Can You Start a Fire With Moonlight and a Giant Magnifying Glass

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In this video I check if it is possible to start a fire with a magnifying glass and moonlight. I talk about the conservation of etendue.
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*Any experiment you try is at YOUR OWN RISK. The Action Lab assumes no responsibility for any injury if you attempt anything you see in this video or on The Action Lab channel.

[@TheActionLab]

The reflected light from the moon is only 7% of the total energy of the moon, 93% of the energy we receive from the moon is from blackbody radiation from the temperature of the moon. So this is why etendue is still relevant with the moonlight

[@mohammadmahdi8086]

What is cost of thermometer

[@foolwise4703]

I DISAGREE! Calling you out on both of your claims: 1st: The equilibrium temperature of the moon in sunlight is about 400 K. At that temperature, Wiens displacement law would put the peak wavelength of black-body radiation from the moons surface in the deep infrared (I calculate about 12 µm = lambda = c/(T *5.879e10 Hz/K) = 3e8/(400K*5.879e10Hz/K) ), which is not visible and gets absorbed in earth's atmosphere. When I look at the moon, it is bright. Ergo, what I am seeing is not black-body-radiation, it is reflected sunlight. 2nd: Etendue I think you are overlooking the differential to the solid angle in the etendue, but I also dont quite understand why you are conflating brightness with temperature. I'll argue that not etendue but radiation flux is the decisive quantity, i.e. the radiation power incident on an area. In an extreme thought experiment, let us put a infinitely large, perfect and flat lense with an infinitely short focus length between the moon and your match (or whatever you want to light). This means that you are imaging the moon in an imaging ratio of infinity to one. You are obviously limited by diffraction, but with a large, flat lense that means you have an effective focal size of half the wavelength. So lets say on the order of a micrometer. This focus now gets ALL the radiation flux that the moon emits into a half-sphere (2 \pi solit angle for the infinite lense). I dont care to run that calculation, but that match goes up in flames! Obviously this is the absolute extreme case, but seems prudent as you made a general claim. The argument should work without infinities, too.

[@DANGJOS]

​@@foolwise4703 You made up an impossible example at the end to prove a point, but didn't bother to do any calculations or serious reasoning, so how did you come to that conclusion? That's actually incorrect. Your suggestion wouldn't work. You cannot focus all of the light into a single point, even aside from the diffraction limit.

[@c-bass7150]

Hey thanks for the video, I just subcribed, would you mind making that same experiment but with an infrared thermometer to pick the temperature of the moonlight on a surface like a wood plank, and then compare it to its shade's temperature? I bet everything I have that the moon's light temperature will be colder than the shady part of the wood s plank, cus we did that and saw it ourselves, but how can the moon light be cold? And colder than the shades? When I saw your video it gave me an idea, to measure the moon's light temperature but magnified, which we havent done. I really wonder if the magnified light will be colder than the regular moon's light. And what if we beam a spot of the shade? Will the shade turn colder? So all these question now that I've seen your video, and thanks for that pal. Can you prove me that the moon light is not colder than the shades, and can we see if it gets colder or not, once magnified please?

[@DANGJOS]

@@c-bass7150 Your observation of the moonlight being colder isn't related to the moonlight; it's related to radiative cooling. Even if you put an object out in the open on a new moon, you will notice that the object is colder than an equivalent object under shade because the shaded object is being heated by the infrared radiation of the shading object.

[@alvingultom2802]

i dont need sleep, i need answers

[@uli659]

Me irl

[@justanthony9236]

Please look 4 me on the comments I've explained this very well...

[@justanthony9236]

Search 4 my answers in comments

[@noahz3429]

@jumpyturltee is your profile your kurzagat custom bird

[@homoonahh6679]

No. No matter how big the lens are

[@anubhav12qw]

KZbin: "Can you start a fire with moon light" My brain: "Nah not possible" ... **Clicks on the link**

[@uxleumas]

wait but he doesn't...

[@kandy5129]

@Space Realms stfu

[@justanthony9236]

No it's not, unless the moon goddess strikes us down lol

[@louisparkinson2215]

Gets rickrolled

[@fundemort]

We dont believe our own brains. Thats why we are here.

[@Mikidy303]

The moon is illuminated by LED, they're much cooler.

[@shikharkumar734]

😅 moon is cool

[@toughtimes6596]

😂😂👍

[@vripscript]

Also doesn't work with LEDs kzbin.info/www/bejne/l5TQdaujeqaceq8 ;p

[@Bob5mith]

You can't tell because it's always facing away from us, but the moon is just a big heatsink on the other side.

[@KonJamo]

A special kind of LEDs call SUNs

[@IncroyablesExperiences]

The max temp rule only works with black body radiation, I mean with several LED focused on a single point we can overtake the LEDs surface temperature?

[@randfee]

correct!

[@faizakhan8697]

correct! and it only focuses on one point and thats why you can start a fire with the sun

[@Chopper153]

No, that's not correct. We are actually concentrating the IR radiation with the lens which melts paper. Visible light has nothing to do with it. Moon doesn't emit IR, so no burning. Also CCT doesn't give the actual surface temperature of the LED, it just tells that a black body will emit similiar radiation at that temperature.

[@patrickstar7693]

@@Chopper153 Well yea IR radiation is much better at starting a fire but you can definitely start a fire as well with visible light. The moonlight is very inefficient in it but with enough focusing it is definetly possible Imagine you dig a hole with a diameter of 100m in the shape of a sphere sector. then you cover the surface perfectly with mirrors and concentrate all the rays at 1 point, just like in a radio antenna. The W/cm^2 would be enormous and you would definitely be able to start a fire.

