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# Solar cutting torch

Ok, so tackling parabolic solar reflectors as my first foray into math in thirty years wasn't such a good idea.
 (+4) [vote for, against]

I've got this idea, and it works in my head so I think it will work out here with the right materials but I can almost guarantee that your guess, (yes, yours) will be better than mine as to whether my mental projector is still functioning.

To start with I need a huge perfect parabolic dish and not a Scheffler reflector because we want a circular convergence.
The temperature I want to reach is around 2000 degrees because all the silicates are molten at about 1200°C and I need a lot of room for error since I will be modifying the dish and none of the surfaces will be 100% reflective so we're going with overkill to ensure that the melting point of rock will be reached.
I'm guessing something like a 30 ft. diameter dish will do the trick but if that is wrong then scale it up to whatever size reaches 2000 degrees.

Now I want to cut a perfect circle at the very bottom of the dish and replace it with an inverted flat mirror on a slider track.
This will have the negative effect of decreasing the potential generated heat by the size of the parabola cut away, but all of the converging rays can now be directed downwards and the set of the slider will determine heat at the focal point because distance from bottom will determine how many rays get reflected away from the upper focal point.

Here's where I don't know if I'm right or not;
If these converging rays were to intersect within a perfectly mirrored tube, would they converge again at a distance as far from the original focal point as the length of the tube?
Also, If the tube were flexible while retaining reflectivity would the curves inside of the tube cancel out over distance so that the end convergence is always that same circular shape?

If both of those things work the way they work in my head then hand-held solar cutting torches would be a pretty cool thing, but what I would really like to see is the end of that flexible tube mirror attached to an X Y Z axis to create a backyard solar CNC machine.

I'm thinking like obsidian hot tubs carved from bed-rock and solid rock cap-stones on rtaining walls and such.

 — 2 fries shy of a happy meal, May 30 2018

Solar powered laser https://www.technol...olar-powered-laser/
It's crazy, but it works. [neutrinos_shadow, May 30 2018]

Magnesium Combustion Engine Magnesium_20Energy_20Cycle
No need for solar-powered lasers. [Wrongfellow, May 30 2018]

you want.. kind of the opposite of this? [Loris, Jun 04 2018]

Pillow fight https://en.wikipedi...ttle_of_Fort_Pillow
"Fort Pillow marked one of the bleakest, saddest events of American military history." [8th of 7, Jun 07 2018]

For a more practical alternative, hook this up to a solar panel https://www.youtube...watch?v=E3YCACZQ72Q
Handheld laser rifle with air assist for nuclear decommissioning [notexactly, Jun 08 2018]

 This sounds a bit like a Cassegrain telescope.

 The central mirror needs to be curved, not flat, otherwise the incident light will reflect off at an angle, hit the main parabola, and bounce back towards the sun.

The "perfectly mirrored tube" sounds like some kind of optical fibre - I'm not sure how much power they can handle.
 — Wrongfellow, May 30 2018

Yes, this is a reflecting telescope with an optical fibre. Unfortunately, though, the only way to get coherent light out of an optical fibre is to put coherent light in. The etendue of the light will be conserved.
 — MaxwellBuchanan, May 30 2018

[Wf] W. The beam from a parabola forms a cone. Put a mirror not quite halfway up the cone and it's like lopping off the top and turning it upside down, ie: it will focus on the other side of the hole cut in the bottom... big mirror though.
 — FlyingToaster, May 30 2018

 // obsidian hot tubs carved from bed-rock and solid rock cap-stones on rtaining walls and such. //

 Ignoring the misspelling of "retaining", we consider it would be useful to draw your attention to the relevant physical properties of silicate minerals.

 You have no doubt observed that those who perform precision work with stone generally eschew the use of heat in favour of mechanical devices, which employ either impact, abrasion, or a mixture of the two. Unlike metals, when a point source of heat is applied to rock, it tends to spall and shatter. This is a consequence of (a) thermal conductivity and (b) coefficient of expansion.

 Rock can indeed be converted from a solid to a liquid, but it is usually necessary to heat the entire mass, very slowly and evenly, until the melting point is reached. Failure to do so can mean it all suddenly becomes very loud and expensive.

