Jump to content

GeeKay

Senior Members
  • Posts

    123
  • Joined

  • Last visited

Everything posted by GeeKay

  1. Yes, my apologies about the "shouty" font. I must have hit the wrong button. Re solar power issues, I do wonder if Earth-based systems will always be sufficient, given our soaring energy needs. The last time I looked we were, globally speaking, consuming around 500 exajoules per annum, and while there will always be dips due to recessions etc, the trend, for all its sawtooth profile, remains remorselessly upwards. So much so it seems that unless there is a global catastrophe of some kind, or else a radical shift in thinking, it will continue to soar. I accept that new technological advances in the nearer term - both with regards to solar energy gathering and the perennial problem of energy storage - may satisfy our needs for quite a while longer yet, and so keep the industry down here on Earth. And, yes, I share the concerns about microwaves beaming down from space. I suppose we will first need to become a true spacefaring species before we learn to harvest all the energies that requires from the environment of space itself. I don't know if this is putting the cart before the horse, or whether the horse is having a free ride, but I'll let posterity decide about that. Many thanks for the links and helpful responses. The Elon Musk link is a gem.
  2. 'Hyperspace' by Michio Kaku is very good on the subject of parallel worlds. Highly recommended - and not just by me!
  3. Assuming for the moment that the technology will be available in the not-too-distant future, could the Earth's energy needs be met entirely by solar power one day? By this I mean having the Sun's energies directed from space down to us on Earth via microwave beams, say. As a follow-on question, are there any practical limits to how much energy could be harvested from the Sun? I have in mind an array of gigantic solar panels orbiting the Sun at fairly close quarters - the ever-present threat of solar flares and CMEs notwithstanding. But there may be other solutions about which I am entirely ignorant. Finally, is the physics concerning the above already in place, if not the technology and political wherewithal? Many thanks.
  4. My apologies. By a "non-magnetically charged object" I meant non-ferrous minerals and metals, like copper, nickel, cobalt, etc.
  5. Thank you. To clarify things then: any non-magnetically charged object gravitationally drawn to an ultra-compact body like a neutron star can, depending on its trajectory, impact upon any part of its surface, not just at its magnetic poles.
  6. Neutron stars have been described as the most powerful bar magnets in the known universe. This being so, is it possible for the magnetic fields of such compact objects to take precedence even over their gravity fields? An example: would a small object captured by a given neutron star wind up impacting upon one or other of its magnetic poles, rather than gravity pulling it down to impact anywhere else on the star's surface/photosphere? Many thanks.
  7. Many thanks for the explanations - brick analogies and all Yes, I think I finally understand the equation now. On a personal note, I suffered badly on the maths front at school. Partly the fault was my own; but I do contend that a substantial chunk of it was due to the teaching practices typical during those times, especially when it came to rote-learning techniques. This method has its uses, but for me back then, especially when it came to the teaching of maths, it was heavy on the 'how' and light on the 'why'. It wasn't until I did GCSE Maths as a mature student that I began to understand that maths is a language - and a wonderful language at that. At least I know that now, even if I remain a poor reader of numbers. I just wanted to say that. End of personal note.
  8. Regarding these "two pieces of information, force and time", I'd appreciate it very much if you could provide me with an example how a given final velocity may be calculated. Many thanks.
  9. The quote below is the most succinct description I've found on the net explaining the relationship between spacecraft velocity and performance: "The speed of a rocket is directly affected by 2 factors. The first is mass ratio, which is a ratio the weight of the rocket at lift-off compared to the weight of the rocket at engine shutdown. The second factor is specific impulse, which is the amount of thrust produced from each pound of propellant per second. The higher the mass ratio and the higher the specific impulse, the faster the rocket can go." Mass ratio I understand. Likewise, I can get my head around specific impulse - although I still have to strain it a bit. What I don't understand is how all this translates into spacecraft velocity. It's all very well to talk about exhaust velocity, but at risk of sounding fatuous, were I a petrolhead wanting to buy a sports car, I might be interested in fuel consumption (possibly) and knowing how efficiently the exhaust functions (well, maybe) but really, I'd love to know how fast the car goes. Unfortunately, concerning specific impulse and 'forward' velocity as it apples to spacecraft, I can find nothing anywhere that can join up these two dots. Many thanks. PS. Again, I apologise for the crassness of the question. But how can one find out if you don't ask?
  10. I've just read an article on the BBC website (see link below) in which experimentalists have reduced the speed of light by remodelling photons. Does this mean that the frequency of light is also reduced? http://www.bbc.co.uk/news/uk-scotland-glasgow-west-30944584
  11. Yes, on reflection I have to agree. . . at least in part. There were some fine moments in the film, especially visually. But it did drag in places. I'm afraid I still don't understand the 'timeloop' sequence, though the tensions it created certainly added to the drama. Timeloops? Is this a reading of the multiverse concept?
