Slashdot Mirror
The Solar Death Ray
Ant writes the "Solar Death Ray is made of 112 mirrors mounted on a platform 4 feet wide and 6 feet tall. Each mirror is a square roughly 3.5 inches on edge. All these mirrors focus the sun to a single spot 5 feet, 6 inches from the mirror platform. A wooden fork extends from the mirror base to the area near the focus and serves as a mounting point for Solar Death Ray targets. The mirror platform is mounted to the support frame on a pivot that allows the platform to be angled. The whole system is mounted on a set of wheels. The goal of the Web site was to show the results of the targeted items when the solar death ray was used."
Ummmm, shields aren't concave, they're convex. I suppose they could be turned around, but then the handles and stuff counteract the effectiveness of the "focusing". Also, focusing only really helps at near the focal length. Beyond twice the focal length it should disperse rays that started as parallel.
--
"Open source is good." - Steve Jobs
"Open source is evil." - Microsoft
Why, you're absolutely right. It's a myth. This guy must have FAKED all those photos!
Although I found the justification for the Hootie and the Blowfish tape hilarious, he should be flogged with a bamboo cane for burning that tetris disk. That thing was a fucking museum piece!
...die now and save the world from idiot pollution.
A message delivered on behalf of all living things
They were attempting to replicate what Greeks could have reasonably done with the technology they had available. The myth isn't that you can use a bunch of mirrors to set things on fire. The myth is that Greeks 2500 years ago were able fire ships some distance away in a harbor. They wouldn't have been using any sort parabolic mirror and even a concave one of any reflectivity at all would be a serious stretch. The Mythbusters did a decent job of showing that the ancient Greeks probably didn't have sufficient mastery of optics to make a practical sunlight weapon.
However, the 'busters did fail to take into account the diffence in performance between a dozen random studio hands and a couple of hundred trained militiamen.
If you want to burn a ship that's several hundred meters away with a reflection from the sun, it doesn't matter very much whether the mirrors have exactly the right curvature or are flat. Even a perfect curved mirror would create a perfect image of the sun the diameter of which depends on the distance between the mirror and the image. At 200 m, you could focus the sun to a 2 m diameter disc. As long as the individual reflectors are significantly smaller than 2 m, it doesn't make much of a difference.
Avantslash: low-bandwidth mobile slashdot.
Mythbusters is far too quick to "bust" myths that are actually true to some extent. They make a couple of (usually poorly designed) tries to replicate the circumstances, and then when their small number of tests fail they declare the myth "busted".
This is a perfect example. Mythbusters claims to have "busted" the solar death ray myth, yet the guys in this article were successful in lighting shop rags, pairs of old jeans, boardgames, etc on fire, and have pictures to prove it.
I hate to be the one to point this out, but um. They haven't actually killed anything. This more accurately should be called a Solar Plastic-Melting Ray.
No, he did kill some something: Army men. Okay, maybe they are made of plastic, but they're still men.
24 beers in a case, 24 hours in a day. Coincidence? I think not!
You'd be right if there were no atmosphere.
actually it does, which is why you shouldn't point your telescope at the moon for you would burn your retinae within a few seconds - you have to use filters. Same goes for the sun except you'd probably burn your face before you can get your eye to the eyepiece...
TODO: 753) write sig.
Ahh.... see you have to kill the troll. No way around it sadly :\.
Most people aren't thought about after they're gone. "I wonder where Rob got the plutonium" is better than most get.
A parabolic array only matters when you are trying to focus a signal. The Greeks were only interested in energy, and had no concern for phases. Therefore they don't need anything other than clear line of sight to the target for everyone. Each person just has to figure out which of the (many) bright spots is the one they control, and keep that more or less on the target. So long as the average energy reaching the target spot is enough it doesn't matter if many are not on target at any particular moment.
They've got the shields anyway, they've got the soldiers anyway. In war, you certainly might prepare a tactic that isn't 100%, especially when the additional resource investment is small.
Promote civility: mod down any post starting with 'ummm'.
They certainly knew geometry and optics. What they didn't know was glass. Crystal lenses have been discovered all over the Mediterranean.
Ancient Greece isn't my specialty -- that would be Egypt -- but I know that by the time the Greeks were trading with the Egyptians, blown glass artifacts start showing up, initially as imports, and later as domestic products. The Egyptians had been making cast-glass jewelry for some time before that. I rather doubt they knew how to make optical-grade glass, though. That the Greeks knew about lenses is, however, established fact.
The Romans, on the other hand, used plate glass extensively in their windows. It only fell out of use at the end of the classic era, when the constant fighting of the middle ages made large, easily broken windows a liability for defenders.
Proud member of the Weirdo-American community.
i doubt that all the different materials called "paper" ignite at the same temperature...
No, they claim to have busted the myth that the ancient Greeks set ships on fire hundreds of feet away. Setting an object on fire with a mirror three or four feet away is a vastly different feat from setting a ship on fire 100 feet away.
Oolite: Elite-like game. For Mac, Linux and Windows
At least half their experiments have been organized so poorly that they failed when its well documented something works, and that was a prime example.
Its entertainment, not science. Don't watch it to learn anything about the reality of the "myths", watch it because its freakin' hot to see Kari bound up in the water torture episode.
(Oops, did I just say too much?)