Granite, an igneous rock, can be melted and re-cast, but for reasons of practicality it is far more common to work the cold crystalline solid into the desired shape and accept a high proportion of wastage.
 — 8th of 7, May 30 2018

With [MaxwellBuchanan] mentioning coherent light, I thought: why not make it a solar-pumped laser? See linky.

 From the link: "A new kind of efficient, solar-powered laser has been developed by researchers at the Tokyo Institute of Technology, in Japan. They hope to use the laser to help them realize their goal of developing a magnesium combustion engine."

Didn't we do that one here? Ah, yes... [link]
 — Wrongfellow, May 30 2018

 //hand-held solar cutting torches would be a pretty cool thing,//

 It would! and I think it's feasible. For reference an oxy acetlyene cutting torch seems to be about 3-4kW. Can we deliver that much light to a few square mm at the end of a torch-like tool? I think so.

 Your parabolic reflector at 30ft should give you about 109kW if you believe figures on solar radiation being 1.4kW/m2. That is, of course, subject to modification. You either don't want or can't use about 1kW of that. UV tends to destroy things and IR covers a very wide range of wavelengths which don't like doing what they're told. So you really get about 38kW.

 Shave 20% for a cheap, non perfectly shaped mirror. Then what you want is a collimator. That gives you nice parallel light. What you then need is a liquid light guide, which is just the job for broad spectrum high power applications. I put 300W down a 5mm one. Let's assume you can get 10x that through, which gives a 20mm guide which will be about 80% efficient. Now you have 24kW of colimated light coming out of your light guide and presumably a fan or something to get rid of that 6kW waste heat.

 Throw a lens on it and you have more than enough raw power coming out the end. The problem becomes what you're aiming it at. You can see rock, which means it reflects visible light. How much power you can actually deliver into the surface is very much going to depend on the material. Rock is going to be a nightmare, before you know it your sun-torch hits a quartz crystal and a 14kW reflection blinds poor Jim's good eye. Switching it on and off is practically impossible, any shutter at the work end would have to either absorb (and melt) or reflect (melt the light guide).

There would be no safe way to work with the thing, or even be in the room. Unless it was cloudy, or night, or early/late/eclipsy.
 — bs0u0155, May 31 2018

It seems to me you can switch it off by steering the main reflector away from the sun. It might not be that quick, but at least you don't have to deal with dumping all that energy into some kind of dummy load.
 — Wrongfellow, May 31 2018

 Just tip the reflector at the focus, like a heliograph.

 // parabolic reflector at 30ft should give you about 109kW //

Only during the day ...
 — 8th of 7, May 31 2018

 //Only during the day ...//

mid day
 — bs0u0155, May 31 2018

 //Cassegrain telescopes// are cool. An inversion reflected from an outversion is a flatversion.

 //Etendue// is a good word, but what's with the French? It should be anti-ombre.

 //when a point source of heat is applied to rock, it tends to spall and shatter. This is a consequence of (a) thermal conductivity and (b) coefficient of expansion.//

 I don't mind polishing rock smooth, I wanted a way to purposely cause little micro-explosions so that very rough forms are cored. I work with stone a lot and I see something like this carving thin deep ridges which can be easily chipped away saving thousands of dollars in diamond wheels.Obsidian might have been a stretch.

 //Switching it on and off is practically impossible, any shutter at the work end would have to either absorb (and melt) or reflect (melt the light guide).There would be no safe way to work with the thing, or even be in the room. Unless it was cloudy, or night, or early/late/eclipsy.//

The temperature at the end of the optic cable could become ambient in less than one second by rapidly sliding the flat mirror towards the base... no more reflected light, no more heat.
 — 2 fries shy of a happy meal, Jun 01 2018

 The laser weapons being developed by various militaries use pulsed, rather than continuous, beams.

 Would this be better at rock-drilling if you added some kind of mirrored fan, just inside the inner reflector, which rotates at high speed, alternately reflecting and admitting the light, to create a high speed pulsing effect?

Or perhaps spinning the inner reflector on an axis that's perpendicular to the axis of the outer parabola?
 — Wrongfellow, Jun 01 2018

 I'm thinking the bed has the 6 axis gubbins, and the cutter has the constant solar track. [+].

