h a l f b a k e r yOn the one hand, true. On the other hand, bollocks.
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Jim has been reading a bit about electromagnetickery and feels in the mood to endow you all with knowledge...
As far as Jim can tell all that electromagnickery coming off the big sphere at the center of the solar system pretty much heads off into space at the speed of light. Unless of course something
gets in its way --- like the earth for example.
Now you can imagine the radiation hitting the surface of the earth as a giant eight minute sphere --- the exact surface area of which is --- well pretty large. You can also imagine that no more or less energy has been added to this sphere since it was only as large as the sun. The energy hitting the surface of the earth, per square unit, is quite alot less compared to energy emmitted from the sun, per square unit.
Anyhows Jim reckons eight light minutes to one is a safe ratio for handling nuclear radiation so has devised a container with internal surface area equal to eight light minutes (squared) of the contained radius. It is a sphere covered internally with cones that point centrally.
Sic..
Dyson'r Sphere
http://en.wikipedia.org/wiki/Dyson_sphere
[MisterQED, Sep 22 2009]
Meow.
Schr_f6dinger_27s_20Dyson_20Shell
Shameful self-appreciation. [theleopard, Sep 23 2009]
The Multispectral Sun
http://www.windows....=elem&portal=vocals
"...different wavelengths of EM radiation behave differently when they reach Earth's atmosphere. Fortunately for us, most of the high energy X-rays and ultraviolet radiation are absorbed by our atmosphere far above our heads, preventing them from frying us..." suggesting that the 8 light minute thing might be a red-herring - what you need is a mile or two of atmosphere as well. [zen_tom, Sep 24 2009]
everything "jim" ever wanted to know about black body radiation
http://en.wikipedia.org/wiki/Black_body
In short: his sphere will heat up, and glow. [ye_river_xiv, Sep 25 2009]
Time Cube Theory: this is what real madness looks like.
http://www.timecube.com/
[sninctown, Sep 25 2009]
[link]
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could you arrange those words, most of which I understood, in a manner which makes some sort of sense ? |
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Pretty sure I got the basic idea. It's not distance or diffusion that makes the sun safe, it's the earth's magnetic and ionic protection. Thus, MFD bad science. |
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(Think the idea is to create a container with a convoluted inner surface such that the power coming from a radioactive/nuclear source is spread over an area equal to a sphere 8 light minutes in diameter) |
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ah, of course... ummm... nope, no clue. |
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oh wait.... small containment device for fissionables ? |
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I think even if it's only one atom thick, an 8 light-minute radius Dyson sphere isn't going to be foldable down to any sort of reasonable size. |
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or is he trying for a containment device that spreads everything out to 1kw/m2 or something. |
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//feels in the mood to endow you all with knowledge...// ... and...? |
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I guess the big moment came & went.
Jim? Jim? You OK? You're not dead, are you? |
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As [FT] notes, what you are talking about is a Dyson's Sphere, a giant spherical solar cell with a sun in the middle. |
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I don't know what the cones are about, maybe it is so the light isn't reflected back and overheat the sun. |
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Sigh --- this is clearly not a "dyson sphere" because the inside of one of those is --- well spherical... |
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I have to admit that the dyson sphere has the advantage of being simply undeniable. Although I deny the feasibility of such a sphere --- it is just a bit too big... |
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To wit --- Jim has been contemplating further the inner surface of the eight light minute sphere (and has added the word "squared" above :). |
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Jim is concerned by the reduction in total mass of the eight light minute sphere as compared to a dyson sphere --- clearly the input engery by unit of mass is going to be vastly higher here but that is a different problem all together. |
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yeah, but I still don't think you can fold an 8 light-minute sphere into anything you can put in your pocket (of course I still don't understand what the idea's about, but that doesn't stop me from having an opinion) |
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// If I understand, the idea is to make a relatively small sphere, but with the inner surface so convoluted as to have the same surface area as an 8-light-minute sphere. |
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Oh! Sorry for the misunderstanding, then. (Trots from the "this is a Dyson sphere" camp to the "huh?" camp.) |
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The answer to the question huh is simple... |
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Firstly the inner surface of something like an eight light minute sphere would be an inside out golf ball --- the ball is hollow and the dimples are bumps. To shrink the radius of the ball further while maintaining the inner surface area the dimples need to become longer and sharper. To shrink the radius of the ball further the dimples need to become dimpled etc etc... |
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At the end of the day the eight light minute sphere is going to be fairly solid. |
