One of our readers asked us this question. What would happen if the moon was covered with a highly reflective material (such as tin foil)? Would the earth be lit all day? How would this affect our daily life?

Short answer: During full moons it would be about 8x brighter.

Bright Moon

Long answer: The albedo of a body determines how much light it reflects. For the moon, that number is about 0.1, meaning that it reflects about 10% of the light. This book has a nice table of albedos for various building materials, including “bright aluminum foil,” which it lists an albedo of 0.8, or 80%.

Therefore, the moon now reflects 8x more light. Depending on the moon phase, we’ll receive variable amounts of light on the earth. For reference, I want to show your some numbers for the luminous flux (or lux) or various light sources. Although this sounds like what a mad scientist might call his death ray, I assure you this just means how much light we get on a given area.

Anyway:

Cloudly, moonless night: 0.0001 lux
Full moon: 0.27–1.0 lux
Twilight: 3.4 lux
Full moon (with aluminum foil): 2.2-8.0 lux
Dim Office Building Hallway: 80 lux
Sunrise/Sunset: 400 lux
Direct sunlight: 32000–100000 lux

Blue Sky

So you’ll easily be able to see at night provided there is moonlight. Since the full moon is now considerably brighter than twilight, I’d suspect the sky would take on more of a navy blue color and that we’d have fewer stars visible in the night sky. The Milky Way is already quite hard to see when there is moonlight, and with a foiled-moon it will be a sight reserved for the few moonless nights each month.

Earth Shine

Even the light from a crescent moon covered in aluminum foil is brighter than a full moon without one. Fun fact: you can actually see the dark part of the crescent moon even without aluminum wrapping. Even though the dark part is not receiving direct sunlight, it’s being illuminated by sunlight reflected from the earth (in much the same way the earths get a little bit of light from the moon). This is called earth shine, and would be easily resolvable at night, and it might even be possible to see it during the day.

Categorized in:

Fact List, Whatif,

Last Update: April 25, 2016

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