 Hello everyone. Happy Easter to those who celebrate it. I guess those really celebrated aren't here. Before I get started let me tell you about my super power and I use that in quotes. When I use certain software for the first time I almost always find some bug that results in me wasting time trying to fix it and needing help from some expert. Yes I know it's a very lame superpower. But at least I leave a trail of of known software bugs in my wake. Like this screen behind me it needs my avatar name so that I can control it. It would not work for me until it was discovered that my avatar name was too long. I had to change my avatar name. I mean it was many thanks to tagline. Tagline spent a lot of time helping me to land on it as well. Also thanks to Chantel who invited me to speak. I've been wanting to try this. In fact I've been preparing a presentation on celestial orbits and I normally take months to do it. So that one won't be ready for a few months yet. I still have much to learn. And then last Sunday Chantel invited me to speak about the moon on Easter. What seven days to prepare? No she said I have a choice. I can speak on Friday or Saturday so that's five or six days instead of seven. Just peachy. But it's it's holy week for in a number of countries including Mexico, Samantha. So yes there's there are fewer distractions so I was able to do this. Required much cutting and pasting from the internet. Mostly Wikipedia's articles about the moon. No diagrams of my own here. And I am grateful for this opportunity to speak so even though I'll be saying things like if I've had more time I could have done this or that. I'm actually not complaining. I'm really advertising my next presentation. I think this presentation is great. Then you'll really love my next one. Actually because I have more time for that one. So talking about the moon on Easter is appropriate. Given that Easter Sunday is defined as the first Sunday after the first full moon of spring. I'll be talking a bit about that later on. Also there are more than a hundred moons in our solar system and so I wanted to be very specific by using a name for the one I'm talking about. So I use the Latin name Luna which is also incidentally the Spanish name for the moon. But I could have used this Greek name. I could say Salim Earth's moon which is the Greek goddess of the moon in Greek mythology. I should point out I'm not an expert on the moon. I'm not a selenologist. I'm really an interstellar matter kind of guy. I specialize in observing molecular clouds in nearby galaxies. My name is William Wall. I'm a researcher at the National Institute of Astrophysics, Optics, Electronics and Tone and Seamplip, Webb, Mexico. Here's a picture of me in in Cyprus Falls Park in West Vancouver. My wife took this picture of me last year and as you can see my shirt has a fresh set of batteries because it's glowing nicely and nice healthy green color. You can see it from here. Here it is the large millimeter telescope Alfonso Serrano. This is about a two hour drive from our our institute. It's the largest telescope of its kind. Filled aperture 50 meter aperture for observing at wavelengths of one to four millimeters for observing molecular lines in the interstellar medium. It's on Sierra Negra which is a dormant volcano or extinct. I hope it's extinct volcano but I think it's dormant. It's next to a dormant boulder as well. This has an adaptive surface so that the primary surface actually has panels that can be reshaped to compensate for distortions in the back structure. So it maintains this parabolic shape and it was an element in the event horizon telescope that imaged the black hole in the galaxy m87 and no I'm not part of that collaboration. So getting onto the moon here's a photo of the near side of the moon and the far side of the moon. This I believe was taken with the lunar reconnaissance orbiter the LRO and you can see let's see one side is permanently fixed towards us. This is the near side and this away from us with a thicker crust. There you see thin areas of the inner crust. They're called the lunar seas the maria and why the moon has two different faces like this and why one side is locked towards the earth is because of tidal locking and I'll discuss that later. I mean this whole topic is far too vast to do at justice in only one hour. You really need full length courses including lunar geology, lunar missions, and maybe even on the lunar orbit itself. So today I'm only going to touch on certain highlights that I consider to be important or that I consider to be the most interesting my point of view. This is the basic outline. Start with the motivation why this subject is interesting lunar basics basic details formation and structure of the moon. The moon's orbit about the earth missions to the moon. I won't talk much about these there have just been so many I'll just point out how many they've been there have been that it's just really impressive. The future of humanity in the moon and here's a really cool photo of the moon. I like this because right there that little dot right there I'm going to move this out of the way but you know that little dot that's the international space station which is orbiting the earth not the moon but it is passed in front of the moon. Another interesting thing to notice is that these maria at this particular orient are a serenitatus andatatus and qualitatus you can almost use that like a hands of a clock almost see so it's pointing sort of at two o'clock you have to add two so it's like four in the morning and check here oh it's four in the morning okay I'll sort of use this as a clock anyway let's check is the far side hit by more meteors oh yeah I like the jokes I'm coming to the jokes as a matter of fact yeah so I decided to build a restaurant on the moon the food is great but there's no atmosphere and how does the man on the moon cut his hair he clips it that was from a nine-year-old shot anyway the point I'm making there is that the moon has been a part of our culture for a long time and there are a number of things that we've done because of the moon inspired by the moon including including jokes great jokes and bad jokes too okay um yeah the near side does look more interesting this is the far side hit by more meteors uh I don't think so I think I think it's the same um it's the same rate I believe um maybe slightly less because of the of the earth is blocking the blocking the but maybe not blocking it so much because the moon is the earth is so far away that's a good question I don't have a good answer for that I think it's on average about the same motivation why is the moon interesting now the reason I'm doing this is I realize I'm preaching preaching to the choir I don't have to motivate this audience what I'm really trying to do is I'm motivating people to motivate others um um when we're talking to people who are not as interested in