Friday, October 02, 2015

Moonshine and Lunacy

I got an email from a reader yesterday asking for help in understanding a video that she’d seen, in which a citizen-scientist performs an experiment with a very surprising result: moonlight makes things colder! How could this be? To find out, I took a dive into the well-intentioned but deeply problematic world of Youtube science.

The first thing that I discovered on this journey was that this experiment is a popular one, particularly among “Flat Earth” theorists. (I wish I were kidding about that, but the idea of a flat earth seems to have experienced a resurgence in popularity this year.) A quick search for “Moonlight cold” turned up multiple videos on Youtube, most of which show some variation of the following experiment being performed:

An object is placed outside under a full moon, partly in the shade and partly in direct moonlight. The experimenter gives the thing some time to reach equilibrium, then takes a temperature measurement with an infrared “laser” thermometer, which reveals the moonlit side to be lower in temperature, sometimes by as much as a few degrees!

Obviously, something’s afoot here, but it’s not so simple as a hoax—nearly everyone making these videos is very much convinced that they’re seeing a real effect. So how does this phenomenon arise? While you probably don’t need convincing that it’s not “heat-sucking moon beams” at work, it’s absolutely worth exploring how these earnest attempts at science can go so wrong.

A handful of these videos are shot in near-complete darkness, as even a full moon can’t provide enough light for the average cell phone camera, so practically the only discernable features in the footage are the thermometer’s laser aiming dot and backlit temperature display. Still, I admire the creators of these videos for their effort to reduce the noise in their data and provide a cleaner signal; noise is one of the biggest sources of error in any experimental setup. However, these home experiments fall victim to a far more significant source of error: poor instrumentation.

There are two factors common to virtually all these videos: a point-and-shoot infrared thermometer, and a yokel behind the camera who has no idea how the device he’s holding works. See, while it’s tempting to assume that your “laser thermometer” is telling you the temperature at the illuminated spot, that’s only half the story—the laser actually doesn’t do anything besides help you aim! The actual measurement apparatus uses a lens to focus infrared radiation from your target onto a digital sensor. What this means is that, rather than taking the temperature at a point, you’re taking the temperature of a circle centered at that point. How big the circle is depends on how far away you are from your target, along with the internal optics of the thermometer.

A standard IR thermometer has a D:S (distance to spot) ratio of roughly 10:1, meaning that making a measurement from ten feet away will give you the average temperature of a spot one foot in diameter. In the video below (which has twenty-something-thousand views, as of this writing), the experimenter seems to be standing at least ten feet away from his target, trying to check the temperature on either side of a wallet. Once you understand how the IR thermometer works, it’s plain to see where his anomalous result comes from: the spot he’s measuring on the moonlit side includes the ground beyond the edge of his pool deck, which is doubtless cooler than the stone that makes up the patio.

You'll want to skip to about 8:50, unless you've got time to kill.

The potential for this kind of error is why it’s important to repeat your measurements in different ways; if he had moved the wallet to the other side of his table’s shadow, he might have noticed that the temperature difference vanishes!

This brings me to my last point. The beast that aggregates these errors into a katamari of colossal wrongness (and the real reason so many people are apparently convinced that the moon emits some kind of anti-photon) is one of modern science’s greatest enemies: reporting bias.

If the guy who made that video had noticed, halfway through filming, that he wasn’t getting the results he expected, do you think we’d have seen it? Statistically, for every person who finds that moonlight makes things colder, there’s at least one who conducted the same experiment and found that it has no effect, or even the opposite, making things warmer! (Which technically it should, but it’s likely a micro-kelvin kind of difference.) The difference between the two cases is that the null hypothesis is obvious, while the alternative is literally incredible, so only the latter gets uploaded and viewed and shared. When you consider that the uploader gets paid by advertisers based on the number of views they get, you realize that this system incentivizes bad science, not just socially but financially.

Unfortunately, this problem isn’t exclusive to Youtubers howling at the moon—it permeates the real world in serious ways. If a flipped coin land on “heads” ten times in a row, it’s very reasonable to suspect that it’s a weighted coin, but it becomes a different story entirely if you find out that someone spent all afternoon flipping in order to get that ten-heads streak. In the same way, unreported repeat trials can make a statistical fluke seem like good data, which can be a huge issue if we're talking about something like the efficacy of a nutritional supplement.

