exchemist

Yeah....assuming you can create -ve energy density somehow........ Which is a bit like switching off gravity, if I'm not mistaken. 😀

But there is no theoretical way to move space itself. It's a bit like saying we could all fly if we could switch gravity off. Which is sort of true, except that we can't switch gravity off.

Oh you sound very familiar now. Bye.

In electronics, what's the difference between a topological surface and a.......surface?

I've had a thought about what may be the source of my confusion. It only makes sense to apply conservation laws in the context of an interaction. An interaction "collapses the wave function", or at any rate the property in question takes on a specific value at that instant. So then there is no uncertainty principle issue, as the value of the property has become definite. (But I am conscious of struggling with half remembered stuff from half a century ago, so I may well be speaking ex ano.)

UNQUOTE Would you mind not corrupting the text of my posts, when you quote them, with spammy links? Thanks. Reported for spamming.

Hmm, fair point about energy. I'm afraid I don't know QFT, so I am not sure of the connection between the path integral formalism and the uncertainty principle. AS I understand the concept of expectation values of a property it is the average result one would get from a series of measurements on a series of identical systems. Some individual members of the series would be below and some above. So if the expectation value corresponds to the value predicted by conservation, some of the results might not. Is this a wrong picture?

Yes. That's why I would welcome comment on my understanding of this point by a real physicist. @Genady's previous contribution did not seem to me to tackle it head on. But for instance, vacuum fluctuations imply a temporary violation of conservation of energy, I think, which averages out to zero.

It’s not a measurement problem though. It’s an uncertainty built into reality. I only mention “measurement” as that is something that resolves uncertainty into a defined value in the course of an interaction. As I understand it, momentum and energy are conserved on average, but there is a fuzzy halo around individual values for a given QM entity at a given instant.

I suppose the expectation value of a measurement will be in accordance with conservation, which would seem to leave a bit of Heisenbergian wiggle room on individual measurements. But I'm not a physicist.

Well I at least have evaluated it and reported my findings in this thread. But any pushback you may have read about elsewhere is far from odd, actually. Culinary tradition is often something people have strong views about. Just think of the arguments in Italy about Bolognese, or whether to use Marsala or Amaretto in tiramisu. Or in Spain about paella.

I haven't heard that since I was about 8, in 1962 or so. Brings back memories of primary school.

Well yes, but microwaving hot water isn't a great idea. If the cup is clean you can get superheating, bumping and a trip to hospital when you take the cup out again. Though if you mean microwave it with the teabag already in it, that could work, I suppose. Yes, it's strange they don't seem to be part of the culinary culture in the USA - or not 20 years ago. I use the kettle all the time time, not just for tea. If I need boiling water for cooking vegetables, or pasta, or something like that, I boil the kettle, as it is so much faster. But it is true that in the UK the primary purpose of a kettle is to provide actually boiling water, to pour over the tea leaves in the (prewarmed) teapot. So, having bought a kettle primarily for that, it makes obvious sense to use it for other purposes too. Not sure what the primary purpose of a kettle would be in a coffee drinking nation like Germany. But they may just appreciate the speed and efficiency.

Haha. Well, it is an issue in a lot of places, not just the States. Continental hotels almost always offer a hot water urn and teabags. I resort to using one cupful of hot water to warm the cup as much as I can, then discard that and brew the teabag in the cup with a fresh cupful. In the US one issue seems to be the absence of electric kettles. When my late wife and I moved to Houston in 1999 for a couple of years we found it really hard to buy one, though we did manage in the end. Seems they heat a pan of water on the cooker if they want boiling water. One can get electric kettles in France without difficulty, however. It's just the hotels, apparently.

All too often, giving you a cold teacup, a teabag and water in an urn at about 80C.

The Italians do the same and it’s just the job on a hot day in Sicily. And the Arabs drink it “ahmar, red”, hot, in a glass in which it can indeed look red. There are different ways to drink tea. But what is in all cases essential is to brew it properly, which is where our continental and transatlantic cousins can get it a bit wrong, generally not using water that is hot enough.

This discussion took place 6 months ago.

How horrible.

Cost is not the issue. It is the unwillingness of any supplier to sell lethal drugs for executions.

Strange. I would have expected CO2 to be far more uncomfortable than nitrogen, given that, at least as I understand it, the breathing reflex, i.e. a sense of suffocation, is driven by the concentration of CO2 in the blood rather than the level of oxygen. Have I got this wrong or are there other effects at play?

Haha, what a nutter! I’ve just tried a tiny pinch of salt in my tea. Can’t taste the salt and the tea certainly does not seem bitter, but then it doesn’t usually. Maybe it makes the 2nd half of the cup, when the tea has cooled below the optimum, a bit nicer. Interesting.

Yes I'll wear a pinstriped suit and bowler and carry a furled umbrella. No baseball cap and hideous golfing trousers for me!

The person behind this is apparently a serious tea drinker who puts milk in her tea a l'anglaise and says Britain is one of the few places where can reliably expect a decent cup of tea. So she's not some wacky Californian vagina-steaming nutcase, apparently. She says a very small amount of salt, not enough to make the tea perceptibly salty in taste, deactivates the taste buds that detect bitterness. What I don't quite follow is that if you put milk in your tea (a habit I think we got from India), that too cuts the bitterness from the tannins. So why do we need both? However I might try it this afternoon, just to see if I can detect a difference. What is funny about this story is the humorous, faux-panicky statement put out by the US embassy in London, averring that no way was the USA now trying to tell the Brits how to make tea!

Exactly. That’s what the potassium nitrate, aka saltpetre, does in gunpowder. KNO3, in which O stands for oxygen. Nitroglycerine is glyceryl trinitrate. - NO3 again. This is true of many explosives. The oxidiser is within the explosive, sometimes even within the same molecule, as with nitroglycerine. Ammonium nitrate fertiliser can also explode - there was such a disaster in Beirut, I think it was, a few years ago.

Do your homework.