I'm going to find out this afternoon. I've got two of these at home (the medium sized and the large one). I'm guessing the overall shape is the same between those and the small size one pictured in the article. We'll see!
It concentrates the sun from what I could understand from the article. Should work the same for any spherical bowl (parabolic would work even better) that is shiny enough.
The curvature of the bowl would also influence the "focus point", apparently Blanda is curved in such a way that the mirror's focus point is within the bowl, thus being able to set its contents on fire (in the same way the walkie talkie is curved such that its focus point is the focus point is on the sidewalk opposite the building)
Of course. As a matter of fact I once bought that very exact bowl for making a S band dish antenna.
There's a small caveat: The bottom of the bowl is flattened (so that it doesn't roll around). That's not a big deal though if you use a dipole feed; since the dipol radiates mostly normal to its axis (look up the pattern if it's unclear what I mean) a dipole mounted at the center and perpendicular to that flatted base will actually not "see" much of that flat base and work only against the curved part.
Due to the rather small radius and being a spherical shape the directivity/gain is not that great, compared to a parabolic dish antenna. But it's cheap and works well enough if you have to cover only a couple of km.
However keep in mind that regulations likely limit maximum transmission power to something like 20dB(m) EIRP, so depending on how much directivity gain you get, you'll have to reduce the TX power by that amount to stay legal… or get a license.
You'd probably be better off with a magnifying or fresnel lens (or set of lenses), they're available as portable/survival tools (sometimes called "fire lenses" or "burning glass").
Fresnel are convenient as they're available in flexible flat rectangular plastic (e.g. credit-card sized). You lose in image quality so it's not great if you're trying to look at mosses or small critters, but to set stuff on fire it's really great as they're light, easy to pack and can be much larger than glass magnifying lenses (of equivalent or lower convenience).
I carry three or four different means to set a fire in the backpack I carry when I go hiking; a credit-card sized fresnel lens is one of them.
I also like to scavenge the huge fresnel lens from larger (40+ inch) rear-projection TVs - these are often thrown out by people during our "bulk-trash pickup" days. It only takes a few minutes of work to remove the front screen of the TV (they are designed to be removed). A few more minutes will net you a huge silver first-surface mirror, too.
The fresnel lens from one of these TVs - mounted in a proper frame - can easily melt steel and rock. You have to be very careful when using it (wear proper clothing, plus welding goggles and gloves), and store it properly out of the sun afterward (because it can easily set things randomly on fire you don't want set on fire).
The same phenomenon occurs with glass spheres. If you think about it it is obvious enough (most people are familiar with how a magnifying glass concentrates the ray of the sun in a single spot), but it is something people tend to overlook when employing glass spheres as elements of your interior design — e.g., glass door knobs, large marbles, and decorative knick-knacks (which people have a tendency to place on their windowsills).
Every once in a while a house fire is started because the sun sat at just the right angle at a certain time of the year, placing the focal point on the curtains. But because the risk is so low (it doesn't happen that frequently) many people are completely unaware of the phenomenon.
Actually one of the official 'old school' tool to measure sun exposure thru the day in meteo stations is a glass sphere with a calibrated piece of paper underneath. Needs to be changed everyday, but the burn mark is quite neatly drawn on the chart.
I was stationed at a very remote weather station where apparently, in previous years, some of the meteorologists were too lazy to change the sun exposure sheets during the year. Just before the relief voyage came there was a sunny day and they 'recorded' the whole year's data.
I keep looking at it, my brain confused why I can't see through what is clearly a transparent object. It doesn't feel like I'm looking through it, though inverted; it feels like I'm seeing a weird depiction of the nature scene around me plastered on its surface.
You can see the tracks of the days and the cloud cover in those photographs. Note that the multiple year ones have multiple days going over a single track.
Aside from the extreme reciprocity failure in the film, its "only" about three stops from a one day exposure to a one week exposure... and another two stops to a month, and then another three and a half stops to a year.
Thanks for the reminder on the reciprocity rules! I used to take super-long exposure with my 4x5/10x8 view cameras as well... basically after a few minutes, it doesn't /really/ matter anymore so stop counting in minutes/seconds, more in teacups+newspaper pages :-)
I always loved the tonal range you get on way, WAY overexposed film.
The correction for a 1200 second (20m) exposure on Kodak black and white film was at 12x (for 14400s, 4h). However, the extrapolation for the curve for Provia 100F put the reciprocity failure for 1200s at 2.35 for a 3000 second exposure.
Looking at the methods and results is interesting, though I've gone nearly full digital now.
Old overhead projectors used to have a big lens that focused the light from the lamp. I was present at a lecture where one spontaneously ignited because it was left standing (turned off) near the window where the sunlight was falling on it.