[@ModelLights]

First just go to one of the solar concentrator power plants, I bet you can get a simple fire going with very little extra lensing. (They may keep the Sunlight distributed a bit more than where it would work for moonlight directly.) Exactly. Say you put a hypothetical lens near the Sun, right next to the surface. Concentrate 3 areas onto 1 area. Surface temp exceeded at the concentration point. Instead of LEDs, get 3 diode lasers so it's easy. 3 to 1 point, easily exceed the energy output level of 1 'surface' at the target. No thermodynamics laws broken, you 'stole' the energy that would have hit 2 other areas. Total average is still slightly less, but easy to exceed the single surface temp. Focusing is a direct multiplier, that 'limit law' is going to be about a specific range of cases. You can't exceed the total average in thermodynamics. If you take the heat from 3x the area and put it almost all into 1 area, you can easily exceed the initial distributed temp even though the total average heat is still lower. Your total can't exceed the total beginning, and that mentioned law is probably something very specific and has to be applied exactly correctly to be valid. It's probably about a large, distributed field emitter like a surface emitting at all angles (IOW not a laser and emitting at only one stright out angle) there's no way to get a single lens that will focus it in a way to get enough of it all focused at one point. The lens won't focus all radiation from all areas all to the same exact point or similar.

[@IncroyablesExperiences]

As the moon isn't the source of light it's not a black body radiating so there is no link between its temperature and its light. If we use a mirror before a lenz we can always (in theory) reach the 6000K of the sun while the mirror is cool. Maybe it's different as the moon is a screen diffusing light instead of mirror? (But a screen is reflecting, still not a black body)

[@romankalinchuk2750]

He spits out assumptions like they're facts. It didn't sound accurate to me either since the moon is reflecting, not generating the heat. Some of the heat gets absorbed to heat the surface of the moon. The moon is a terrible mirror and reflects only %12 of the light that hits it. Plus, it gets scattered and reflected out into space so whatever light gets to earth is extremely weak. The ratio of the sunlight to moonlight on the brightest full moon is about 398,110 to 1 according to space.com. So with some simple math which is probably not accurate, to get the same energy as 1 square inch of full sunlight on earth, you would need a magnifying glass that is roughly 2765 square feet. That's 52.58 feet x 52.58 feet square. A huge magnifying glass just to feel some heat.

[@IncroyablesExperiences]

@@romankalinchuk2750 He is often right and his assumptions are generally great and missing elsewhere on KZbin, hope an expert will help us!

[@Chicken_Little_Syndrome]

@@romankalinchuk2750 Your comment is based on assumption too. In fact, a lot of "settled" science is based on unexamined assumptions. But most people do not understand human psychology and won't accept centuries-long groupthink, enforced with Pavlovian conditioning as the answer to the question: "Why could everyone be so wrong for so long?".

[@MarkPaupst-tz2nk]

Yes it is ask god

[@DANGJOS]

@@romankalinchuk2750 Creating a giant magnifying glass, of the size you mentioned, won't help. You won't concentrate the light down to a square inch; the light will be spread across a much larger area. And the temperature of the moon is important information, especially because it absorbs most of the sunlight. It gives you an idea of how much intensity the moon can output.

[@yoru0121]

8:07 This is wrong. The second law of thermodynamics only applies to a closed system. The Earth and the Moon is not a closed system. The Moon "glows" by reflecting sunlight, meaning that the Earth-Moon system is constantly getting external energy input from the Sun, and is therefore not closed. It is possible to start a fire by focusing moonlight, just not by a lens/mirror that is close to us and far from the moon. Theoretically, if you can place a HUGE lens/mirror very close to the moon and focus light onto a small surface on the Earth, it can definitely start a fire.

[@OkNoBigDeal]

You’re just moving closer to the heat source.

[@YbisZX]

No. Nothing will change because of the lens size or position. Or you think the Moon suddenly starts suck more energy from the Sun just because you put the lens? The lens focuses only the light reflected by the moon.

[@yoru0121]

@@OkNoBigDeal What I mean is, the closer you place a lens/mirror to the moon, the easier it is to cover a larger solid angle to capture light reflected from the moon. The real reason that the power you get from moonlight is limited has nothing to do with the law of thermodynamics. It is because any lens/mirror that you can place on Earth can only cover a small solid angle as seen from the moon because it is so far away from the moon. It actually doesn't matter how much *your* field of view is covered (contrary to what the video says). It is the field of the view that the lens/mirror covers as seen from the moon that matters.

[@yoru0121]

@@YbisZX Yes, the lens focuses only the light reflected by the moon, and that's definitely more than enough to start a fire, or boil water, etc. It is just how much of that light you can collect and focus via a lens or a mirror, and that does depend on the size and position of the lens.

[@YbisZX]

@@yoru0121 Did you even listen to what this man said from 4:38? A giant lens just creates a large image of the Moon, not a small spot. "Conservation of etendue" will not let you focus better than perfect focus.

[@abhaymehta5537]

This looks like a perfect sponsored video

[@neillunavat]

No

[@Niyaz_]

@@neillunavat yes

[@neillunavat]

@@Niyaz_ (ˉ(∞)ˉ)

[@josephnevin]

Sponsored by the moon.. illuminating the night sky since 3.5 billion years.

[@justanthony9236]

Sponsored by stupidity " check my note in the comments

[@GossamerGhoul]

You say: "It's not possible to use magnified moonlight to start fires" I hear: "I'm a quitter who will never make it as a Bond villain"

[@124Musick]

This^

[@georgealexoo2996]

6:20 i opened my mouth cuz i got flashbacks from the dentist

[@PratameshMistry]

XD

[@untidybalde_3137]

XD

[@sillierthangooberous]

XD

[@goodday9760]

DX

[@eri9986]

🙏

[@GregoMorgan]

The moon isn't a black body. Moon light is reflected sun light, not radiation from the moon being heated by the sun. There's no reason you couldn't get a spot hotter than its surface. That's like saying if you magnify sunlight that's reflected by a cold mirror you won't be able to get any warmth because of the mirror.

[@freedivingchina5144]

In fact, the reason is different from what he explains and has to do more with optics and the fact that light is radiated and reflected from a source with finite size at a finite distance hence light rays are not parallel. His explanation is partially correct but not 100% accurate. The thermodinamic limit is mentioning is related to the maximum concentration factor (number of times light can be concentrated) and the maximum power obtainable is the radiation intensity coming from the moon times that factor. Size of the lens doesnt matter but concentration factor. A bigger lense would create a bigger spot, nothing else.

[@Jay.Harry.WhiteHall]

You could have used a black paper while focusing the moon light.

[@DANGJOS]

@The Wise Santa It still wouldn't have worked, but you're right, he should have. By the way, what are you getting me for Christmas?

