exchemist

Interesting that there is so much water, considering the high temperatures - 900C- on the sunward side (it's tidally locked, apparently). One would think water would be lost into space at such temperatures, as the fraction of light molecules with velocity > escape velocity must be significant, I'd have thought. But then if, as they suggest, it started out in an orbit of similar radius to that of Jupiter, and was later kicked inward, we are probably not looking at an equilibrium state.

I say: malevolent, mad ballocks.

Thymine has a methyl substituent in the 5 position, which uracil does not have. The numbering is just a way to denote the ring substituents. With heterocycles it is normal to pick one of the hetero atoms as position 1 and the others then follow round the ring.

It will certainly depend on battery capacity, just as a big engine will be usually more powerful than a small one. However it will also depend on the battery technology and design as well.

I think they have to be entities, because something continues to exist in between interactions. If that were not the case, we would be unable to predict the properties of the entity in the next interaction, which is what QM enables us to do with great success.

The weight of a battery pack depends on how it is designed. It is not something you can work out from electrical performance data. You would not expect to be able to work out the weight of a petrol engine from its power output, would you? Because, again, It depends on the design.

I must say it has always seemed to me that the notion of "particles" is a fairly preposterous construct, when one thinks about it: the idea of an entity with no physical dimensions but nevertheless finite properties such as mass, charge, intrinsic angular momentum etc. Just as artificial as "waves", really. Originally, in classical physics, the concept of particles was merely used to simply physics problems to their essentials, for ease of modelling. Like you, it has often seemed to me that QM entities only behave like particles when they interact. Reading Rovelli's Helgoland last year, I was quite impressed by his idea that QM entities only have defined properties at all when they interact, so we should perhaps let go our idea that they possess them in a continuous sense in between.

Yes, I think the point is that "r dot" signifies velocity in the direction of r, which means radially. That's what I and others have been saying. What is misleading, it seems to me, is that the film accompanies this by showing a film of someone jogging round the circumference, i.e. not moving radially. I suppose there is a little bit of radial motion, in that the jogger is moving up and down a little as he runs. Whether that is enough to cause a sensation of his head moving sideways to left and the right, as it goes up and down, I am not sure. It will depend on the radius of the circular tube he is running inside. It's a very small diameter tube in the film. Whereas If you think of 2001, for instance, the space station is hundreds of metres across. (The effect of r dot will be much less because ω will be much less: you need a lower rotation rate to simulate 1g of gravity in a larger ring.) The two guys trying to throw a ball to one another, across the centre of the circle as they rotate, is a much better example of what happens, I feel. That is radial motion, so that is the scenario in which the Coriolis effect arises.

I'm not sure the Coriolis effect would have that dramatic an impact. In most uses of rotation to produce artificial gravity that I have read about, the spacecraft would take the form of a tubular wheel. According to my understanding , the Coriolis effect would chiefly affect objects moving radially, rather than circumferentially. Or am I missing something?

The Ipcress File and Get Carter.

OK fair enough, you mean there is no cleaning chemical impregnating the cloth. Yes, one is just as well off using a regular spectacle-cleaning cloth, from the optician or wherever.

It is, as I suspected, a microfibre cloth though, not "just a cloth".

Anyone who wears spectacles will know that you need a microfibre cloth to clean the lenses properly so that you don't get reflections, glare in sunlight etc. I don't know what an Apple cloth is but I suspect what you need is a cloth for cleaning lenses, not just any old piece of fabric. At any rate, that is what I use to clean the screen on my laptop.

Im not an expert on this but I wonder if the valves may not work so well with a compressible medium as they do with an incompressible one. If the %volume change of the pump chamber over its operating cycle is not that great, the pressure differences it creates may be too small to actuate the valves properly. This could explain why, when the pump is wet, you get better pumping, due to the moisture helping to seal round the edges of the valves, or else that it lubricates them so they function more smoothly. Whereas, when the pump is operating with a liquid medium, the pressure from whatever actuates the diaphragm will be instantly transmitted in full to the valves, because the fluid is incompressible, making the valve action more positive. But this is only speculation on my part, based on dimly remembered experience of dismantling an SU electric fuel pump on a Morris Minor I owned in the mid 1970s, when I was a student.

What is the Mohs scale hardness of each of these? What is artaclase?

If one thinks of the most widespread mineral material used by early man for building and for early artifacts, the rest can be confirmed fairly easily, using Moh hardness as a check.

Well of course. That's what several of us have been saying: when gases accumulate in hollows or high points, they do so because they are not mixed, i.e. before they have a chance to diffuse away into the general body of the atmosphere. The point we are taking issue with is your apparent contention, earlier in this thread, that mixtures of gases can spontaneously separate, or stratify, at least partially, under the influence of gravity. It is this that I am saying is not supported by your references.

Thanks. I've had a look at these but none of them seem to me to assert anything about gases concentrating themselves from a mixed state.

Well I am open to being corrected on the basis of solid evidence if you have any. If you have had to deal with methane accumulating in buildings you should find it easy to point to a standard, building regulation or paper that says methane or hydrogen will become more concentrated, i.e. with molecules moving against the concentration gradient due to difference in molecular weight. On the face of it, though, this seems ridiculous to me, though I do acknowledge that at very high artificial g forces, in a gas centrifuge, you can see a bit of partial separation due to this. This scenario will be where @sethoflagos's thermodynamic analysis has a practical application.

I've already answered this. If the gas is released as a stream (i.e. unmixed with air), it will do what you say until it diffuses into the surrounding air. Once it has done that it will not do what you say. This was also true of poison gas in WW1. After a while it dissipates. But this will be relatively slow for gases with high molecular weight, due to lower molecular velocity. There is no way that mixed gases will separate appreciably under the influence of gravity. You can do that sort of thing - very partially - in a gas centrifuge, but that involves very high multiples of g. You have yet to offer any reference supporting your contention that heavy and light components in the atmosphere will spontaneously separate , at least partially, under the influence of gravity.

Now it is you that is avoiding my question. What reference can you point to that says the atmosphere stratifies by gravitational separation of its constituent gases.

The lighter gases will diffuse downward. I do not believe they will spontaneously separate at high points, as you suggest. However if a stream of a light gas is introduced, that may rise initially, until diffusion or other processes dissipate it into the general body of air. This will be quite rapid, especially with hydrogen, due to the low molecular weight and consequent high average speed of the molecules. Have you a source for this idea that atmospheric composition changes with altitude, because of density differences between its component gases? I have not come across this. The compositional variations I am familiar with are due to chemical processes, e.g. ozone formation. If this indeed does occur, it must be a very small effect, detectable only over altitude differences of many km. Not something you would ever see in a building.

What intrigues me is how the risk of the microwave beam going off-target is managed. I see the beam is said to be too diffuse to harm living organisms. But I wonder about that, if the power being beamed is several GW in intensity. I can see they should be able to avoid the most obviously dangerous parts of the microwave spectrum, e.g. water absorption region, but it still seems a bit glib to me.

But again this is not spontaneous separation by density. Diffusion alone will mix gases of different density eventually. This should be obvious if you think what happens to a dense gas released into a vacuum chamber. It does not all collect at the bottom. That shows that molecular speeds are sufficient to far outweigh the effect of gravity on individual molecules. What may cause confusion is that the mean speed of molecules with greater mass is lower, at a given temperature. So their rate of dissipation by diffusion will be lower.

OK, give it a try then and let us know how it goes.