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GeeKay

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Everything posted by GeeKay

  1. Yes, I think I begin to get it now. Thanks, studiot, for your detailed and helpful explanations. Food for thought, indeed. G
  2. It could be that the use of the adjectival 'super' in superposition has been confusing me. If measurement is the key that defines whether a quantum system is in superposition or not, then what about measured versus unmeasured? Personally I suspect the opposite of Spain is located somewhere in the South Pacific. . .
  3. A few years ago one of my nieces, then aged twelve, asked me what "the opposite of superposition" is. Her question completely stumped me at the time. It still does. I have since considered placeholder answers like: normal position, position, classical position, etc. None of them seem satisfactory, however. This same question (with full quotation marks) also continues to stump Google. NB. I am prepared to be told that the question is nonsensical - that it'll be like asking what the opposite of Spain is, for example. Still, I'm up for it.
  4. Regarding ventilation: this used to be potentially an issue given the room's double glazing. It was necessary to block off the window's trickle vent, this due to the wind persistently recreating Bob Dylan-like harmonica sound-effects with it (worse still, given the prevailing wind direction in this part of the world, the house itself is situated near the top of a south-west facing hill with an uninterrupted view of the horizon). The room isn't particularly dusty, although I will now give it an early spring clean. Allergens remain an unknown at present. On the other hand, I do keep the door ope
  5. This is from a person who spends several hours a day word-processing in a smallish upstairs boxroom (2.4m x 3.8m) that faces south-west. The room is centrally heated (20 C) and efficiently double-glazed. For sometime now I have suffered from minor, but persistent respiratory problems, stuffy nose, throat-clearing issues. I also have chronic sinusitis, which I plan to do something about just as soon as Covid-19 finally abates. . . whenever that might be? Meanwhile, these respiratory problems have all but vanished since using a humidifier. It seems that it more than compensates for the roo
  6. It should bother you - if only because the "wilfully ignorant" tend to vote into office the kind of dickheads who are currently doing the rest of us NO favours whatsoever. Anyone care for a re-run of 2017? Then there's this. . . https://www.nytimes.com/2019/12/28/climate/trump-administration-war-on-science.html
  7. This is a valid point. . . as far as it goes. It's just that it's not enough any longer. In the age of the internet it's no longer a matter of leading a person to a book; rather it's a case of leading the book to the person.
  8. Many thanks for the link. Yes, the fact that both are just opinion pieces illustrates how so-called "truthers" like Mark Steele can patrol their chosen agendas the way they do. This is more an internet problem than a purely science-based one. Still, speaking as a layperson/armchair observer here, it might be helpful if scientists took on Steele and his ilk more directly. There's no chance of getting such folk (and the majority of their camp followers) to alter their views by reasoned debate, of course - not when these views are buttressed by emotional convictions. All the same it would surely
  9. Is there any truth in the proposition that 5G is harmful to health? Many thanks. https://blogs.scientificamerican.com/observations/we-have-no-reason-to-believe-5g-is-safe/#
  10. swansont - many thanks for your succinct answer to what has been a long-term headache for me. Much appreciated!
  11. I am tying up the loose ends of a SF short story I wrote last year, featuring a neutron star. Right now, though, I'm stuck over a long-term problem concerning the star's luminosity. It's surface temperature is 8,200 K and has a diameter of 20 kms. My problem has consisted of trying (and failing) to calculate what the star's absolute magnitude would be. I'm afraid this is beyond my abilities to solve, and unfortunately I don't know anyone among my friends who has the mathematical nous to help me out here. So I would be extremely appreciative if someone here could put me out of my misery. Many
  12. What would be the theoretical maximum spin-rate of a small asteroid (25 - 100m diameter?) if it were, for example, composed of a single 'monolithic' chunk of iron? This question arose after reading up on the subject in a Wikipedia article. Listed in it is one such asteroid with a spin-rate of around 30 seconds. Could this be bettered, given the above parameters? Many thanks. https://en.wikipedia.org/wiki/List_of_fast_rotators_(minor_planets)
  13. Yes, I understand now. In other words the only 'practical' way for an object to decelerate while passing through an intense gravitational field would depend on powered means, not inertial. Moreover, the fact that the incoming object is moving at 0.01c relative to a given mass would (I should imagine) rule out all variations of power assist - this insofar that the proper velocities of nearly all stars aren't remotely relativistic, that's to say within local frames. Many thanks for clearing up this matter for me.