[@Jay.Harry.WhiteHall]

@@DANGJOS A golden face mask , an I- Phone 12 and a better president.

[@m.a4491]

@@Jay.Harry.WhiteHall I'm so happy US got rid of that orange clown, the world is now a better place

[@THESLlCK]

@@m.a4491 speak for yourself, I don't want trumanilaszerpressure

[@ori61511]

@@THESLlCK he did speak for himself

[@Enderkruemel]

I think the only postible way to Do this is to use solarpannels and use the Electric Power to get heat. It is postible, becourse at fullmoon my solarpannels are able to get 80w, and 80w are able to create enough heat for a fire.

[@damiangreen299]

Wait a minute, I think there are some assumptions made regarding to the conservation of etendue that aren't true in all cases. The concept of etendue only applies to situations where the size of the lens, or pupil, is relatively small or distant compared to the light source. In the case of the moon, any lens that we construct here on earth would be sufficiently small for the etendue principal to apply, however, if we were able to create a giant mirror array that orbited the moon and surrounded it almost completely, then we should be able to reflect a significant portion of the total light energy that is being reflected off the moon and focus it to a single point. In that vastly different case, we should be able to heat something up to a temperature that is significantly warmer than any particular point on the moon's surface because the amount of energy at any point on the surface of the moon would be much less concentrated than what is being focused at the target point.

[@HAWXLEADER]

If you covered the moon with a giant mirror array then there would be almost no light for you to reflect :-P

[@cezarcatalin1406]

HAWXLEADER You can put that giant mirror array on Earth, the principle still applies. If you take light from the moon in very many points and redirect it towards one point (with mirrors) you could literally boil water or set something on fire.

[@GeckyWecky]

Boring, Shutup NERD! /s

[@DANGJOS]

@Damian Green I don't think so. Any curved mirror would reflect the light into a fairly large image. You wouldn't be able to concentrate it anywhere near a point.

[@DANGJOS]

@@divine308 That's not at all true. You can never focus a lot of light to a single point. It depends on the shape of the light source. The moon is quite large, so any image created by a 200 foot lens or mirror would be much larger than a millimeter. And even if you used a point source (like a basketball putting out the same amount of light as the moon), there is a diffraction limit that prevents visible wavelengths from being concentrated to a point. The reason he is citing for the violation of thermodynamics, is the fact that you are allowing heat to flow from cold to hot, which is not possible in thermodynamics, unless work is performed. Now technically, this would apply to something producing its own light, like the sun, but still, I doubt you can use moonlight to heat something up to a higher temperature than the moon's surface. I don't think the optics allow it.

[@GraveUypo]

i wish i didn't already know that you can't make a projection of something hotter than the surface of the object you're projecting

[@gonzalezm244]

Humble brag

[@uxleumas]

@@gonzalezm244 i mean, if you've watched his other videos...

[@gonzalezm244]

@@uxleumas He’s a very good teacher indeed

[@dienosorpo]

Umm yes you can, if somethings is like 200 C in an area of like 3 cubic meters and you focus all that energy into one small point of one milliliter the energy won’t just disappear. I don’t think it has anything to due with the temperature, I mean the energy the sun emits it’s not heat energy, it’s radiation...

[@UncleKennysPlace]

@@dienosorpo So heat energy doesn't radiate?

[@dingo_ate_my_spaghetti5454]

In the last 2 years I have seen a ton of videos with sponsors and ads on youtube and this is the most useful sponsored item.

[@ELECTRICINVEST]

I wish you didn’t have “Automatic” ISO set up. The camera keeps over correcting and making it hard to see what you actually see. Next time have the Camera’s ISO on Manual so the brightness stays the same so we (the viewer) actually can see an image closer to what you see.

[@toddbob644]

Some flat earthers believe that moon light is cold... But then again they also believe the earth is flat...

[@Silvertinge291]

They are also idiots

[@toddbob644]

@@Silvertinge291 Ding! That is correct!

[@DANGJOS]

@@toddbob644 Funny enough, I actually just did a calculation that says the temperature magnified moonlight should bring an object to is 194 Kelvin, at best. They would probably take that to mean that moonlight is cold, but all it means is that is the temperature if nothing else was illuminating it.

[@toddbob644]

@@DANGJOS Flerfs are pretty funny sometimes... in the sad way...

[@tomg0]

Nearly all of the light coming from the moon comes from light reflected from the sun, and not long wave light radiated due to the moon’s temperature. Therefore the temperature of the moon has almost nothing to do with the maximum temperature that you could obtain on earth. Also, there is a common misconception that infrared light and only infrared light is what causes heating. This is not true. Visible light has a higher frequency than infrared light and thus more able to heat. Light is RADIATED by objects when they have heat energy, and at lower temperatures, this is predominantly infrared light, with the average frequency increasing with temperature, which is why the object starts to glow red when it gets really hot. You could definitely start a fire with the light energy from the moon. The problem is harnessing it because of the low power density. You would probably need a capture area of around 50 ft x 50 ft and a more complex multi-lens system. You could just use a lot of photovoltaic cells and hook them up to a resistive heating element. You would need around 20,000 square meters of solar panels (20% efficiency) to capture the necessary power, but it’s possible. You could also store the energy collected over a period of time, and release it all at once when the capacitor/battery is charged.

[@veryfrozen3271]

Moon is plasma light

[@lahshad]

6:20 My eyes start burning.

[@PopeGoliath]

Yeah my eyes were watering in expectation of pain. Amazing what our brains do on automatic.

[@mr.strongwood2161]

This is probably the only sponsor I've actually been interested in

[@VivekYadav-ds8oz]

How, though? Let's say the surface is emitting 50 J/m^2, and using a lens I concentrate that energy on a much smaller scale. Isn't the same energy, 50 J that was per metre squared area, now on much smaller area, therefore intensity of light has increased?

[@StefanReich]

Yes. James is wrong on this one

[@oskarstenlund]

No actually, that's the corpuscle fallacy.