science we we uh we should have good arguments as to why science is interesting and why certain subjects are particularly interesting and also um the motivations even if you are already motivated the the reasons are can be still quite interesting I think we should practice motivating others and I've grouped it into four uh groups of reasons okay why is the moon interesting seasons the moon has affected our seasons and I'll talk about that uh tides uh there are tides on the earth and the moon and the earth has induced tides uh on the moon as I said before there's tidal locking one face has been locked towards the earth uh and I'll talk about that eclipses you can do interesting science you're in the eclipses if you have a solar eclipse where the moon is blocking the sun uh you can see the corona of the sun more easily so you can do science that's only a short time the only electric occultations what that means is the moon will blocks the view of certain objects in the background like asteroids and if you time occultations um when an asteroid goes behind the moon and then uh reappears from different places on the earth you can refine its orbital elements um right for example moon has been used in navigation you can work out your longitude using the moon uh allooners yes now but still good to still good to have the old methods some example of a lunar eclipse here the moon is passing into it's in the penumbra it hasn't passed into the umbra of the eclipse and we'll talk about what penumbra and umbra mean later uh you can have a base for exploration for scientific experiments settlements um even industrializing the moon i'll talk a little bit about that later we can understand the formation and structure of the earth better and of course the moon has inspired us scientifically inspired us to explore romantically literally artistically religiously of course Easter is defined in terms of um i have an example of being artistically inspired here this famous painting by Vincent van Gogh and yes that's my terrible pronunciation of dutch i'm sure that's painful to shantel my apologies uh Vincent van Gogh sounds a little too angrily to me anyway so you see the moon this is the starry night and here's the moon appearing here it's a crescent moon looks like it's a waning crescent we'll talk about the phases of the moon later let's see not the messages i think i have uh yes i haven't been following this correctly is that crater visible that's a good question i'm not sure which side of the the moon that's on uh i have a diagram of the moon that'll show later of the lunar near side that's labeled so we'll take a look at that so i'm checking my fan mail every now and then okay lunar basics some basics of the moon basic details that we should all know before proceeding so not surprisingly the moon has an elliptical orbit so you can see i think the eccentricity here has been slightly exaggerated but you can see that this is this is the minor axis that i'm indicating here the minor axis the orbit the earth is at one focal point of the ellipse and there's the other focal point more or less there when the moon uh passes closest to the earth that's called uh perigee once past farthest from the earth that's apogee along the major axis of the and the perigee distance will up very slightly because the eccentricity of the ellipse varies 357 000 kilometers at perigee and something like 406 000 kilometers of apogee the semi-major axis this is sort of like the average distance of the moon from the earth semi-major is like half of this distance here so it's half of this distance 384 000 kilometers and for those of you who speak american that's 240 000 miles this is uh eccentricity of 0.055 that actually varies slightly because of the moon's orbit the moon is returned by other bodies in the solar Jupiter the orbital period i give two orbital periods here and we'll talk about what those mean later um what they mean exactly the 27.3 days is the sidereal period that's relative to the distant stars you can think of them as being fixed on a celestial sphere almost but the way of defining a coordinate system in that coordinate system the moon orbits the earth in 27.3 days but to actually go from say full moon to full moon from one from through all its phases or new moon to new moon it takes a little longer it's called the synodic period that's 29.5 days and that's because the earth is going around the sun month it's gone distance around so to come back to the same phase the moon has to go a little further there's a diagram for that well inclination 5.1 degrees to the ecliptic so here's the earth and moon obviously not to scale and distance here but um here's let's see there's the ecliptic this plane here this represents the earth's orbit around the sun this plane includes the sun it's called the ecliptic it's to a good approximation the ecliptic of much of the solar system or the the plane of the solar system and the moon you'll notice orbits in a plane that's only slightly different from the ecliptic only five degrees off and that is very interesting because the overwhelming majority of moons in our solar system orbit their planets in their equatorial plane so for the earth let's see here's the equator here so you can imagine continuing this plane outwards the moon is not in the in the equatorial plane of the earth which is inclined at 23.4 degrees to the ecliptic basically this angle here this angle here same as the axial tilt 23.4 degrees um this is called the obliquity of the ecliptic and it's what determines our seasons and we'll talk about that a little bit later that's that's been affected by the moon um as I said before it's tightly locked to the earth so as a near side and a far side there is no such thing as a permanent dark side of the moon with all due respect to pink floyd um I will mention a dark side occasionally in this talk but I'm not talking about a permanent dark side any side of the moon will be dark at any given moment some more characteristics of the earth and moon the mean radius um is about one quarter that of earth flattening 0.1 percent what that means is the moon is is very close to a perfect sphere its mass is like one eighth of one eightieth of the earth's the density is about 60 of the earth's surface gravity as we know is like one sixth that of earth's 1.62 meters per second squared for for earth that's 9.8 meters per second squared on the earth's surface escape velocity 2.4 kilometers per second basically for the earth that's like 11 kilometers per second that's important because you can use the moon for constructing you can use the moon for resources for constructing things in space and you can launch these things into space very easily because it only takes one twentieth of the escape energy of the earth so the escape energy is much lower by a factor of 20 um the rotational period the rotational period is the same as the orbital period