Big table-top loupes for fine electronics work are similar fire hazards. Ours now all have shutters and big warnings that the shutter must be closed when not in use.
Well, melt the paint on cars. I suspect that the amount of energy required to melt an entire car would be quite a lot more than even a skyscraper worth of surface area could gather from the sun.
> This isn't the first time Viñoly's architecture has raised eyebrows as well as temperatures: His Vdara Hotel in Las Vegas has been criticized for directing sunbeams onto the swimming pool deck that are hot enough to melt plastic and singe people's hair. The hotspot became known as the "Vdara death ray."
Based on this I'm inclined to believe Viñoly fits the negative "rockstar architect" stereotype. I mean, making that mistake once is one thing, but then doing it again?
> I suspect that the amount of energy required to melt an entire car would be quite a lot more than even a skyscraper worth of surface area could gather from the sun.
Actually, https://en.wikipedia.org/wiki/Solar_furnace ... The furnace in Odeillo, France can reach up to 3500 °C, and it's cross section is just about 50x50 meters. Of course, your typical skyscraper won't create those temperatures accidentially, but if you have the surface area of a skyscraper side in mirrors and can arrange them like you want... it gets pretty pretty hot.
That's the temperature, about the energy: Steel melts at 1370 °C, specific heat of carbon steel is 490 J/kg K. I can't find the actually melting energy. But this means, roughly, that you need 168.5 kWh to raise a ton of steel to melting temperature. The Wikipedia article says the Odeillo device creates 3200 kW (although that paragraph seems to be cut off)., so in principle it should be possible to melt a car. Scary thing.
Heck - if you purchase a new F-150, a simple engine fire can melt the entire thing to almost nothing (the truck is mostly made from aluminum - one of their prototypes a year or so ago on a test run caught fire to amusing results - no one was injured, fortunately)...
Indeed, some friends of mine in college had an acrylic sphere that they left on a couch while they went to class. They came back to find the FDNY finishing up putting out the fire it caused.
In my high school one of the girls left one of those magnifying makeup mirrors in the passenger footwell of her car. It was a hot day, so she cracked the windows a bit.
Hours later as we were eating lunch the sun struck the mirror at just the right angle, and as we look over at the parking lot there's smoke billowing out of the car. Luckily there was no fire, but there was a line burned across the underside of the dashboard. It looked like someone had taken an acetylene torch to it.
> Also, people can't apply what they were supposed to learn in high school physics.
Well, it's very rare and therefore you don't think about it.
I make telescope mirrors, so I can't be accused of being unaware of the laws of optics. Yet until now I never thought about crystal balls (heck, even acrylic balls) as a potential fire hazard inside the house.
Well, it's very rare and therefore you don't think about it.
Approximately spherical transparent objects are common. Approximately cylindrical and spherical reflective surfaces are common. Situations where you can apply high school physics are very, very common. Most of us just don't, because we're not trained to do so. We're trained to do the homework problems and answer the test questions. But don't we learn this stuff so we can use the knowledge in life?
I can't be accused of being unaware of the laws of optics. Yet until now I never thought about crystal balls (heck, even acrylic balls) as a potential fire hazard
So you're over halfway there. Now we collectively have a chance to learn the meta-lesson about applying knowledge.
Also clear water bottles (filled with water). In 1991 there was a brief period where homeowners all over Japan were putting clear PET bottles (PolyEthylene Terephthalate) at the edge of their properties because it was asserted on some talk show that the sparkles would keep animals away. This ended abruptly when a series of fires were started by the bottles.
Its a fairly common thing in restaurants, at least in the South, to hang outside clear plastic bags half full of water from any sort of awning or overhang, especially around dumpsters.
Supposedly it confuses flies and they'll leave the area alone. I've never seen any evidence of this.
Yeah, like Mythbusters is definitive science. I'll half ass this with my high school level of education and TV budget and deadline and fail and declare it definitively busted!
No science is definitive. Even Isaac Newton was overturned.
As near as I can tell they have put the most effort into duplicating Archimedes Heat Ray. They attempted it three times with large budgets and demonstrated why it was possible, but entirely impractical.
After they showed that just being wet was enough to save the boat (when would a boat ever be wet?!) they then offered a replacement explanation and had an example of a flaming arrow. It took one archer and required a fraction of the cost, could be reliably duplicated thousands of times (in battle) and had better range than a team of guys with mirrors.
I haven't seen the episodes, but I wonder if in history (if it isn't just a made up legend) that a couple of actual events have become conflated due to lack of knowledge by the witnesses?