As someone who loves unconventional theories, I can say from personal experience that there’s a deeply forlorn feeling you get when an idea that you thought was revolutionary turns out to be bunk; it’s like waking from a flying dream to discover that it’s Tuesday and you’re late for work. People fight that waking feeling, usually subconsciously, because our beliefs are guided by emotions rather than logic an embarrassing amount of the time, and because everyone wants to be the new Galileo. But science—GOOD science—is the struggle against that instinct to cling to the dream as it dissolves around you, because as Randall Munroe said, "You don't use science to show that you're right. You use science to become right."

The null hypothesis, that the moon just reflects light from the sun, will never "go viral". It's not profitable, or terribly exciting, and it doesn't have the symmetrical allure of its contrived alternatives. But precisely for those reasons, it's essential that it be defended, that we demand extraordinary evidence from those who make extraordinary claims, and with zeal to match theirs. It's a scientist's duty to shake awake those dreamers who've taken in a touch too much moonshine, because there's a real world out here that needs exploring, and it's full of more wonder than anyone could dream up.


  1. Perhaps what they are really measuring is the radiative cooling of the night sky. If the moon is occluded, it means there is a warmer terrestrial object between the object and the night sky.

    1. Im curious if anyone has tried this experiment during a clear, moonless night by measuring the exact same object in the same spots at the same time of night. Is there still a difference? By the youtubers hypothesis, there is no moonlight so the answer would be No. If someone could show me this i may be more inclined to believe this theory.

      David, I too was always under the assumption that the shaded spot was warmer the same way the earth is warmer with a cloud cover. An object shading our test spot radiates the heat lost by the spot back towards it, warming it slightly. This is opposed to the unshaded spot that radiates its heat up through the cloudless sky which, in turn, radiates significantly less heat back.

  2. How much energy does the moon reflect on the earth? Even a micro kelvin must it seems have an measurable effect on the temperature at night and every night since time immemorial for large energy input.

  3. David,
    You're too clever for your own good!

    Now that you mention it, one of those videos featured a guy using a symmetrical 2 kW lamp to illuminate the experiment, along with an umbrella to occlude the moon, and that's a good geometric arrangement for that effect to emerge, especially if the underside of the umbrella reflects some of that light/heat.
    Instrumentation error still strikes me as a better explanation, but this is a great bit of let's-make-it-work thinking!

  4. Maybe less writing could have been dedicated to chortling and more simple staying what could have been done to make them more sound. Personally, I have an IR thermometer and tonight's a full moon. I can easily just measure my side walk several times, then shade one side, and take measurements every 60 seconds of both sides. What's wrong with that? What should I do differently to spare me the intellectual ridicule?

  5. I mean, really. Something riles people up out from the sofa and had then actually excited to conduct an experiment, and your advice is for the science community to staunchly defend the moon reflecting sunlight theory "shaking awake" these pathetic dreamers, and "demand" proof. Such ego and pride! What are you so afraid of? Oh it's such an obvious fact, why be threatened to those that challenge it? Have YOU conducted ant similar experiments, or is it just beneath you, you're so certain? Such faith! This religion of yours is so dedicate, you instruct your minions to rip them to shreds, like a good priest should.
    Nevermind all that bullshit feel good crap those like Nye, our Tyson try to harvest. No, you'll have none of that!
    When did you get so jaded and disillusional?

    1. Actually, his response was that we should demand rigorous and controlled experimentation from people that would come up with radical alternate explanations.

      Perhaps it would have been better if he said we teach these armchair scientists how to apply the scientific method more robustly.

      You're right- that the armchair scientists went out and did this is to be all they need is a little discipline.

      I think I have come up with a more rigorous way to test the "moon is a cold ray" hypothesis. I hope to have time sometime over the next couple of months to test it...for the best results, I may have to wait until spring...I think the cold winter months may cause issues.

    2. The Moon emits cold light this is a fact. Your heliocentric bias is getting in the way of real science. The instruments used in these experiments vary but the results are always the same the Moon emits a cold or cooling light. And if you would like to criticize them then show us how the experiment should work instead of throwing punches from the safety of tge science crowd

  6. You are avoiding the issue here: is the light from the moon cold or warm? It seems we all know the answer so there is no reason to set up an experiment. But say we are new to this world and the matters of light and shade - what would be the best way to show the effects of the moon's light upon the earth?
    What is this about a flat earth and where does that enter into the situation?
    Use your scientific mind and give us a straight answer, please.

  7. Dunce- you asked "How much energy does the moon reflect on the earth?"

    The answer? None. Heat is not is transferred via either conduction, convection, and/or raditation.

