posted
Comment: persists over the years -- is there any truth to it at all?
"angry fans in a south american soccer match pull out mirrors and use the sun to fry the referee to a crisp!"
Posts: 36029 | From: Admin | Registered: Feb 2000
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posted
I call probable BS. If the Mythbusters couldn't do it to a ship, then I doubt 30,000 soccer hooligans with hand mirrors could do it to a referee.
OTOH, I can see them blinding the ref with that tactic.
- Pseudo "she blinded me with soccer" Croat
-------------------- "At all events, people who deny the influence of smaller nations should remember that the Croats have the rest of us by the throats." - Norman Davies, Europe: A History
God wants spiritual fruits, not religious nuts. Posts: 4578 | From: Sunrise, FL | Registered: Apr 2002
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quote:Originally posted by Pseudo_Croat: I call probable BS. If the Mythbusters couldn't do it to a ship, then I doubt 30,000 soccer hooligans with hand mirrors could do it to a referee.
I don't understand why you say so. Did the Mythbusters use 30,000 mirrors? What is the temperature required to burn wood? How about skin?
Posts: 4922 | From: Kyoto, Japan | Registered: Sep 2005
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quote:What is the temperature required to burn wood?
What is the temperature required to burn a referee?
-------------------- "Ladies and gentlemen, this is what is commonly known as money. It comes in all sizes, colours, and denominations - like people." Posts: 997 | From: Maidstone, UK | Registered: Jun 2006
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The 30000 mirrors wouldn't all be focused on the exact same part of the ref's body, mind.
Posts: 124 | From: London, England | Registered: May 2006
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I've noticed recently that Soccer referees are wearing all sorts of different colours, aside from the traditional black. Given that black absorbs more radiant heat than any other colour, would this affect the number of mirrors required?
-------------------- "Ladies and gentlemen, this is what is commonly known as money. It comes in all sizes, colours, and denominations - like people." Posts: 997 | From: Maidstone, UK | Registered: Jun 2006
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quote:Originally posted by Ganzfeld: I don't understand why you say so. Did the Mythbusters use 30,000 mirrors? What is the temperature required to burn wood? How about skin?
The Mythbusters used two large mirrors IIRC. I don't understand why you think that many smaller mirrors would be sufficient to burn a person if two big ones couldn't.
Regarding the autoignition temperatures of wood and skin: According to Ray Bradbury's famous novel, 451 degrees Fahrenheit (233 degrees Celsius) is the autoignition temperature for paper. I assume wood would not be too dissimilar, since wood and paper are both mostly cellulose. Couldn't find any similar data on skin (even tried Googling for "autoignition temperature skin", but all I got were a bunch of MSDS's), but I guess I didn't Google the right things.
- Pseudo "murder in the third degree" Croat
-------------------- "At all events, people who deny the influence of smaller nations should remember that the Croats have the rest of us by the throats." - Norman Davies, Europe: A History
God wants spiritual fruits, not religious nuts. Posts: 4578 | From: Sunrise, FL | Registered: Apr 2002
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posted
A) The skin isn't going to auto-ignite until its is dehydrated. (Temperature remains constant during state-change, so the skin isn't going to go above 100 degree until it loses its water.
B) It takes A LOT of energy to evaporate water. (5 times as much as it takes to heat water from to 100 degrees celsius)
C) in order to get the last bit of energy needed to evaporate, water can take heat away from surrounding object, reducing their temperature.
There's really no way to fry a wet moving object with the sun.
Now if somebody went up and knocked the referee unconcious, then there might be a possibility...
Posts: 201 | From: Toronto, ON | Registered: Jun 2006
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quote:Originally posted by DaGuyWitBluGlasses: A) The skin isn't going to auto-ignite until its is dehydrated. (Temperature remains constant during state-change, so the skin isn't going to go above 100 degree until it loses its water.
B) It takes A LOT of energy to evaporate water. (5 times as much as it takes to heat water from to 100 degrees celsius)
C) in order to get the last bit of energy needed to evaporate, water can take heat away from surrounding object, reducing their temperature.
There's really no way to fry a wet moving object with the sun.
Now if somebody went up and knocked the referee unconcious, then there might be a possibility...
Who said the ref has to ignite? "Fry to a crisp" isn't very specific.
It may be difficult to keep enough light on him while he's moving but how many hundreds of times do you think a magnifying glass magnifies the sun? So as long as a few hundred of the mirrors (assuming they are of very good quality) are hitting the ref in at least one spot consistently, what's to stop him from getting burned.
