John Cuthber

To my mind, the interesting thing about the astronomical unit is that it was fairly widely used before anyone really knew how big it was. http://curious.astro.cornell.edu/physics/62-our-solar-system/planets-and-dwarf-planets/venus/262-how-did-a-transit-of-venus-provide-astronomers-with-the-first-measurement-of-the-earth-sun-distance-intermediate Another interesting issue is that the abbreviation AU is also used for Absorption Units (in spectroscopy) and for also fro Angstrom units (not everybody has an "Å" on their keyboard.) The former issue can be resolved by context- only one of them is a unit of length. The second can be resolved by asking "is it bigger than a breadbox?" A similar approach can be taken with the distinction between the nanometre (nm) and teh nautical mile (nm)

I haven't seen the show, and probably won't but I'm wondering what sot of plot device this BArGaIn is. My first guess would be that it's a MacGuffin https://en.wikipedia.org/wiki/MacGuffin But it occurreed to me that it's a bit specific for that. Is it one of these? https://en.wikipedia.org/wiki/Plot_device

Digital filters designed explicitly to be tunable to a (digitally) given frequency are pretty commonplace. So, if you start off with a fairly rubbish sine wave (say an integrated square wave), you can get an output that's a very good sine wave. t's often going to be noise, rather than harmonics, that dominate the "impurities" in the output. If you don't need a very high frequency you can get an very good sine wave by "anding" two fast square waves with different frequencies together and filtering the result. If you use, for example a 1 MHz square wave and a 1.001 MHz square wave (derived from a PLL if you like) then the output is 1KHz and most of the noise is still in the MHz regions which makes it easy to remove, even with a fixed filter. For audio purposes, you ca ignore it- it's far too high to hear.

You don't need to. There are chips that pretty much do it for you. (Other chips are available) https://www.intersil.com/en/products/timing-and-digital/dsp/dsp-digital-filters/HSP43220.html With a 96 dB attenuation for out-of-band signals you could start with white noise and get a pretty good sine wave. I'd still stick a low pass RC filter on the output. As an exercise for the interested reader, imagine that you are feeding the signal into a traditional 600 ohm load and that it's an audio signal delivering 1 mW. How good does harmonic rejection of a 1 KHz signal need to be before the johnson noise in the input resistor exceeds the sum of the errors due to harmonics? (i.e. at what point does improved harmonic reduction become pointless?)

Today I learned how difficult it is to keep count of the zeroes. 299 792 458 m / s It confuses matters even further when you realise that some folks use the , where others use the . to delineate the decimal point and the thousands separator. In the UK 343 m/s is a bit faster than 300.000 m/s The speeds are about 3E2 and 3E8 m/s. Sound is roughly a million times slower than light

On a related note, why is Trump so bothered about a book? It's not as if many of his supporters actually read much.

The problem is when people also shorten hexamethylene diisocyanate (AKA HDI) to Methylene di-isocyanate and then get one or other mixed up with hydrogenated MDI (AKA HMDI) officially known as bis isocyanatocyclohexylmethane They seem to have chosen a bunch of compounds that are bound to get muddled.

Methyl diisocyanate doesn't make sense. Do you mean methylene diphenyl diisocyanate? The route of exposure isn't as important as you might expect. It's possible to get asthma by skin contact with these things.

Essentially the answer to that is "maybe". Isocyanates themselves are very reactive and are often derivatised before analysis by reaction with, for example, dibutlylamine. The substituted dibutyl urea is then measured by GC/MS. However, it's perfectly possible for the dibutylamine to react with a polyurethane and to give exactly the same product. (you don't see ammonolysis as often as hydrolysis- but it still happens) Similarly, anything that involves heating the polyurethane might cause it to decompose forming isocyanates. My view is that, regardless of the apparent measurements (and there are studies that support both sides), isocyanates are unstable in the presence of water and there's always water around.

Describing occupational asthma (which is a permanent condition) as a "warning mechanism" is, at best a poor joke. The measurement of "free isocyanate" is about as close to religion as analytical chemistry gets. Almost any technique that could measure it could also generate it, so it's a matter of faith whether the free isocyanate was present or not.

Isocyanates react with water (which is always present in the air). Even if the manufacturing process didn't get rid of them, the air woud. Some foams are potentially rather flammable, but there's no great risk associated with them.

That's a little bit frightening, and (perhaps unexpectedly) about 40 years too late.

Today I learned that Intel will sell you a chip with 17 qbits https://newsroom.intel.com/news/intel-delivers-17-qubit-superconducting-chip-advanced-packaging-qutech/ And it needs rather specialist cooling ( 0.02K). Classical computing isn't dead yet, though it may not be long.

Today I learned that the man in that video thinks that H2O2 is "2 parts hydrogen and 1 part oxygen" (about 1 min 10sec.) He thinks it's use by the body is a recent discovery Well, this wasn't new 30 years back when I was a student. https://en.wikipedia.org/wiki/Respiratory_burst I always thought the main use of it in cleaning wounds was that thebubbles would lift the dirt out. It simply doesn't last long enough in the body to do much harm (except in the rather weird situation of causing an embolism)

They didn't make a habit of it; they usually only did it once. Today I learned that it was international bad joke day.

Today I learned that someone actually did a check on how well waterglass preserves eggs.

No. It's a reflex action- like when you put your hand on something hot + pull it away before you even know it's painful. (And that's before we get into the question of whether or not flies are conscious.

Well, that may be true in your opinion, however, in fact, it's not. The reflexes can still happen even in a brain dead individual http://www.sciencedirect.com/science/article/pii/S0041134503012752 The classic "test of reflexes" is this one https://en.wikipedia.org/wiki/Patellar_reflex And if you get someone else to tap your knee just under the cap you will notice an odd effect. You see your foot move before you feel the tap. You can't have made, even an unconscious, decision to move the foot before you felt the stimulus.

They do. https://www.thoughtco.com/do-insects-have-brains-1968477 Similar reactions are found in most animals, including us. https://en.wikipedia.org/wiki/Reflex_arc

Why?

Well, it's clear to me that, without evidence, you are making stuff up.

All the good chemistry jokes argon.

Does "making up random stuff" count as philosophy? If philosophy proceeds without bothering to see if it is right or not then it's hard to tell the two apart. Before you ask Is philosophy more advanced than science in understanding reality because ... you need to check that philosophy Is more advanced than science in understanding reality

Today I learned that Stringjunky doesn't distinguish between weight and density. I must get involved with trading kilos of lead vs kilos of feathers.

I discovered that: It's impossible to talk about poop without someone making a "bullshit" pun there's gold in there (presumably significantly more in some cases than others; I quite like Goldschläger.) The nitrogen in poop is almost certainly worth more than the gold.