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So huh... As far as I know this sort of surface is reflective with respect to (at least) xrays. And if you will allow a small "what if" it may be possible to reduce the internal energy of each ray at each reflection... |
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Exactly if a contained ray is incident to the surface of the sphere enough times it will become progressively less energetic --- to the point where it could be emitted as a whole lot of relatively harmless light. |
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So where does all that energy go --- well I reckon it could be useful when it comes down to making a good brew. |
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OK, so we understand the idea of having a larger surface area on the inside of an empty sphere - but why, and what for? |
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Are you going to enclose a sun, or some blob of radioactive stuff? |
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And, assuming you are going to enclose something, what happens next? Large surface areas aren't anything new, and I don't understand the relevance of the somewhat arbitrary idea of squishing the size of an object that has the the surface area of of a sphere with a radius of 8 light minutes. |
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Some maths, the surface area of a sphere is calculated with the formula: |
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So if 8 light minutes = 143 900 379 840 meters |
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A = 4 x 3.14 x 143 900 379 840
Which = 1.80738877 × 10¹² m² |
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So you're suggesting an object with that internal surface area, at some (unspecified) smaller size. Why is that? And what happens next? |
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tell ya what: work out the minimum size your "ball" is going to be if it's actually composed of atoms of obtanium and allows light to pass through the crevasses, and get back to me ;) |
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OK, so we've got a Dyson Sphere that's got a radius of one light minute and has a whole bunch of ice-cream cones stuck on the inside - what happens next? Who said that a Dyson Sphere had to have a diameter of 8lm and what are the particular advantages of having a smaller one than that? |
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It's the Van Allen belts and the ozone layer which stop harmful radiation reaching Earth's surface, not the distance from the Sun
Concerning the size of a Dyson sphere scrunched up, if you had one made of gold leaf it would have a volume equivalent to a solid sphere sixty-five kilometres in diameter. Were it one gold atom thick, it would form a sphere eighteen metres across. I think. |
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oh i get it, he wants to move to 1lm away from the sun onto a crumpled up Dyson sphere... why isn't clear. |
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If you have a sphere of 8 light minutes radius, the temperature of the sphere will come to an equilibrium at the temperature at which the outer surface of the sphere is radiating heat at the same rate as it is being received on the inside, i.e., the energy output rate of the whole sun. |
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You shrink it down, and now it has to get hotter in order to pass the same amount of energy in the same amount of time. |
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You are going to try to cheat this by making a surface where the flux vectors are not normal to the surface - the light doesn't hit it straight on. Sounds good, except: it also gets radiated off the outer face in a non-straight-away direction (every point on the surface emits in a spherical pattern; if it's folded, it'll radiate on itself. (eewwww...)) So now some of the material not only has to get rid of the outbound heat of the first instance, it also has to re-emit re-absorbed heat. |
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Jim needs to go read up on black body radiation. I hate to pull the [mfd] trigger, but this really is "bad science". |
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This is some sort of radiation sink... for what I'm not sure.... in case you need to pick up the sun? |
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OK, I'm getting closer to the [madness], it's a massively "cone folded" Dyson's Sphere, which is interesting, but has some issues. First //Anyhows Jim reckons eight light minutes to one is a safe ratio for handling nuclear radiation// Well, not really, only if you are first shielded by large magnetic field and an intact ozone layer. You forgot the solar wind and solar flares. |
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So let's forget human habitation, the original idea for Dyson's Spheres is for power generation, so this ideas seems to be about making kind of a Hoberman Dyson's Sphere and creating a Dyson's Sphere with enough inner volume to allow it to be made MUCH smaller. So I'll say this is at least interesting (+). |
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anybody else remembering the scene in a Red Dwarf episode where they're all trying to explain to the Cat what a black hole (or something) is ?... |
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The earth's travels take it along the surface of the 8lm sphere, so the suggestion is surely to take it along the convoluted surface ~1lm away from the sun, rendering the radiation harmless (in comparison to the acceleration profile) |
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//So now some of the material not only has to get rid of the outbound heat of the first instance, it also has to re-emit re-absorbed heat. |
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Shudder --- I get the feeling [lurch] visited me (doh Jim) as I was sleeping... |
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For the purposes of radition containment perhaps its possible to cheat even further. Lets say rebound energy is not radiated at all --- lets say it is reflected back to the source. |