Hopefully, the future will use increased population to extrapolate knowledge and computing to reduce this to a pen.
 — wjt, Jun 01 2018

A pen with a 30ft parabolic dish on one end of it?
 — Wrongfellow, Jun 01 2018

Isn't there a curved steel&glass building in London that routinely parboils anybody parked in a particular spot across the road ?
 — FlyingToaster, Jun 01 2018

There was … the "Walkie-talkie". It's fixed now (allegedly).
 — 8th of 7, Jun 01 2018

//it's fixed now// could be "fixed" for \$10 ; just put up a "solar car recharge station" sign.
 — FlyingToaster, Jun 01 2018

 They did. It melted.

 // British Hostile Architecture, perhaps even get some of our buildings classed as weapons. //

Heathrow ? The only so-called international air terminal whos mission statement is "You'll Never Leave" ...
 — 8th of 7, Jun 01 2018

 // If these converging rays were to intersect within a perfectly mirrored tube, would they converge again at a distance as far from the original focal point as the length of the tube? //

 No.

 The rays converge from different angles, because they come from different heights on the paraboloid. Therefore, they will also diverge at different angles, and therefore strike the tube wall at different distances from the focus. This, combined with the different angles, means the second focus will be spread out along the axis of the tube, and this will only get worse with more reflections.

 // Can we deliver that much light to a few square mm at the end of a torch- like tool? I think so. //

 Due to the above, the best you can get is by holding the end of the tube directly against your workpiece so that the rays at least don't have a chance to diverge after exiting the tube. This will mean that your hotspot is as wide as the tube. Making the tube tapered will only make it worse; the angled walls will result in the light gradually being reversed.

 This is also dictated by the laws of etendue, which, while seeming at first to be counterintuitive, are derived simply from the laws of thermodynamics, which are very intuitive.

 // Then what you want is a collimator. That gives you nice parallel light. //

 Yes. I guess that approach might work, as long as you don't try to make a universal collimator (which is illegal by the same laws). You could, I think, take the focused light from the paraboloid and feed it into a properly designed collimator, which would make the rays parallel. Then you could focus that beam down to a point at the head.

However, it will probably have to be a beam as wide as the paraboloid, by those same laws of etendue. This means that the paraboloid and collimator would be redundant, because sunlight is already parallel!
 — notexactly, Jun 03 2018

<instant gut reaction> //sunlight is already parallel!//</instant gut reaction> Coming parallel of and through the surface reactions of the sun ?
 — wjt, Jun 03 2018

What? It's parallel because the sun is so far away. The difference between 93 million miles and infinity is negligible, at least as far as angles are concerned.
 — notexactly, Jun 03 2018

 //This is also dictated by the laws of etendue, which, while seeming at first to be counterintuitive, are derived simply from the laws of thermodynamics, which are very intuitive.//

That's what I was getting at earlier. I'm not convinced that this is optically feasible.
 — MaxwellBuchanan, Jun 03 2018

 This will work.

It just needs, as [Wrongfellow] eluded, a the large area array of reflective mirrors concentrating light on the huge perfect parabolic dish.
 — wjt, Jun 03 2018

 It'd work ; I'm not sure the word "practical" would come into play, though.

 A parabola focusing onto a curved plate which focuses the light collimated through the hole (so at this point you have a "white laser"(ish) arrangement), into the articulating mechanism, hanging off the bottom.

 That worthy chunk of optics is an articulable arm, at the back of which is a flat mirror which bends at half the angle of the arm. So now you have a white laser beam that comes through the hole, bounces off the mirror and shoots through the axis of the arm, and will remain on axis - no mirror-tube needed.

 Feel free to put another mini parabola on the end, like the first one, except use a flat mirror in order to get a point focus on the other side of its hole.

Or a lens.
 — FlyingToaster, Jun 03 2018

 Nope. There are some things you can't do with light - it's all to do (as both I and [notextactly] have mentioned) to do with etendue. I can't claim to understand the optics in detail, but I had a similar issue a while ago where I wanted to concentrate light to a point. In the end, I asked Brad Amos who knows a lot about optics - he's the guy who invented the first working confocal microscope, and now has his own company designing and manufacturing microscopes - so he really, really knows.

 You can concentrate sunlight down to an extent, but not indefinitely; and trying to collimate after concentrating it doesn't work.

