1603: Flashlights

Explain xkcd: It's 'cause you're dumb.
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Due to a typo, I initially found a forum for serious Fleshlight enthusiasts, and it turns out their highest-end models are ALSO capable of setting trees on fire. They're impossible to use without severe burns, but some of them swear it's worth it.
Title text: Due to a typo, I initially found a forum for serious Fleshlight enthusiasts, and it turns out their highest-end models are ALSO capable of setting trees on fire. They're impossible to use without severe burns, but some of them swear it's worth it.


In this comic, Cueball has acquired or built a new high powered flashlight ("torch" in British English), which he wants to demonstrate to Megan. When Cueball refers to older flashlights as dim and finnicky, this gives reason to assume that the flashlight he is holding is going to be ridiculously overengineered.

Indeed, when he switches it on outside the house, the intense light beam completely drowns out the scene. Only the reflected light from the forest lights up the part of Cueball and Megan's faces that are turned towards it. Megan is holding up a hand, apparently to shield her eyes.

Cueball comments that the flashlight lights up the entire forest, but Megan observes that it is the trees that are on fire, indicating that Cueball's flashlight is so overpowered that the energy of its beam is sufficient to cause the organic matter of trees to combust.

Of course, a flashlight that cannot safely be pointed at things is fairly useless for the traditional purpose of a flashlight, which would be to find things in the dark by directing light over them. This mundane and practical reasoning does not seem to matter to Cueball of course, who appears only interested in the intensity and brightness the device is capable of achieving. The comic may refer to the flashlight forums Budget Light Forum or candlepowerforums, devoted to people discussing new LED emitters and who can build the brightest flashlight using them.

Cueball might allude to a number of technical improvements, notably xenon-based incandescent bulbs, multiple-LED assemblies, Lithium batteries (usually used for photography flashes) or rechargeable batteries. A number of companies market "tactical" flashlights that are supposedly powerful enough to incapacitate an opponent, using terms such as "scorching" to advertise their products. See for instance this video about a Wicked Lasers Torch of the brand Torch that ignites paper and melts stuff. Not strong enough to put a forest on fire but it is not safe to point at anything close by!

Randall has also looked at what lasers could do of damage in two what if? articles: Laser Pointer and Laser Umbrella.

The title text refers to Fleshlight, a brand of masturbation appliances for phalluses modeled after various human orifices. Cueball (or Randall) claims that he only arrived on a forum for Fleshlight enthusiasts due to a typo. Apart from the "e" vs. "a" in Fleshlight, they are also fashioned to look like oversized flashlights. On that forum he found out that the highest-end models of their product lines was also capable of setting trees on fire. This would probably happen due to violent vibrations inside the orifice, or excessively powerful internal heating. Anything powerful enough to burn trees would indeed cause the user severe burns in a very unpleasant area. But some of the enthusiasts swear that it is still worth it, in the same manner that Cueball only cares about the intensity of the flashlight, regardless of the consequences. Maybe they are just trying to trick you into doing something stupid! Or maybe they're just into that kind of thing.

References to Fleshlight is a recurring theme in xkcd and using powerful "sex toys" that cause severe burns (on a woman though) have previously been alluded to in 596: Latitude.


[Cueball carries a flashlight walking towards Megan who is sitting on a couch.]
Cueball: Remember how flashlights sucked when we were kids? Always dim and finnicky?
Megan: I guess?
[Cueball and Megan walking to the left.]
Cueball: Well, I discovered there are now internet flashlight enthusiasts.
Cueball: And the technology has... improved.
Megan: OK, Let's see.
[It is dark outside where Cueball turns on the flashlight. The beam is very bright and very visible even seen from the side. Backscattered light reflects off Cueball and Megan's faces, turning them into bright white beings in the dark. The facade of the house and the stairs are also visible in the same manner, with deep dark shadows where anything is in the shadow. Megan averts her face from the light holds up a hand to cover her eyes. When the flashlight turns on it even makes a sound, written in white above the beam:]
Flashlight: Fwoosh
[Cueball and Megan look at what the beam falls on (outside the frame). Megan has taken her hand down. Both their faces are only lit up like a crescent moon. Cueball is holding the flashlight with both hands as if it is pushing back on him. The text is written in white on the dark sky above them.]
Cueball: See how it lights up the whole forest?
Megan: ...The trees are on fire.
Cueball: Real bright, though.

