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The Death Magnifying Glass is Now Approaching

Maybe slightly more plausible
  [vote for,

So let's explore the physics of a mainstay of science-fiction: the venerable space ship / planetary shield.

These are amazing devices. In most versions, ordinary light can penetrate these things, yet high-powered and oddly- slowly-moving laser blasts cannot. Nor can masses like ships stand up to these weird energy shields for whatever reason unless they are quite overwhelmingly large.

In Rogue One, the planetary shield prevents data communications, like such as the Death Star schematics from being sent through. Yet however, ordinary light, and presumably every environmentally-necessary wavelength penetrates both ways.

This is the key to undoing the Empire. Enter Infrared warfare. The rebels simply send a few thousand large mirrors to warm up whatever Imperial stronghold planet is of interest past the point to where their base is designed to handle. The AC craps out, and the battle is won.

RayfordSteele, Apr 27 2017

Blaster http://starwars.wikia.com/wiki/Blaster
// oddly- slowly-moving laser blasts //"A blaster was any type of ranged weapon that fired bolts of intense plasma energy, often mistaken as lasers. Operating under the same principles as laser weaponry, blasters converted energy-rich gas to a glowing particle beam that could melt through targets." [notexactly, Apr 27 2017]

Looking down the barrel of a gun http://www.space.co...r-strike-earth.html
The closest thing to a real death star out there at the moment... [RayfordSteele, Apr 29 2017]


       I think these shields work by quizzing each photon that approaches them as to its intention. If it is approaching the planet/ship/base with an intention to destroy and kill, it is denied access; on the other hand if it is just communicating the beauty of the cosmos then that's fine. So maybe the cunning solution should be to teach photons to lie?
hippo, Apr 27 2017

       Which mechanism will allow us to isolate the uniquely waggish Gilbert Hardingite photon class.
calum, Apr 27 2017

       but signal interference works without bringing down the entire electromagnetic spectrum.
theircompetitor, Apr 27 2017

       How about, as a cheaper option, a huge gas cloud? A sufficient quantity of any transparent gas, released into space at the right point between a star and an orbiting object, would expand to create a colossal lens. The focal length would be immense, but it would capture and focus a large part of the star's energy onto the target.
MaxwellBuchanan, Apr 27 2017

       Hmm, I was looking at a magnifying glass in the 100 Yen shop, and noted that, with that packaging, the only way to see it is a magnifying glass is by the distortion of text printed behind it on the card.   

       I suggest flogging a gazillion purely flat plate glass ones with specially printed distorted text behind them to thwart any galactic overlord with a plan to toast a planet.
not_morrison_rm, Apr 27 2017

       Nice one Max. Hard to defeat.
RayfordSteele, Apr 27 2017

       There's a lawyer outside. Says he represents some ants.
pertinax, Apr 28 2017

       //a huge gas cloud?//   

       So, back-of-the-envelope, how would it work? How much gas would it take?   

       We can assume that a cloud of gas, released in space, will expand spherically. So, what we have is a spherical lens (the gas cloud) with a density gradient, from high in the centre to low at the periphery. That's OK - gradient lenses are a thing, and their optics are quite well understood.   

       Now, we could use physics and mathematics and other ics to work out how much gas will be needed, but that would be troublesome. So we'll guesstimate instead. Let's assume (for no particular reason other than dodgy intuition) that the gas cloud will have an average pressure of about 1 millibar. I am guessing that, at millibar pressures, the gas will expand so slowly (over distances of thousands of miles) that it will be effectively stable for several days. So, let's go with 1 millibar average pressure.   

       How big do we want this cloud to be? Its cross-sectional area will determine how much sunlight it can focus, as will its proximity to the sun (if it's closer, it will intercept more sunlight). But we also want to focus it down onto a planet-sized area, so it will have to be roughly one focal length away from the planet.   

       So what's the focal length? I have no real idea. However, Earth's atmosphere noticeably refracts sunlight (which is why the sun goes a slightly odd shape when it's near the horizon). So, the atmosphere is bending sunlight by a good fraction of a degree, over distances of only a few hundred miles. Our lens is about a thousand times less dense, but it's also going to be very thick, so I'm guessing it will still bend light by maybe a tenth of a degree.   

       [pauses to find new envelope-back].   

       The point is that the focal length of our gas lens is going to be much, much much less than the Earth-Sun distance, which means that the lens is going to need to be relatively close to the earth. So, the solar flux hitting the lens will be about the same as the solar flux hitting Earth.   

       In that case, how big does the lens have to be? Well, I am pretty sure that if the amount of sunlight hitting the Earth were increased 100-fold for a few days (the lifespan of our gassy lens, before it disperses), things would get toasted more or less completely. So, our lens wants to be about 10 times the diameter of the Earth.   

       So, then, how much gas does it take to fill a sphere with a diameter of 120,000km, to an average density of 1mbar? That's a volume of roughly 4 x 60,000^3 cubic kilometers, or about 10^15 cubic kilometers, or 10^24 cubic metres, or 10^27 litres. At atmospheric pressure (1 bar) that would be about 10^26 moles of gas, but we're down at 1mbar, so it's only 10^23 moles of gas. If we were using oxygen, that would be something like 10^24 grams of gas, or 10^18 tons.   