If being "wet" were any obstacle to getting cooked in sunlight then solar cookers wouldn't work. But they do.
Posts: 4922 | From: Kyoto, Japan | Registered: Sep 2005
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quote:Originally posted by Ganzfeld: I don't understand why you say so. Did the Mythbusters use 30,000 mirrors? What is the temperature required to burn wood? How about skin?
The Mythbusters used two large mirrors IIRC. I don't understand why you think that many smaller mirrors would be sufficient to burn a person if two big ones couldn't.
Then you don't understand the concept. (And it sounds like Mythbusters don't either.) Two mirrors doubles the sunlight (or triples it if the object is in the sun). Imagine trying to burn something with a magnifying glass if you make the image of the sun (the round spot) only one third the area of the glass. You'll get it a little warm. Now make that image of the sun a tiny spot, one three-hundredth of the lens area. It will smolder and, if you're careful (or not?), you can start a fire. Three hundred mirrors can concentrate the sunlight three hundred times. So you make it much much hotter than with two mirrors. Of course, mirrors aren't perfect but more of them certainly means more radiation, more light, more heat.
ETA - About the perfection of the mirrors - if mythbusters used two curved mirrors to concetrate light from far away then they would have had to have had very perfect curves and focused them just right. Only large, expensive telescopes have such mirrors. (What did they use?) However, that is not a problem with a huge number of smaller mirrors. As long as the number hitting one spot at any given time is a large number, it's the same for the object whether these mirrors are always the same ones or different ones. So you'd only have to get say, one in ten of those 30,000 fans to hit one spot at any given time, which is the same as saying that each fan would only have to hit that spot one-tenth of the time.
Posts: 4922 | From: Kyoto, Japan | Registered: Sep 2005
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posted
I think this fails for the very same reason Mythbusters failed. It's simply not practical to focus that many mirrors at the same time at a small enough point to ignite it. The more people who are trying to aim their mirror, the harder it becomes, as it soon becomes almost impossible to guess which reflection comes from the mirror you are holding. The distance also makes it harder.
Much easier to bring a flame thrower.
-------------------- /Troberg Posts: 4360 | From: Borlänge, Sweden | Registered: Nov 2005
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quote:Originally posted by Troberg: I think this fails for the very same reason Mythbusters failed. It's simply not practical to focus that many mirrors at the same time at a small enough point to ignite it. The more people who are trying to aim their mirror, the harder it becomes, as it soon becomes almost impossible to guess which reflection comes from the mirror you are holding.
True. But the more people you have the less accurate you need to be. With practice, you could move your mirror off the target very quickly, see your own spot, and get back on target. It probably would be difficult but that's not the same as being impossible.
I think Mythbusters failed because they didn't have enough mirrors. If they used curved mirrors then they would have to be extremely high quality and also kept in focus, adding one full dimension you have to control. If they used flat mirrors, what can you do with two? Maybe warm something up a bit but that's it. If you have 30,000 of 10 x 10 cm each, that's the combined area of 300 square meters of sunlight. If only ten percent at any given time are able to hit the target of 10x10cm, that's hundreds of times the heat of the sun. It's gonna give somebody an awful sunburn in a very short time, at the very least. Whether or not that ten percent is achievable can be debated. As I say, it probably takes some practice.
Posts: 4922 | From: Kyoto, Japan | Registered: Sep 2005
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quote:Originally posted by DaGuyWitBluGlasses: A) The skin isn't going to auto-ignite until its is dehydrated. (Temperature remains constant during state-change, so the skin isn't going to go above 100 degree until it loses its water.
B) It takes A LOT of energy to evaporate water. (5 times as much as it takes to heat water from to 100 degrees celsius)
C) in order to get the last bit of energy needed to evaporate, water can take heat away from surrounding object, reducing their temperature.
There's really no way to fry a wet moving object with the sun.
Now if somebody went up and knocked the referee unconcious, then there might be a possibility...
Wouldn't just need to set his clothes on fire rather than his skin?
-------------------- Silence should never under any circumstances be construed as agreement. A lot of the time, it's simply a reflection that someone just said something so stupid that no response could possibly do it justice. - Ramblin' Dave Posts: 8528 | From: Nottingham, England | Registered: Feb 2000
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This is how they light the Olympic torch. Although, to be fair, I can't tell if it's wood, paper, matches, propane or human flesh they are igniting here. (look second picture from left on top row).