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Is that it? I swear there must be more to the joke than this explanation implies. It just describes what's going on in the comic. Enchantedsleeper (talk) 10:29, 13 November 2015 (UTC)

-- Sometimes a cigar is just a cigar. Pete (talk) 11:19, 13 November 2015 (UTC)

but sometimes there is no spoon 06:03, 14 November 2015 (UTC)
Ceci n'est pas une pipe. Sobsz (talk) 08:27, 14 November 2015 (UTC)

Is the 'joke' based on the ambiguity of the phrase "light up the trees" meaning either illuminate the trees or set fire to them too obvious? RIIW - Ponder it (talk) 19:59, 16 November 2015 (UTC)

I think that the joke is about subcultures and enthusiasts in general. Much like there are communities dedicated to getting the best performance out of PCs and coffee makers (to name two examples), this comic imagines a hardcore community of torch users dedicated to “overclocking” torches to operate at extreme levels far beyond their manufactured intent. Regardless of whether or not such a subculture exists in reality, the humour is in the possibility that a common household object could attract such a fervent modding community that the limitations and functionality of the devices could be taken to their comical extreme. Compare 1095: Crazy Straws. 09:15, 16 November 2015 (UTC)

"A typo", uh? Sure, sure, of course it was only a typo, Randall ;) 10:38, 13 November 2015 (UTC)

I also think the type was that he searched on flashlight instead and found the flashlight enthusiast page from that ;-) --Kynde (talk) 14:58, 13 November 2015 (UTC)

I think it's unfair to assume lack of detail in the explanation, the fact that research was obviously done on the meaning of fleshlight an it's association to the comic, is more than I would have original got from the comic by itself. However if you perceive additional meaning please share, the thing I love about 'This' website is for the ability for others to add their interpretations. --Igwarrender (talk) 10:52, 13 November 2015 (UTC)

I wonder if you could use a high-powered fleshlight to cook a sausage...RedHatGuy68 (talk) 05:15, 17 November 2015 (UTC) Quote:

When Cueball refers to classic Flashlights(torches) as dim and finnicky, this gives reason to assume that the flashlight he is holding is going to be ridiculously overengineered.

I disagree. In the generation of Randall (and me), the flashlights most of us had as kids really did suck and were dim and finnicky. That's not an exaggeration which, as is implied in the explanation, is used to prepare the joke. It's more of an explanation on why he is interested in modern flashlights in the first place. -- 10:58, 13 November 2015 (UTC)

AND they almost always had at least half flat batteries. 11:41, 13 November 2015 (UTC)
Exactly. I never tried xenon, but the difference between old lightbulb based flashlights and modern LED-based ones, even with the same battery, is obvious. -- Hkmaly (talk) 15:40, 14 November 2015 (UTC)

Nope...nothing to do with fleshlights. There are in fact multiple flashlight enthusiast forums that have nothing to to with sex toys. Use your favorites search engine to search "flashlight enthusiasts: 10:50, 14 November 2015 (UTC)

It's funny how "the explanation" has a need to point out that there were no prior knowledge about fleshlights. (according to Wikipedia) 12:44, 13 November 2015 (UTC)

I never leave for work without my trusty Lumapower EDC-LM31 with its Cree XML(U2) LED and its 3.7 volt size 14500 Lithium Ion cell. But I'm not a flashlight geek! Besides, 420 lumens is no where near enough power to set trees on fire. (Personally, I think this comic is an example of Rule 34. Randall was originally thinking about Fleshlights, typo'd into flashlights, and discovered a sort of geeky torch porn sort of thing out there. Also, the flashlight I describe is real, but has nothing on the stuff you'll see in Candlepower Forums.) Co149 (talk) 12:52, 13 November 2015 (UTC)

The 100,000 lumen lamps (X-LED MRK72 or is that MKR72?) have to be water-cooled! That's plenty hot enough for me. 14:07, 13 November 2015 (UTC)
There are videos of flashlights that set things on fire, without lensens etc. One of them is this video of an Magic Scorpion flashlight, a halogen variant. But I've also seen video's of (custom-built) LED flashlight that set things to smolder. 14:56, 13 November 2015 (UTC)
It's not lumen that sets things on fire, it's lux. All you need is a good focus. -- 17:11, 13 November 2015 (UTC)
Also note this flashlight, which is just a bunch of ultra-bright LEDs crammed into a case that resembles an oversized flashlight and on full power drains its battery in about 15 minutes...and lights up a city street like it's day. --NXTangl 21:33, 13 November 2015 (UTC)