  12. Yes, I should have done my homework about quasars before popping the question. Three additional thoughts, though: (1) possible disruptive effects caused by the 'merging' of two SMBHs - gravity waves etc? (2) colliding galactic gas and dust clouds? (3) dark matter? I mention these colliding aspects, having ascertained that the closing velocity between the two galaxies is approx 110 km/s (or very roughly equal to the distance between the Earth and the Moon covered in an hour). This doesn't strike me as inordinately fast, at least not by cosmic standards. But it's still fairly brisk - brisk enough, I would imagine, to have all manner of effects at the 'local' level - the interstellar medium, planetary systems etc.
  13. With regards to the future merging of the Andromeda Galaxy with our own Milky Way, would this event create a quasar? If so, would this in turn eradicate all existing life in both galaxies? (assuming, of course, that Earth isn't the only repository of life in our part of the universe). Many thanks.
  14. I'm no expert on this, but I'm inclined to agree with Moontanman about seemingly being able to fly around on Titan, using a pair of borrowed wings. I wonder if I read it in Starship Century - an article by Robert Zubrin, possibly?
  15. With regards to Interstellar (which as enjoyable as it was, induced in this viewer some time-dilation issues of its own, given its length) I found this interview in a recent Scientific American article, in which Kip Thorne explores some of the physics contained in the film. PS. I'm not sure if this link functions properly, but it's worth a try. http://blogs.scientificamerican.com/observations/2014/11/28/parsing-the-science-of-interstellar-with-physicist-kip-thorne/
  16. Many thanks: l learnt a great deal about optics from this thread. So the upshot then is that the size of the pupil determines its capability to resolve incoming light within a given spectrum of wavelengths. And this limiting factor applies whether one is viewing an object with or without the aid of magnifying glasses, and so forth. So the only way a human being is able to 'view' infrared radiation, for instance, is to use an infrared scanner of some kind, an external device that detects infrared radiation - i.e heat - and converts this radiation into 'visible' light. Re depth of field: I well recall a childhood memory of my brother and I taking turns to watch incoming traffic through a pair of fairly powerful binoculars while travelling in our father's car. It made for quite a strange visual experience - comic-strip Special Relativity for beginnners almost. Not to be recommended while driving, however.
  17. Yes, I'm looking forward to the advent of the James Webb Telescope and although I'm not superstitious, I'll be tempted to cross my fingers when launch day finally comes. Enthalpy, thank you for your comments about the transparency of the atmosphere. Intriguingly, the Bortle Scale - or someone referring to it - did claim an upper naked-eye limit of +7 magnitude, albeit under 'exceptionable' viewing circumstances. If so, then I guess this degree of clarity would also apply to space itself.
  18. If glasses do not increase the resolving power of the eye, what's the situation with binoculars, telescopes etc? Or is there a trade-off here between resolution and field-width? I'm sorry if this seems a stupid question.
  19. Re. the Rayleigh criterion. Yes, I begin to understand now. This raises another question, though: if the eye's resolving power is determined by the size of the pupil, does this explain how glasses (or other forms of external lenses) can overcome this problem?
  20. I understand that there's a definite relationship between the size of an eye and the wavelengths it can receive. This being so, just how small can an eye be, while still able to receive light in the visual spectrum? NB. Here, I'm referring to what might be described as 'camera' (or animal) eyes, rather than the compound eyes of insects. Many thanks.
  21. Just a suggestion: could the alleged meteorite once have been a moon of the Pitbull asteroid, but which was pulled away by Earth's gravity? I've no idea if Pitball ever came close enough to pass within Earth's Hill Sphere, but I do recall a close flyby made fairly recently (2013?) by another asteroid, which definitely had a moon, albeit a very small one.
  22. Having recently chanced upon the Bortle Scale, I'm intrigued to know just how much increase there would be in stellar luminosity as observed from space - say, from the ISS. For the sake of argument, I'm discounting the effects of spacesuit visors etc. Many thanks. http://en.wikipedia.org/wiki/Bortle_scale
  23. Yes, I do support the SETI programme - though I am aware of its inherent dangers (ref. Stephen Hawking). We don't know for sure if an intelligent species has to first get through an 'ethical' bottleneck in order to become a space-faring species. The SF novels by Larry Niven are instructive here. Unlikely though it might be in actuality, it's just possible to conceive of an alien species with 25th century space technology and the morality of The Beano (a British children's comic). Personally, I'm inclined towards the view aired by Frank Zappa, who when asked a related question, responded by saying that he considered the universe to be composed mostly of stupidity. It's the less 'stupid' parts we're discussing here, I guess.
  24. So I gather then that a fairly largish object (an astronaut, say) could safely stand on that part of Phobos facing Mars and not be borne away by the Martian gravity field - or its tidal forces, I mean?
  25. it would appear that any spacecraft being inserted into a fairly stable and fuel-efficient orbit round Phobos (and possibly Deimos too) requires a non-Keplerian orbit, such as are described in the link below. http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/42478/1/12-3014.pdf
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.