GeeKay

I apologise for this somewhat obvious question, but does a telescope's limiting magnitude increase when using time-lapse photography - this compared to real-time viewing?

Yes, our reach appears to be growing exponentially longer, but at the expense of our grasp? That question, though, more properly belongs to another thread. . . There is something else, though. . . one aspect about monopoles that has long intrigued me. I understand that they could (in theory?) speed up the processes inside a fusion reactor by serving as a catalyst. But how this could be achieved in a nuts and bolts sense I still find baffling. In other words, just how - albeit it in layman's terms - can a magnetic monopole catalyse the fusing of hydrogen atoms? Or am I missing out on something important here? Again, many thanks.

Thanks again for the imput. Yes, I get what you say about the Higgs particle. Having read "The Particle at the End of the Universe' by Sean Carroll, I can quite understand the adventures the researchers had tracking down that pesky boson. Whether magnetic monopoles - should they exist at all - involve the same kind of protracted hunt, time will only tell, I guess.

Thanks, imatfaal. I guess the real point I am trying to make has less to do with whether magnetic monopoles exist or not. All I can hope for here is that scientists will eventually discover them, or failing that, make a fundamental discovery in a related field that ends all further speculation about their existence: end of question. Instead, assuming for the sake of this argument that they do exist, my main point of interest here is centred on their properties, especially how these properties may conceivably apply to their potential uses as a future power source. This is the sort of information I am seeking. . . conjectures, if you will. That seems a reasonable question to ask.

Hi, I have, albeit reluctantly, almost come round to accepting what appears to be a fairly widespread view in the scientific community: that monopoles do not exist, at least according to the current models we have about the universe, post Big Bang. This is to say that the likes of Ampere, Gauss and Maxwell have thus far proved correct, over that of Curie and Dirac. Nonetheless, part of me has always wondered if this will be the full story on the subject of monopoles. I'm also extremely wary about scientists making negative pronouncements before all the the evidence has been examined - or even discovered. Clarke's First Law ("When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong") springs to mind here. The great Lord Kelvin's comment about X-rays being a hoax is a prime example of this ingrained attitude in action. On the other hand we are no longer saddled with obsolete theories harping on about phlogiston or the aether. So will monopole theories seem no less quaintly wrong-headed in another hundred years' time? That was my take on the situation until quite recently, that is to say until I read 'The Eerie Silence' by Professor Paul Davies. He discusses monopoles in some detail in the chapter 'Evidence for a Galactic Diaspora', and although he too hedges his speculations about their existence, what does emerge is a tantalising glimpse into what might be round the next dozen or so corners, were monopoles finally proven to exist. In particular, the potential any such monopole technology would offer humanity - for good or for ill - almost seems to rival the fabled attributes of antimatter as a power source. Could this possibly be true? Or in interpreting the data, am I misreading myself back into the world of Leonardo's helicopters? I have since then scoured the internet for more information of the subject of monopoles as a (potential) power source. Unfortunately, if not altogether surprisingly, the results so far have been meagre in the extreme. I am therefore interested to know what the thoughts are by other members of this forum, and whether anyone is able to throw some fresh light on this subject. Many thanks.

Sorry for the confusion: I was referring to those variable stars (e.g. UV Ceti), certain red/brown dwarf stars and their ilk that are classed as flare stars. On a related point (this has been proposed by others, and it's worth mentioning again) I wonder if generating an artificial magnetic field around Mars might one day offer some global protection for any future colonies against inclement solar weather?

Thanks again! I gather then that aurorae on Mars are strictly localised, occurring only in those parts of the regolith with crustal magnetism. All this leaves me wondering about the long-term risks of trying to establish a planet-wide colony on Mars. I would imagine that a major CME impacting upon those unprotected parts of Mars - which is to say most of the planet's surface - would have a devastating effect upon anyone foolish enough to be caught in the open. Then there are the solar flares themselves, which could in theory strike the Martian surface without any advance warning whatsoever. Our Sun might not be a flare star, but it might as well be one, seen from a potential colonist's point of view.

Ah, yes, I understand now. Thank you, Acme. One thing that hadn't been clear to me until reading this NASA article was the propensity solar flares have for charging up and accelerating particles that lie in their path. I think it was this more than anything else that created the confusion in the first place. On a related issue: I heard that aurora had recently been detected on Mars. I don't know how extensive this was, but given that Mars doesn't have a global magnetic field, I'm a bit puzzled how solar activity, such as CMEs, are able to generate aurora on Mars in the first place. Many thanks.

I am trying to understand the composition of solar flares: whether they are purely electromagnetic, for example, which to say they ALL propagate through space at the speed of light, or else composed of (or include) high-energy particles. The reason for the 'ALL' is because I keep coming across conflicting descriptions of solar flares, with many accounts actually referring to CMEs, or else discussing solar flares and CMEs as if they were merely two terms for the same phenomena. For example, did Richard Carrington (and most of the world) witness in 1859 a solar flare or a CME? I've come across both explanations. Finally, it seems that solar flares cause aurorae, and at the same time they most definitely do not cause aurorae. . . Help!

So I take it then that even if the primary body was a white dwarf, or something even denser - a neutron star, say - the same Roche limit rules apply, as they pertain to a far less dense satellite in orbit round the above object. . . a water-ice comet, to take an extreme example? I mention this because some commentators on the internet, in discussing the Roche limit, referred to relative densities. Unfortunately, for whatever reason, it all left me feeling confused, rather than enlightened.

Thank you. That's what I wanted to hear

One possible one-way voyage to Mars (or anywhere else for that matter) involving human visitants could be achieved by those suffering from terminal illnesses of one kind or another. Obviously, it would be essential for the astronaut not to be incapacitated by the illness - at least remaining reasonably fit and well until the end of the mission. Computer technology would enable a dignified, and possibly private, act of self-administered euthanasia. Many observers, I'm sure, would still regard such an enterprise as ghoulish. Still, if I were granted a "once in a lifetime" opportunity to go to Mars under these terms, would I accept it? Oh, yes, for sure

If I may quote Wikipedia here: "The Roche limit is the distance within which a celestial body, held together only by its own gravity, will disintegrate due to a second celestial body's tidal forces exceeding the first body's gravitational self-attraction." This being so, in the case of a Solar-mass body, does its Roche limit, as it applies to a given satellite, remain the same, regardless of its diameter? In other words, would the limit stay put, even if the Sun were magically shrunken into a white dwarf, while retaining its original mass? Many thanks.

While it seems that some scientists/astronomers/pundits now have a fair idea about the average distribution of dust grains in outer space (one per million cubic metres, according to one source, ref. link below), I can find no such confident claims when it comes to the distribution of micrometeoroids in the interstellar medium - i.e. objects around 300 - 500 micrometers diameter (or wide). The silence here - if silence it is - intrigues me almost as much as my desire to know the answer. Maybe the answer lies in the future. Who knows? I don't, that's for sure http://science.jrank.org/pages/3656/Interstellar-Matter.html

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.

'Hyperspace' by Michio Kaku is very good on the subject of parallel worlds. Highly recommended - and not just by me!

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.

My apologies. By a "non-magnetically charged object" I meant non-ferrous minerals and metals, like copper, nickel, cobalt, etc.

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.

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.

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.

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.

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?

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

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?