Perhaps there were a bunch of soldiers with mirrored shields, and they did shine their shields to "blind" the incoming ships. Then archers shot flaming arrows against the ships...
...and the legend of mirrored shields setting fire to a ship was born?
This seems highly plausible to me. The polishing wouldn't even need to be intentional, just a bunch of people taking good care of their equipment could create the effect.
There's also this parabolic solar camp stove I spotted on the REI site a few months ago. Seems like an absolute gimmick, but the few reviews are all very positive:
The Boy Scout handbook (1980's version) had an aluminum foil solar oven design for cooking a hot dog. It was a version of that psychology test of putting marshmallows in front of kids. The patient scouts got a cooked hotdog in about 45 minutes - on a bright summer day. I ate a raw one after about 10.
Unfortunately, my kids already know from watching How It's Made that most wiener-type sausages sold in the US are fully cooked at the factory, and when you "cook" them at home, you're just heating them up. One would just eat it without bothering with the foil for even one minute, and the other doesn't eat hot dogs at any temperature.
I remember, as part of a wilderness survival challenge, being told to eat some breakfast, then they gave me one match, a juice can, a raw egg, and two uncooked pork sausage links. The "correct" solution was to build a fire, drink the juice, cut the top off the can, grease the inside of the can with cooking sausage, and then fry your egg in the greased can. Alternate solutions turned out to be a whole lot easier--left as an exercise for the reader because many of them are disgusting.
Knowing how to do this was of great comfort to me, because sausages, eggs, and juice cans actually grow on trees in the woods near me. Along with plastic tarps and alkaline batteries. It felt like the sort of thing that might give kids just enough confidence to wander off alone to die in the actual wilderness, or to miraculously return in five years speaking fluent Wolf, with plenty of helpful suggestions for the next edition of the manual--such as a primer on the intricacies of wolf pack politics.
That manual probably should have just skipped the solar oven and gone straight to starting a fire with the foil. (As though your average Boy Scout doesn't already know too many ways to set something on fire. Have you ever seen someone start a bonfire by shooting an arrow into it? That guy was probably a Boy Scout, and the secret he wouldn't tell you is that the tinder had KMnO4 in it, and the arrow popped a hidden balloon with some glycerol in it. It wasn't actually a ghost.)
It's dyed pink to prevent confusion with common table salt (and it isn't the same as the "pink artisan table salts" you sometimes see, either); in fact, the amount used in curing sausage and other cured meats is actually very low in proportion.
Such cures are used for ham and bacon making, too. The actual meat isn't cooked in any manner, but is perfectly safe to eat - though technically raw. In the case of hame and bacon, the meat (after curing) will usually then go thru a secondary smoking process, which also tends to dry out the outer layer of meat, further protecting it from bacterial intrusion.
Those that aren't cooked are smoked. 100% of all frankfurters, wieners, hot dogs, and bologna intended for sale in the US is safe to eat cold, as long as it has been kept sufficiently cold since it was packaged.
If it wasn't cooked or smoked, you can't call it by those names.
The most common [pathogenic] contaminant is Listeria. This would be on the surface, so if you want to be strict about food safety, you can just drop your cold hot dogs in boiling water for a few seconds before eating them. But if you're really that concerned about food, why are you eating sausages at all?
As noted in that wikipedia article, when combined with glycerol or other glycerin containing products (like automotive antifreeze) it can also be used as a fire starter. It can be easily found online or at home improvement stores, as it is sold for water softening and filtration purposes.
Grant Thompson ("King of Random") documents how to make a survival fire starter kit using this knowledge:
In short, keeping a bit of potassium permanganate in your car with you, should you get lost and don't have another source of fire making with you, might be a wise thing (then again, if you know anything about automobiles, there are tons of ways to use parts in them for starting a fire).
I saw one of these work at the Annapolis Boat Show a few years ago. Given that it was an October afternoon in Maryland, the angle of the sun was not ideal (and there were a lot of vendor tents in the way). It still made a hot hotdog in about 15 minutes. I'm sure it could do much better in the summer with a clear view of the sun.
Admittedly the sunshine in Southern Italy where I tested that (or Andalusia, Southern Spain, as in the TV program above) is probably much different from the one in Sweden, but on a good day it is most probably strong enough even in North Europe.
If you do some research, you'll find a ton more examples. When I was around 11 years old, as part of a "science project" I built a small solar cooker to cook hotdogs with. I built a linear parabolic reflector (so that the focus was a line, instead of a spot), and placed the hotdog on this line using a skewer (a straightened piece of coathanger wire). It worked rather well.