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Now the temperature of the eight light minute sphere is dependent only on the perfection of the reflection... |
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I'm going to second lurch's [marked-for-deletion] - bad science - though to be honest, I'm still not sure what it is we are achieving here - objects with high surface areas are already known to mankind, and Dyson spheres (wrinkly or otherwise) are well posited if impractical concepts. This idea fails to clearly describe either. |
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Concerning [nineteenthly] thinking... |
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///Concerning the size of a Dyson sphere scrunched up, if you had one made of gold leaf it would have a volume equivalent to a solid sphere sixty-five kilometres in diameter. Were it one gold atom thick, it would form a sphere eighteen metres across. I think. |
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The thing about a Dyson sphere is that all the contained radiation slams into and must be absorbed/used/radiated by it --- thats why it is so big and so thick (if you excuse my jest)... |
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An eight light minute sphere can be significantly smaller because the radiated energy will glance across (literally) a myriad of surfaces. |
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//An eight light minute sphere can be significantly smaller because the radiated energy will glance across (literally) a myriad of surfaces.// |
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Right, so we are saying then that the problem with building a Dyson sphere is that it would get too hot, and that by building a smaller, but wrinkly one, this issue will be resolved? |
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As to the 'glancing off' process - it's sadly not going to work since the energy has to go somewhere, and, like [lurch] pointed out earlier, if you've enclosed the star, then the energy has to stay within the sphere. You could have used mirrors and had the same effect. Or just built a really tiny Dyson sphere just 99cm above the star's surface, same problem, still unsolved. Or, if enclosing a whole star is too hard, just open a window every now and then to let some of the energy out, and things can cool off a bit. |
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Sounds like Schrödinger's Dyson Shell to me... [linky-chops!] |
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Actually I never said anything about building a dyson sphere and certainly nothing about it getting too hot --- because it obviously doesn't. The input energy per square (or even cubed) unit is not very high. |
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Having said that if you could place a reflective surface (on the inside of a dyson sphere) that accepts an input ray at the norm (which you can't) then the input energy is zero... |
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[Thats how come el capitan america carrys a little shield] |
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BUT WHAT'S IT FUCKING FOR ? |
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Ok [FT], its not for enclosing a star but something more along the lines of a radioactive isotope. Given the vastly smaller enclosed radius the actual surface area is not anywhere near eight light minutes squared. |
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Jim reckons that only the ratio of surface areas that must be equivalent to a dyson sphere... |
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oh ok: inside-out porcupine. |
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Sorry, I still don't see what this is for, and (as usual) am getting annoyed with this tediuous process of having to tease out some form of sense (which seems to chop and change with each of the poster's annotations - as if he's making it up as he goes along) To be perfectly honest, I don't know why I bother. I think I'll try to avoid the aggravation next time - it's just not worth it. |
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So, for the final time - and in plain language if you'd be kind enough to extend the courtesy - what does this do, and what is it for? |
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... its a better thermos for nuclear radiation ... |
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Right, so this is a thermos flask with a rippled internal edge? |
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And why nuclear radiation? What about regular electromagnetic radiation (as you mention in your bit about "electromagnickery" which isn't, in the technical sense "nuclear" i.e. alpha or beta radiation - gamma being essentially the same as regular old EM - or was that bit just fluff?) |
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If it's EM radiation, such as the IR radiated from a flask of hot coffee - then the higher surface area in the thermos flask will be just as good as a flat surface, for the reasons described by lurch in the dyson sphere model - if it's a closed system, be it a thermos flask or a dyson sphere, the total radiated energy is the same - that's one part I don't get. |
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Or are you planning to hold nuclear waste? And the surface area is designed to capture alpha and beta particles? |
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What's the frequency Kenneth? |
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// The thing about a Dyson sphere is that all the contained radiation slams into and must be absorbed/used/radiated by it --- thats why it is so big and so thick (if you excuse my jest)... // |
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I was under the impression that whereas the ultimate Dyson sphere would be a solid shell around a star, before you get there you'd have a swarm of space stations orbiting it. The actual solid sphere is more a thought experiment, isn't it? I mean, in the absence of unobtainium/scrith?