[@southeasegirl2329]

The Action Lab 2020 = Can You Start a Fire With Moonlight 2022.. 2200 = Can You Start a Fire With Earthlight

[@124Musick]

Lmao

[@irbomusic]

3:44 "So right now, if this were the sunlight, my hand would be on fire right now." I thought the moon's light came from the sun

[@DaRkStAr317]

I’m a retard but I think it’s Because since it’s being reflected it’s not as bright as the sun and even I the video I think he said that the sun is 400,000 times brighter than the moon

[@irbomusic]

@@DaRkStAr317 The moon's light isn't as bright as the raw sun's light but the moon's light still originates from the sun

[@DaRkStAr317]

@@irbomusic ik

[@irbomusic]

@@DaRkStAr317 Ohhhh never mind I understand what you're saying. Yeah, I know. I'm just saying the way he worded it made it sound like the moon's light wasn't from the sun.

[@DaRkStAr317]

@@irbomusic oh yeah lol i get what you mean

[@69k_gold]

James in 2025: *Creates a second Sun for Earth* Also James: Hey Juana you wanna stick your hand on the Sun and see if it burns your hand?

[@RomanoPRODUCTION]

Johanna. Unless she turns into an hispanic woman

[@MichaelZimmermann]

that blanket sponsor was so unexpected and clever :D

[@conspiracydawg]

Theoretically, if you used an array of mirrors to reflect moonlight from different directions into a single area, and then focused them with lenses, would that give an increase in temperature compared to a single lens?

[@ADANTHEGIANT]

I would like to know this answer too.

[@naturenurture84]

Can you start fire using magnifying glass with something hotter like a torch or welding light?

[@hyperhektor7733]

yes because welding light is very hot

[@memesfromdeepspace1075]

Actually there experiment using dozen of super bright lamp and then focused on plat off metal and actually its melt (just little )

[@renedekker9806]

Your videos are normally pretty good, but this one falls short in my opinion. Whether the lens distributes the light over a larger area (as the video claims), or whether it focuses it on a smaller area, depends on how far the target is from the lens. If the target paper is in the focal point of the lens, the light will be focussed on a very small spot that is brighter than the surrounding area. That's why you see that bright spot. As a result that spot will get warmer than the surrounding area. You would have measured that if you would have focused it long enough on the same spot. The moon is not 100 degrees Celcius. The temperature can range from anywhere between -173 Celcius at (moon)night time to +127 Celcius at (moon)daytime. The temperature has an influence on how much IR radiation the moon transmits. But the large bulk of the light coming from the moon is not IR light from the moon itself, but reflected light from the Sun. Therefore, the temperature of the moon has no influence on the maximum temperature that you can reach by focussing the (reflected) sunlight. Whether you can actually burn paper with it, I don't know, because that depends on how good you can focus the light (the quality of the lens), and how fast the heat distributes inside the paper. But you should definitely be able to determine a raise in temperature.

[@DANGJOS]

The reflected light from the sun is even weaker than the black body radiation emitted, so that's even worse.

[@spywalkz1]

Now this is going to be interesting

[@hipeopleidkwhatisgoingon]

Lol yes

[@prominout8079]

Yes ofcourse

[@lorenalopezabad]

Same

[@aayushgautam580]

In ancient India, palaces of kings were lit up using reflectors , reflecting the moon light so efficiently that courtrooms didn’t much required burning torches and stuff at night

[@yatindramanas96]

Your videos are the best ways to experience the laws we read in the books! Really love the content!👌🏼

[@IndianBoy77]

Sun : Tungsten bulb Moon : LED bulb Simple science 😀

[@bunnykiller]

sun tungsten bulb, moon dirty mirror

[@bunnykiller]

this is going to give "proof" for the flat earthers that moon light is cold....

[@Richard-bq3ni]

Yep. Already found some in the comments.

[@sohopedeco]

I thought he would pull it off.

[@DANGJOS]

It wouldn't surprise me if they made this claim.

[@hyouki8529]

Proof for a flat earther is useless

[@Justwantahover]

But concentrated moonlight (according to flat earthers) should still get a significant temperature difference (but "colder" instead) so the world isn't flat and it still disproves flat earther's claims.

[@hongry-life]

No, moonlight gives cold, not warmth. Measure the temp on an object in moonlight and the same in shadow

[@androidlogin3065]

What about using optical fibers to concentrate all ligth rays on the same exact spot? As more fibers you add, more energy you put on that spot, so theorically you can reach a high temperature from a colder ligth source. Thecnically it is correct that such configuration is not a "lens", it van be called a concentrator, something similar to use a lot of tiny mirrors to focus all the ligth in a single point, as more ligth you focus on the same spot, more energy you put on that spot. At home i can burn a peace of paper with a set of really cold led linterns just by fovusing all ligth into the same exact spot with multiple lens, or with optic fibers, or with concave mirrors; and the paper burns instantaneousy. As more ligth sources i add, more temperature i will get on that spot, remember the key is focus all ligth on the same spot. That is a lot diferent than using one single lens, but it allows to have a spot hotter than the ligth source. If you create a dison sphere of mirrors and concentrate the sun ligth onto a single 0.1 mm diameter sphere, the hot in such point will be much greater than the sun surface hot, but agaun that is not a 'lens' it is a concentrator.

[@melonenlord2723]

I thought the same. I don't think, that the secound law of thermodynamics is ment for creating and redirecting light in a specific way. It's more for objects, that emits light on it onw in all directions by heat radiation. The hotter object will always emit more energy in form from light to the colder one than the colder object can emit to the hotter one. Or it works like he said in another video like focusing a laser. It's just negative Kelvin temperature or so. :D

[@androidlogin3065]

@@t.c.b4722 As i said "one lens" is very different as multi lens, multi optic fiber, multi mirrors and dyson sphere. But the main objective, burn a paper with moon ligth is possible with concentration, but that requieres more than one lens, or mirros or something like dyson sphere, etx, in shory words, concentrate ligth on one spot.

[@mixtermuxter8602]

I bet you can start a fire with moonlight - maybe not a lens, but you can definitely do it. Moonlight has energy, so you just need to collect enough of it to start a fire. You could just visit a solar farm and ask them to run their stuff at night, even if it's low voltage you can charge an electric condenser and generate a spark

[@jjackandbrian5624]

My friend got one of those lenses from some old TV at the dump and we used it to melt a penny... also put a hole in his driveway... his mother was not happy

[@hschokker86]

I expected this answer based on the video (I believe you made) on the same effect with the sun. Would it not be (theoretically) possible to create a higher temperature with multiple lenses and mirrors, overlapping the output of multiple lenses?