If you want to use sunlight to melt rock, I'd suggest the way to do it is to have an array of solar cells rather than a parabolic dish, and use them to power a regular laser. That way, you get the controllability of a laser; you can choose the wavelength that works best for rock; you can turn it on and off at will; you don't have to track the sun very closely; and you can control the power; and you can get all your heat in a small spot. I'm not seeing the advantages of a big sunlight-concentrator over this, even if it would work.
 — MaxwellBuchanan, Jun 03 2018

 //buy a laser// well, duh, though I don't imagine they're cheap at the "melts rock" power level.

 Much less sq.m'age taken up then that of 20%-max efficiency solar cells, into a what, 10(?)% efficiency laser.

 "etendue is conserved as light travels through free space and at refractions or reflections" - ex Wikipedia

Wonder if a 3D printer would produce a fine enough result, as sections of the primary and secondary mirrors, to be covered with aluminum foil.
 — FlyingToaster, Jun 03 2018

 // I don't imagine they're cheap at the "melts rock" energy level. //

 Well, Alibaba will get you a 10wK bare-bones laser for (amazingly) about \$2000. You may think that \$2000 is not cheap, but it does have the advantage that it will actually work.

I am pretty sure you can't focus the sun's energy to a useful spot on the end of flexible light guide. If you could, it would cost you lot more in high-spec optical components than a laser.
 — MaxwellBuchanan, Jun 03 2018

What about the other way, like an insect eye. 10,000 high temperature fibre optic cables (500mm light disc), each gathering light with a little parabolic flower, all aligned to the needed spot. A very Lexx thought.
 — wjt, Jun 03 2018

 // 10,000 high temperature fibre optic cables (500mm light disc), each gathering light with a little parabolic flower, all aligned to the needed spot. //

Are you suggesting tapered fibers? If so, refer to what I said earlier about tapered tubes.
 — notexactly, Jun 03 2018

Not sure how this is very different from the solar arrays used for power generation. These concentrate solar energy on a crucible with salt or lithium in and this molten material is then pumped through some system which gets useful energy out of it.
 — hippo, Jun 04 2018

I think the difference here is that the light is supposedly carried by a light-guide to the melting tool.
 — MaxwellBuchanan, Jun 04 2018

But why mess about with light-guides? Big solar arrays focus hundreds of mirrors onto a point, supplying sufficient energy to melt salt. It's much more straightforward and foolproof to do it this way and, if you need to do anything more complicated like using it as a cutting tool, just move the target to the highly-concentrated energy point, rather than vice versa.
 — hippo, Jun 04 2018

That is a not unreasonable point. I think the attraction was in having a tool you could wield.
 — MaxwellBuchanan, Jun 04 2018

Ah yes, and it is, of course more attractive to wield big powerful tools rather than the target on which those tools act. This is a metaphor undoubtedly explored in tedious, boring detail in a million unread post-modern feminism/gender studies PhD theses.
 — hippo, Jun 04 2018

I've linked to an artist who used a big lens and sand to make a 3d printer. Maybe you could turn it on its side and melt it out instead?
 — Loris, Jun 04 2018

 The light flowers were to bounce as much light into the tubes. That sinter printer project was a great culmination of technology for art.

Isn't a pen just a remote joy stick, differently held? Then again, no one wants to do the tedious colouring in.
 — wjt, Jun 05 2018

 Well now my head hurts... but in a good way.

 // No.The rays converge from different angles, because they come from different heights on the paraboloid. Therefore, they will also diverge at different angles, and therefore strike the tube wall at different distances from the focus. This, combined with the different angles, means the second focus will be spread out along the axis of the tube, and this will only get worse with more reflections.//

 The tube thing maybe not working I can understand, but I still bet that given perfectly symmetrical materials the light would re-converge at a point small enough to do the job.I see the light rays creating circular back-to-back cone shapes down the tube where in-between each reflection-cone they refocus at points. Bends in the tube should cancel out as long as they emerge from a straight section. In fact it should be possible to minimize distortion by creating the inner tube from facets rather than round... triangular would work well and allow for twists as well... in my head anyway.

 Like I've said, it shows me things when I zone-out and I never really know if what I'm seeing will work out here in reality.The whole hand-held power-wand isn't Freudian in the least.

 no really...