    Since the moon is in space, convection and conduction are out, so the only way the moon can transfer energy to earth is via radiation.

    Radiation happens to be the absolute least efficient way to transfer energy, so the amount of radiated heat from the moon would be very small, and the teeny tiny amount of the moon's reflected light that is shining on the little patch of ground where you are standing measuring its temperature would have several magnitudes less heat than that.

    I guess theoretically there'd be a thermometer accurate enough to detect this heat input from the moon, but in actuality it would be so swamped out by other heat sources closer by you would never detect its signal with equipment we have on hand. Certainly not to measure a several degree temperature change.

  8. TWOM you asked: is the light from the moon cold or warm?

    The real question is- is light from the moon a heat source or a heat sink relative to the unlighted earth?

    If it's the latter, especially to the degree these homegrown experiments are purporting to find, that would be an extraordinary development...would run counter to the laws of physics as we know it...and likely would have shown up in other ways already.

    The Youtubers who video this don't understand the import of what they are claiming...but once you do understand it, you realize why the first reaction is appopriately major skepticism.

    1. No the reaction should be major research. And a following reaction as to how science never picked up on this in the last few centuries

  9. OP is a fail. You talk a lot of smack on behalf of "science", while offering none of the sort. You write as though, anyone but you, or a "scientist" is a moron that does not understand how to conduct experiments or "science". You have no answer, then continue with babble that everyone is stupid except you and "scientists". You are the epitome of evidence that the word "science" has been commandeered by regurgitating, mindless parrots. Guess what fake scientist with ZERO understanding of this world OR the cosmos? Moonlight magnifies colder. So go flush your freemason degree and mortarboard hat down the toilet. You have been bamboozled to live your entire adult life in a lie. Lolz. Joke's on you. BTW, when the truth is exposed to the whole world about the true form and nature Earth and the heavens, don't walk around acting like 'you knew it all along'. Sucka....

    1. This is nice, except the author in no ways said that everyone other than "scientists" or "him" are morons who don't understand science.

      What he did say is the the majority of these "moon calling" experiments that have been posted on YouTube contain rather blatantly obvious measurement error, and many of those posters did not seem to understand how infrared thermometers worked.

      That doesn't make them morons...just inexperienced at setting up a proper controlled experiment.

    2. Ill call all these flat-earth, cold moon believers morons. Everyone knows the earth is round... and hollow.

  10. Anyone can wag the dog. I see bias in your rhetoric alternately to your blog. Prove it. I have done this test myself on many different surfaces and the results are 1 degree F. up to 4 degrees F. at any range. I'll check back in the spring to see your experiment debunking this phenomenon. Likewise, I will wonder how many takes did not make the editing.

    1. And can we see your experimental setup?

  11. Hi again.
    On 29 December, 2015 I went out during the Waning Gibbous moon and tested the temperature difference of direct moonlight and shade. I held a temperature gun 3 feet from ground and rotated 15 degrees back and forth in and out of direct moonlight and shade. The results can be found here.

    Still looking forward to your test and the results.

  12. Why argue?

    The Oxford English Dictionary defines the scientific method as "a method or procedure consisting in systematic observation, measurement, and experiment, and the formulation, testing, and modification of hypotheses."

    Next full moon is Jan. 23. If it is a clear night, measure the temperature in the moon shade and the moon light.

    That is all there is to it.

  13. This article is written with a very defensive attitude. Wouldn't it be more scientific to present the views of the Youtubers and then offer scientific rational or experiments to show where they made their errors? Rather you attack those who you didn't agree with without any credible rebuttal. How difficult would it be to run the experiment and show the "unbiased" and controlled results instead. I agree with the comment earlier... if this was shown to be accurate, it would open a scientific door that could change the way we think about the universe and science.

  14. Jon Emeigh, tomorrow is full moon.

  15. Well, I too have been around the stupidity of Flat Earth. Let me say they have nothing. But it is were I heard of this occurrence. I was sure it had something to do with where the tests were performed in proximity to warmer objects etc.. But I performed the test, as prescribed, and it's true. there was a difference of 2 degrees Celsius in favor of the shade. It's possible that moon Light has a wave effect against the radiating warmth of the Earth but I really don't know.

  16. Definitely looking for someone to confirm or deny this experiment with acceptable methods instead of just talk trash talk those who are actually doing the experiment. This phenomenon has been redorded time and time again by many people for many years. I'll be awaiting follow up comments with more to contribute to this than just naysaying from behind a computer keyboard.

