter! The daytime sky would be bright! Unless someone can show the math otherwise, I think you can bluntly estimate 360^2 = ~130k times brighter, all other things being equal.

That's fun to think about. I don't think I've seen a good visualization of what that visual environment would look like in the visible spectrum in human dynamic range. Could be more watts per square exposed meter than anything organic can exist at...

Likewise, it wouldn't probably be great at, for example, telling you which alloy of aluminum something you found in a scrapyard is, unlike some other ways of zapping things to know what they are.

I would imagine there aren't many disadvantages to keeping your walking-related bones solid and marrow-filled and your flight-related bones hollow. Plus, the flight-related bones which you have to waggle around all day at high speeds are next to your basal vertebrate lungs, which I would guess is easier to evolve air sacs into than the legs.

Thinking about all the chicken bones I've gambled with gnawing into over the years, I think maybe a lot of bird vertebrae have marrow, too. Unfortunately, that part of the chicken tastes kinda gross usually :/

I've also seen air sacs mentioned in vertebrae, in some context (help, paleontologists/ornithological anatomists?), so maybe those can have both? Is it neck vertebrae ('cervical'? It's been years since that 'Dinosaurs' class in undergrad...) that have the sacs? Am I thinking of sauropods, not avians now? Lotta cobwebs in this part of my brain...

Flight bones ('arms and hands') are fully hollow, spines have marrow and air sacs, walkin' bones ('pelvis, legs, and feet') are usually marrow-filled? Is that broadly true of bird skeletons?

You need a place for the metal to enter the empty space of the mold, and others for the air the metal is displacing to escape. The metal also contracts a bit as it cools and solidifies, and a good mold is designed such that the main filling sprue is where most of that happens, usually in the form of a giant dimple on top. These vents and filling holes, once filled with metal, leave behind the stem-like sprues on the solid casting....

But, what I described is more applicable to investment casting than die casting.

Die casting is actually a little more specific than just 'pour metal into mold,' but all of the above is largely still true. It's more like a glorified waffle iron process, where molten metal is poured into half of a mold, then another half (or, say, a third core between two sandwiched halves to cast something hollow) is pressed in, usually under some force, which forces the molten metal into both halves, and any excess volume 'squirts' out through the vent/sprue holes, leaving behind sprues and, where the mold halves meet, flat, usually razor-sharp flashing.

Oh, hey, the Airy Disk! I remember that from an undergrad physics class. Wikipedia reminds me that I'd know that ~1.22 factor for 'infinite' focus anywhere...

Light mostly doesn't scatter in a vacuum, but it does a little teeny bit because of the photons interacting with each other as they travel almost parallel but not the same wavelength and polarity (that would be laser light).

In the solar system, it's pretty negligible. If you get outside the atmosphere, the size of your lens/reflector and the brightness for far-out objects are the only limits to human-scale resolution. I don't know the math off the top of my head, but I doubt self-interference in the light would cause problems with even milimeter-on-Pluto-from-Earth resolution if you had a big enough telescope to capture and magnify that image.

Can anyone with more optics/physics/astronomy than me confirm, deny, or elaborate on that?