[@danieletrabalza5943]

There is still something not clear to me: what is the temperature necessary to start a fire on a paper? Is it more than 100 degrees celsius?

[@Grim_Beard]

Ask Ray Bradbury.

[@bunnykiller]

500-1000F

[@Skeptical_Numbat]

Interesting. Finally an explanation of this effect I've been observing for years. A perhaps for useful question is: "Can solar cells be powered at all by moonlight..?" Having even a fraction of daily power output would be useful when expanded over the surface area of several thousand km of solar panels (eg: across an entire city). Enough for the low voltage LED lighting of public paths, or even self-cleaning mechanisms on the panels themselves (preventing the buildup of dust that'd reduce their efficiency during the day).

[@Skeptical_Numbat]

@@t.c.b4722 Intriguing. Even at it's current low W/m² power generation (⊕), I can easily see *Thermoradiative Cells* being an excellent surfacing material in cities, where there are already large masses of concrete constantly accumulating tremendous quantities of heat from the sunlight. In several Australian cities, the surface temperature of concrete paths/walls/buildings easily exceeds *45°C* during summer, which could form a potent (if inefficient) power reservoir. As well, by removing a portion of each day's heat, it would reduce the cumulative affect of multiple days sunlight, making the environment more compatible for life. ⊕ Though this will emphatically improve with new graphene-based components.

[@sdjhgfkshfswdfhskljh3360]

Even if they can, output power will be ~1million times less than from the Sun. So 100 watt panel will produce 0.0001 watts of power. For comparison, indicator LED typically consumes 10mA@2V=0.02 watts of power.

[@drdonavon]

The moon is not a black body radiator, it has some reflective properties. So although i do doubt that you could start a fire, I'm not sure that you can use all of the arguments you have used. If you point a telescope at the moon it can damage your eyes. This is actually a warning when you buy one. This is because there is some reflected light and with the right optics the intensity can reach high enough to at least cause eye damage. Again not sure if you could practically get the intensity of the light high enough to start a fire, but I think that is more of a practical than theoretical limit. This problem with breaking the second law of thermodynamics I think is accurate when talking about sunshine, and you could not use optics to create a temperature from concentrated sunshine that exceeds the temperature of the surface of the sun. This applies because the sun is a black body radiator. The visible light that comes from the moon is all reflected because the moon is not warm enough to radiate in the visible range as a black body. The reason we use the term black body is because it has to be a totally non-reflective object to use the black body radiation as a model.

[@ericerpelding686]

Interesting. What if you tried to make a "Moon Reflector Cooker" by reflecting the lunar rays over an area and concentrating them to a focal point? would that be able to ignite a piece of paper?

[@ConstantChaos1]

In practice? Almost definitely not, but purely from a physics standpoint I don't see anything that would prevent it, it would be super huge and inefficient even compared to solar cookers on a rainy day but yeah, at some point you will have concentrated enough energy to cause at least some change in temp and eventually ignite something. Pretty much if you cast a wide enough well tuned enough net you can do almost anything, im not going to run the numbers cuz I dropped out of engineering cuz I couldn't be bothered to (so I became a first-responder and trained chef.... I don't know how to relax but that's besides the point)

[@harbirnain]

Solar irradiance ~ 1400 Watts per sq meter. Lunar irradiance = 0.004 Watts per sq meter. So you'd need a lens with a surface area 350,000 times to get the same effect with the moon as you would with the sun. If your convex lens is 4 inches across, you'd need a square fresnel lens 440 feet on each side to concentrate the energy from the moon to the same level that your convex lens gets from the sun. Suffice to say without even seeing the video that you're not anywhere near that. But of course you knew that before you ever acquired that huge fresnel lens. so kudos to you for doing it any way to show folks just how weak moon light is. You know what blows my mind? The Moon's "ashen glow". Sun light reflects off the earth then some tiny fraction of it hits the moon then some of some tiny fraction of that tiny fraction comes back to Earth, and we humans can see it very very faintly illuminating the whole of the moon when it's not full, contrasting against the crescent of the moon that's illuminated directly by the sun. Of course it helps that the water covered earth is much much more reflective than the moon, which has the reflectivity of tarmac (its not white!) That the human eye has the dynamic range to both see in direct sunlight, and also see the tiny tiny tiny fraction of reflects off the earth and then off the moon is just mind blowing.

[@a_diamond]

*accidentally sets Moon on fire...* O-o

[@mystcat3]

Fire doesn't exists in moon

[@Bleepbleepblorbus]

@@mystcat3 no but fire is more dangerous in space

[@DylanMoss]

This is definitely incorrect. When you focus light you aren't creating energy, you are concentrating it to a point in order to reach the combustion temp of paper. When you use a magnifying glass, the area around the focal point is darker (which is where the 'stolen' energy comes from). In principle, you have the total energy radiating from the surface of the moon available (not just any one point, whatever that means) and your only limitation is designing a device that can redirect enough of it and limit loss by absorption/reflection/scattering. Here's a thought experiment. Considering that the moon delivers 0.0006 watts per m^2 (look it up), 1000 m^2 of moonlight would deliver 600 milliwatts of energy. A handheld laser with that output usually has a spot size of 2 mm diameter at close range and is of course capable of igniting paper. So, you'd need a huge collection area and you'll have a tough time dealing with the different refractive indexes of the different wavelengths to collect them all in a 2 mm spot, but no laws of thermodynamics are in danger.

[@JamesFreeman]

That rule would only apply on the surface of the magnifying lens, at the focal point it's not true

[@rhcrcgvp]

I just read Wikipedia's page on etendue and you are correct.

[@borkshaw3835]

He looks like he’s expecting the viewers to punch him through the screen

[@bombastik87]

I feel like there's an error with these considerations. That "conservation of temperature is wrong" there's conservation of energy and temperature depends on density of energy. I do believe that theorically by reflecting and directing the moon light towards a sufficiently small piece of something, you can burn it.

[@jasdeepsinghgrover2470]

Isn't moon simply reflecting the light. How is the second law applicable here? A mirror can burn paper without getting equally hot so why can't moon light?

