<p>As discussed in <a href="https://space.stackexchange.com/questions/20143/which-apollo-mystery-was-said-to-be-finally-solved-by-a-better-rendering-engin/20145#20145">a previous question from this Stack</a>, back in 2014, NVidia recreated the famous photo of Buzz Aldrin exiting the lunar module, using their hardware to simulate the different sources of light in the scene. <a href="https://www.youtube.com/watch?v=O9y_AVYMEUs" rel="noreferrer">Here's a link to the youtube video.</a> I think this is a useful visualization for this question, because it allows us to separate out the different sources of light on the moon in a way that we can't with real photos.</p>
<p>This pair of images shows the scene while calculating only the direct light from the sun, then adding in the reflected light from the objects in the scene (including the surface, parts of the lander itself, and Buzz's space suit).
<a href="https://i.sstatic.net/GpZff.gif" rel="noreferrer"><img src="https://i.sstatic.net/GpZff.gif" alt="The lander in silhouette, and then pretty well lit." /></a></p>
<p>Comparing those two alone, I think it's clear there's plenty of scattered light from the surface to read by. Even with its 0.12 albedo, there's a lot of reflected light in the scene.</p>
<p>But wait, there's more, because what they found was they also needed to account for Neil Armstrong's white suit just behind the camera acting like a fill-lighting reflector.
<a href="https://i.sstatic.net/oms8a.gif" rel="noreferrer"><img src="https://i.sstatic.net/oms8a.gif" alt="The same scene but much better lit in the deeply shadowed areas." /></a></p>
<p>If our lunar bookworm was wearing a white or otherwise reflective suit, that could provide even more light to read by.</p>

CC BY-SA 4.0
2024-12-19T16:36:37.110Z
2024-12-20T13:30:46.533Z
2024-12-20T13:30:46.533Z
Darth Pseudonym
<p>Some people find it <a href="https://boards.straightdope.com/t/can-you-read-by-moonlight/633086/2" rel="noreferrer">possible to read</a>, with difficulty, by the light of the full moon on earth. As you get closer to the moon, the total brightness only goes up. On the moon, there would be no problem, even if your suit were coated with Vantablack.</p>
<p>This may be surprising, since the moon's surface, in an absolute sense, is dark gray, often described as being roughly the color of asphalt. But the human eye adjusts to a huge range of brightness levels; light that is ten times dimmer than direct sunlight is still quite easy to see by.</p>

CC BY-SA 4.0
2024-12-22T02:09:12.643Z
This is a really neat way to solve the problem without doing pesky math :)
Benjamin Kuykendall
CC BY-SA 4.0
2024-12-22T10:14:21.020Z
1000 times less than the direct sunlight brightness is still pretty much OK illumination for a habitable room or a workplace.
fraxinus
CC BY-SA 4.0
2024-12-21T14:40:56.793Z
2024-12-21T14:40:56.793Z
Mark Foskey
<p>Super back-of-the-envelope calculation, but it should at least be within a few orders of magnitude, which as we shall see is sufficient.</p>
<ul>
<li>Consider the intensity on earth of the light of the full moon.</li>
<li>The surface area of the moon is roughly 37,930,000 km², so the area reflecting light to the earth is roughly 19 million km².</li>
<li>The distance to the lunar horizon at 1 m elevation is roughly 1.86 km, giving a visible area of about 10.9 km².</li>
<li>The ratio between the area illuminating the book and the area illuminating the earth is around 5.73 × 10⁻⁷.</li>
<li>The average distance between the moon and the earth is 384,400 km.</li>
<li>The ratio between 384,400 km and 1 m is 384,400,000.</li>
<li>The intensity of light is proportional to the square of the distance.</li>
<li>The reflected light on the moon is roughly 1.48 × 10¹⁷ times as intense as the reflected light on earth, but the surface
area is roughly 5.73 × 10⁻⁷ times as great.  The product of these
factors is 8.47 × 10¹⁰.</li>
</ul>
<p>Now this is a huge figure, and I'm sure I've overlooked many things, and I suspect very strongly that the actual figure is rather smaller, but it seems nonetheless highly likely that the reflected light illuminating the book is considerably more intense than the light of even the brightest full moon.</p>
<p>Of course, unlike the light of the full moon, this light is probably competing with light reflecting off of much more reflective surfaces, and struggling to make it through your gold-coated spacesuit visor and your constricted pupils and to register on your bright-adapted retina, so whether it's enough to read by is a question that requires additional analysis.</p>

