 Greetings and welcome to the Introduction to Astronomy. In this lecture we are going to talk about the moon landing, and did we actually land on the moon? Now let's take a look at what we know here, and what we'll see. First of all, let's talk about the Apollo missions. There were six missions that landed on the moon. That was Apollo 11 and 12, and Apollo's 14 through 17. Apollo 13 is the one that had an incident on the way to the moon and was never able to land there. These occurred between July of 1969 and December of 1972, and during that time 12 astronauts walked on the surface of the moon, and a number of others either flew around the moon or stayed up in orbit, as in each mission one astronaut would remain in the command module orbiting the moon while the other two explored the surface. But even decades and decades later now, there are those who doubt whether these actually occurred. So we have images, let's take a look at one here, and here we see one image of this landing. Here is an image from the lunar orbit seeing the moon as a little over half phase, little over half illuminated. And we also have, of course, images from walking on the moon. So here we see an image of one of the astronauts with the lunar lander and some of the equipment here. So what is some of the evidence that we did land on the moon? Well, certainly we have the direct observations of the astronauts. We have moon rocks, such as the one shown that have been returned to Earth. And we have things like the landing sites that have been seen by the lunar reconnaissance orbiter. So here we can see the landing site with the lunar module there and various other equipment that was left behind. You could even see a little bit of the paths that astronauts took here, and, for example, out to exploring another crater. However, of course, these cannot be seen from Earth. They're much too small to be seen, even with a powerful telescope from Earth. So could this be faked? Well, I would say no, but certainly the evidence that I'm giving you here is not going to convince anyone who really believes that it is a conspiracy or hoax. So the fact that there are moon rocks, how do you tell the difference between a moon rock and an Earth rock? Well, it requires scientific tests that were done, and, of course, if you believe that those are faked, then obviously you're not going to assume that the rest of it is faked as well. So specifically these are not going to convince anyone that believes it is a hoax. So what is some of the things that are often given as evidence for the hoax? Well, you see images like this where there are no stars in the sky. So why don't we see stars in the sky? It's nighttime there. And we do see stars in the sky, not in this image, but we do see them in other images, and such as this one also taken from the moon, looking out toward Earth and seeing a number of the stars in the sky. The difference is that you have a big bright area on the lunar surface. So when you're looking at the moon, the moon is relatively bright and very glaring. So you're not going to see the much fainter stars in the sky when you have the moon in the image as well. So it's going to be how bright it would be looking out as if you go out on a snowy day, even though it will look incredibly bright, and it makes it harder to see fainter objects. Well, the same kind of thing is happening here. There's simply not enough contrast to be able to pick up the stars in the same image. Is the flag waving? Well, it sure looks like it's waving here in this image. However, that is due to the fact that there is no atmosphere on the moon, and if you did not have this bar up at the top up here, then the flag would just hang straight down. So that is holding it up, and on the first one the bar kind of jammed, preventing it from extending fully, and that left the flag a little bit rippled, which makes it look like it's waving. However, we can also look at this another way, and we can look at two images together, side by side taken one after another, and you can see that the astronaut moved slightly between the images, but the flag remains essentially unchanged. It's barely any difference. You can see the flag looks exactly the same. Whereas the astronaut is moving and has moved slightly between these two images taken close together. Now, we can also... What about the moon rocks? We have lots of moon rocks that have been brought back to Earth, and there is a thought that some of them seem to have prop numbers listed on them. One especially would be the one shown here, which certainly looks like it has a C on it. However, that is not on the original images of that same rock, so it's not going to be a prop number. It's probably some kind of piece of hair that got stuck in the print when it was being done, or some kind of defect within that print as it was being made. So no evidence that there are actually prop numbers there. And we've seen lots of astronauts, and we haven't seen anybody carrying a camera around to take these pictures. Well, part of it was that the astronaut could not free up their hands, needed their hands for other things, so the camera is actually built into the spacesuit here. So they could take the pictures that way of each other, and that's where the camera is that is taking the images. It's actually built into the spacesuit because the astronauts were trying to be able to move around so to make things as efficient as they could and leave their hands free for other things that would be built in. Now, let's go ahead and look at our last piece here. How about objects illuminated in shadows? Well, we would say on the moon you shouldn't see anything in the shadowed regions. So we have the sun here. You can see the shadow being cast down this way, and you can see that the sun is therefore up to the upper left-hand side. Now, how is part of the lunar rover and part of the astronaut? You would think that the part in shadow would be completely dark. However, it won't be because you will also get scattered light from the ground. Light from the ground is also being scattered up and indirectly illuminating those regions in shadow. So they are not completely dark shadows, but do have some light traveling within them. So since there's some light there, objects in shadow will still be visible. A few other thoughts would be we have the reflectors on the moon so that we can send signals back and forth. We can look at the radio transmissions that occurred from the moon. Now, we think about this back in the late 1960s, early 1970s, we'd have known these had to have come from the moon because we weren't the only people monitoring them. So would other countries at the time, we were in the middle of the Cold War, and if the United States had been faking this, then the Soviet Union probably would not have wasted any time pointing that out to the rest of the world. So it would have involved a conspiracy here, involves not just the United States, but also the Soviet Union being involved, and at that time, I'd not likely that the two were going to be working together on something like this. Communications delay. Well, when we speak to astronauts on the moon, there's always a little bit of a delay between when signals are sent and when signals are received. On my left hand, I have a feather. On my right hand, a hammer. And I guess one of the reasons we got here today was because of a gentleman named Galileo a long time ago who made a rather significant discovery about falling objects in gravity fields. And we thought that where would be a better place to confirm his findings and on the moon. And so we thought we'd try it here for you. The feather happens to be appropriately a Falcon feather for our Falcon. And I'll drop the two of them here and hopefully they'll hit the ground at the same time. How about that? How about that? Mr. Galileo was correct in his findings. So we see there a couple of things. First of all, note that they fell at a much slower rate than you would expect on Earth. If you drop something heavy like a hammer, it falls a lot faster than what we saw in the image here. Gravity on the moon being one sixth, it will fall a lot slower. It'll take it six times longer to reach the ground on the moon than it would on Earth. And you also noted a little bit of that communications delay at the end from the time they hit the ground. It was about two and a half seconds before those on Earth actually commented. So that took them time to see it, a second, a little over a second, and then to respond, and then for that signal to get back to us. So it takes multiple times for us to be able to get those signals. So let's go ahead and finish up with our summary and what we've looked at this time is that between 1969 and 1972 there were 12 astronauts that walked on the moon and to this day we still have some who believe that these moon landings never occurred. However, to doubt these really requires you have to disbelieve that everything NASA and other space agencies have ever done. So if you have to really believe that it's not just a conspiracy of NASA but it has to be everything including a lot of countries that don't necessarily get along well together to put all of this together to make the moon landings a hoax. So that concludes this lecture on did we land on the moon. We'll be back again next time for another topic in astronomy. So until then, have a great day everyone and I will see you in class.