[@izuy303]

@@t.c.b4722 wouldn't a sun lit mirror be quite cold yet it could still light a fire if you concentrate it(through either lenses or use a focusing mirror)? Wouldn't most of the heat come from reflected sunlight rather than lunar blackbody radiation?

[@jasdeepsinghgrover2470]

@@t.c.b4722 we are referring to reflected light. The law of conservation of energy and second law of thermodynamics are referring to the source(sun) and the absorbing destination paper but not for reflecting or refracting materials(moon) . I am by no way an expert but would love to know if it is possible then how.

[@richardparker334]

Nice magnifying glass

[@johnschewe6358]

Etendue isn't a measure of brightness, it's a measure of the randomness of the angle of light. The idea is that one cannot straighten light with lenses once it is already at an angle. The only way to make a beam of light brighter using lenses is by focusing the beam into a smaller cross sectional area. But that becomes increasingly difficult the more varied the angle of light is in the beam as lenses and mirrors will have a tendency to amplify the variance. But with a laser, or an already straight beam of light, a lens can easily bend the edges inward to cause the focal point to be brighter, but the result after it hits the surface is the light is scattered more. Making it harder to collect them into a single focal point again. Once again though your understanding of hot vs cold and the second law of thermodynamics doesn't make any sense. Temperature is not correlated with energy, it's a ratio of energy to mass. The more energy a mass has, the hotter it is. But the smaller group of mass with the same energy would also feel hotter. It's why a candle can be very hot, but you can also put it out with pinched fingers without getting singed.

[@lalitajeniar341]

I luv ur videos....they r different but awesome

[@steadfasttherenowned2460]

I had a huge lens off a 60inch old school big screen TV. It would melt pop cans and I even got it to sag some glass on a good summer day.

[@darkhound6461]

Recommendations is faster than notification KZbin is really drunk.

[@mdtarequzzaman5485]

I agree with it too, it was in my recommended before the notifications

[@dat1pengu1n]

ye

[@AeroGraphica]

Always thought that the light from the moon was cold because its surface already absorbed all the heating radiation coming from the Sun, but ok... If the moon surface was a mirror reflecting all sun's wavelengths, you could start a fire from it ...

[@E9X330]

Reflecting all wavelengths doesn't mean reflect every photon that hits it

[@mdtarequzzaman5485]

I thought you were gonna set the moon on fire with that magnifying glass

[@architbhagat]

Yeah i thought that too 😂😂

[@OnTheRiver66]

I always learn from your videos! I never expected the reason for this being that the focused image can never be hotter than the object itself!

[@DANGJOS]

@@danstiurca7963 No, it isn't wrong.

[@DANGJOS]

@@danstiurca7963 Explain how you would get a spot hotter than the source with a magnifying lens.

[@DANGJOS]

@@danstiurca7963 So no explanation. I shouldn't be surprised

[@justitroyal7032]

Never taught of a heated blanket

[@salihkarayel]

Wow, they're very common where i live

[@Yeetuz.Deletuz]

@@salihkarayel damn, its soo hot here

[@salihkarayel]

@Suprith Turkey

[@boomstick4054]

My ex was sleeping under an electric blanket....I walked past the bedroom door, saw sparks . The electric blanket was shorted out....smoking, trying to burn. I pulled the blanket off of the bed, threw it out in the yard. Of course it startled her, being woke up this way. No more electric blankets for me.

[@xcelorams_just_box]

Love from india brother!😇

[@lohitlingala1958]

Me too Btw love science

[@manasjindal3254]

Me also love from india

[@ashutosh6449]

Watching from Mumbai the capital city of Maharashtra

[@Javierjr1224]

0:50 when he laid down and just gave a thumbs up. That made me LOL

[@philippbointner3840]

that heated blanket interested me more then the whole video xd

[@lianned2635]

Well, but Moon actually reflects the light of the Sun... That's why it shines visible light. 100 degrees corresponds to far infrared light. Then with a VERY large mirror it should be possible to reach the temperature of the Sun, right?

[@Richard-bq3ni]

What he said was, that focusing the moon light, you can never get any hotter than the moon surface, which seems to be around 100C. So it doesn't matter how large the lens of mirror is.

[@Richard-bq3ni]

@BLACKVIEW USA Yeah sure. That is why you can see shadows in craters and around mountains if you use a telescope. Oh well, flatties will be flatties.

[@lianned2635]

@ Richard This limitation (that you cannot achieve in the lens' focus higher temperature then the surface of the light source) applies for bodies that EMIT light, like the Sun. It doesn't apply for bodies that REFLECT light, like the Moon!

[@yoru0121]

@@lianned2635 Exactly. The second law of thermodynamics only applies to a closed system. The Earth and the Moon is not a closed system because the moon is constantly getting external energy input from the Sun.

[@Richard-bq3ni]

@@lianned2635 In that case, could it be that most of the IR light (that is essential heat) has been absorbed by the moon (so it's surface heats up) and a part of the visible light is reflected? This way you cannot heat something with the focused light since it has been stripped from the part (IR) that is capable of heating something up? Just an idea, not a statement 😉

[@Le1fGaming]

When I was young, me and my dad did a science experiment where we looked at temperatures and the moon light was actually colder than the shade, so maybe it can’t heat stuff up but it might be able to cool stuff down and maybe even freeze something

[@storminmormin14]

I’m gonna get cataracts from all the UV I exposed my eyes to courtesy of starting fire with magnifying glasses.

[@DANGJOS]

Wear UV blocking sunglasses next time.

[@vimaladadhich7934]

Superb ideas sir. Just in love with ur mind.😍😍 I wish you would be my school science teacher🤩 and one more thing sir... sir can you plz make a video in which you will be applying the waterproof spray in water beneath the water level i.e. spraying the waterproof spray inside water and not on it....plz sir....🙏🙏

[@rolininthemud]

I'm a little confused. He said that you can't heat something up to be hotter than the moon by just focusing moon light, because that would break thermodynamics. The moon is not hot so heat cannot flow from the moon to the thing being "heated." But the light is originally coming from the sun right? The moon is just reflecting light, and I know you can use mirrors to reflect light to heat things... What's the difference here? Isn't the moon similar to a giant space mirror?

