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Everything posted by pzkpfw

  1. I try to avoid magical thinking, but a certain, um, speculators recent ranting threats had me wondering.
  2. The OP also included "... What about home stereos, car stereos; do they lack the CD now ? From 8 track to cassette to CD to MP3 to nothing. Where do modern people keep their music, videos, movies ..." and that's where a lot of the conversation went. As for personal files, for years I've seen a heck of a lot more USB connected hard drives (now transitioning to SSD) used than CD. Add to that a good cloud backup solution, still no need for CD's. I'm not sure I'd trust a writable CD for very long term storage. Not a regular HDD either. Probably they key with digital information is to keep transferring to newer formats (and in multiples). (... don't want to end up like NASA, with data stored on tapes for which they have trouble finding readers.)
  3. My large pile of CD's is in a box somewhere, next to my two beer crates of vinyl. Not taking up room in my lounge, not getting scratched or lost. Instead, everything I ever owned - and much much more - is available via Spotify, on my PS3, connected to my stereo. (No antivirus needed.) I already have internet etc anyway, so that's no extra cost. And Spotify itself costs less per month than one CD per month would have cost. And in any case, it's bundled with my cell phone plan so works out cheaper than sticker price. (Yes, no free lunch and all that.) With bluetooth, and access via my phone, which has GB and GB of space (and Spotify allows downloads) I have my music everywhere. I don't miss CD's.
  4. Ever been in a 747 and have a ships' radar pick you out?
  5. You started the thread, it's up to you to provide something of substance to back up your claim of a "theory". Instead you've spent most of your time complaining about another poster. Let it go. Try "doing science".
  6. Post #49 here contains some great animations that I think are relevant: https://www.physicsforums.com/threads/the-velocity-of-a-moving-frame-of-reference.972860/page-2
  7. pzkpfw


    Polarising filters may be relevant.
  8. It's not about transparency, it's about the light from stars being dim and being washed-out by daylight. Your eyes can't cope with bright light from your surroundings, and see the stars. Same reason photos taken on the Moon generally don't show stars - even though there's practically no atmosphere there. A satellite camera will be arranged so that direct sunlight doesn't cause the same issue. There's no reason for simple air to be one-way transparent. edit: at night, where do you think the atmosphere goes to make stars visible?
  9. The news today has an item about Trump calming the hawks. I wouldn't put it past them for this to all be a beat-up to give Trump a "victory". i.e. manufacture a near-crisis out of nothing, so he can be shown to have averted it. (I really hate to sound conspiracist. But here it is.)
  10. How about a coil, with the magnet * arranged so when you spin the head of the cane it generates electricity and light an LED? (* Dunno about ball-shaped magnets)
  11. Retrospectively interpreting vague writings to fit later knowledge. Weak. Wake me up when your "god" gets a cellphone and learns to communicate better than with an oil stain that looks like St. Barnabus, or burnt cheese on toast.
  12. Already covered but I thought it would be good to reiterate some of it: the difference between maximum and minimum there is not "seconds". The moon has a day that's about 27 Earth days long. So a rock on the surface (depending on where it is) might be in Sun for about 13.5 Earth days, then in darkness for 13.5 Earth days. It's over those time frames that the rock heats up and cools down. The idea that an astronaut is exposed to almost instant swings from max to min, when in sunlight or shadow doesn't make sense. The sun does not heat things up that fast (unless you're much closer!) and things don't lose heat that fast (especially in an almost vacuum). I'd also point out that the Apollo landings occurred in Lunar morning to avoid the extremes of heat: A good resource - http://www.clavius.org/envheat.html --- In terms of "dark spots", were you thinking that at some far distance you'd be "in between" rays of light coming from the sun? (Is this what you meant by "between the arrows" in your post after studiot's diagram?) Basically, there's so much light coming from the sun, at so many angles (and it's not actually a point source) that anywhere where you can see it at all, you'll not be "between" all the rays of light from it. Think of it as "bazillions" of arrows. An object will have more of those arrows hitting it when close, than when far away. But it's not going to be "between" all of the arrows. Looking at studiot's diagram, imagine another twenty arrows between the two drawn, and imagine the arc "A" is an actual metal plate. All of those arrows would hit the metal plate. If you move that plate out as far as "C" (but keep it the same size), then some of the arrows will pass to the left and right of it (so it won't get as hot). But some will still hit it. Instead of twenty arrows, now imagine a "bazillion". Space around the Sun is flooded with light. You'll not find a place where the plate is between all of the arrows (but if you keep moving further away you'll find eventually there are so few arrows hitting the plate, that they can't be detected.)
  13. A given object will receive more light when close to the sun, than the same size object further away. Just stand close to a heater (say, an open fire) then move further away. The heat (IR light) is spreading as it moves away from the source. (Maybe think of a balloon. When it's small, a coin on the surface has a certain amount of rubber under it. Blow up the balloon some more, and the same coin will have less rubber under it, as it's been stretched out as the balloon expands to make the larger radius (representing further distance from sun)). On the other hand, the energy radiated out into space by the thumb, or coin, will be pretty much the same regardless.
  14. The way I see it, machines don't buy goods or services. While machines can and will take over many kinds of job, the owners of those machines/robots will still need a market to sell whatever those jobs do, to. e.g. say car manufacturing is totally taken over by robots. Great for the profitability of the car factories. But, if "everyone" has lost their job to a machine, who buys those cars? (Yeah, a bad and only partly worked through example.) So there'll be a re-balancing, if things go that way. Either people will find other kinds of jobs, or there's going to be a serious change in the way society works - more redistribution of wealth (taxation --> social benefits) and jobs (job sharing). Stuff like that. (I remember doing a school project when I was 12 (1982). It was about the "future" as posited by some "futurist". Apparently when machines eventually do all that work we would all get more leisure time. We'd all be working just 3 days a week and spending the rest of the time at the tennis club or something. I doubt it will ever be quite like that in reality, but there will be changes.)
  15. I have a B.Sc. in Computing. Did some math (linear algebra and discrete math) in that, but not a lot. It's a bit of a myth that computing is all about math. For me the question here is what are the other papers? If they are computing papers, for a computer science degree, what's the issue? If they are on Frisbee use or rhythmic gymnastics, then there's an issue.
  16. Has any son of a circumcised man ever been born pre-circumcised? There have been very very many circumcised men, so that's a pretty large sample. (I'm willing to bet the answer is "no"!) ---- Edit: just to note on re-reading the OP, HIV is something that can be transmitted, it's a disease. But from parent to child wouldn't actually be particularly easy (to my poor medical knowledge), unless to a baby in-utero. An HIV positive parent hugging their child won't pass on the disease.
  17. Most people will experience or perceive movement in this image. That does not prove that there is any.
  18. Can be done: https://electrek.co/2018/01/23/tesla-giant-battery-australia-1-million/ (here used mainly as a smoothing mechanism.) But as above, current battery technology just isn't what it needs to be, to be cost effective in the long run to be the main storage mechanism. (One alternative that always amused me, hydroelectric dams where water is pumped back up into the reservoir when power is cheap, to be used later when the power wasn't so cheap. Could also be used to "store power" from renewables.)
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