The most efficient solar cookers, though, are solar ovens. As an adult, I've built ones using cardboard and tinfoil and cooked rice, beans, and made cornbread. You usually can't get them above 100 C (because of boiling and the vapor lowering the effective temperature inside), but if you can keep them properly oriented to the sun over hours, and keep the inner temp high enough, the oven can act as a very effective slow cooker for all kinds of food.
The trick with either one (concentrator or oven) is making them portable (easier with a concentrator - but it is possible to do it with an oven, too - if you change the design a bit). Check out some of the DIY plans out there; you'll be surprised at what is possible.
Not pyro-based fun, BUT a fun project nonetheless.
Take a laser-pointer(s) and at multiple intervals map the trail of the reflection. Find out where the focal point is, and post for fun.
For bonus geekiness use some dry-ice to better illuminate the path.
At my daughter's 2nd birthday, my mom had to put out a fire that spontaneously occurred in a bowl of chips outside. Not sure if it was this bowl or a doppelganger.
I hope they don't change the design. This would be great for camping/hiking/backpacking. Having a bowl that's also capable of starting a fire is a nice extra safety measure and it takes up almost no space because you pack stuff into it.
I can't quite remember the exact make or model, but years ago there was a lightweight folding camp chair which has a removable plastic support. Its shape was perfect for a makeshift arm splint. Many people suggested that this camp chair should be part of their go-to gear. The following year the chair was redesigned without the removable support :(
Curious how clickbaiting works now. Taking the articles title "This Ikea Bowl has been setting things on fire", the "This" is an interesting word choice that is a great reminder of the "You won't believe THIS simple trick to..." that started the whole craze. I'd be curious to see some A/B testing on semi-baiting titles vs something more descriptive like the original source 'Ikea investigates after 'bowl sets Swede's grapes on fire'
I would so love to build and own one - sadly, I don't think I'll ever be able to, because they likely won't be sold to regular consumers here in the US. Even as a flat-pack kit, I think regulators would figure out a way to keep them out of the market due to crash-testing compliance and/or pollution control/EPA issues.
So if I ever wanted to have something like one, I would have to homebrew it myself. I know it is possible to get such a vehicle legally registered, but it probably isn't super-easy, unless I start with a donor vehicle frame.
Simply your argument by just replacing the pronoun with an article. "An Ikea bowl has been setting things on fire." The pronoun "this" references something inside the link that you can't yet see, pulling you into it (baiting a click). In contrast, the article "an" is informative without being seductive.
Edit: mod just changed "this" to "an." Your a/b test is on :)
Every time I see a link from atlasobscura.com, it seems to be click baity. Some kind of high brow clickbait, but still clickbait recycled from around the internet.
Clickbait purveyors are certainly conducting large-scale A/B testing on their content as it's presented and shared. You even see it on twitter where journos will post ten stings for the same article and wait for one to win out. It's bizarre.
Where is the line between clickbait and attention grabbing headline. In the case of "You won't believe THIS simple trick to..." I'd definitely call it clickbait - but in this instance, the title reflects exactly what the article is about, and while the modified title on HN does a far better representation of the contents, I personally don't see the harm in how Atlas Obscura worded the title.
Or maybe I am just really susceptible to clickbait titles...
This is a very minor example, but compare the title to just "Ikea Bowl Has Been Setting Things on Fire". The word "this" naturally prompts the response "which one?", just like something saying "look at this" in real life. Again it's very minor, but the extra word adds nothing except a slight suggestion that this particular example is especially interesting and you should click to see it.
Compare "Florida Man Escapes Prison" to "This Florida Man Escaped Prison". You'd scroll past the first, but you might not scroll past the second, because it seems like there must be something particularly interesting about this florida man, so you might as well take a second to click and see the picture.
Reddit has a bot that summarizes articles. A browser extension that replaces each Buzz! Feed! Headline! with such a summary would be an interesting programming exercise.
Or maybe not Buzzfeed, since even the summary will cause brain cancer.
A major clickbait technique is to set up an "information gap". The headline almost tells you something interesting, but leaves out the most critical bit. This makes you feel uncomfortable because you almost had something but ended up deprived and are just one click away from closure.
So, the difference between "An IKEA bowl" and "This IKEA bowl" is that "a bowl" is a complete idea. "This bowl" stresses that it's talking about a specific bowl, but leaves out which bowl it is stressing.
I was pretty certain I knew which bowl they were talking about before I clicked thru. While I didn't know the exact name of the bowl, I've been to Ikea enough to have an idea when I'm in the kitchenwares department.
Something I like to do when I'm out shopping is to look at products and figure out how to repurpose them into something else; I've often looked at this bowl and said to myself "That would be an almost perfect solar concentrator".