Concerning the cones, how tall are they exactly? The point is going to come, is it not, when they topple? |
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Which way would they topple? |
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It seems to me that your actually questioning why more surface area is desirable when containing nuclear radiation. |
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In the original text I (er Jim) states... |
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" You can also imagine that no more or less energy has been added to this sphere since it was only as large as the sun." |
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Now this means that (magnetic fields aside) there is really nothing between you and the sun... that is literally nothing between you and a massive fusion/fission reactor. The only thing reducing the amount of radiation you receive is (massive) dissipation (due to surface area expansion). |
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So the idea is not to try and block radiation but to dissipate it across a virtual eight minute sphere. With regards to absorption per unit mass I have described how this *must* be handled by a reflective surface. And the reflective surface must be perfect (or there abouts)... |
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The interesting thing about anything more energetic than a light ray is that the reflective surface must be tangential to the direction of travel. So each ray must be deflected just a little bit over and over and over again
--- hence the massively convoluted surface
--- and hence yes this is exactly a thermos for nuclear radiation. |
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So what happens when all the possible photon paths within the sphere are full? Well each deflection event must reduce ray energy the ray energy must be used purposefully and the spent ray must be vented from the sphere... |
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With regards to reflection of gamma rays --- that's not been done yet as far as I know. But since achieving this is more likely than building a dyson sphere I personally recomend not bothering to look for one built by some as yet unknown civilisation... |
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So in conclusion and in the style of a charlies angle, "... thats kicking your big lead shield in the arse..." |
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(completely irrelevant - just thrown in to confuse things .... ) |
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Charlie was always so obtuse. |
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Anyone want to run the numbers to see how small this could be, assuming it's built out of little carbon structures (nanotubes,etc.)? Let's say for the fun of it that it's made out of a bunch of carbon spheres with diameter 10^-8 meters. The area of one such sphere is 4*pi*(10^-8)^2, or about 10^-15 square meters. A 1 AU radius Dyson sphere has an internal surface area of about 2.83*10^23 square meters. So, assuming no volume or surface area change when reconfiguring the spheres into a convoluted surface, about 3*10^38 of the little carbon spheres are needed to get enough surface. These spheres each have a volume of 4/3 *pi*(10^-8)^2, for a total of about 1.25 × 10^15 m^3. Assuming 75% packing efficiency, this means a volume of about 1.7*10^15 m^3 is needed. |
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This is a sphere with radius, as an order-of-magnitude approximation, of about 100 kilometers or 50 miles. Hey, this is now in the realm of wildly impractical instead of downright impossible. Sweeeet. |
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Radiation absorption usually requires thick, dense materials. 50 miles of carbon would block most radiations. |
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Gamma radiation is emitted by atomic nuclei. They are also absorbed by and interact with atomic nuclei, because that is the size range of their wavelengths. |
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Imagine this: throw a basketball at an angle at a chain-link fence. You can pretty well tell which way it's going to bounce off. Next, pick up a marble and try the same thing. Since the marble is not large enough to span the distance between adjacent wires, it only interacts with a single wire, possibly two; quite often, none. The direction of the line-up of wires doesn't come into play. It's all about the angle of impact, if any, on the first wire. |
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Same applies with "reflective surfaces" and gamma rays. At that scale, "reflective surface" is a non-concept. |
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What does matter is how many nuclei (not surfaces) can you place along any given gamma photon flight path, and that equates to density and depth, not convolutedness. |
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I think the issues here are manifold. |
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1: A sun (or other radiating body) is emitting electromagnetic radiation. |
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2: The intensity of radiative energy decreases according to the inverse square law, and therefore at some distance, it should be safe for humans to view that radiating body. |
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3: "Jim" proposes that by building a shell around this radiating body at exactly eight light minutes away... something... good... will occur.... something... good... that would not occur simply by standing eight light minutes away. |
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4: "Jim" proposes that at a distance of 8 light minutes away, a human should safely be able to view a radiating body. |
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5: "Jim" proposes that the actual shell can be made smaller than an object with a radius of eight light minutes if it is capable of reflecting the radiation of the body so many times that the total distance the radiation must travel before reaching the human is still eight light minutes. |
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Assuming that this is the intent of the original post, a number of questions promptly come to mind: |
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1:Does not the earth's thick atmosphere and magnetic field play every bit as much a role in our protection from the negative affects of the sun, thereby suggesting that the "eight light minute" distance hypotheis "Jim" arrived at is incorrect? Considering the great expense paid to line both the apollo capsules, and the space suits with gold to protect against radiation, and increased cancer rates among astronauts, I would suspect that the eight light-minute hypotheis is incorrect with regards to our sun. |
