John Cuthber

"Why did textbooks get so big?" We learned more stuff...?

No point asking then. Would a passing mod care to close the thread?

Yes they do.

You seem to have it the wrong way round. The definition of isotopes is that they have different numbers of neutrons. Cooling oxygen until it liquefies does not change the number of neutrons. So it does not make any new isotopes. What changes is the temperature, rather than anything else. Isotopes have slightly different boiling points, but it is not the change in boiling point that makes them different isotopes.

The presence of an impurity such as CO2 will lower the freezing point of water. But my guess is that this is essentially a supercooling phenomenon.

That's not about waste disposal, is it? So... No; hydroponics is not about waste disposal, but nor is the thread. Trying to get back to the topic isn't normally called "misdirection". It remains the case that improvements in fertiliser technology have been made since the Neolithic era.

You seem to have missed the point. regardless of whether we are talking about "cave-men" using green manure or animal manure, the users of hydroponics think they have made an improvement over the Neolithic technology. It may have been key to Neolithic society. It is still important. However, it has, in at least some circumstances, been "substantially improved upon". (Unless, of course, you think the hydroponic farmers are actually using tech that is sells good than the traditional approach). You are technically right in saying it doesn't answer the question but consider this. "Is the Whitehouse made from cheese because of pressure from the dairy lobby?" Arguably, the answer to that is "no". But pointing out that the Whitehouse is not actually made of cheese is not a bad thing.

Because they think they have made a significant step forward since the use of manure.

The hydroponic farmers might argue about that.

Not very relevant if you are using N2O4 as the oxidant. 😉

Yes, I know but £ S and d are different units for the same thing. I can add a kilo of potatoes to a pound of minced beef adn an ounce of flour. But I don't get 3 anythings of stew.

Yes, and he wasn't 9 anything.

Did anyone suggest that they might be? It's "one whole anything" or "one of anything" but it's not "one whole of anything". One whole what? I guess it's "one whole instance of anything".

If someone thinks you need an MSDS for the stuff you put on your food, they have failed to understand risk assessment.

I think that part of the reason they use ferrocyanide is that it alters the crystal growth leading to a change in caking behaviour and also perhaps crystal form. Adding a little copper sulphate solution to the salt solution will form an insoluble copper ferrocyanide precipitate which you can filter off. People are still doing work on this sort of thing https://pubs.acs.org/doi/full/10.1021/cg201661y?mobileUi=0 It's a good idea to filter solutions before letting them crystallise, even if the best you can do it so filter through a paper tissue. However, I think the problem you have there is capillary creep. A couple of drops of cooking oil on the string above the level of the liquid may help keep the solution where it is meant to be.

"Why can't you re-burn hydrogen" Because you can't burn "ash".

Stinky.

I found melting the platter with a blowtorch to be very satisfying. Ferric chloride attacks aluminium very vigorously. Be careful of the fumes released. It's probably best done outside. You might need to scratch through the magnetic layer to let the etchant get to the substrate.

The standard way of depicting mirrors in a ray diagram is a line with shading on the "back" of it. https://en.wikipedia.org/wiki/Geometrical_optics#/media/File:Reflection_angles.svg Interestingly, the PIAB model works for a particle in the universe.

Here is a page from Peter Atkins' book "Physical Chemistry" which refers to a particle in a box. The purpose of the box is to exclude the environment. It's as close to a free body diagram as anything else. He was a good lecturer, but his habit of producing new editions of the book was annoyingly good at dropping their re-sale value. That's why I still have mine from '84. When I was there, Oxon had the largest chemistry department in the Western world.

I am curious. Studiot, when you got a hat pump installed, did you also upgrade the insulation?

Not really. This circuit generates a distorted sine wave in which the phase of the distortion is arbitrary WRT the sine wave. https://en.wikipedia.org/wiki/Phase-fired_controller Obviously, you can resolve any arbitrary phase into a sin and cosine component. In that case, you only need two phases, as long as you don't mind one of the amplitudes being negative.

How do I distinguish that from being fat? Also, it may have escaped your notice but essentially everyone is "peasant stock". However, that's enough time wasted on a random number generator.

BMI is a system by which a doctor can tell a patient "You are too fat" while causing less offense. Reading anything more into it is fishy. It's a bit like IQ.

Because it didn't make sense. BS1363 was introduced in 1947. It predates any EU standard. The UK BS1363 plug is wired with brown, blue and green/ yellow wires. The BRown wire goes to the Bottom Right pin. The BLue wire goes to the Bottom Left pin. Remarkably few people seem to understand this. There was a very old standard BS546 where the wires were black and red, but there's no good reason to revert to that . It went at about the same time as round-pin plugs. There was a relatively recent change of standard for wiring the socket that goes with that plug. Previously the house wiring was done with red, black and bare T&E cable. This was changed to match the colours used in the flex from the cable to the equipment. This was done deliberately; it was brought in at the same time as a requirement that any new installations needed to be verified by a competent electrician. Before that change, the "householder" could do their own work on the system. If you think about it you will see how they needed to change the wiring somehow in order to distinguish old wiring (which doesn't need a certificate) from new wiring (which does). The "old colours" cable is still available on eBay etc- it's not clear why...