 I was daydreaming about how it might have been possible to create those stone walls in Peru using technology that would have been available then, (no \$2000.00 lasers).I figured that they might have been able to build almost perfect parabolic reflectors by keeping pools of wet mud constantly spinning and then, as they dried, they would naturally assume that shape. Line them with flakes of Mica or another highly reflective mineral and you've got a couple of thousand cave-man degrees of seriously potent Juju.Adding a flat reflector would allow for roughly shaping rocks using existing sections of wall as a template by bouncing enough light downwards.Flip the new rock over and it falls right into place so tight you can't wedge a knife-blade between them.The tube part wouldn't have been a thing then but I can more easily imagine hundreds of men rolling massive dishes back and forth all day carving rock walls into shapes that we can't figure out how to create without lasers than I can imagine them meticulously chiseling them as close to perfect as they are.

 Moving rocks around under a stationary point of light is hard, moving a dish on rollers would be relatively easy.

 See... I wonder things like; how was the first parabolic reflector discovered. (and I'm not talking about 17th century Yada-yada dude who wrote it down first no, the "real" first dude) They had knowledge of parabolic reflectors thousands of years before the math for them by following nature, like that curve a long hanging rope assumes which is the basis for all ancient arches and such.Well... I bet the "first" guy to discover this phenomenon was playing near a back eddy in a pool of water which at certain times of the day would focus enough light to light a bundle of dry grass on fire as if by magic.

 Like... Merlin's teacher was probably just the first dude to figure out that his farts were flammable and he could keep them in a sheep-stomach bladder under his armpit and re-light them later to make fire-balls. Early science.

 You ever wonder who was first and try to jump into their shoes?First fire? First garden? First button? First alcohol? First sail? First nail? First splint? First... whatever? It's a fun game.

 No, no.No more stories now. The Excalibur tale can wait for another time.We've a big day ahead of us tomorrow and you all need your beauty-sleep.Everyone's got their teeth brushed? Ok then way y'go now.

...and no pillow fights!
 — 2 fries shy of a happy meal, Jun 07 2018

 // no pillow fights! //

 — 8th of 7, Jun 07 2018

 //how it might have been possible to create those stone walls in Peru using technology that would have been available then// The only information I can find on "stone walls in Peru" shows walls made of individual stones, rather than fused stone.

 If you mean "how did they get the rocks to fit so perfectly", there was a documentary a few years ago where they showed how it can easily be done. If I recall correctly, the method is:

 (1) Cut the rocks roughly to shape in the usual way.

 (2) Put one rock on top of the other, with a banana leaf in between.

 (3) Lift the top rock off. Where the rocks are stained with green juice from the banana leaf, those are the high points. Bash those bits with another rock.

 (4) When the green stain is more or less uniform, the rocks are fitted perfectly to within about 50 microns tolerance.

The point about the Peruvians is not that they were smart enough to invent a parabolic solar rock-melting laser. The point is that they were smart enough to shape rocks to within 50 microns using a banana leaf.
 — MaxwellBuchanan, Jun 07 2018

 ^ Yeah... I don't buy that. You see the size of some of those rocks?They didn't lift them over and over again.That's crazy. I would have made my bosses lots of money back then.Not so much now...

 //pillow fights/////Regrettably, too late ... .///

 Well that's just a friggin downer Billy.Keep it up and I'll tell you how I became the Iberostar Hotel wet-pillow-fight on a surfboard champion...

 Turns out that small and fast beats large and top-heavy when the floor is moving.

 Alright no more stories! Don't make me come up there.

 Early day.

Get some sleep.
 — 2 fries shy of a happy meal, Jun 07 2018

//You see the size of some of those rocks? They didn't lift them over and over again//

Lifting big rocks is not so hard - for this, you only have to lift them at one end which is simple to do with a big enough lever, chock them, knock off the high-spots identified with the banana leaf, and then do the same with the other end.
 — hippo, Jun 08 2018

 //That's crazy. // But the idea that they had some sort of 30ft parabolic solar concentrator to melt rocks which they wiggled around at the focal point (and which, in itself, would not be very useful in fitting rocks together) isn't? There's also the fact that, as [8th] pointed out really quite some time ago, focussing intense heat onto a large rock will just split it in an exciting but often not useful way. Then again, there's also the fact that the surfaces of the closely- fitting rocks show plenty of tool marks from pounding, yet somehow lack that glassy once-melted look.

