- #1

zdcyclops

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If the moon were a light bulb how many watts would it be.

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- Thread starter zdcyclops
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- #1

zdcyclops

- 15

- 5

If the moon were a light bulb how many watts would it be.

- #2

hyunxu

- 57

- 16

More than 2.345E watts it may be.But still need to research because moon is non-luminous and glows with help of sunlight.If the moon were a light bulb how many watts would it be.

- #3

.Scott

Science Advisor

Homework Helper

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Average lunar albedo is 12%. Solar intensity is about 1050 W/m^2.If the moon were a light bulb how many watts would it be.

Lunar diameter is 3474 Km.

So: about 0.12 * 1.05 * pi * 3.474^2 *1,000,000 KW

That's excluding illumination from Earth.

Roughly 4.8 GW

- #4

- 17,806

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I arrived at 1,200 TW with your calculation: ##0.12 \cdot \pi \cdot r^2 \cdot 1.05\, kWm^{-2}## with ##r=1,737,000 \,m##Average lunar albedo is 12%. Solar intensity is about 1050 W/m^2.

Lunar diameter is 3474 Km.

So: about 0.12 * 1.05 * pi * 3.474^2 *1,000,000 KW

That's excluding illumination from Earth.

Roughly 4.8 GW

But I haven't checked, whether the ##1,05 \,kWm^{-2}## fits to the 400 trillion trillion watts they've claimed here for the sun.

- #5

berkeman

Mentor

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Do you mean the total effective luminous power of the Moon, or do you mean what size lightbulb would be the equivalent of the Moon's illumination through a window in your home at night?If the moon were a light bulb how many watts would it be.

https://www.coopersofstortford.co.uk/images/products/large/st09845i.jpg

- #6

- 3,755

- 1,730

We are 384,000 km from the Moon, so that's 5.6e17 lumens total spread out over a the surface of a sphere with a radius equal to the Earth-Moon distance.

If we are going to treat this like a normal light bulb radiating in all directions, then this is would be the total Lumen output, but if we are only going to treat the Sunlit side of the Moon, we can divide this in half. (I'm ignoring any losses caused by the light passing through the atmosphere).

How much wattage this equates to for a light bulb depends on its efficiency. An incandescent bulb produces about 15 Lumens per watt, but an LED bulb typically produces 80 lumens per watt.

If you are talking about what would be the equivalent for a standard light bulb at typical distances, 0.3 lux is about as much light as you would get from a single 60 watt incandescent bulb at a distance of 14.6 meters or a 1/4 watt incandescent at a distance of 1 meter.

- #7

- 17,806

- 19,004

Going in the opposite direction, The illuminance of a full Moon on a clear night can be 0.3 lux or 0.3 lumen/m2

We are 384,000 km from the Moon, so that's 5.6e17 lumens total spread out over a the surface of a sphere with a radius equal to the Earth-Moon distance.

That makes ##37,300 \,TW## resp. ##7,000 \,TW##. The previous calculation with the albedo gave ##1,200 \,TW##. The gap is closing down. A factor between ##1## and ##30## seems acceptable considering the overall dimensions.How much wattage this equates to for a light bulb depends on its efficiency. An incandescent bulb produces about 15 Lumens per watt, but an LED bulb typically produces 80 lumens per watt.

- #8

zdcyclops

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- #9

- 3,755

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That entirely depends on the size and type of light bulb. A typical 60 watt bulb is ~3 cm in radius, and if perfectly circular have a surface area of 57.8 cm

If 0.3 lumen/m

- #10

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This makes zero sense. The moon is not a light source.

If you are asking about how much light is reflected off the moon's surface from the sun, than

Zz.

- #11

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If the moon were a light bulb how many watts would it be.

None, surely?

"There is no dark side of the moon. As a matter of fact, it's all dark!"

- #12

zdcyclops

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- #13

berkeman

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Ah, thanks for clarifying. We don't discuss or debunk nonsense here at the PF. Thread is done.

- #14

jim mcnamara

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The moon does not emit visible light like a light bulb.

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