as I've mentioned before because it's tidally locked and faces towards us all the time axial tilt as I mentioned before um the ecliptic to its own orbital planes it's more the albedo this is a measure of its reflectivity if it's one that reflects all the light back but it's only 0.136 so the moon is actually has a very dark surface it appears bright to us because it's the well it's the largest object in the night sky and it's fairly close to us so it seems bright to us but it actually absorbs like 86 percent of it's a temperature the surface temperature varies it's a mean of about 220 kelvins so 273 kelvins is zero degrees celsius is the freezing point of water so this is like minus 50 celsius it's almost the same in fahrenheit that particular temperature uh 100 kelvins minus 173 celsius which is uh something like minus 300 fahrenheit and it can actually go up to 390 kelvins and um so uh that's about 120 degrees celsius which is above the boiling point of water the angular diameter most people are surprised when when i say this always picture the moon is being somehow very big in the sky but it's not it's only half a degree and you can verify this yourself you don't have to take my word for it one finger at arm's length has an angular thickness of like one to one and a half degrees so it would cover the moon it would cover the moon like two to three times over you can try this yourself stick your finger up at arm's length pointing towards the full moon and see see what let's see how small let's see check my fan mail again okay yeah it's really hot sauna i wouldn't recommend being there without a suit though appropriately attired lunar formation and structure okay so see there's a mention of this crater it's you'll see a little kovsky i it's not labeled here i don't see it labeled here but it might actually be on the near side but okay so this is let's see the crater kopernicus kepler crater tico which we vanglicized to taiko and you can see the the lunar marae here these are or lava is welled up on the surface i'll explain why that happened or at least give one hypothesis which seems very likely so these three marae serenotatus i've actually i actually remember this i don't remember the other features without looking at a diagram marae tranquillotatus and marae fricundotatus these here you can think of them actually sort of the um the hand the hour hand of clock yeah so this is the from the northern hemisphere i have to emphasize oh this is a northern hemisphere view so you see this towards the south when i said this angle looks like it's the the hour hand is pointing at 10 o'clock so what you do is you add two hours and you get midnight so this is when the full moon would be at midnight so if you actually see them over here okay over here then you can say oh this is something like uh it's in four in the morning over here maybe six in the morning so you can use this as a clock see over here so this is like early evening another thing you can do is keep in mind that the moon is is is uh i'm talking about if you see the moon in a photo you can you can work out the time that the photo was taken that's what i was getting at but now you can say well if you see the moon in a photo and it's half a degree in size and suppose you see a building here like it looks like this big here against the moon so you can figure out how far this photo was taken away from away from the way from the way from the building the building say three uh three stories high these stories about three meters so the building would be uh roughly 10 meters high and say that that would mean that the total moon in this picture would be let's see that's about three times that or maybe four times that so 30 30 meters high the moon appear it would appear in that photo so 30 times 120 is like three and a half kilometers so you know you're just building that that photo was taken one thing is you can are the seas caused by meteor impacts um there have been hypotheses that suggest that that could have happened that when the moon formed really close to the earth the other earth somehow focus the the meteor falls meteorite uh i suppose they'd be called meteorite impacts onto the surface of the earth but no there's another another mechanism uh which has to do with melting of the melting of the near side and i'll talk about that in a little while so this is um this is a beautiful image um not just because of the color scheme i mean this is a topographic map it was done with the uh the lunar reconnaissance orbiter they had this is laser altimetry so it's very very precise measurements of of this of the elevation draws from plus seven kilometers to minus six kilometers that's a 13 kilometer range which is like two thirds what you find on earth the extreme range on earth is something like 20 kilometers zero is like the lunar sea level um there were no seas on on on the on the moon but that's so it's a term that's used and these are the lunar seas which never had water in them but it was one time believe that they did have water in them and these are fairly low at like minus four minus three kilometers and then you have you have the lunar highlands which are higher they sort of like one kilometer and the the main features you see on the moon are the uh are the lunar seas uh the lunar highlands and of course you see plenty of impact so the main features we'll talk about so formation um this is gonna answer barricade's question um the failing hypothesis now is that the earth moon system formed after an impact now this is absolutely after the earth formed 4.6 billion years ago so there's a mars sized body it was called thea and that's again from Greek mythology she was the mother of saline with the proto earth there was a giant impact that blasted material to earth's orbit so this is what is being depicted here in this artist um artist's conception and then the material created and formed the moon and some have said that that can explain why the earth and moon have similar geology but the moon have very similar geology so that might not be sufficient maybe what happened was thea the impact with thea vaporized both of them well i formed a large disk and later accreted to the earth and the moon so that would homogenize everything another idea or variation on this idea said before the far side has a crust that's thicker about 48 kilometers thicker of the near side um now why are the near side and far side distinct the explanation here is actually i like the explanation i don't know if it's going to prove to be true or not this is this is a hypothesis so i mean it's not not hasn't been fully confirmed yet um when the earth and moon formed the moon was much closer than it is now like supposedly 40 degrees across you know nearly towards the magnitude closer than it is now but keep in mind that the tides and i'll talk about the tides what the exact are they go inversely like the distance cubed