It feels to me that "their highest-end models are ALSO capable of setting trees on fire." is some advertisement where the tree is a metaphore for one's organ. as such it is clear that "They're impossible to use without severe burns". which makes it really twisted that "some [people] swear it's worth it" (talk) (please sign your comments with ~~~~)

I think the burning trees joke comes from this ["...even fry and egg"] thing. --Arturo Jain (talk) 14:26, 13 November 2015 (UTC)

Should the explanation contain something about the prevalence of internet forums dedicated to enthusiasts of various activities or hobbies? Smperron (talk) 17:33, 13 November 2015 (UTC)

Currently no (albeit indirect) link to https://what-if.xkcd.com/13/ or others like 119? Ok, so only going to be an incidental link, but... 17:37, 13 November 2015 (UTC)

it is missimg reference to another comic where randall makes a joke about flashlight and fleshlight. The comic had a star wars setting with death vader and luke skywalker. https://xkcd.com/1397/ --anonymous 15:08, 13 November 2015 (UTC)

"Let's" appears to be missing an apostrophe. 20:23, 13 November 2015 (UTC)

Now, see, this is why we Brits call them 'torches'. Less risky with finger trouble. (Hint - don't google 'finger trouble') Jdluk (talk) 21:52, 13 November 2015 (UTC)

could it be referencing http://www.wickedlasers.com/torch ? 17:54, 13 November 2015 (UTC)an internet flashlight enthusiast

Why are there personal opinions like "maybe they're trying to trick you!" in the main body? Weird. 02:26, 14 November 2015 (UTC)

It is not personal. If someone tries to tell you that something is worth trying in spite of promissing you will get a severe burn, it could be to see if they could fool you into doing so. Some people are like that... Either that or they are pretty crazy with their fetishes. But some people are also like that. hence both explanations are OK. -- Kynde (talk) (please sign your comments with ~~~~)

"Of course, a flashlight that cannot safely be pointed at things is fairly useless for the traditional purpose of a flashlight". Really now? A flashlight that set targets on fire is pretty useful - you only need to flash something once, and it'll stay illuminated without having to keep the flashlight on! 05:26, 14 November 2015 (UTC) (talk) 12:34, 5 June 2012 (UTC) (please sign your comments with ~~~~)

Just gonna leave this here https://youtu.be/MGANrd7u4o0 11:31, 14 November 2015 (UTC)


I'm missing too much information and don't really know how to do this myself anyway; Perhaps someone would be willing to do some calculations on how much force Cueball would experience pushing him back due to the momentum of the light being emitted from his flashlight. Relevant factors off the top of my head:
1 - The diameter of the beam at the point of contact with the trees has to be wide enough to encompass multiple trees. The trees do not completely fill the area due to overall shape and gaps between leaves.
2 - The trees are on fire within a few seconds of turning on the flashlight.
3 - The leaves would obviously ignite first. How much energy do they have to absorb to combust?
4 - The trees are still alive and, therefore, wet. In addition to the ignition energy, the beam also has to dry out the leaves first. (right?)
5 - The flashlight is a bright white color and is emitting light across the entire visible spectrum and, maybe, a significant amount to either side of the visible spectrum as well (assuming the light is produced by a heated filament. Less so with an excited gas or white LEDs) What does the absorption spectrum of a leaf look like? The lower the percentage of light absorbed by the leaf, the stronger the flashlight has to be to dump enough energy into it. (talk) (please sign your comments with ~~~~)

I think this comic's idea, flashlights lighting up the trees, is based in part on the work by this Danish person who posts detailed and technical reviews of hundreds of flashlights, including "beam shots", photos of how well they light up the trees behind his house: http://lygte-info.dk/review/Beamshot%20AA-CR%202012-07%20UK.html [stolkin] (talk) (please sign your comments with ~~~~)

this in a torch www.youtube.com/watch?v=budMkPhUE4c or this https://www.youtube.com/watch?v=UVntaa0DDhY Needforsuv (talk) 19:49, 18 November 2015 (UTC)

Why would Randall use "trees" in the title text when "wood" was ... right there? Miamiclay (talk) 05:45, 29 November 2015 (UTC)