CC BY-SA 4.0
2024-12-21T10:46:43.317Z
The light will be as intense as a full moon, but standing on the surface the full moon will thousands of times larger.
Jasen
CC BY-SA 4.0
2024-12-20T12:40:52.980Z
2024-12-21T15:11:02.120Z
2024-12-21T15:11:02.120Z
phoog
<p>Imagine you are on the (day-side) surface of the Moon, trying to read a book. You are oriented so that no direct sunlight reaches the pages (i.e. with the book cover facing the Sun). Since the Moon has no atmosphere, you cannot rely on scattered light, but... would the light reflected by the Moon surface do the job?</p>

CC BY-SA 4.0
2024-12-19T16:14:35.687Z
So you're laying on your back and holding the book up between your face and the sun, and trying to read -- is that right? Also, are we counting only the reflections from moon dust? Because as mentioned in [a previous question from this stack](https://space.stackexchange.com/questions/20143/which-apollo-mystery-was-said-to-be-finally-solved-by-a-better-rendering-engin/20145#20145), the light reflecting off a white space suit can be a very significant contributor to lighting on the moon.
Darth Pseudonym
CC BY-SA 4.0
2024-12-19T16:17:02.083Z
This is one of my favorite moon photos, and it clearly shows there's a huge amount of light on the "shadowed" side of Buzz, but Neil and the lander are both on that side of Buzz so you aren't getting just the light from surface scattering. https://www.nasa.gov/image-article/buzz-aldrin-moon/
Darth Pseudonym
CC BY-SA 4.0
2024-12-22T16:11:47.900Z
No, because your eyes would adapt to the light levels being reflected by your surroundings.
Jack Aidley
CC BY-SA 4.0
2024-12-23T13:46:57.517Z
Look down on a fully sunlit dark grey gravelly patch of ground and then look up at the sky.  The two have roughly the same surface brightnesses.
eshaya
<the-moon><light><space><visible-light>
Would reflected sunlight suffice to read a book on the surface of the Moon?
summer
# Would reflected sunlight suffice to read a book on the surface of the Moon?

(Asked by: username_0 on 2024-12-19)

Imagine you are on the (day-side) surface of the Moon, trying to read a book. You are oriented so that no direct sunlight reaches the pages (i.e. with the book cover facing the Sun). Since the Moon has no atmosphere, you cannot rely on scattered light, but... would the light reflected by the Moon surface do the job?

**Tags:** the-moon, light, space, visible-light
> **Comments:**
> **username_1**: So you're laying on your back and holding the book up between your face and the sun, and trying to read -- is that right? Also, are we counting only the reflections from moon dust? Because as mentioned in [a previous question from this stack](https://space.stackexchange.com/questions/20143/which-apollo-mystery-was-said-to-be-finally-solved-by-a-better-rendering-engin/20145#20145), the light reflecting off a white space suit can be a very significant contributor to lighting on the moon.  
> **username_1**: This is one of my favorite moon photos, and it clearly shows there's a huge amount of light on the "shadowed" side of Buzz, but Neil and the lander are both on that side of Buzz so you aren't getting just the light from surface scattering. https://www.nasa.gov/image-article/buzz-aldrin-moon/  
> **username_2**: No, because your eyes would adapt to the light levels being reflected by your surroundings.  
> **username_3**: Look down on a fully sunlit dark grey gravelly patch of ground and then look up at the sky.  The two have roughly the same surface brightnesses.  

