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Sunday, August 21, 2016

Flat Earth Follies: Moonlight is cold light

I can't even believe we have to have this conversation but apparently we do.

I have a Tsing 300 infrared thermometer that I use for both cooking and A/C analysis around the house. It's an inexpensive model but gets the job done. It reads a 1" spot at 1' - I took readings at this distance.

So I went outside on a heavily cloudy night (so there was absolutely no moonlight to magically cool things down) and started testing the temperature of various objects in various locations.

First object is a painted railing inside a stairwell. Still night air, all measurements taken on parts of the rail shaded from the two 60 watt bulbs that are pretty far away.

Bottom: 69 degrees
Middle: 70.7 degrees
Top: 75.1 degrees

So height seemed to matter a lot (for this spot, we can't assume this always holds), 6 degree increase over approximately 19.25 feet. So that's one possible source of error.

Down at ground level, far away from any building or lights I then took several measurements of the ground.

Open to the sky: 69.4
Just in shade of tree: 69.9
Ground closer to tree: 70.4

So NO moon light and it's warmer under the tree at night.  But if I ONLY took these same measurements in moonlight I might incorrectly attribute this to the moonlight. That would be a FALSE conclusion.

Next, I walked around an area equally open to the sky and took ground temperature measurements over an approx 50' circumference, I got:


So every few feet I got different readings, up to a 5 degree swing, even a 4 degree swing in two spots not far from each other.

So this tells me that even very local conditions can vary greatly and magical 'lunar light cooling' has NOTHING WHAT-SO-EVER to do with it.

I was also able to easily reproduce it being warmer under a tree without any moonlight so it doesn't matter WHY it can be warmer under something than in the open air, we know that moonlight cannot be assumed to be the cause.

It could be biological activity, it could reduce the effects of wind, it could be higher humidity, or all of the above. Every spot is probably different.

In short, people claiming the moonlight has a cooling effect failed to have any control data.

This is why science exists - to study the ways we FAIL and make sure to avoid repeating those errors in the future. Sadly our Flat Earth friends eschew science and so repeat even the most gratuitous failings of our past.

This failure is the very tempting Post hoc ergo propter hoc fallacy, "I moved the thermometer out of the moon light and the temperature increased, therefore the moonlight was cooling it down!" but this experiment clearly shows no such thing.


  1. These devices typically have an error range of 1-2 degrees, probably in part for some reasons noted

    1. Yes, I didn't talk about the margin of error here but that is always an important consideration.

      "Any measurement that you make, without knowledge of the uncertainty, is meaningless." ~ Walter Lewin

      And if you wanted to prove the cooling effect of moonlight you would need to show #1 it requires moonlight (I showed it didn't) and #2 that your measurements exceed your margin of error and natural temperature variations.

    2. I did the test, measuring it directly, using an all mirror telescope.
      The moon is indeed warmer than dark space around it.
      My signal to strength is way above margins of errors.

  2. I'm pretty sure it's just due to the fact that night is opposite of day. Sun is opposite of moon. And the effects are opposite from each other as well. Daytime shade is cooler. Nighttime shade is warmer. Daytime direct sunlight is warmer. Nighttime direct moon light is cooler. The sun produces its own light. The moon doesn't.

    1. I think it's because the objects around a shaded space are warmer than the cooler air overhead. When open to the sky the ground and air in that area can better radiate away their warmth to the cooler open sky.

  3. 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:

  4. So did you find out? I've seen some videos on YouTube where it 'seems' pretty concrete that moonlight is colder than shade


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