Usually, I'm looking to repurpose things for solar power usage or for robotics; Ikea actually has plenty of products to satisfy both.
Well, pretty much all headlines here are click-bait. In the common case, the scope the article actually applies to, is blown out of proportion. I think its because we're hardwired to ignore one-offs. "One person used a curved metallic bowl to cause a fire" sounds kinda boring.
Another one thats on the front page - "How to read and understand a scientific paper: a guide for non-scientists" is actually "A serious of unverified tips that might help you become somewhat familiar with a limited subset of scientific papers whose jargon you should already familiar with" Scientific papers are written for other scientists, no "guide" is going to allow a layperson, who is completely unfamilar with the topic, in understanding the paper. If you are not a physicist you simply can't grok the theory of the alternating-gradient synchotron. You might become kinda-sorta-familiar in a wikipedia sense by looking up each term and reading the paper but you're never going to be able to field questions on the topic (usually possible only for someone who understands a topic).
If you live in the US (or you know someone), and you have bulk-trash pickup (or can scavenge otherwise) - look around for an old 40 or 50 inch rear-projection television. All of them use a large fresnel lens for the screen (they also have an interest lenticular lens as well - but that isn't as useful due to it's short focal length). This lens, properly mounted, is capable of melting glass, rock, steel, etc. IE - if you use one as a solar concentrator, know what you are doing, as they can be very dangerous (not a toy). There are plenty of instructables and such online detailing how to build and use one - for instance:
I think it would actually be quite difficult to start a fire with this. Speaking as a former boy scout who had to build a fire with a magnifying glass for wilderness survival merit badge - it's really easy get smoke, it's quite difficult to get a flame.
The article claims that he "set a piece of newspaper on fire" using the bowl, but after watching the video I just saw some smoldering paper - no flames. I'm betting the grape stem just smoldered a bit as well.
You have to have very good airflow with dry, fine tinder in order to start a fire with a magnifying glass or parabolic mirror... unless of course you build a lens or mirror of monstrous proportions.
I still maintain that it is much more difficult to start a fire with a lens or mirror than people seem to think. Post a video of using your fresnel lens on different material types (paper, cardboard, wood, pine needles) and see how quickly you can get a visible flame. I'm betting you won't be able to easily get a visible flame on most materials you try.
> I still maintain that it is much more difficult to start a fire with a lens or mirror than people seem to think.
I'd have to agree with you. When I go hiking, I carry around 3 or 4 different kinds of "fire making" things, just in case I need them for any reason. I also practice with them on occasion to know what to do when I really need them.
It isn't easy to start a fire from scratch. It takes a bit of work, a bit of knowledge, and a ton of patience and perseverance. If you don't have any of that, you'll have a hard road ahead of you.
Even using good tinder plus magnesium bar shavings and a flint striker isn't as easy as you'd hope. In fact, it can be very frustrating. But once you get it going, it's very satisfying.
This is why I also carry a Bic lighter, strike-anywhere matches (in a waterproof container), esbit tablets, and a fresnel lens - all as backup fire sources.
it's not hard for me for any of these. But then, I build telescopes and microscopes in my spare time and so I'm quite familiar with getting a good focus.
this immediately reminded me of a trick to make a fire with a chocolate bare and a soda can. You can use the (fine grit) chocolate to polish the bowl under the can to a mirror finish, add sun and voila
131 comments
[ 4.2 ms ] story [ 217 ms ] thread[0] https://en.wikipedia.org/wiki/Solar_cooker
There's a small caveat: The bottom of the bowl is flattened (so that it doesn't roll around). That's not a big deal though if you use a dipole feed; since the dipol radiates mostly normal to its axis (look up the pattern if it's unclear what I mean) a dipole mounted at the center and perpendicular to that flatted base will actually not "see" much of that flat base and work only against the curved part.
Due to the rather small radius and being a spherical shape the directivity/gain is not that great, compared to a parabolic dish antenna. But it's cheap and works well enough if you have to cover only a couple of km.
However keep in mind that regulations likely limit maximum transmission power to something like 20dB(m) EIRP, so depending on how much directivity gain you get, you'll have to reduce the TX power by that amount to stay legal… or get a license.
It's also on my list of things to bring on a desert island.
Fresnel are convenient as they're available in flexible flat rectangular plastic (e.g. credit-card sized). You lose in image quality so it's not great if you're trying to look at mosses or small critters, but to set stuff on fire it's really great as they're light, easy to pack and can be much larger than glass magnifying lenses (of equivalent or lower convenience).
I also like to scavenge the huge fresnel lens from larger (40+ inch) rear-projection TVs - these are often thrown out by people during our "bulk-trash pickup" days. It only takes a few minutes of work to remove the front screen of the TV (they are designed to be removed). A few more minutes will net you a huge silver first-surface mirror, too.
