There are some really amazing detergents out there. My go-to for cleaning anything I don't have specific information about is Tergajet. It's gentle, extremely powerful, low-foaming (so machine compatible), oxidizing, bleach compatible, and contains a protein degradation enzyme potent enough to disrupt prions: https://technotes.alconox.com/detergents/tergazyme/do-enzyme...
The downside to this magic stuff is that it's fairly expensive ($45 for 4 pounds). So, not for wanton use. But well worth it to solve tough problems or when time is more important than money.
Sure, tens to hundreds of thousands of years ago nobody was working with metals at all. And the centrifugal fan he uses is a modern invention; the oldest mention of them in the literature is less than 500 years old, in De Re Metallica.
It's really interesting to think about the "could have done this but didn't" stuff!
Silver chloride is one of the less sensitive silver halides you can use in photography, but it works; it dates to about 2500 years ago when someone (the Lydians?) figured out you could separate silver from gold by firing it with salt. So you could have done photography 2500 years ago instead of 200 years ago.
There's lots of stuff in optics that only requires a Fizeau interferometer (made of a candle flame and a razor blade, Bronze Age stuff), abrasives (Paleolithic), reflective metal (Bronze Age again; Newton's mirrors were just a high-tin bronze), abrasives, and an unreasonable amount of patience. Imhotep could have made a Dobsonian telescope and seen the moons of Jupiter 4700 years ago if he'd known that was a worthwhile thing to do.
Speaking of metrology, I've heard conflicting stories about surface plates: one story that the Babylonians knew about grinding three surfaces alternately against one another to make them all flat, and another that Maudslay originated the technique only about 220 years ago. (Or, sometimes, Maudslay's apprentice Whitworth.) This is clearly a technique you could have employed in the Neolithic.
Sorption pumps for fine vacuum (usually 1e-2 mbar) require a high-surface-area sorbent (zeolite or maybe even kieselguhr or ball-milled non-zeolite clay: Neolithic), probably glassblowing (Roman Republic era in Syria), sealed joints (apparently Victorians used sealing wax successfully up to HV though not UHV, and sealing wax is pine resin and beeswax: probably Paleolithic), and some way to heat up the sorbent (fire: Paleolithic). Fine vacuum is enough for thermos bottles (dewars) and CVD, among other things.
Conceivably you could have just luted together an opaque vacuum apparatus from glazed earthenware (which dates from probably 3500 years ago), using sealing wax to seal the joints. But debugging the thing or manipulating anything inside of it would have been an invincible challenge.
Sorption pumping works better if you can also cool the sorbent down, too; dry ice is today made by explosive decompression of carbon dioxide, similar to how puffed corn and rice can be made with a grain-puffing cannon, and regularly is by Chinese street vendors. Pure carbon dioxide is available by calcining limestone (thus the name: Neolithic) in a metal vessel (Bronze Age) that bubbles the result into water into a "gasometer", a bucket floating upside down. Compressing the carbon dioxide sufficiently probably requires the accurately cylindrical bores produced for the first time for things like the Dardanelles Gun (15th century). But possibly not; the firepiston in Madagascar is at least 1500 years old, dating back to the time of the Western Roman Empire, and I think it can achieve sufficiently high compression.
Mercury has been known all over the world since antiquity, though usually as a precious metal rather than a demonic pollutant. Mercury plus glassblowing (Roman Republic, again) is enough for a Sprengel pump, which can achieve 1 mPa, high vacuum, 1000 times higher vacuum than an ordinary sorption pump (though some sorption pumps are even better than the Sprengel pump). High vacuum is sufficient to make vacuum tubes.
The Pidgeon process to refine magnesium requires dolomite, ferrosilicon, and a reducing atmosphere or vacuum. You get ferrosilicon by firing iron, coke, and silica in acid refractory (such as silica). Magnesium is especially demanding of reducing atmospheres; in particular nitrogen and carbon dioxide are not good enough, so you need something like hydrogen (or, again, vacuum) to distill the magnesium out of the reaction vessel. As a structural metal magnesium isn't very useful unless you also have aluminum or zinc or manganese or silicon, which the ancients didn't; but it's a first-rate incendiary weapon and thermite reducer, permitting both the easy achievement of very high temperatures and the thermite reduction of nearly all other metals.