  14. I'm wondering if it's possible to use the gravitational field of a massive object to decelerate a spacecraft moving at high velocity. An example is this: if a spacecraft moving purely on inertia at one percent light-speed performed a flyby of a one sol mass neutron star (or black hole) at a given altitude, would the gravity field cause the spacecraft to swing round the star, slow it up or else deflect its trajectory in a meaningful way? According to one online calculator the escape velocity of a solar mass neutron star at a distance of 25,000 km equals 3,000 km/s or 0.01 c. At this distance th
  15. Hi Yes, I'm looking forward to trying out these ideas once I get the offending discs back from a friend of mine whose been investigating the problem. I'll start with Phil for All's solution - this being a likely cause, given my tendency to fumble around with the player remote when watching films in subdued lighting. Failing that, I'll attempt to change the movie's audio setup in the discs' formating options (thanks, Memammal) and see what happens. Again, thanks for all the helpful advice - I've learnt a great deal from it
  16. Certainly seems to be. One question, though: how come the the discs and/or the player have started playing up like this? I say this because they always played okay in the past, using the existing player. It's only now I've started having this problem here. Thanks for getting back to me, by the way.
  17. I'm afraid I don't - the only Blu-ray player I have is the one I use for the TV (both my PCs are DVD-only). However, a friend of mine reports that the discs play fine on his own Blu-ray player. So it seems the source of the problem lies with my player. Yet it has no troubles playing my other Blu-ray films. That's what's bugging me, perhaps more than anything else.
  18. A strange conundrum: nowadays whenever I try to play my Blu-ray edition of 'The Lord of the Rings', I get plenty of video, but no audio. That's to say there's audio throughout the preamble (adverts etc) that comes before the main feature starts. But as soon as the actual cinematic part of the disc begins it goes completely silent. The same problem exists on all three discs - though, interestingly enough, it doesn't occur on any of the special features discs bundled with the boxed edition. They come out loud and clear! No other Blu-ray film or DVD of mine has this weird and wonderful audio issu
  19. I gather that Mars regularly experiences aurorae, this despite the planet's lack of a global magnetic field. It's also stated that these aurorae occur in the ultraviolet wavebands. I assume from this that these displays are invisible to the human eye. This being so, I'm intrigued to come across artistic interpretations on the net that suggest how "auroras will look on certain parts of Mars" (to quote the text accompanying one such image). Does this mean that aurorae are actually visible, after all? Or am I missing something here?
  20. Ah, yes, I understand now. Thanks for pointing this out to me. I had intended to use the image of an incoming comet and a rogue minor planet (of Ceres mass) passing through the solar system as an analogy for the expansiveness of sub-atomic space. But I can see now that this is no analogy at all. PS. Those cloud chamber shots are astonishing!
  21. Yes, I should have used 'concentration' rather than 'density'. I stand corrected. So I guess then that if 1 cm2 of skin contains (in round figures) a quadrillion atoms, this means that there's an excess of around 15,000 more atoms than those neutrinos passing through this same area per second. But as Janus points out, a given 'atom' consists mostly of space, which explains why the strike rate is so low. (At some point I'm going to sit down and calculate exactly what this means at a sub-atomic level). Still, I'm intrigued as to why there appears to be such a glaring contrast between the strike
  22. I understand that around 65 billion neutrinos pass through every square centimetre of human skin (or any other skin for that matter) per second. I also gather that a human being can expect to be struck by an individual neutrino perhaps once or twice in a lifetime. These statistics, if true, are remarkable on several counts. Nevertheless, in order to get an handle on what this continual neutrino blitztkrieg really means at an atomic level, I've been trying to find out what the average density of atoms there are in a given square (not cubic) centimetre of human skin - but no luck so far. Does an
  23. Thanks for unsticking my brain - and to ajb for supplying the correct formula. Just one other point - well, two actually: I assume that kilometers and kilos respectively should be used as a metric when applying the above formula to a given celestial body. The second point is rather more complicated: how does one use the formula's solution as a means of calculating a celestial's body's focal sphere? As examples, a minimum of 550 AU is cited for the Sun, 15,300 AU for the Earth, and a focal sphere of just 10 million km for Sirius B, but I don't know how these figures are derived. (I'm afraid
  24. I came upon this statement about gravity lensing the other day. It reads: "The ratio of a planet's radius squared to its mass lets us calculate the distance a spacecraft must reach to take advantage of gravity lensing." It's the first part of this statement that I can't understand - "The ratio of a planet's radius" especially. While I know the meaning of each individual word, I simply cannot string them together in any meaningful sense. Neither can Google apparently. Any suggestions?
  25. Yes, I think I've got that. I guess then there's no reason why the calendars of both planets should coincide in any particular way.
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