[@sutapadey5274]

the paper is getting heated but not burnt

[@a_diamond]

The light that lights up the Moon is *Sunlight*..... It doesn't make light of it's own...

[@rolininthemud]

@@a_diamond yeah exactly, so couldn't the sunlight coming from the moon be focused to heat things?

[@a_diamond]

@@rolininthemud Take a solar panel, and put it in the light of a full moon. You'll get power. Not tons of it, but not none.

[@rolininthemud]

@@a_diamond oh yeah that's another good point. If a solar panel could capture energy from moonlight and store it in a battery then that solar panel could power a heater. If the heater was hearing something small enough and the solar panel was large enough I think the heater could get hotter than the moon. Would that break thermodynamics?

[@paragjh284]

Ancient Indian text already knows this from thousands of years. It is stated that the moon light is cold in nature and full moon light of winter( Kartik) showers elixer of life and at that, it is the perfect time to harvest the medicinal herbs, because that time those herbs contain higest concentration of active components.

[@arashahsani]

search for E43c D67ay 43=ri 67=ub

[@perschistence2651]

Of course, you can start a fire with moonlight. Just save the energy from it and release it later in a way shorter amount of time.

[@sdjhgfkshfswdfhskljh3360]

Next experiment is to collect energy from radio waves. Not standing right next to transmitter of course.

[@perschistence2651]

@@sdjhgfkshfswdfhskljh3360 In fact, I know someone who did this and it worked! It is even controversial here in Germany if it should be illegal, because you are stealing energy from the signal, be it an extremely small portion of it.

[@sdjhgfkshfswdfhskljh3360]

​@@perschistence2651 such device is just a radio receiver. It is illegal if you steal energy from power lines this way (= standing next to the transmitter).

[@sdjhgfkshfswdfhskljh3360]

@@perschistence2651 I was trying to do this too. But even for collecting energy from my computer mouse it looks like I need transformer with thousand turns. For high frequency transformer may be smaller, but I don't have other equipment to debug this device except for sound card input :)

[@DANGJOS]

@@sdjhgfkshfswdfhskljh3360 But wouldn't the waves just have radiated away to the ambient anyway? It's just waste energy, is it not?

[@komr323]

I have been thinking about this for 30 years since I was a kid, and you have just confirmed me. Thank you

[@petrhawliczek3302]

I think that is not true. The Moon light is not emitted, but reflected Sun light. So the visible photons from the moon have the same temperature as surface of the Sun. So with big enough lens You can sure burn the fire with the Moon light.

[@gentaermaji191]

but then you're implying that the moon's surface receives heat as hot as the surface of the sun from the photons. I think that's not the case because then the moon would melt from the temperature. I think that the photons must've decreased in temperature when reaching the moon and then reduced some more by the moon (dissipated by the rocks or something) that's why moonlight is not that hot. Of course I could be totally wrong because I'm just guessing.

[@petrhawliczek3302]

@@gentaermaji191 Well example: You will reflect Sun light by mirror. Then You can focus this reflected light and still burn a paper. The mirror cam be cold, but it is energy of reflection photons what burning the paper, not the emitted photons by mirror. So I disagree with conclusion of this video.

[@gentaermaji191]

@@petrhawliczek3302 That's an interesting point. Guess I'll take it for now. But isn't the sunlight we receive is a lot less hot due to the atmosphere, so the mirror doesn't melt? What I'm saying is maybe the sunlight received by the moon is also a lot less hot so the reflected light can't be as hot as the surface of the sun.

[@petrhawliczek3302]

@@gentaermaji191 It depends on the color / wavelength of the photons. Suns surface is hot about 5800K - that is also the main wavelength. So in theory You can melt something until temperature about 5800K. And this moon experiment will be ok if there will be new moon (not reflecting the sunlight). Then max temperature will be max temperature of the surface of Moon. But then Moon reflect the Sunlight, then the energy of reflecting photons are the same as Suns surface temperature.

[@glasshalfempty1984]

4:47 bless you.

[@MikeEnIke007]

You’re answering all the questions that I never thought to ask

[@Tletna]

..But, you cannot increase the actual numbers of photons, rather you can only change their paths..so if you're ever increasing the cross-sectional area they hit or pass through, you're decreasing the amplitude or concentration of brightness - you're not keeping it the same. The maximum heat/brightness possible stays the same or goes down if spread out more. Though technically, you can concentrate a part of the light rays into a smaller space, that is how a magnifying glass can start fires with the hotter sun light, but not moonlight.

[@user-or9cj3vk6t]

Moonlight is colder than the temperature in the shadow of moonlight. It gives off it's own light (nothing to do with the sun). It is cold light. Elementary school level!

[@HugoFilho.]

"Moonlight is colder than shadow" Nope, objects exposed to open sky are colder than objects at a shadow because the object that causes the shadow blocks the heat loss(the Moon makes no difference) "It gives off its own light" Lunar craters have shadows in them, so it disproves the idea of the moon making its own light "Its cold light" Cold light doesnt exist

[@LEVEL_EARTH_PRODUCTIONS]

It's hard for normies to let logic and truth override their fictional indoctrination.

[@squasholantern6343]

Its crazy to rap my head around the moons light which is energy, but it's cold.

[@robmckennie4203]

i read the post on randal's What If blog ages ago, and I wasn't convinced by that either. the thermodynamic argument is completely unconvincing, because the light isn't coming *from* the moon, we're not talking about trying to gather all the black-body radiation of an object and use that to heat something else, we're talking about light that's coming from the sun and being _reflected_ by the moon. however inefficient, you can get power out of a solar panel from moonlight, if I use that power to heat a small electric element am I violating the laws of thermodynamics? light is made of photons, right? photons have energy, and by absorbing a photon into an object i can heat it up. the moon reflects photons from the sun. so, what is stopping me from taking those photons and using them to heat up an object?