so if you reduce the distance by a factor of 10 the tide thousand back then it would have been like 40 to 50 thousand times stronger than it is now tidal forces because the earth and moon were so close together so that that tidal locking mechanism would have been thousands of times stronger which locked one face of the moon towards the earth and one away from the earth but the earth was molten about 4 000 degrees fahrenheit 2500 uh 4500 fahrenheit 2500 celsius this melted the near side of the moon so it does sort of like has a melted face i mean the crust is thinner here though it did flow elsewhere i mean this is an interesting idea why i why i it appeals to me is that the tidal locking mechanism is tied to the distinctness of the two faces those two go hand in hand so it does appeal to me whether it's right or not again time will tell uh i don't think it flowed that far but that's an interesting question um it would be hard to explain how it would flow uphill i mean did the melted near side crust flow to the far side to make it thicker now i don't see how that could have happened because it would have to float uphill the melting might have deformed the moon in some way it would have been a very uh traumatic event for the moon that'd been alive okay structure so we see a structure here this is um similar to the earth i mean in the earth you have a solid iron inner core and a fluid iron outer core and this is done of course because there are our seismometers placed on the moon there's no real geological activity on the moon but there are impacts which can for exterior structures similar to that of the earth solid and rich inner core fluid outer core there's partially molten boundary here um crystallization of the magma ocean would have created a mantle from the precipitation the sinking of silicate minerals when i say silicate minerals keep in mind i'm not a geologist so i've oversimplified what media uh an article they're talking about pyroxene and olivine and different types of silicate minerals um i strongly recommend that we have a geologist speak to us about the moon someday talking about the volcanic surface features these include the uh lunar maria and the uh lunar highlands is it is deformed isn't yeah okay yeah that's a good question um moon does seem to be deformed in a very large in a very large scale sense okay the lunar marae dark and relatively featureless lunar planes maria single and the singular is marae i'm sure i'm mispronouncing it once believed to be filled with water but there is no water of course oh well there's a bit of water towards the poles uh frozen ice for water ice in the they're bass pools of basaltic lava these these are similar to terrestrial basalts as i said there are a lot of similarities between the earth and moon that suggests that came from the earth but they have a bit more iron and no minerals altered by water and these levels erupted or flowed into the depressions associated with the impact of the depressions that almost all of these maria are on the near side they cover 35 or 1% of the near side and only 2% of the far side this sort of looks like a lunar maria looks like more than 2% maybe it's not a multi marae i keep repeating this image because i really like this image here lunar highlands okay lighter colored regions and i mean lighter colored in the naked eye not not not the not this this colored image they're called terai or highlands because they're higher than most maria they've been radiometrically dated um that's one reason why the lunar missions have been important we know a lot more about the moon now than we did because we actually have samples of moon rocks that we can we can date and do other experiments on so we know more about the moon and more about how the earth evolved and how the moon formed and they may represent cumulates of basically feldspar different kinds of feldspar in contrast to earth none of these none of the major mountains were formed by plate tectonics i don't think there is anything like plate tectonics on the moon and impact craters um as i mentioned before this is this is uh the taiko on the lunar reconnaissance orbiter so a big crater is something like i guess it's like 90 kilometers across this image is 20 kilometers across okay they formed when an asteroids or climates or comets collide with the lunar surface and there are roughly 300 000 larger than one kilometer on the moon's near side alone and the lunar geological timescale was based on major impact events nectarus embryum oriental multiple rings of uplifted material i mean one reason i like this image here because it shows what's called central uplift and of course there's uplift in ring and the ring here and this happens because these high energy impacts turn the rock into like a viscous fluid not exactly uh not exactly liquid but it flows and it splashes around so you have looks like a splash frozen in time lack of atmosphere means you have lack of weather lack of recent geological processes so these crater craters are well preserved and um after the period of heavy bombardment which happened like 4.6 billion years ago on apparently another period i mentioned down here um after that there was a nearly constant rate of craters forming and that can be used to estimate the age of the surface which can be checked with radiometric aging well there was another period of heavy bombardment about 4 billion years ago check my fan mail again oh that's an interesting yeah barrigan brings up an interesting point planets are the definition that for a planet now is that you have a body that's uh rigid body forces are overcome by gravity to give you a roughly spherical shape like spheroid and the planet also has to have no Disney characters that's right and the planet also has to have cleared its orbit so if the planet has moons will that help it clear the orbital a little faster that's an interesting point i hadn't thought about that i would guess it might and i show this image again because i'm really impressed by it there's a lot of a lot of beautiful data here yeah that's an interesting structure is that is that a moray okay moons orbit about the earth before i just said lunar orbit but that's a little ambiguous talking about the moon orbiting around the earth so i have this this i copied from wikipedia okay so here's the earth and let's see i got stuff in the way here and here's the moon and see this is the scale the distance and the sizes are to scale so you can see they're separated by quite a bit compared to their sizes which is actually quite remarkable when you think about it because the moon raises very high tides on the earth many meters and we live in horseshoe bay and when i'm in canada i live in horseshoe bay a few months of the year and that's in west vancouver the tides there range from low to high of like two and a half to three meters or about eight to ten feet and this is done by this