The fresnel lens from one of these TVs - mounted in a proper frame - can easily melt steel and rock. You have to be very careful when using it (wear proper clothing, plus welding goggles and gloves), and store it properly out of the sun afterward (because it can easily set things randomly on fire you don't want set on fire).
Every once in a while a house fire is started because the sun sat at just the right angle at a certain time of the year, placing the focal point on the curtains. But because the risk is so low (it doesn't happen that frequently) many people are completely unaware of the phenomenon.
EDIT: Found it again https://en.wikipedia.org/wiki/Campbell%E2%80%93Stokes_record...
I keep looking at it, my brain confused why I can't see through what is clearly a transparent object. It doesn't feel like I'm looking through it, though inverted; it feels like I'm seeing a weird depiction of the nature scene around me plastered on its surface.
https://www.treehugger.com/solar-technology/solar-prototype-...
https://cleantechnica.com/2013/12/23/solar-ball-lens-improve...
Not solid glass, though (I don't know what it is, but I imagine there's an upper limit on size of solid glass spheres that can be made)...
You can see the tracks of the days and the cloud cover in those photographs. Note that the multiple year ones have multiple days going over a single track.
Aside from the extreme reciprocity failure in the film, its "only" about three stops from a one day exposure to a one week exposure... and another two stops to a month, and then another three and a half stops to a year.
The correction for a 1200 second (20m) exposure on Kodak black and white film was at 12x (for 14400s, 4h). However, the extrapolation for the curve for Provia 100F put the reciprocity failure for 1200s at 2.35 for a 3000 second exposure.
Looking at the methods and results is interesting, though I've gone nearly full digital now.
Big table-top loupes for fine electronics work are similar fire hazards. Ours now all have shutters and big warnings that the shutter must be closed when not in use.
> This isn't the first time Viñoly's architecture has raised eyebrows as well as temperatures: His Vdara Hotel in Las Vegas has been criticized for directing sunbeams onto the swimming pool deck that are hot enough to melt plastic and singe people's hair. The hotspot became known as the "Vdara death ray."
Based on this I'm inclined to believe Viñoly fits the negative "rockstar architect" stereotype. I mean, making that mistake once is one thing, but then doing it again?
Actually, https://en.wikipedia.org/wiki/Solar_furnace ... The furnace in Odeillo, France can reach up to 3500 °C, and it's cross section is just about 50x50 meters. Of course, your typical skyscraper won't create those temperatures accidentially, but if you have the surface area of a skyscraper side in mirrors and can arrange them like you want... it gets pretty pretty hot.
That's the temperature, about the energy: Steel melts at 1370 °C, specific heat of carbon steel is 490 J/kg K. I can't find the actually melting energy. But this means, roughly, that you need 168.5 kWh to raise a ton of steel to melting temperature. The Wikipedia article says the Odeillo device creates 3200 kW (although that paragraph seems to be cut off)., so in principle it should be possible to melt a car. Scary thing.
https://www.youtube.com/watch?v=QV-Y74YH51M
Hours later as we were eating lunch the sun struck the mirror at just the right angle, and as we look over at the parking lot there's smoke billowing out of the car. Luckily there was no fire, but there was a line burned across the underside of the dashboard. It looked like someone had taken an acetylene torch to it.
Also, people can't apply what they were supposed to learn in high school physics. It's not only Brazil that has this problem:
http://v.cx/2010/04/feynman-brazil-education
Well, it's very rare and therefore you don't think about it.
I make telescope mirrors, so I can't be accused of being unaware of the laws of optics. Yet until now I never thought about crystal balls (heck, even acrylic balls) as a potential fire hazard inside the house.
Approximately spherical transparent objects are common. Approximately cylindrical and spherical reflective surfaces are common. Situations where you can apply high school physics are very, very common. Most of us just don't, because we're not trained to do so. We're trained to do the homework problems and answer the test questions. But don't we learn this stuff so we can use the knowledge in life?
I can't be accused of being unaware of the laws of optics. Yet until now I never thought about crystal balls (heck, even acrylic balls) as a potential fire hazard
So you're over halfway there. Now we collectively have a chance to learn the meta-lesson about applying knowledge.
Also clear water bottles (filled with water). In 1991 there was a brief period where homeowners all over Japan were putting clear PET bottles (PolyEthylene Terephthalate) at the edge of their properties because it was asserted on some talk show that the sparkles would keep animals away. This ended abruptly when a series of fires were started by the bottles.
