<p>The strength of the light from the Sun scales with the inverse square of distance [note 1]. That means that we would need to have the Earth-Moon system at $\frac{1}{\sqrt{2}}$ (approx 0.7) AU for the full Moon to be twice as bright [note 2].</p>

<p>Note 1: The fact that the Sun is not a point source of light has only a very minor effect on the scaling.
Note 2: Technically, it will be slightly brighter because more of the absorbed radiation will be radiated away in the visible spectrum. This is however also a negligible effect.</p>

CC BY-SA 3.0
2016-04-08T09:56:09.317Z
I can't understand why you answer $ \frac { 1 } { \sqrt { 2 } } $, would you please explain more?
user115608
CC BY-SA 3.0
2016-04-08T10:52:39.250Z
@user115608 "The inverse of the square root of how much more light."
SE - stop firing the good guys
CC BY-SA 3.0
2016-04-08T11:07:44.500Z
"The strength of the light from the Sun scales with the inverse square of distance",why it is so?
user115608
CC BY-SA 3.0
2016-04-08T11:24:17.717Z
@user115608 Check out the inverse square law here: https://en.wikipedia.org/wiki/Inverse-square_law
SE - stop firing the good guys
CC BY-SA 3.0
2016-04-09T07:02:56.483Z
Coincidentally, that close to the orbital distance of Venus. If you doubled tge the brightness of the moon like this you also double the brightness of the sun, and probably cook most of life on Earth.
James K
CC BY-SA 3.0
2016-04-09T07:06:59.167Z
@JamesKilfiger Minor side effect.
SE - stop firing the good guys
CC BY-SA 3.0
2016-04-08T08:46:58.787Z
2016-04-08T08:46:58.787Z
SE - stop firing the good guys
<p>If we want the full moon to be 2 times more bright,how we should change the distance between the sun and the earth? </p>

<p>Thanks for your help. </p>

<the-sun><the-moon><light><luminosity>
The relation between the light of full moon and the distance between the sun and the earth
Rsm
# The relation between the light of full moon and the distance between the sun and the earth

(Asked by: username_0 on 2016-04-08)

If we want the full moon to be 2 times more bright,how we should change the distance between the sun and the earth?

Thanks for your help.

**Tags:** the-sun, the-moon, light, luminosity


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## 1 answers

### Answer by username_1 on 2016-04-08. Score: 2

The strength of the light from the Sun scales with the inverse square of distance [note 1]. That means that we would need to have the Earth-Moon system at $\frac{1}{\sqrt{2}}$ (approx 0.7) AU for the full Moon to be twice as bright [note 2].

Note 1: The fact that the Sun is not a point source of light has only a very minor effect on the scaling.
Note 2: Technically, it will be slightly brighter because more of the absorbed radiation will be radiated away in the visible spectrum. This is however also a negligible effect.

> **Comments:**
> **username_2**: I can't understand why you answer $ \frac { 1 } { \sqrt { 2 } } $, would you please explain more?  
> **username_1**: @username_2 "The inverse of the square root of how much more light."  
> **username_2**: "The strength of the light from the Sun scales with the inverse square of distance",why it is so?  
> **username_1**: @username_2 Check out the inverse square law here: https://en.wikipedia.org/wiki/Inverse-square_law  
> **username_3**: Coincidentally, that close to the orbital distance of Venus. If you doubled tge the brightness of the moon like this you also double the brightness of the sun, and probably cook most of life on Earth.  
> **username_1**: @JamesKilfiger Minor side effect.  

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