---

## 3 answers

### Answer by username_1 on 2024-12-19. Score: 33

As discussed in [a previous question from this Stack](https://space.stackexchange.com/questions/20143/which-apollo-mystery-was-said-to-be-finally-solved-by-a-better-rendering-engin/20145#20145), back in 2014, NVidia recreated the famous photo of Buzz Aldrin exiting the lunar module, using their hardware to simulate the different sources of light in the scene. [Here's a link to the youtube video.](https://www.youtube.com/watch?v=O9y_AVYMEUs) I think this is a useful visualization for this question, because it allows us to separate out the different sources of light on the moon in a way that we can't with real photos.

This pair of images shows the scene while calculating only the direct light from the sun, then adding in the reflected light from the objects in the scene (including the surface, parts of the lander itself, and Buzz's space suit).
[![The lander in silhouette, and then pretty well lit.](https://i.sstatic.net/GpZff.gif)](https://i.sstatic.net/GpZff.gif)

Comparing those two alone, I think it's clear there's plenty of scattered light from the surface to read by. Even with its 0.12 albedo, there's a lot of reflected light in the scene.

But wait, there's more, because what they found was they also needed to account for Neil Armstrong's white suit just behind the camera acting like a fill-lighting reflector.
[![The same scene but much better lit in the deeply shadowed areas.](https://i.sstatic.net/oms8a.gif)](https://i.sstatic.net/oms8a.gif)

If our lunar bookworm was wearing a white or otherwise reflective suit, that could provide even more light to read by.


---

### Answer by username_4 on 2024-12-21. Score: 7

Some people find it [possible to read](https://boards.straightdope.com/t/can-you-read-by-moonlight/633086/2), with difficulty, by the light of the full moon on earth. As you get closer to the moon, the total brightness only goes up. On the moon, there would be no problem, even if your suit were coated with Vantablack.

This may be surprising, since the moon's surface, in an absolute sense, is dark gray, often described as being roughly the color of asphalt. But the human eye adjusts to a huge range of brightness levels; light that is ten times dimmer than direct sunlight is still quite easy to see by.

> **Comments:**
> **username_5**: This is a really neat way to solve the problem without doing pesky math :)  
> **username_6**: 1000 times less than the direct sunlight brightness is still pretty much OK illumination for a habitable room or a workplace.  

---

### Answer by username_7 on 2024-12-20. Score: 7

Super back-of-the-envelope calculation, but it should at least be within a few orders of magnitude, which as we shall see is sufficient.

* Consider the intensity on earth of the light of the full moon.
* The surface area of the moon is roughly 37,930,000 km², so the area reflecting light to the earth is roughly 19 million km².
* The distance to the lunar horizon at 1 m elevation is roughly 1.86 km, giving a visible area of about 10.9 km².
* The ratio between the area illuminating the book and the area illuminating the earth is around 5.73 × 10⁻⁷.
* The average distance between the moon and the earth is 384,400 km.
* The ratio between 384,400 km and 1 m is 384,400,000.
* The intensity of light is proportional to the square of the distance.
* The reflected light on the moon is roughly 1.48 × 10¹⁷ times as intense as the reflected light on earth, but the surface
  area is roughly 5.73 × 10⁻⁷ times as great. The product of these
  factors is 8.47 × 10¹⁰.

Now this is a huge figure, and I'm sure I've overlooked many things, and I suspect very strongly that the actual figure is rather smaller, but it seems nonetheless highly likely that the reflected light illuminating the book is considerably more intense than the light of even the brightest full moon.

Of course, unlike the light of the full moon, this light is probably competing with light reflecting off of much more reflective surfaces, and struggling to make it through your gold-coated spacesuit visor and your constricted pupils and to register on your bright-adapted retina, so whether it's enough to read by is a question that requires additional analysis.

> **Comments:**
> **username_8**: The light will be as intense as a full moon, but standing on the surface the full moon will thousands of times larger.  

---