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2: Assuming that totally inclosing a radiative source such as the sun is desirable, wouldn't reflecting all the radiative energy from that source back towards the source alter the mass-heat equillibrium that the sun maintains in order to keep it's current size and output? If so, might this not lead to an alteration in the size of the massively hot gas contained within the sun, and possibly causing the inclosing material to become compromised? Surely such a risk is worthy of considering, at least casually, in a presumed cost-benefit analysis of this plan? |
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3: Would not all radiating bodies have some similar limitations inbuilt into the considerations of how one might fully inclose them? |
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4: Isn't a fancy Thermos for a sun, or other radiating body kind of pointless unless you have a need to move it, and a means whereby to do so? |
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5: Among the radiative materials we do move today, isn't it likely that the existing storage containers might be lighter-weight, and more compact than something with enough surface area in it to let all radiations bounce around for a distance of eight light minutes? |
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6: Presuing one could fully enclose a radiating sun, or other body, wouldn't the energy normally given off by that body build up INSIDE the enclosing structure, rather than being radiated off into space? |
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7: Doesn't something requiring construction efforts equivalent to building a Dyson sphere warrant some discussion as to what purpose it would serve? That is, beyond saying "It'll be a Thermos," discussing the uses one can put that thermos to. |
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Jim isn't proposing a Dyson sphere; he's proposing a much smaller sphere (about a hundred miles in diameter if my maths are right) mostly filled with nanoscale "cones" pointed toward a lump of radiation-emitting stuff at the center of the sphere. That way, there's the same radiation per area hitting the surface of the cones inside as there would be hitting the inside of a Dyson sphere. |
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but what would be put at the center of said 100-mile diameter sphere? -- Yes, a radiating body, but WHAT radiating body? Nuclear waste? What amount of nuclear waste would require that kind of containment? |
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As far as cost/benefit is concerned, why would someone make something this convoluted if it could be done the normal way for far less money? |
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I am fairly puzzled by the numbers myself... |
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eight light minutes = 143,900,379,840 m
eight light minute sphere = 3.1060979 × 10^22 m2 |
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radius of the sun = 695,500,000 m
suns area = 5.804643 × 10^18 m2 |
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The ratio of radius' is (only) 200 and the ratio of areas is (only) 5500. If I assume a contained radius of 1 metre then I would expect the same dissipation as compared to the sun and an actual sphere with radius eight light minutes after only 130 metres --- and the "eight light minute sphere" of this is much smaller than described above... |
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[lurch] again brought up the problems with (the probablity of) reflecting a high energy ray --- and Jim is waiting to read about the solution... |
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As far as I know the problem is that the probability of reflecting a ray decreases with increasing frequency (or energy) --- but only if the reflective surface is uniform. |
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[I understand that a high energy photon is a positive negative pair following two sine waves crossing at 90 degrees (or 90 degrees out of phase) and spinning (one way or the other) about the vector of travel. With increasing frequency this pair spends more time crossing so can drill through stuff at normal tempertaures.] |
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Keep in mind that what you are describing is a visualization, not the
actual photon. |
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//two sine waves crossing at 90 degrees (or 90 degrees out of
phase)...// the sine waves are describing magnitude of field strength
(magnetic and electric field strength are the two axes, and the
photon's energy is oscillating back and forth between the two) -
don't get caught up in thinking it's an actual physical displacement |
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//With increasing frequency this pair spends more time crossing so
can drill through stuff at normal tempertaures.// Another
visualization to be careful of. If the photon's magnetic field can
cause the displacement of electrical charge carriers in a material,
the motion of the charge carriers creates its own magnetic field, and
the photon's energy is dumped into that. Upon rebounding, the
magnetic field collapses, sending the energy back to the photon,
which then effects a change in the motion of the photon's electric
field. Thus, the material reflects. If the charge carrier doesn't
rebound - say, hops into a different energy state and stays there,
then the photon's energy is stolen: the photon is absorbed. (And
never partially, mind you; all or nothing. That's quantization.) So, to
wrap up, in order for the photon to interact, there must be
mobilizable charge carriers of opposite sign separated by distances
of the same scale as the oscillation length (wavelength) of the
photon's fields. |
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If you enclose any power source inside any sphere, the
system will increase in energy until the total power
radiated from the outside of the sphere is equal to that
produced by the power source. It does not matter if your
sphere is reflective, or absorptive, or any combination
thereof. The energy has to go somewhere, as it can
neither be created nor destroyed (the exception is your
source, if nuclear, where matter is converted into energy)
This is why the expected output of a Dyson Sphere is a
shifted wavelength, not a decrease in total energy
emitted.