body here way out here so actually quite remarkable there are another another theory meanwhile another theory for what and how they how the moon formed i think that's the best theory for the for the moment the best hypothesis i prefer to say but again time will tell so yeah i like this diagram as well because it really shows the how far apart they are in terms of their sizes okay so this diagram will take a little bit of explaining and i think it's important because we're talking about the phases of the moon what are the phases of the moon we go from new moon to new moon in this diagram and as we go from new moon to new moon new moon uh and we're going through full moon here we go from new moon to full moon to new moon again the point we're making is that there are two motions here the sun is up here these are the rays from the sun okay and our viewpoint it's like we're attached to the distant stars and we're looking back so we're in a coordinate system that's not revolving with the earth around the sun so there's two movements there's a movement of the earth around the sun and there's also the movement of the moon around the earth there are two so it's a complicated dance of three bodies and the phase of the moon is simply the is simply the uh represented by the fraction of the side towards us the lunar near side that is illuminated by the sun at new moon which is this part right here we uh we don't see the moon um i guess you could see the moon under proper conditions but it's pretty dark the dark side that's towards us is the the lunar near side as always then when you go to what's called waxing crescent that's over here you can see that the sun this visible from earth we can see at least part of the lunar near side part of it's then we come over here to um when you see that the moon and the earth are at right angles with the sun the sun is that right or the moon's at right angles with the sun as far as the earth is concerned this is called the first quarter so from new moon waxing crescent first quarter and then we have waxing gibbous which is all gibbous you can check some dictionaries a lot here waxing gibbous because the moon has moved over here you can see most of the near side now most of the illuminated near side full moon of course it's fully illuminated by the near side it's fully illuminated by then that's the phases repeat in the waning sense waning gibbous wain last quarter waning crescent and then new moon but if you look at this orientation here when the moon returns to this particular orientation with respect to the distant stars then it's completed one sidereal orbit and that's that's almost here not quite but but in order but you can see that the moon is now not in the same place with respect to the sun and earth suns over here earth here but the moon is not there in order to be a new moon to be a new moon it has to be on this line so it takes longer for it to come back to new moon position then in the sidereal sense so this is called the synodic period so to go from new moon to new moon it takes longer than to complete one orbit in the sidereal sense now there are two things i want to add to that one is this difference between the synodic period and the sidereal period also applies to the earth rotating the earth rotates of course in 24 hours but as it does so it doesn't go very far but it does move around the sun a bit so that means that the earth surface is being illuminated from a different angle and so we can now see that the solar day is actually slightly longer than the sidereal day about about four minutes longer and that's important because we have what's called the parent solar day and that actually changes as the earth goes around the sun because it goes at different speeds at different times of the year because it's not a completely circular orbit but the parent solar day varies very slightly and we want a more accurate clock or a more uniform clock so we don't use a parent solar time we use what's called mean solar time called mean time which is an averaged out version of parent solar time and very specifically what we use is the mean time at the standard longitude that is closest to us and that's called standard time and we're using day i savings time which is just a variation of that where you add an hour another thing i want to point out is that if you'll notice the moon it seems to be in front of the front of the earth's here so why isn't it blocking the light from the sun here why isn't the earth blocking the light towards the moon and you have eclipse and eclipse every month and the answer is no because again the moon is orbiting in a different plane from the earth's orbit around the sun five degrees out of the plane and the intersection of those two planes called the line of node it won't necessarily point at the sun but sometimes it will point at the sun and when it does you can have an eclipse if the moon is in the right position so this has been a long-winded explanation i hope you're able to follow that let's see okay we'll comment so far i guess for so i can see okay so here's a diagram to demonstrate eclipse is a little better i like this diagram this came from stack overflow let's see so it's this this big plane here this is the ecliptic as the earth goes around the sun this is the orbit of the earth around the sun and you can see that here's the moon's orbit moon's orbital plane is distinct from the ecliptic plane and this has probably been exaggerated a bit it's not that big a difference but if you have okay and here's the what's called the line of nodes okay this is the intersection between the two planes if this line of nodes is not pointing at the sun then you can see that the earth does not block the moon when the moon is full and the moon if the moon is new it does not block the earth does not block the light from the from the sun but as the as the moon and earth orbit around the sun you can have this line of nodes this line of of intersection between the two planes pointing at the sun and then you will have either lunar eclipse so in this case it's a solar eclipse or a lunar eclipse if the moon is in the right place when that line of nodes is pointing at the sun so this is this is actually quite simple conceptually i mean a lot of astronomy especially nearby astronomy in the solar system is geometry rather um eclipse shadows as i've mentioned before they have an umbra and a penumbra and the umbra is the darker inner part and the penumbra is the lighter outer part there's a difference because the sun is not a point source it's extended so an observer standing in the penumbra would still see part of the sun he would see a partial eclipse but if he's in the dark inner part he would not see the sun at all even though it's extended so a new moon or full moon can result in an eclipse but only if you have a certain alignment it doesn't have to be a perfect alignment and we'll talk a