  17. I'd try this experiment with something other than the IR thermometer. I'd also try it in more than one way. The more data you have the better your results would be.

    I did go outside and wave around my IR thermometer and I got varying results. It did, in some cases, appear that areas in moonlight were cooler. Though the warmer areas were under things like chairs so my thinking is the chair provided some kind of slight insulation to heat radiating away? I also measured where a house blocked the moon and got nearly identical temperatures in both shadow and moonlight. I didn't record any of those measurements because I was just messing about.

    I'll try the experiment again at some point and put more thought into it to make sure the results are not skewed one way or the other. I like to think there's a logical explanation for why things happen. So, we'll see.

  18. Even more stupid cooling moonlight video. .

  19. The Jig is Up. NAZI NASA Zionist Freemason fake science is in trouble. They are planning their final false flag.... "We came from Aliens" Time to wake up to their lies.

  20. The idea of cool Moonlight is religiously motivated for the most part, as is the belief in a flat Earth. This is a deeply held and irrational belief. There is no point in talking to these people. I have posted how flawed and more to the point, pointless their experiments are, I get mostly insults.

  21. Funny thing about the "religious motivation" bit is that it isn't really even there. There's a passage in the book of Job (oldest Book in the whole Bible, by the way) that describes the Earth as "turning like clay on a potter's wheel". You know. On its axis.

    The only "flat earth" in the whole silly book is Jesus standing on a mountain seeing all the nations of the Earth, which reeks of allegory if you're not an idiot.

    The simple fact is that the Jews had enough interactions with and respect for the Greeks that a belief in a round Earth likely permeated their culture.

    But seriously, this is actually weird. Like, go outside and tell me you can't feel it on your skin. It's really trippy.

  22. So is moonlight cooler than non-moonlight? Im trying to learn, please dont make me go to my local uni to ask them to test.

  23. Their is more then one video. If you are so convinced one way or another, do the experiment yourself. Post it and lets see. You have already announced your biased attitude, so yours will be under the gavel more then most.

    In Ezekiel 7:2 it is translated “four corners” and again in Isaiah 11:12 “four corners.

  24. This article is a disinformation service, bumped up on the search query 'cold' + 'moonlight', intended as a handle for anyone desperate for something to hang onto. It is a sort of dogmatic scientific sermon, full of credible rhetoric, but containing no real valid information to satisfy actual curiosity.

    Such standardized propaganda is easy to spot from the use of buzz-words like 'lunatic' and 'bunk', which are given to the copywriters to include and turn up over and over in such texts.

    1. Have you heard of Occam's Razor? Because your hypothesis about this post involves a lot of extraneous elements.
      Look really hard at the word "lunacy" and see if you can figure out why I chose it.
      HINT: Latin root words might help.

  25. Interesting. Several people commented that the amateur "scientist" was an interested and motivated experimenter and shouldn't be derided. Nothing could be further from the truth. He confirmed his bias and ignored readings that countered his expectations. What's more, he praises god at the end of the video. End of story.

  26. Whatever... using flat earth to cast a questionable light on this issue... sobif the moon is radiating suns light.. still would make things in direct moonlight slightly warmer... and thank you for the tutorial on the workings of the ir thermometer.. apparently you are the only leraned one here.. if the ir wasnt accurate it would not be used

  27. This question of the moon cooling was brought up on the Atheist Experience show on Sun 17 Jul 2016 by a Muslim caller living in Dubai. The caller's ultimate reason for believing this was the Quran. The caller also believed the moon created its own light. Interesting, doing some google research, many of the page 1 sites on whether the moon creates its own light or not say that the Quran states the moon is reflected light, but this is due to translation, with the Muslim sites trying to shoe horn science saying the moon is reflected light, and those trying to push flat earth ideas saying it says the moon is luminescence.
    But, I was really puzzled that a Muslim living in Dubai would think that moon shade would be warmer than moon light, surely having experienced that sun shade is cooler than being directly in the sun.

    The answer as to what is happening in most of these youTube videos was given by Dr Forrester: "I did go outside and wave around my IR thermometer and I got varying results." Moving the measurement just a short distance with these devices will give different results, and you could find cool or hot spots in and out of shaded or non-shaded areas.

