exchemist

Doesn't the last of these just make you go orange - and become rash?

I don't see Russell on the list. That seems a curious omission. @TheVat's list is more the sort of thing I would have expected - though it is Eurocentric, I suppose.

OK, as this is homework, we ought to go through this in stages to help you understand, rather than just giving you the answer. First, do you understand why the aluminium ring jumps? Second, in the version with two rings, typically the second ring differs from the first in one important respect. What is this and why do you think it might make a difference to its behaviour?

Will it experience a force?

That's what I would have thought. But it would be nice if someone would care to summarise the Meissner-Ochsenfeld effect and what force it can generate. All I know is that a superconductor repels a magnetic field from its interior, but why this produces a force, in what direction, and of what magnitude for a given field strength, is something I have never studied. I had a quick look on Wiki but it was not very informative.

I know, but I read the query as assuming such waves could ignite it, so to disabuse the poster of that notion I tried to explain how gunpowder was actually ignited in practice.

No it was the felt hammer, inside the piano, that was painted. There was a bang, a certain amount of dust and dead ladybirds - and an eerie pause in the singing.

One snag I can think of is that the angle of the Earth's field is steeply inclined. So instead of just floating up or staying where you were, I would have though you would shoot off or slide down at an angle. But I'm not familiar with Meissner-Ochsenfeld effect so I'll have to let someone else check the robot's maths.

Yes, a few problems with your question. Firstly, radio and sound waves don't exert a force - or not to any significant extent - and secondly a force will not ignite gunpowder in any case. You need essentially to set fire to it somehow. You may have seen sailors firing c.18th cannons in films, for instance. That's why we call it "firing" them. A special match was used, applied to a hole in the gun and that would set it off. There was later something called the "percussion cap", in which a small amount of mercury fulminate, Hg(CNO)₂, was used. That is a highly unstable compound that will explode if struck sharply. This could be used to ignite the gunpowder. So with that system, applying a force, by hitting a capsule of this, could indirectly ignite a charge of gunpowder. There are other explosives that detonate when receiving a shock, most notoriously nitroglycerine, but also less hideously dangerous things such as picric acid* and nitrogen triiodide, both of which I have made at school, hem hem. But back to your question, there isn't actually the problem you imagine with gunpowder, so there is no need for your proposed solution. By the way, if you want to stop gunpowder from burning you just wet it. (In fact historically this was the basis of an early HM Customs and Excise test for distilled alcohol. "Proof spirit" was the weakest solution of alcohol in water which, when used to wet gunpowder, would not prevent it from burning.) * A friend of mine at university had a funny story about a school practical joke, involving painting the hammer of a single piano key with it, the key in question being played only in the bridging passage between two verses of the school song. You can probably imagine the effect.

If you mix up sugar yourself, though, you will need to measure or calculate the density for yourself. If you are prepared to do that, you could simply buy Lyle's Golden Syrup in the supermarket and use that.

I presume it has to be miscible with water. If so, would glycerol fit the bill?

Is Translate that bad?

Hovercraft eels ouant tobacconist bouncy bouncy.

What are you talking about?

“Fictional habitats”

Well yes. When you say "colonise", it implies taking over territory that was not previously theirs.

No. The water is adsorbed in the pores and will stay there. But the obvious thing to do is dry them out, in an oven at 120C for a few hours.

For colonisers they don't seem to be doing a very good job. Unless David Icke is right about the Lizard People, I suppose.

Yes, that could be it. Though I don't buy the notion it is unsafe to eat from dishes with cracked glaze. Bacteria and fungus are all around us and I don't see why a few traces in the cracks in a glazed dish are likely to be pathogenic.

You can put glass jars into a microwave and they stay cool. Though some glazes on earthenware get hot and crack (I have found, to my chagrin).

I suppose in theory, as it is water that is absorbing the microwaves, once it has gone the silica gel should cool down, as it should be transparent to microwaves of the frequency used. So the process ought to be OK, I think.

I'm quoting Douglas Adams but the point is a serious one. The distances involved are vast and massive bodies such as spacecraft can only travel at a fraction of c*. Physical travel from one habitable planet to another would take centuries, and centuries more to get back, and to what end? My own view is that intelligent life from elsewhere would have long ago realised it would be a colossal waste of time and instead would put their efforts into remote sensing - if they were interested in our planet at all. (It fact, it may be just arrogance on our part to imagine we would be that interesting.) * If it is proposed that alien civilisations may have found out how to travel faster than light, my response is that is unjustified, whimsical, wish-driven speculation rather than science. There is no objective reason so far to distrust Relativity.

Why not? Because "in space travel the numbers are awful".

Indeed I am assuming that, since we know it to be the case. And I'm afraid you do accept these stories uncritically. We've established the Arawn story is rot. You could have questioned it. After all, its rotation period is less than 6 times that of the Earth, a far bigger body. And nowhere on the internet is there any support for the idea it could not be naturally stable. If you had checked that, it should have rung some alarm bells. But no, you just pushed it out as evidence of aliens (suitable hedged with caveats, but that is what you meant). Have you learnt from the Arawn story that the source you used for that cannot be trusted?

Except that we are not a bunch of primitives and these things have been investigated, on numerous occasions, with nothing to show for it. What has instead been revealed by many such investigations is the under-appreciated capacity of people to make mistakes in identification, to delude themselves and to fabricate. You, for example, have shown yourself willing to accept, uncritically, a number of stories, at random, with no linking feature, apparently because they support a pre-existing belief in alien visitations. When one of them is shown to be nonsense, it does not give you a moment's pause: you just move smoothly onto the next one, as if the first one had never existed. You never stop to ask yourself why you were fooled, or how to avoid being fooled again. Hence the scepticism of people like me about this stuff, when put forward by people with your sort of mindset.