It's a bit like all the fruitloops who decided that extraterrestrials must have built the pyramids, because the fruitloops themselves couldn't figure out how to move big rocks. It turns out that the answer to moving big rocks is not to ask fruitloops to do it. Well, that and having huge amounts of cheap labour.
 — MaxwellBuchanan, Jun 08 2018

 // extraterrestrials must have built the pyramids //

 We only did the bottom layer. We laid out a nice square level base for them. Look, we said, there you are. See our Cube over there ? You just keep building up the layers of blocks until you have a nice cubic structure just like that. It's easy. You have the ground plan. Just keep adding layers. You can't go wrong, it's SO simple.

 And did they listen ? No, they didn't. The lazy sods just heaped stuff up and made an ugly triangular pile.

Ungrateful, we call it.
 — 8th of 7, Jun 08 2018

 // focussing intense heat onto a large rock will just split it in an exciting but often not useful way. Then again, there's also the fact that the surfaces of the closely- fitting rocks show plenty of tool marks from pounding, yet somehow lack that glassy once-melted look.//

 The melting/micro explosions would carve ony rough shapes. finishing would be by hand... maybe using leaves at that stage.

 //It's a bit like all the fruitloops who decided that extraterrestrials must have built the pyramids, because the fruitloops themselves couldn't figure out how to move big rocks.//

 You should probably throw in a few more 'you don't want to be like those guys do ya?' fruitloop references for effect.

 I saw a thing in my head.I relayed the thing I saw in my head.I conveyed the pathway that led to the thing in I saw in my head.

 I like it...

 ...and I grow weary of being compared to others in order to fit some sort of category you seem to insist I must fit in 'your' head.I've never met anybody like me and I bet you haven't either.So Why should I allow myself to be labelled by you or anyone else?

 — 2 fries shy of a happy meal, Jun 09 2018

The labels are for my own convenience. And no, you don't want to be like those guys, do ya?
 — MaxwellBuchanan, Jun 09 2018

 So... I try to figure out how regular folks could have done a thing and I am instantly lumped in with Alien-huggers huh?

 Notice how nobody ever adds "why" one wouldn't want to be like those guys?

 If you're asking me whether I think that aliens have interacted with humans, then yes.I think that the American public was scheduled to be informed and that a little test was in order to determine possible reaction to the news.After the unfortunate response to the War Of The Worlds radio fiasco it was then decided that waiting and indoctrination would be a better idea.

 Ever notice how ancient Sumerian writings never made it into history class even though they are the oldest writings ever found?Whether they are factual or not is irrelevant. That they were purposely not taught makes me wonder just how much else is purposely not taught.

 aaaaanyway... I was talking with a satellite dish installation guy and he said that the older larger dishes are pretty easy to come by now so I think I'm going to cobble together a small-ish version of this when I get settled again.I might try the primitive version as well. There's this rapid-setting self-leveler that cures in one hour and I like the idea of being able to determine focal point length by the rate of spin.hmmm I wonder how cheaply I can get my hands on a chunk of Mica.

...Ooh, or Galena. Galena would be good.
 — 2 fries shy of a happy meal, Jun 09 2018

 Oh, just the American public, then? Still, I guess that would make sense. The aliens probably came looking for sasquatch.

Also, I'm a little disappointed in your education system over there. You mean they didn't cover the Enmerkar legends, Gilgamesh, or Lament for Ur in the original Sumerian? Jeez, you had it rough. You'll be telling me next they didn't do Greek or Latin. We were so sick of Sumerian by the 3rd year that we were really glad to move on to heiroglyphics.
 — MaxwellBuchanan, Jun 09 2018

What, the American public??
 — MaxwellBuchanan, Jun 09 2018

 Yes ... "Populace formerly known as Joe Six-Pack", all reduced to little glyps. There's an app for it.

 // We were so sick of Sumerian by the 3rd year that we were really glad to move on to heiroglyphics. //

 Not surprising, all those Mesopotamian languages are cuneiformly dull and uninspired.

Wheatsheaf, wiggly line, sort-of boat-thing, beetle, beetle, giant eye, fish, beetle, thing like a hacksaw stood on end, big foot, palm frond ? Duck, fish, wiggly line, wiggly line, snake, lamp, Apollo 11 L.E.M. with mickey-mouse ears, beetle or possibly a 2CV with a parcel carrier ... papyrus reed, wheatsheaf, wheatsheaf, giant eye, symbol strangely like a crashed helicopter, beetle ! Smiley-face symbol, but in profile.
 — 8th of 7, Jun 09 2018

//Wheatsheaf, wiggly line, sort-of boat-thing, beetle, beetle, giant eye, fish, beetle, thing like a hacksaw stood on end, big foot, palm frond ? Duck, fish, wiggly line, wiggly line, snake, lamp, beetle ... papyrus reed, wheatsheaf, wheatsheaf, giant eye, duck, beetle ! Smiley-face symbol, but in profile.// That's what she said.
 — MaxwellBuchanan, Jun 09 2018

 That's what we thought ... we suppose that if it has to be explained, it's not actually funny.