bit more about eclipses because they are interesting let's see i did have the work this the other way around let me see yeah here it is i'll go back to the supermoon moon in a minute i seem to have them out of order so here's a lunar eclipse um it's not quite a total eclipse yet because the moon hasn't reached the penumbra and this is not to this is not to scale the sun would be further away uh based on its size here but when it passes into the umbra you have a total eclipse when it's in the penumbra and again this penumbra you have only partial eclipses because you can see part of the sun lunar eclipses occur from two to five times a year although they're not always total eclipses they're not total and total remember is when the moon is completely in the umbra and during total eclipses the moon is bathed in a dark red light sometimes called the blood red because of our association of the moon with horror movies due to refraction through the earth's atmosphere and this is why sunsets i mean it's the same reason why sunsets are on earth are red so a lunar observer if you imagine that you're standing on the lunar surface you would see a bright red ring encircling the earth and this is the earth's atmosphere you would see the earth's atmosphere if you were standing on the moon during a total lunar eclipse then there's a total and then there's what's called the solar eclipse where the moon casts its shadow on the earth and these can occur like two to three times per year though not necessarily over land so cruise ships that actually clips cruises and these can be of any of these three types there's a partial eclipse where it never becomes a total eclipse and then there's a total eclipse where you can see the see the sun's corona the photographs sun but you can also have an annular annular eclipses occur because the earth's orbit is elliptical the moon's orbit is elliptical so you can have the angular size of the moon less than that of the sun so you can see a thin ring of the sun's photosphere here see any questions here no questions no comments okay at least maybe i've just missed them let me check back okay okay yeah the problem and when you touch the screen that fills this box so that makes it difficult let's see okay sorry i've been missing comments because there are so many uh there's so many uh messages in the in the in the box that uh say slide presentation touched which is distracting me from the comments i did my undergrad at university at the tip of the bay of funding incredible ties yes the bay of funding that's an excellent point the bay of funding has a particular natural resonance so the ties are apparently like 20 meters high so that's like 70 uh 70 feet high absolutely incredible really like that slide i wish i knew which slide that was maybe it's the one with the the planes okay uh okay so not that the uh i'm not sure what not that means we're in a biplanetary system yeah you could think of the earth and the moon as a biplanetary system because the moon is actually fairly large compared to the earth i believe the composition of the moon suggests it is related to the earth and not captured by the earth yeah that's that's that's definitely a good point um but uh capturing it's not easy to capture one body from another i mean if it comes in with enough um if it was free uh free body and then it gets into it can't get into orbit around another body without losing kinetic energy and there are ways that can happen like if you have collisions or if it's a three body uh free body interaction um so in order to get the thea and get the earth and the moon so similar you need them to be um homogenized by by the interaction um at least some believe that i wonder if when the moon was closer there was a time when there was an eclipse every month um um yeah well when the moon's 40 degrees in size of course there was nothing alive on the surface of that time on the surface of the earth at that time but the moon has moved outwards some have said that it's an interesting coincidence that the moon and the sun have the same angular size but uh if you went back uh like a billion years or so the moon was had a larger angular size and in the future it'll have a smaller angular size so we're just living in a privileged age i guess see what else we got 10 meters oh i don't know i think the yeah that's that's a good question like i think the bay of fundy has tides that are actually 20 meters high and is grinding into each other okay oh yes that's yeah that's right there is another hypothesis it's a suggests that a couple of moons were formed and that they ended up ended up um uh coalescing but yeah i mean someone can check that on the web the bay of fundy's tides i think they're actually i think they are actually uh oh but wait a minute no you're actually from near there as i recall these tides let's just do a quick check how it ranges up to 40 feet so that's 12 meters okay yeah so it's closer to what you said no what i said and i understood it to be like 20 meters but okay i stand corrected okay supermoon going back one what exactly is the supermoon and you can see here let's see they have the full moon at perigee or the full moon at apogee and you can see that the angular size is is noticeably different so if you have a full moon at perigee i mean the sun is over here okay and the sun's light's coming in this way here's the new moon at apogee so as i said if you well if you have the major axis of the moon's orbit pointing towards the sun and the apogee is over here away from the sun then you can have a full moon at perigee and that's basically what the supermoon is okay tides the concept tides is not really that difficult to understand it's basically differential gravitational force um the force of gravity falls off like one over distance squared which means that it gets weaker with distance which means there's a gradient in that force which means that the near side of a body that is pulled more is more pulled more strongly by its orbiting partner than the far side so the moon on the earth and vice versa this pulls both bodies into egg-like shapes so i have a diagram here which i don't entirely like because it doesn't show the moon as being bulging and the moon does actually bulge it has its own tides and that's important because it led to tidal locking what happens is the moon's gravity pulls on this side of the earth strongly that pulls more strongly at the center than it pulls on the far side and that stretches out the earth and because oceans water flows very easily you see clearly in ocean uses produces waves land so that's why you get the tides but the interesting thing is as they show in this diagram which is one reason why i do like the diagram is it shows the offset of the bulges from the earth moon line so you have the earth moon line here but the tidal bulges are offset from that and that's because of the earth's rotation which is