This photograph was taken on the moon. The astronaut's shadow on the ground shows clearly that the sun is behind him and about 45 degrees up. He is standing upright. Why then is much of his spacesuit front not also in black shadow?

Ditto the near-facing parts of the moon-buggy on the other side of the crate?

Because God enabled IDL.

There...are...THREE...lights!

Sorry, trying to channel my best Capt. Picard. There are three sources of light in the scene, Not just the one. The sun, the earth, and the ground. The earth and moon, of course, are reflected sunlight And if you're wondering where the earth is, look in the reflection on the helmet visor. It's coming up in front of him and on the horizon, behind whoever took that shot..

[EClark1894]

There are three sources of light in the scene, Not just the one.

Forgive my pedantic nature, but the sun is indeed the only source of light in this scene (ignoring other stars). The rest is reflected light, as you say.

The bright object reflected in his visor, immediately above his own shadow but below the horizon, is an object on the moon surface fully lit by the sun - maybe the other astronaut with a camera, or the giant moon rabbit, or god....

stand in a dark room.

take a torch (flashlight) and point at the wall.

switch on.

there's your answer behind you. surfaces reflect light. infact the Moon itself reflects sunlight.. thats moonlight.

How much does lack of an atmosphere and the moon's material affect the lighting?

But why is the astronaut's shadow on the ground so dark, but the front side of the astronaut, which is equally hidden from the sunlight, is nearly as bright as in a CGI image rendered in "no shadows" mode? Is it earthlight? If the earth is rising there, its light will suffer no horizon haze loss from atmosphere; but how many times brighter is (the Earth as seen from the Moon) than (the Moon as seen from Earth)? (I have seen "the old moon in the new moon's arms" plenty of times, i.e. a crescent moon and the rest of the moon can be seen by earthlight shining on it.)

If the earth is just risen there, its nearly horizontal light would shine much more on the standing astronaut than on the ground; but is not illuminating the front of the rock under the tripod at left foreground anything like as much. And likely the astronaut's spacesuit would reflect much more light than the moon's surface.

And I suppose, that a 4th source of light may be the camera's flash.

Does anyone know where on the moon that image was taken? That will decide where the earth is in the sky.

bagginsbill posted at 10:50PM Fri, 13 May 2016 - #4269005

Because God enabled IDL.

Reply of the Year.

Anthony Appleyard posted at 3:52PM Fri, 13 May 2016 - #4269065

But why is the astronaut's shadow on the ground so dark, but the front side of the astronaut, which is equally hidden from the sunlight, is nearly as bright as in a CGI image rendered in "no shadows" mode?

There are two things going on here. The first is exposure-related. The suits are white. The moon's surface is dark gray. If you look at that large rock on the left that the stand-thingy is on, you'll see the same effect. The rock is slightly lighter than the rest of the surface and on its shadowed side you can just make out some of the detail of the rock, but the shadow on the dirt is nearly pitch black, like Charles Duke's shadow (the flight was Apollo 16, by the by). The white suit is simply reflecting more light.

The second issue is that the photo has been manipulated and its exposure adjusted. John Young was panning across the scene while Duke stopped to watch him film, and the frames of that film were cleaned up and composited into a panoramic image, of which your image is part of. This is what the original imagery looked like, with the frame showing Duke:

You'll note the lens flaring, blowouts, and other image artifacts that were corrected (such as the removal of the image number at the bottom and the focus crosses from the camera.)

Oh, and that this is in colour (note that you can see the gold in the visor reflection).

[icprncss2]

How much does lack of an atmosphere and the moon's material affect the lighting?

You can see from the image - in spite of the bright sunlight the sky is black, because there is no atmosphere to refract and reflect the sunlight like on Earth. For planets and moons with no atmosphere, the sky is perfectly black both day and night.

But why is the astronaut's shadow on the ground so dark

There is no ambient light from the sky, so nothing to soften the shadows, except perhaps some earthlight, but that's not especially bright.

but the front side of the astronaut, which is equally hidden from the sunlight, is nearly as bright as in a CGI image rendered in "no shadows" mode

The surface of the moon is mostly a fine sand, with lots of diffuse reflection. Surfaces above the ground are strongly illuminated by this reflected light, even when in complete sun shadow.

By the way, the moon moves in 'synchronous rotation' with (or: is 'tidally locked' to) the Earth, meaning that it rotates around its axis in the same time that it takes to orbit around the Earth, and in the same direction - anti-clockwise when viewed from the North. This means that we only ever see the same face of the moon, as I'm sure you already knew (although due to lunar libration it appears to 'wobble' by several degrees N-S and E-W, so that we get to see up to about 59% of its surface over time).

This also means that when viewed from any point on the moon the Earth doesn't move around much in the sky - only a few degrees over time due to lunar libration. It doesn't rise and set like the sun and moon do when viewed from the Earth. Any references to 'Earthrise' or 'Earthset' on the moon are from the viewpoint of an orbiting craft, not from a point on the moon's surface.

Is this an Apollo 11 photo? If so, the Apollo 11 landing site was in the Sea of Tranquility around 24 degrees from the central point of the moon's visible face. This means that the Earth would have been at an altitude of around 66 degrees, not on the horizon.

EDIT: I just read the above post.. so it was Apollo 16, not 11. The Apollo 16 landing site was somewhat closer to the centre of the moon's face, so the Earth would have been at a higher altitude.

Thanks.