The one about the High Priest, the jar of oil and the dancing girl was pretty good though.
 — 8th of 7, Jun 09 2018

It's even funnier when you realize that "wavey leaf" is actually a pun. You only get it if you know Sumerian Rhyming Slang, though.
 — MaxwellBuchanan, Jun 09 2018

 //Oh, just the American public, then? Still, I guess that would make sense. The aliens probably came looking for sasquatch.//

 America was a young country. They didn't have entrenched power-bases controlling information, it was a free-for-all. I think it tried to actually inform people there for a while before their politicians started getting shot and selling out. Hell, they were even allowed to have actual genius there for a bit.

 But not anymore. People might get upset.

Sasquatches are alright in my book. They had every opportunity to harm me and didn't take it. I owe them one... unlike most people I've met.
 — 2 fries shy of a happy meal, Jun 09 2018

Yes, gosh, you had a lucky escape there, [2fries].
 — MaxwellBuchanan, Jun 10 2018

 Naw, I think they're probably gentle, but they sure don't like it when you camp out in their ranges.Ranges are those thousands and thousands of miles of old-growth trees on the sides of mountains.Trees make up the large green sections on satellite images of North America.

It's almost like Sasquatch need those two things to not be imaginary for some folks.
Hey! If you guys replanted your forests I bet maybe some would come for a visit.
 — 2 fries shy of a happy meal, Jun 10 2018

//Trees make up the large green sections on satellite images of North America.// except that light green one : that's Lake Erie, again. Oh, and Salton Sea, etc.
 — FlyingToaster, Jun 10 2018

//If you guys replanted your forests I bet maybe some would come for a visit.// I suspect it would be cheaper just to drink a lot.
 — MaxwellBuchanan, Jun 10 2018

Why not both?!..
<gets carried around on shoulders of cheering crowd like that little girl in the Gorditas commercial>
Yeti digress.
 — 2 fries shy of a happy meal, Jun 10 2018

 Haha.

 The problem with the forests-and-drinking idea is that - in the summer - it might attract wandering Canucks (in the winter they're all too busy either playing or watching ice hockey).

So then you need a way of sorting them. Simplest thing is to wave an ice hockey stick in front of them - if they get excited, and try to hit one another on the head, there's your Canadians, right there.
 — 8th of 7, Jun 10 2018

You seem to be under the impression that hockey, forests and beer are mutually exclusive.
 — FlyingToaster, Jun 10 2018

No, they're not, that's the problem.
 — 8th of 7, Jun 10 2018

You call it "a problem", I call it "February".
 — FlyingToaster, Jun 10 2018

 I reckon the collimator is useful. Without the collimator, you can focus the sunlight to as small a spot as possible, and make that spot the opening of the liquid light guide. With the collimator, you could focus it to an area maybe 10 times as large, make that larger spot the opening to a larger liquid light guide, after passing through the collimator, then at the other end of the liquid light guide, focus it to reduce the spot size 10 times, to the same size as the version without the collimator. The collimator wouldn’t give perfectly parallel light, but it would be closer to parallel than without it.

Advantages: less concentrated light until the final focus, so it’s less damaging to anything that absorbs it. Light is closer to parallel so it can be reflected with total internal reflection. Light being closer to parallel is taking a more direct path, so less light loss due to reflections and absorption along the liquid light guide. Disadvantage: the light guide is bigger.
 — caspian, Oct 13 2018

 Ooh, I like that hand-held laser link!

If anyone has a spare one kicking around to lend I promise not to break into armored vehicles or anything with it.
 — 2 fries shy of a happy meal, Oct 14 2018

 I got bored a while ago, and worked out you could do the Archimedes death ray thingy with as few as 1,800 soldiers with very shiny shields. Of course the pay was lower in those day.

There's a hop-light joke in there somewhere.
 — not_morrison_rm, Oct 14 2018

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