Supposedly it confuses flies and they'll leave the area alone. I've never seen any evidence of this.
http://www.bbc.com/news/uk-england-london-23930675
http://www.telegraph.co.uk/news/newstopics/howaboutthat/1029...
Reminds me of https://twitter.com/ThePracticalDev/status/68767208615275315...
http://shamenun.com/
Wikipedia: "The device, sometimes called the "Archimedes heat ray", was used to focus sunlight onto approaching ships, causing them to catch fire. "
https://en.wikipedia.org/wiki/Archimedes
Here's an interesting write-up about the team of MIT students that worked with them on the second try: http://web.mit.edu/2.009/www/experiments/deathray/10_Mythbus...
As near as I can tell they have put the most effort into duplicating Archimedes Heat Ray. They attempted it three times with large budgets and demonstrated why it was possible, but entirely impractical.
After they showed that just being wet was enough to save the boat (when would a boat ever be wet?!) they then offered a replacement explanation and had an example of a flaming arrow. It took one archer and required a fraction of the cost, could be reliably duplicated thousands of times (in battle) and had better range than a team of guys with mirrors.
Perhaps there were a bunch of soldiers with mirrored shields, and they did shine their shields to "blind" the incoming ships. Then archers shot flaming arrows against the ships...
...and the legend of mirrored shields setting fire to a ship was born?
https://www.rei.com/product/100561/gosun-sport-solar-camp-st...
I remember, as part of a wilderness survival challenge, being told to eat some breakfast, then they gave me one match, a juice can, a raw egg, and two uncooked pork sausage links. The "correct" solution was to build a fire, drink the juice, cut the top off the can, grease the inside of the can with cooking sausage, and then fry your egg in the greased can. Alternate solutions turned out to be a whole lot easier--left as an exercise for the reader because many of them are disgusting.
Knowing how to do this was of great comfort to me, because sausages, eggs, and juice cans actually grow on trees in the woods near me. Along with plastic tarps and alkaline batteries. It felt like the sort of thing that might give kids just enough confidence to wander off alone to die in the actual wilderness, or to miraculously return in five years speaking fluent Wolf, with plenty of helpful suggestions for the next edition of the manual--such as a primer on the intricacies of wolf pack politics.
That manual probably should have just skipped the solar oven and gone straight to starting a fire with the foil. (As though your average Boy Scout doesn't already know too many ways to set something on fire. Have you ever seen someone start a bonfire by shooting an arrow into it? That guy was probably a Boy Scout, and the secret he wouldn't tell you is that the tinder had KMnO4 in it, and the arrow popped a hidden balloon with some glycerol in it. It wasn't actually a ghost.)
I don't know if I would say most, but some may be.
From my experience, hotdogs (and other sausage products) typically contain a ton of what is known as "pink curing salt" (aka "Prague powder"):
https://en.wikipedia.org/wiki/Curing_salt
It's dyed pink to prevent confusion with common table salt (and it isn't the same as the "pink artisan table salts" you sometimes see, either); in fact, the amount used in curing sausage and other cured meats is actually very low in proportion.
Such cures are used for ham and bacon making, too. The actual meat isn't cooked in any manner, but is perfectly safe to eat - though technically raw. In the case of hame and bacon, the meat (after curing) will usually then go thru a secondary smoking process, which also tends to dry out the outer layer of meat, further protecting it from bacterial intrusion.
If it wasn't cooked or smoked, you can't call it by those names.
The most common [pathogenic] contaminant is Listeria. This would be on the surface, so if you want to be strict about food safety, you can just drop your cold hot dogs in boiling water for a few seconds before eating them. But if you're really that concerned about food, why are you eating sausages at all?
For those that don't know, KMnO4 is also known as potassium permanganate:
https://en.wikipedia.org/wiki/Potassium_permanganate
As noted in that wikipedia article, when combined with glycerol or other glycerin containing products (like automotive antifreeze) it can also be used as a fire starter. It can be easily found online or at home improvement stores, as it is sold for water softening and filtration purposes.
Grant Thompson ("King of Random") documents how to make a survival fire starter kit using this knowledge:
https://www.youtube.com/watch?v=ja_6Yin9JuM
In short, keeping a bit of potassium permanganate in your car with you, should you get lost and don't have another source of fire making with you, might be a wise thing (then again, if you know anything about automobiles, there are tons of ways to use parts in them for starting a fire).
Got a bottle of KMnO4 next to my iron filter and at least one jug of glycol antifreeze in the garage.
Guess what I'm doing when I get home :-)
and it worked nicely (to set to fire some wood).
Admittedly the sunshine in Southern Italy where I tested that (or Andalusia, Southern Spain, as in the TV program above) is probably much different from the one in Sweden, but on a good day it is most probably strong enough even in North Europe.
http://www.motherearthnews.com/diy/how-to-build-a-solar-cook...