I have a book called Archimedes revenge, which a layman's book on the marvels of mathematics. Briefly, they discuss his defence of Syracuse. One of the godlike weapons he had, according to legend, was a set of mirrors that could set ships aflame.
The book describes the need for a adjustable focal point and a stationary target. As the wiki link states, none of this is possible in a seige.
posted
The original (polished shields against ships) was used against the Roman attack on Syracuse in 212BC by Archimedes. It was ultimately unsuccessful as Syracuse was sacked and Archimedes killed (much to the disgust of the Roman General).
The mirrors against referee in the OP is a short story by Arthur C Clarke in his collection 'Tales from the White Hart'. The story is set in SouthAmerican soccer match where the ref is outageiously favouring the visiting team and the home supporters use reflective programmes to solve the problem. The entire book is made up of stories using pseudo-science to tell a tall (pub boasting) story, often of the 'shaggy dog' type (one of the others has a submarine paid by Californians to tow a hollow artificial iceberg off Miami).
NB The collection was first published in 1957 so this story has been around a long time.
Posts: 135 | From: UK | Registered: Jan 2006
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I wouldn't call what the MIT group did with Mythbusters a "failure". Here are some pictures: http://web.mit.edu/2.009/www/lectures/10_Mythbusters.html And they are still only working with a few square meters of sunlight, total.
Posts: 4922 | From: Kyoto, Japan | Registered: Sep 2005
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Ganzfeld, the link says that they had 300 1 ft x 1 ft mirrors. That works out to be about 30 square meters, hardly a few.
-------------------- IIRC, it wasn't the shoe bomber's loud prayers that sparked the takedown by the other passengers; it was that he was trying to light his shoe on fire. Very, very different. Canuckistan Posts: 3694 | From: Arizona | Registered: Aug 2005
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It really wouln't take anywhere near 30 square meters of mirror to "toast" part of a person.
1m2 of mirror will ignite a hot dog if done right. For example, this parabolic mirror.
One square foot of sunlight, when focused with a cheap fresnel lens, will easily melt metal.
30,000 mirror directed onto the area the size of a single mirror would be more than enough energy to "cook the ref". Alignment would be tricky but not impossible.
So, back to the OP. Fans doing it to a soccer ref is certainly a UL. Not because the physics wouldn't work, but because giving 30,000 mirrors to 30,000 hooligans is unlikely to produce the result you want.
Posts: 629 | From: Greenwood, IN | Registered: Dec 2005
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Eddy, you're asking purely for research purposes, of course?
No. I'm asking for amusement purposes.
Perhaps 30,000 well organised people with mirrors in a stadium on a sunny day could ignite/fry/char/damage something the size, shape and composition of a soccer referee, provided the something remained still enough for them all to focus.
Unfortunately, soccer referees have this irritating habit of running around the pitch all the time, to better follow the action and look out for any infringement of the rules.
I would think that the mirror users would have to be very dedicated to wait for the unfortunate official to stand still long enough, then simultaniously direct their mirrors upon him.
-------------------- "Ladies and gentlemen, this is what is commonly known as money. It comes in all sizes, colours, and denominations - like people." Posts: 997 | From: Maidstone, UK | Registered: Jun 2006
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How long would it be before 15,000 of those soccer fans would be blinding/trying to burn the other 15,000 instead of the ref?
-------------------- IIRC, it wasn't the shoe bomber's loud prayers that sparked the takedown by the other passengers; it was that he was trying to light his shoe on fire. Very, very different. Canuckistan Posts: 3694 | From: Arizona | Registered: Aug 2005
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quote:Originally posted by GenYus: Ganzfeld, the link says that they had 300 1 ft x 1 ft mirrors. That works out to be about 30 square meters, hardly a few.
Yeah, I was told at the beginning of this thread that they had failed and that they only had two mirors, both of which turned out to be not true.
Posts: 4922 | From: Kyoto, Japan | Registered: Sep 2005
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quote:Posted by GenYus How long would it be before 15,000 of those soccer fans would be blinding/trying to burn the other 15,000 instead of the ref?
About 30 minutes before the game starts.
-------------------- "Ladies and gentlemen, this is what is commonly known as money. It comes in all sizes, colours, and denominations - like people." Posts: 997 | From: Maidstone, UK | Registered: Jun 2006
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