 Greetings and welcome to the Astronomy Picture of the Day podcast. Today's picture for January 22 of 2024 is titled Shadows of Mountain and Moon. So, what do we see here? Well, here we see the moon at first quarter phase up above the mountain, and we note that the shadows are very similar. Now, that should be expected. Why? Because the sun is off to the right on this image, and the sun is what is causing both of these shadows that we see. So, it is illuminating the portion of the moon facing it, and at the same time illuminating the portion of the mountain facing it. So, part of the mountain will be in daylight there, and we see that on the right-hand side of the mountain, and part of it will be in darkness on the left. Well, the same thing happens with the moon, and the moon will be partially illuminated, and that's the right-hand side, and we see that quarter phase of the moon, and the left-hand side of the moon is completely unilluminated, completely not blocked, completely blocked out. Now, you note that we can see some of the side of the mountain, but we're not seeing the moon. Well, some of the mountain is actually illuminated by light that is scattered around from other directions. So, we can see that even though it's in shadow, it's not completely blocked out. The moon actually has the same thing. That darker portion of the moon on the left is actually being illuminated by Earth. However, it is illuminated so much less. It is much less and much fainter that for the exposure it will not show. So, we do get what we call Earthshine, which occurs when light from the sun strikes Earth, bounces to the moon, and then bounces back to Earth. And sometimes we see that when the moon is very faint. That occurs generally at the very thin crescent phases. So, the more of the moon that is illuminated, the brighter it appears, and the more it overwhelms the Earthshine itself. Now, if you'll note at the top of the mountain here, we see some portion of it that is illuminated even on the left-hand side. So, while it looks like there is that dividing line between light and dark, we see some areas that don't quite meet that. Well, some of them sticking up a little bit higher may be up above and are not blocked out from the other partions of the mountain. So, we can see that, and we also see that on craters on the moon. And while we can't see it in this image, there are portions of the moon where the light can strike part of it, or part of things can be illuminated, but not all of them within a crater. For example, a central peak mountain in a crater could be illuminated even though much of the floor of the crater is still in darkness, because it's sticking up higher. We see the same thing on Earth. If you watch the sun as the sun rises or sets, you will note that the sun might not be visible from the ground, but is illuminating high tall trees or other tall objects around. And it then takes a little bit of time for that to work its way down to the ground as, say, the sun is rising, or the sun will disappear as it sets, and we will see darkness on the ground, but some of the trees up higher in the sky and clouds even higher remain illuminated even after the sun itself has set for somebody looking on the ground. So here we get a beautifully framed image showing the half phase of the moon, which we call first quarter, as well as the mountain, and we can see how the shadows are related to each other because they are both caused by light from the sun. So that was our picture of the day for January 22nd of 2024. It was titled Shadows of Mountain and Moon. We'll be back again tomorrow for the next picture, previewed to be Skywide. So we'll see what that is about tomorrow. And until then, have a great day, everyone, and I will see you in class.