faster than the moon's orbit around the earth faster than the moon's revolution about the earth so this bulge leads the moon and it pulls on the moon and by pulling on the moon what it's doing is pulling it into a wider orbit sort of like if you have a dance partner and you're twirling around with a dance partner and your arms are stretchy then they'll stretch away from you similar idea of course the moon's orbit is in the prograde sense as the earth's orbit otherwise pulling the moon inwards that's why the moon was very close to begin with when the moon was after the moon formed apparently the yeah the days on earth were much shorter than they are now because the moon is pulling back on the on the tidal bulge of the earth which is slowing the earth's rotation so about every 1.7 milliseconds every century is how the earth's rotation is slowing the days are slowly getting longer as the moon slowly moves outwards at about 4 centimeters per year another way to think of this is that the spin angular momentum of the earth is being transferred to the moon's orbital angular momentum so yeah what will the earth actually stand still and won't rotate anymore and we're talking about a very long time in the future probably um long after the earth has been destroyed by the sun so i don't think that'll happen before something else bad happens which isn't very comforting now tidal locking i'm sure the suspense has been killing you so what exactly is tidal locking so you have one lunar face is towards us on the earth and remember that the moon is also pulled into an egg shape by tidal forces now if the moon were rotating with respect to the earth moon line that egg shape bulging that we saw that is there would move around throughout the moon's interior and this would generate heat because of internal friction so that heat has dissipated the moon's rotational kinetic energy kinetic energy is the energy of movement resulting in its currently tidally locked state and i have an analogy here which is not perfect because human body heat can also do the same thing but if you roll a rubber ball around between your hands and you flatten that ball while doing so the ball heats up as internal friction dissipates the kinetic energy from your hands and this is similar to what's happened with the moon's rotation tidal bulging yeah things are getting a little late and i think i'll be finished soon um the moon stabilizes the rotational axis of the earth this is an important point the moon is in a relatively stable orbit in the long term anyway it pulls on the earth's equatorial bulge the moon is the the earth is not perfectly spherical they're by keeping the earth's rotational axis for wanting too far while it processes tops process imagine you have a spinning top we've many of us have played with tops when we were kids they teach physics so they're they're toy i approve of so if you have spinning top and it's extra wide another way to say that is as higher angular as higher moment of inertia it tends to be more stable because it's more resistant to perturbations specifically perturbational torques that are perpendicular to the so you can imagine that the earth spinning by itself is like a narrow top but if you have the moon orbiting it it's suddenly a wider top the moon in a way is connected physically connected to the earth via gravity it's not rigidly connected but it's connected by gravity and this keeps the obliquity of the ecliptic confined to a fairly narrow range from about 22 degrees to about 24 and a half degrees and this minimizes seasonal extremes making the earth more suitable for life and this is easter of course on the Gregorian calendar so i thought this was this is a pretty cool algorithm Jean Mies writes these astronomical algorithms books uh i strongly recommend this book if you are interested in such algorithms so it's the first day of the first sunday after the first full moon that occurs on or after the march equinox so you can have easter anywhere between 22 march and 25 april and there's a simple method it doesn't may not look simple but i mean there are many steps yes but each each step is actually quite simple it's just division division and yeah there's some additionist traction and what's actually rather amazing to me is that this simple algorithm with each of these simple steps actually has embedded within it implicitly the phases of the moon as well as the julian calendar determining the phases of the moon is not really that simple i mean it's complex in its entirety i suppose but it's representing a rather complex physical process and at the end you get two numbers you get an n and you get a p and they give you the number month and the day of the month and they give you a series of dates that from year to year and that series of dates is actually a pattern because it repeats after 5.7 million years for the julian calendar for the julian calendar two years 5.7 million years is so and male again yes there's a drop of less deep sky stargazing because of the moon that's that's true even for us professional astronomers the ones who do optical astronomy i'm a radio astronomer i have done a bit of optical not much but um yeah i mean when you're putting in your observing proposal what you say is on the nights that you want to observe i mean is the moon going to be a problem for what you're doing uh for some people that is a problem yes um yeah good point barrigan what's the the date that jesus actually rose i think a lot of the stuff that's written in the bible was written hundreds of years afterwards so that's that's uh that's uh not straightforward so yeah that's appropriate for today talking about this algorithm um yeah i strongly recommend this book if you're interested in such algorithms he explains the algorithms um he explains how to do the algorithms very well doesn't explain why they work though which would have made the book much thicker missions to the moon i'm not going to say much about these because you know i mean there's just so many of them i mean this is you know a list that i got from wikipedia and this is only one page each of these pages has like 30 30 missions so they're like 120 missions in total that have been to the moon you can see i see this is mostly in these early days this is russia and the us and this one's important of course apollo 11 first uh human being on the on the surface of the moon and i mean there's there's just there's just so much information here see china's involved let's see uh india israel and future proposed mission missions north korea that one worries me a bit china maybe not as much japan doesn't worry me and of course russia and the us and these proposed missions in the future i mentioned fulcone nine some of these so i think it's going to involve space sex so there'll be a more private missions in the future so i'm not going to go through all this i only cut and pasted this just to show