Even if the em radiation falling on the inner surface of a
1lm or less sphere is distributed over a surface equivalent
to an 8lm sphere, the power coming off the backside will
still resemble the flux from the radiation source at 1lm.
The one exception to this is if the energy is somehow
drained or directed, to whit the inside is coated with PV
panels or similarly utilized. The overall power output of
this system would still be exactly the same as the
radiation source, just that some of it would temporarily be
redirected as another form, that is electricity. (It all
becomes heat at some point, but that point may be
elsewhere/when.)
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What, then, is the benefit of a smaller sphere? It can't be
living area as both surfaces of the convoluted sphere
would be far to hot (not to mention the lack of shielding
from harmful forms of radiation that require either a nice
ionosphere or several feet of various materials such as lead
or water). It must, therefore, be electric power
generation, either PV or thermodynamic. Both of these
methods of power generation prefer higher, not lower,
concentrations of energy input, and thus will function
much more efficiently on a smooth, rather than
convoluted surface.
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This therefore comes down to a solution without a
problem. |
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As far as I can tell, it's not even a solution. |
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At first I thought this was madness. Then I thought it was merely bad science, but bad in an interesting way. I have returned to my first impression. |
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[madness]: you read like someone who has a ravenous hunger for physics texts, unmatched by an ability to either parse what you read, or explain what you think. |
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// the issues here are manifold. // |
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You did that on purpose, didn't you [ye_river_xiv]? |
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Thank you again [lurch] *really like* your desciption of "elastic" charge carriers (of opposite sign) separated by just the right amount. Kind of reminds me of catching an insect with chop sticks... |
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[MechE] yeah you are right --- and yet with regards to handling high energy rays there is merit in looking for a better passive solution for high energy rays (ie not large amounts of lead). Since as far as I can see a lead barrier is all about (irreversible ) absorption rather than reflection --- so the energy is lost (but not destroyed)... |
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And --- with regards to the Dyson sphere --- what is the point of putting "current" solar panels on the inside... they do not work on high energy rays... |
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Photovoltaics can be made, in theory, to work on just about any frequency in the emag spectrum. To low a frequency and you don't get much energy out, but they can be made to work.
Current production cells are all designed for visible light or near infra-red because those are most plentiful inside the atmosphere.
It is definitely possible to go higher frequency, and significant new materials research might be required to produce gammavoltaics, but no new concepts are required. |
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Cheers mate --- it seems we agree and to be honest then I rest my case. As you say, it is better to contain radiation (in the small ie, not entire stars) by reflection/generation than to use a big lead box... |
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I didn't have enough time during lunch to read all of the anno's so this might have already been said, and may not even be relavant at the point in which I am entering the conversation but ... |
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MikeD feels in the mood to endow you with a little something he picked up in physics II : |
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Regardless of the surface area of your strange device, it will still only pick up the radiation contained in the amount of cross sectional surface area occupied by your object set on a sphere whose radius is equal to the distance you plan to orbit this object from the source. |
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The only thing you can do to increase the amount or radiation your object is exposed to is to either make it bigger in the plane orthoganal to the sun, or to move it closer. |
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I also suggest reading up on Gauss. |
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Ummm --- just a thought (which I cannot claim) is not to try and build nano structures with sufficient area to disperse the radiated energy --- but to suspend them in a suitable liquid. |
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Hehehe: I reckon it is best to pack finite nano structures (powder) around the source. |
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