[@Bruh-vd1pp]

KZbin:You wanna see a guy try to burn paper using the moonlight? 1.3k People: Idk man, i guess

[@shikharkumar734]

This wasn’t recommended to me I an old subscriber

[@manasjindal3254]

It's more than 6.4k now

[@currentriver4951]

Is it the elections or to many on ccp virus lockdown

[@victorkingau1242]

@@shikharkumar734 me too

[@nox_cadit]

I'm actually subscribed to his channel for a long time hehehe

[@DemetriosMPapadakes]

This explanation creates more questions than it answers

[@descai10]

It's definitely possible to create a lens big enough to start a fire using the light from the moon. Think of all the light energy bouncing off the moon, if all of that energy was redirected into a single point it would very easily cause fire, in fact it would probably be millions of degrees. If you put a massive magnifying lens the size of the moon right next to the moon, pointing at the earth focusing on a tiny spot, the thing would be a death laser.

[@jlfqam]

It's not about the temperature of the sun but the number of photons that hit a surface unit. That's why you need a magnifying glass or fresnel lens, to concentrate more photons on a surface unit. What heats up matter is the rate of photons that hit atoms and the energy of the photons to be transferred. You can heat up atoms with a high density beam of low energy photons. Lasers do that, high photon rate in small solid angle or surface.

[@Joey_Mendez_Dream_Garage]

Why Steve from Minecraft is in the Thumbnail? Lol

[@steveoo410]

65 percent of the time I don't understand what you are talking about, but your vids are always interesting.

[@wanzafir7908]

well the giant magnifying glass is 2020 and the paper is my future

[@mdtarequzzaman5485]

SAME

[@Adamisgood24]

I'm glad you pronounce "Fresnel" the right way!

[@ultimatefoodzone9577]

Can you burn something with a magnifying glass on moon surface

[@Richard-bq3ni]

You can heat something up. Burning something requires oxygen.

[@BoomShard17]

If it didn't start a fire in a fully lit room at the beginning of the video, I was very skeptical that dim moonlight would cause a fire.

[@robertmorri9332]

I've always heard that it is colder in the moonlight than in its shadow at night .

[@Anomalocaria]

sort of. the reason you might find warmer temperatures in the shade is generally because the object casting the shadow is insulating the object being measured. the more exposed an object is to the open night sky, the cooler it's going to be. the more you cover it, the warmer it's going to be. it's the same reason overcast nights feel stuffy and warm if you live somewhere humid - but then in dry places like deserts the temperature may drop close to freezing at night due to the lack of cloud coverage.

[@TheTruthHz]

It's colder when you're exposed to the night air whether the moon is shining or not. Plus the night is colder if you can see the moon because the sky is then likely clear. Clouds insulate and trap warmer day air just as tree cover or some sort of shelter does.

[@clubdesalud1488]

It is colder. I've done experiments and moon light is ALWAYS colder than its shade. To avoid the idea of the structure causing the shade is also insulating heat, i've taken measurements when the light is coming in at angles where the structure is not over the ground i am measuring. I've even taken measurements off of a wall where part of the wall is in the shade and the other part beside it is in open moon light and there is no roof or anything over said wall. Moon light is ALWAYS colder.

[@sirMAXX77]

This is very interesting, it's like light without the heat.

[@ulyxsigma]

How to read "Moon Light" 1st step: read "Moon" 2nd step: read "Light" 3 and final step : read "Moon Light" I hope it helped congrats if you learned it

[@CupidGTag]

These comments aren’t funny stfu.

[@ulyxsigma]

@@CupidGTag it helped you ikr

[@ulyxsigma]

@Space Realms stfi

[@hyperhektor7733]

;`Moon Lube?

[@TREMILBERG]

You could use a set of several magnifying glasses to focus AR the same point. That could give you a higher temperature than the radiating object.

[@hooman3576]

Hey, frm where do u get ideas? Have u won a lottery for ideas?

[@vivekrawat3322]

I have this same idea I even ask this question on quora but i am not satisfied with there answer so it helped me

[@glennledrew8347]

Excellent! On a related note, the irradiance from a uniformly luminous hemisphere is equivalent to a photographic lens speed of about f/0.6. The reason? At the focus of a lens the light comprising any one image point has converged there on a (nominally, in the absence of aberrations) spherical wavefront. The radius of this wavefront means that the real f/ratio, as a measure of image surface brightness cannot permit the value to go below this, let alone to arbitrarily tiny values as the simple geometry of focal length / aperture would suggest in a naive consideration of the problem.

[@DemetriosMPapadakes]

I'm disgusted by how advertising has creeped into the inside of youtube videos.

[@perschistence2651]

I am not sure if he is right this time. There is no "moonlight". The moon is just a mirror. Of course the mirror does not get very hot, it does not absorb the energy because it reflects it. That does not mean you cannot burn a paper with the reflected light. Let's assume the moon would be a perfect mirror pointed at the earth. Do you really want to tell me you couldn't burn anything with the light, just because the mirror is not hot itself?

[@prominout8079]

Yes sirrrrr

[@1.4142]

can't you focus all of light over a large area onto a single point with mirrors or lenses?

[@Wishingweezy]

Actually I need that blanket can u tell me what is the pin made of whether it will get corroded in washing?(long term?)

[@ProsperousSubconscious]

I think blanket boy missed the point or deliberately dodged it. If the temperature of sunlight can be amplified by a magnifying glass, then moonlight should follow suit to a lesser degree of course. Unless moonlight is not reflected sunlight. Blanket boy's experiment actually leans to the side that says the moon is not reflecting sunlight. It is simple until b.b. tries to confuse the facts with big words and complex theories.

[@thorargent]

So many years back I had this same question, and I found a work-around to make it happen. I made a photovoltaic collector and a light tracker for a large Fresnel lens. I collected enough moonlight and converted it to electricity to charge up a supercapacitor. The electrical discharge from the supercapacitor was sufficient to heat a small bit of nichrome wire which easily started a fire. Done. You can see some of my larger Fresnel collectors on my channel (thorargent). By the way, your explanation is pretty good, but there is another way. You actually can make the spot hotter than the source but at the expense of the information in the image. If you use non-imaging optics, you can actually carry much more of the light to a directed spot, but this is something that is not well known. Just be aware that the method of making the image hotter than the source does exist, within reasonable limits.

[@thom1218]

Ha - I'm surprised you didn't mention an array of solar panels that can easily collect enough moon light into a small capacitor and discharge it at significantly hotter temperatures than 100 degrees C. So, your closing statements that generalize hotter vs colder objects and the conservation of energy need to be noted to only apply to lens configurations, which do not store and concentrate energy.