If you do some research, you'll find a ton more examples. When I was around 11 years old, as part of a "science project" I built a small solar cooker to cook hotdogs with. I built a linear parabolic reflector (so that the focus was a line, instead of a spot), and placed the hotdog on this line using a skewer (a straightened piece of coathanger wire). It worked rather well.
The most efficient solar cookers, though, are solar ovens. As an adult, I've built ones using cardboard and tinfoil and cooked rice, beans, and made cornbread. You usually can't get them above 100 C (because of boiling and the vapor lowering the effective temperature inside), but if you can keep them properly oriented to the sun over hours, and keep the inner temp high enough, the oven can act as a very effective slow cooker for all kinds of food.
The trick with either one (concentrator or oven) is making them portable (easier with a concentrator - but it is possible to do it with an oven, too - if you change the design a bit). Check out some of the DIY plans out there; you'll be surprised at what is possible.
For bonus geekiness use some dry-ice to better illuminate the path.
The global, quite conservative, retailer of everyday products has been disrupting the bowl industry for several decades.
For years since disrupt was far from being the buzzword de jure, and was more associated with Klingon Battlecruisers.
http://oxgvt.com/the-ox-all-terrain-vehicle/
I would so love to build and own one - sadly, I don't think I'll ever be able to, because they likely won't be sold to regular consumers here in the US. Even as a flat-pack kit, I think regulators would figure out a way to keep them out of the market due to crash-testing compliance and/or pollution control/EPA issues.
So if I ever wanted to have something like one, I would have to homebrew it myself. I know it is possible to get such a vehicle legally registered, but it probably isn't super-easy, unless I start with a donor vehicle frame.
Edit: mod just changed "this" to "an." Your a/b test is on :)
Or maybe I am just really susceptible to clickbait titles...
Compare "Florida Man Escapes Prison" to "This Florida Man Escaped Prison". You'd scroll past the first, but you might not scroll past the second, because it seems like there must be something particularly interesting about this florida man, so you might as well take a second to click and see the picture.
Or maybe not Buzzfeed, since even the summary will cause brain cancer.
So, the difference between "An IKEA bowl" and "This IKEA bowl" is that "a bowl" is a complete idea. "This bowl" stresses that it's talking about a specific bowl, but leaves out which bowl it is stressing.
Something I like to do when I'm out shopping is to look at products and figure out how to repurpose them into something else; I've often looked at this bowl and said to myself "That would be an almost perfect solar concentrator".
Usually, I'm looking to repurpose things for solar power usage or for robotics; Ikea actually has plenty of products to satisfy both.
Another one thats on the front page - "How to read and understand a scientific paper: a guide for non-scientists" is actually "A serious of unverified tips that might help you become somewhat familiar with a limited subset of scientific papers whose jargon you should already familiar with" Scientific papers are written for other scientists, no "guide" is going to allow a layperson, who is completely unfamilar with the topic, in understanding the paper. If you are not a physicist you simply can't grok the theory of the alternating-gradient synchotron. You might become kinda-sorta-familiar in a wikipedia sense by looking up each term and reading the paper but you're never going to be able to field questions on the topic (usually possible only for someone who understands a topic).
ps: a video that go well with the PrimitiveTechnology channel
http://www.instructables.com/id/Giant-Fresnel-Lens-Deathray-...
A large fresnel lens is my most wished prize right now, I consider looking into manufacturing one.
[1] to recycle glass, metals etc, maybe produce some cute things or just to ease trashing (bins won't contains large empty bottles, but nice pellets)
The article claims that he "set a piece of newspaper on fire" using the bowl, but after watching the video I just saw some smoldering paper - no flames. I'm betting the grape stem just smoldered a bit as well.
You have to have very good airflow with dry, fine tinder in order to start a fire with a magnifying glass or parabolic mirror... unless of course you build a lens or mirror of monstrous proportions.
I'd have to agree with you. When I go hiking, I carry around 3 or 4 different kinds of "fire making" things, just in case I need them for any reason. I also practice with them on occasion to know what to do when I really need them.
It isn't easy to start a fire from scratch. It takes a bit of work, a bit of knowledge, and a ton of patience and perseverance. If you don't have any of that, you'll have a hard road ahead of you.
Even using good tinder plus magnesium bar shavings and a flint striker isn't as easy as you'd hope. In fact, it can be very frustrating. But once you get it going, it's very satisfying.
This is why I also carry a Bic lighter, strike-anywhere matches (in a waterproof container), esbit tablets, and a fresnel lens - all as backup fire sources.