       This is only about 1000 times more gas than in the Earth's atmosphere.   

       So, there you have it. If you can muster about a thousand planets-worth of atmosphere and release it at the right distance from the planet, you can basically toast the place.   

       Of course, you could also make the lens much less dense (much longer focal length) and put it closer to the sun. This would have the advantage that not only would you need (in fact, require) a lower gas density, but a lens of a given size would intercept more sunlight. In theory, the diameter of the lens would only have to be about 10 times the apparent diameter of the Earth, as viewed from the centre of the sun - very small indeed. However, a lens close to the sun would encounter all kinds of problems, and would probably not be stable for any length of time. Moreover, its orbital speed around the sun would be huge, so it would only be focussed on the Earth for a very, very short time.
MaxwellBuchanan, Apr 28 2017

       Seeing as how the center of the cloud doesn't effectively do anything useful but scatter light, the cloud volume could be significantly reduced to roughly a torus with the proper modified focal shape.
RayfordSteele, Apr 28 2017

       The gas cloud spherical lenses could be combined in a series to modify the focal length, and also the dispersion (and chromatic aberration, if desired) by using an old three element lens design such as the Cooke Triplet.
Ian Tindale, Apr 28 2017

       //Seeing as how the center of the cloud doesn't effectively do anything useful but scatter light, the cloud volume could be significantly reduced to roughly a torus//   

       Ah, but this is a gradient-density lens (inevitably), so the centre of the lens is doing useful stuff. Also, how are you going to make a torus in space?
MaxwellBuchanan, Apr 29 2017

       The old-fashioned way is the best. Donut-making machines are just cheating and the results are not as tasty.   

       Oh, you mean a big one?   

       Maybe with sufficient rotational inertia?
RayfordSteele, Apr 29 2017

       I think I understood the first few sentences. so +
pashute, Apr 30 2017

       Suggests a Scheherazadean solution to interplanetary warfare. Display a story scrolling across the equator in enormous letters with a cliffhanger ending, visible via the magnifying glass.   

       Alternatively, I imagine a shield like frosted glass, scattering the rays.
nineteenthly, May 01 2017

       There's only one of me, I cannot be scattered easily.
RayfordSteele, May 01 2017

       We have to leave and face what's out there sometime. ( purely on title)
wjt, May 11 2017

       "Death magnifying" would presumably make death even more death-like
hippo, May 11 2017

       Unless it refers to the death of death.   

       Unless. What a strange word. To undo less? To negate less? Isn't this the same as saying 'more'?
Ian Tindale, May 11 2017

       It's the same as "moreover" - it's an abbreviation of "unlessover"
hippo, May 11 2017

       //Unless it refers to the death of death.//   

       And with strange aeons...
Wrongfellow, May 11 2017

       //Unless. What a strange word//   

       OK, without any fact-checking or domain knowledge, I think I can mansplain it easily enough: "an" in Shakespearean English seems to be near-enough synonymous with "if" (though perhaps a little closer to "whether"). Then there's a conveniently blurry semantic line between diminution and negation ("Hardly!", I hear you object), which allows us to map "less" to "not".   

       So, with precisely zero data points to back this up, I propose "unless" <= "un" + "less" <= "an" +"less", meaning "if" + "not", which is the meaning you first thought of.
pertinax, May 12 2017

       "Unless" is one of the few words to have made it into English from Ambonese, a major language of the Moluccas, in the course of the spice trade. It actually started out as "Ind-latu", which is a ceremonial spear given to an enemy as a sort of threat of war, and a last chance to back down. It got hijacked by East India Co. traders to mean a threat, and then metamorphosed to mean something that had to be done, "or else". By that time it had got muddled up with the English "lest", and by the time it entered circulation in England it had become "unlest" and then, since the final "t" tended to get ignored in speech, "unless".
MaxwellBuchanan, May 13 2017

       And here I though it originated with the Lorax...   

       Shouldn't it just mean "more?"
RayfordSteele, May 13 2017

       It depends. You may have already lessed, but immediately regret it, in which case you'd rather unless.
Ian Tindale, May 13 2017

       //into English from Ambonese//   

       Soyons serieux, as André Malraux used to say (rather implausibly).
pertinax, May 13 2017

       Jamais, je dit, jamais!
MaxwellBuchanan, May 14 2017

       //weird energy shields//

It was my impression that these are sustained & held in place by one of the great, yet oft unmentioned natural forces; Narrative Tension. On the face of it, they are unstable & prone to imminent collapse or to give way under physical bombardment at any moment. However, this is mere illusion. Their unusual physical state of being forever on the brink of collapse merely serves to create ever more Narrative Tension & thus a feedback loop is created which makes the energy shield self sustaining &, ultimately, impenetrable by hostile forces. It's all very simple really.
DrBob, May 17 2017

       There is also (probably) an as-yet undiscovered well-known formula detailing the relationship between the force of narrative tension and, like Fleming's right-hand rule, the ever present surrounding field of incidental music.
Ian Tindale, May 17 2017

       //he force of narrative tension and, like Fleming's right-hand rule// Actually, I think you'll find that Bond was portrayed as being ambidextrous, at least when it came to guns.
MaxwellBuchanan, May 17 2017


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