Copper and iron with any random kind of electrolyte makes a (rather poor) battery; this permits you to electroplate. The Baghdad Battery surely isn't such a battery, but it demonstrates that the materials available to build one were available starting in the Iron Age. Electroplating is potentially useful for corrosion resistance, but to electroplate copper onto iron you apparently need an intermediate metal like nickel or chromium to get an adherent coating, and to electroplate gold or silver you probably need cyanide or more exotic materials. Alternate possible uses for low-voltage expensive electricity include molten-salt electrolysis and the production of hydrogen from water.
Copper rectifiers and photovoltaic panels pretty much just require heating up a sheet of copper, I think? Similarly copper wires for a generator only require wire drawing (Chalcolithic I think, at least 2nd Dynasty Egypt) and something like shellac (Mahabharata-age India, though rare in Europe until 500 years ago), though many 19th-century electrical machines were instead insulated with silk cloth.
Vapor-compression air conditioners probably need pretty advanced sealing and machining techniques, but desiccant-driven air conditioners can operate entirely at atmospheric pressure. The desiccants are pretty corrosive, but beeswax-painted metal or salt-glazed ceramic pipes are probably fine for magnesium chloride ("bitterns" from making sea salt, Japanese "nigari"), and you can pump it around with a geyser pump.
I think the geyser pump is still under patent, but it can be made of unglazed earthenware or carved out of bamboo (both Neolithic) and driven by either a bellows (Neolithic) or a trompe (Renaissance).
Some years ago I figured out a way to use textile thread (and, say, tree branches) to make logic gates; I posted that to kragen-tol. So you probably could have done digital logic with Neolithic materials science, though only at kHz clock rates. And of course you could have hand-filed clockwork gears out of sheet copper as early as the Chalcolithic, instead of waiting until the Hellenistic period.
Fun question! I would suggest the following (in no particular order), subject to the proviso that you do need to be sat next to them to help manage frustration, especially in the beginning (although my personal take is that they shouldn’t be left to play by themselves at all at that age) - particularly as they learn the controller, general video game conventions, and the specifics of each game:
- Breath of the Wild
- Animal Crossing
- Stardew Valley
- Minecraft
- Super Mario Odyssey
- Super Mario 3D World
- Rayman Legends
- Ratchet & Clank
- It Takes Two
- Slay the Spire
- Journey
- Spiderman and Miles Morales
My son’s favourite superhero - far and away - is Spiderman, in large part thanks to the PlayStation games. Pretty great role model. Kids find swinging through the city utterly exhilarating.
It Takes Two was such a fantastic, memorable experience for both of us - he still talks about it months later. It does require quite a lot of a kid, though - better for when they’ve got a year’s experience.
And trying to catch all the insects and fish in Animal Crossing kicked off a passion in him for the real things, to say nothing of what it taught him about animals generally, time and seasonality.
A Nintendo Switch is probably a good place to start, although as he gets older I’m encouraging him to move more over to the PlayStation (partly because it’s so much cheaper over time!).
Switch Joycons are great for small hands, too, although most kids seem to be able to manipulate a full-size controller by age 4-5.
Trie is probably my favourite ds. I really enjoy this python implementation I learned while studying leetcode because its so succint. Really useful for interviews.
from collections import defaultdict
END = object()
def make_trie():
return defaultdict(make_trie)
def insert(trie, word):
for c in word:
trie = trie[c]
trie[END] = True
On the topic of simulations, I've been learning about Modelica, which is a engineering simulator. Basically, many real world devices can be described using system dynamics and their behaviour codified as differential equations. Modelica allows us to build such models, including mixed-domain models (electrical, mechanics, thermal, chemical, etc.), then the Modelica compiler produces highly optimized C++ code you can run to perform the simulation. It's heavily used in the car industry in Europe, but not widely known in academia.
Context: I'm researching a new book on ordinary differential equations through various real-world simulations, so like an ODEs theory book, but actually applying the concepts to real world systems. Get in touch by email if you're interested in seeing advanced preview of some of the projects that will be developed this summer. Contact info in profile.