    In doing further google research, I came across a phenomena that might explain why it feels cooler on a moon lit night. When looking upon a moon lit landscape, it will at first appear in shades of gray, there is not enough light for the eyes to make out color. After awhile though, the scene will take on a blue tint. This is called the Purkinje shift or dark adaptation. (This is the new thing I learned!) Although why this happens is not really known, I do know that objects colored blue will be perceived to be cooler. A plate of blue spaghetti will appear colder than a plate of red spaghetti. In other words, being out long enough for this blue shift to occur will make one think it has gotten cooler. This shift may also take place when a body has cooled significantly, adding to the effect, and making it seem like moon light cools things. Also, if the full moon can be seen, then it is probably a cloudless night, or near enough, and the ground will cool more.

    Moon light will actually warm a surface, but in an amount that could not be measured by regular measuring device.

    The ancient Hebrew 'cosmology' envisioned a flat disc with a 'firmament' or dome enclosing it and an underworld below. This was later revised when the Jews lived among the Greeks.

    The Earth is warmer with cloud cover, true, it is acting as a blanket to keep warmth in. But, cloud cover on during the day allows the Earth to cool. Mike W. does have a thought experiment that would make it seem like moon light cooled the thermometer at University of Illinois, Department of Physics.
    The are several Biblical references FEs will point out to maintain their view is correct, such as the description of the Earth as a circle, and the mention of four corners (not sure how they reconcile four corners with a circle).

    Nice try, but what your video shows is a display and you labeling the result of the unseen thing being measured as to whether it was in shade or not by what the display showed. Not good, putting it mildly.

  28. I have uploaded a clip to my channel of the Atheist Experience caller "Ali from Dubai".

    Enjoy the cringe!

  29. How does the FE theory explain the violation to the first and second law of thermodynamics? Where would the heat in those objects illuminated by the moon's light go? How do they explain the transfer of heat going from the hot object to the cold object (whichever it would be)? Even if they admit to not being able to explain it but having empirical evidence, they should be able to prove without using the light from the moon that heat CAN be transferred from colder to hotter...

  30. Same results with normal digital Thermometers :

  31. I just did this experiment last night and used the laser pointer only 14 inches away from the surfaces as instructed by the thermometer
    Far from being a yokel the experiment also proved moonlight makes things colder
    Maybe you should just do the experiment instead of believing ANYBODY
    The thermometers only cost like 15-25 dollars online so do it and stop reading
    Ps: the temperature difference showed up best on black fabric which appeared to soak up the moonlight just as black also soaks up sunlight
    The white paper reflected the moonlight and didn't have as giant a temp difference but it was still clearly there

    1. Syd,
      What is the spot-to-distance ratio on your thermometer?

  32. Syd- can you detail your methodology? How did you control for every other factor that could lead to temperature fluctuations?

  33. Never believe to much you see on youtube, especially when some stupid religion or silly god thing is mentioned. Simply pointing a cheap thermometer at something and recording a lower temp does not prove a thing as there could be so many other factors that influence the final reading. As some one else also stated it goes against the laws of thermodynamics.

  34. As others have said, do the experiment yourself. I've done it several nights now over a period of time and I consistently find the moonlit side of various objects colder, sometimes as much as 5-6 degrees!! I also know how to use an IR thermometer, I use one for work all the time.

    Please don't just believe, but test this it yourself. The most dramatic differences seem to be on clear bright moon nights, near or full.


  35. Apologies Moderator i left out some data in the last post please delete that one.

    I have done this experiment myself with a Fresnel Len (a large magnifying class) it is a spot lens that is very strong and gave me a 4 DEG CEL reading in the hot spot or cold spot  and 12.5 DEG CEL in the shade It sounds crazy because the moon does reflect light from the sun I have observed this being an amateur astronomer, and ancient text such as the book of Enoch says it is so. But I have done the experiment and moonlight is indeed cooler. I know this goes against the scientific principles of energy transfer where light usually makes heat because making something cold takes more energy. Anyway my experiment is at
    And Article is at:

  36. Since you know how to do it right have you done the experiment? Or are you just talking with no evidence

  37. I love how there is no experimentation.

    No results.

    No contrary evidence.

    No counterclaims.

    Just derision of the person trying the experiment.

  38. This person speaks a good talk but has obviously never actually done the experiment, it is easily verifiable and repeatable.

  39. I did this experiment two nights ago at full moon with a temperature sensor LM 35 and an Arduino. The datasheet gives it an accuracy of plus/minus 0.5°C. The results:

    Direct (full) moonlight: 5.6°C
    Shadowed moon: 5.6°C
    Focussed moon light: 6.1°C

    I did not expect anything else but it was fun to give it a shot.