that you know there's a lot to talk about i strongly recommend that we get someone giving a talk about lunar missions someone who's qualified to talk about lunar missions they have been important because as i said before we understand better the formation of the moon and also because the astronauts have left instruments there like corner cubes um collecting corner cubes i'm actually measure the distance of the moon so those corner man and missions so many of those future the humanity and the moon so this is particularly interesting this is the uh let's see the lopgate way lunar orbital pathway this is a space station and you can see it's going to be in an orbit around the moon and i think this is particularly exciting international crew of course do interesting science there communications hub human access to and from the lunar surface will we colonize the moon and have industries on the moon the station like this could help and a hub for further destinations help us spread across the solar system so this is american led nasa proposed involves um other countries as usual habitation module holding area for rovers and robots interesting sciences planetary science astrophysics earth observations heliophysics fundamental space biology that could be pretty exciting human health and performance uh staging crew for long-term missions this is a shakedown missions prior to the first crewed mission to mars and yeah don't worry i'm almost finished here i realize i'm running over i'm sorry for that colonizing and industrializing the moon i use this video uh some of you may have heard of isaac arthur he has a channel on youtube i strongly recommend his videos he talks about things like colonization of space the future of space um he also talks about certain scientific scientific um science fiction concepts to see how realistic they are like uh lasers and uh electrician and other things like building habitats for example my son recommended this video he's a real fan told him i'm talking about the moon and circle and he said i just as a source of information and he was right it was quite interesting he watched these videos you have to watch them like two or three times to get all the information it's just to just so dense with information anyway inhabiting the moon building colonies is easy because of the low surface gravity so you can cover craters or lava tubes with domes and you can create large city habitats fairly easily and you have plenty of building material iron aluminum titanium construction it's easy to remove uh move resources to and from the lunar surface as i said it's got 20 times less escape energy so it's it's so easy to move things back and forth you can have a linear mass drivers these are electromagnetic electromagnetic rails that shoot buckets of material into space so you can build space ships space colonies like the anil colonies those are particularly fast um there's large rotating cylinders kilometers in size thrown weather inside because um they can support space exploration and exploitation like mining the asteroids and the lunar far side would be ideal for radio astronomy radio astronomy because it's free from interference from human beings yay radio astronomy yes okay and dangerous biological experiments far from other living things so that's an important point so um we can use the moon to help us spread uh across the stars um spread across the solar system and then eventually the stars and i'll give the last word to prissy shelly with vincent in the background to the moon art thou pale for weariness of climbing heaven and gazing on the earth wandering companionless among the stars that have a different birth and ever changing like a joyless eye that finds no object worth its constancy so maybe in the near future perhaps in the near future the moon will feel less lonely as we humans spread across it and across the stars i thank you for your time and for your interest i'll hang around a bit for questions we are unworthy of the moon okay yes thank you sorry i ran a little late sorry maybe i was facing the wrong way i wasn't looking at my avatar silly me yeah i expanded the screen made sure it was nice and big rare metals or rare earth elements yes there are rare earth elements on the moon yes so it could be a um important resource for rare earth elements which apparently are important for electronics for example yes thank you thank you yeah there are actually 13 full moons per year so we'd have 13 13 months you deeming for magnus that's a good point yes there's something called uh let's see there are deposits of something called creep which is k r e e p the k is for potassium the r or e is rare earth elements and p is for phosphorus should there be life on um i think there would be life but maybe not the kind of life we know now because as i said before the the moon has made the earth um a much more pleasant place to live for life but you know things were more extreme there probably be certain life forms that could could live on the earth still no Easter without the moon yeah if you want me to do this again i'm willing to do this on a saturday maybe more people can show up especially if it's not it's not easter of course this is being recorded anyway so people can watch that tagline couldn't make it might have my celestial orb is talked on by them oh that's that's that's an interesting point space elevator from they've been talking about um if with the proper new materials we could build a space elevator elevator from the earth and uh that would be uh that would extend quite far and that would be uh that would be an interesting way of getting into space now if you did it on the moon there are the advantage of course is that you don't have the same gravity but the point is it would have to be much longer because you want to reach the the um the synchronous point in the orbits where the that synchronous point um the orbital frequency the period of the orbit is equal to the rotation period of the body for earth that distance is 30 38,000 I think 38,000 kilometers on the moon it's much further away because of the long rotation period but yeah what you would um have to be a geosynchronous orbit you want to have it go to the geosynchronous orbit and actually beyond because you need a counterweight so it would uh it would on earth it would extend I don't know I don't know if it has to extend twice as far but maybe it has to extend like twice as far the geosynchronous point which is like 30 36,000 38,000 kilometers which is uh the orbital period would be 24 hours identical to the earth's rotation rate yes it is easier to build on the moon as I said um you can build large structures large domes and that that that would be quite interesting having large cities on the moon it would be easy to do that but the space elevator as I said there there's there are trade-offs and using the moon instead of the earth the space elevator would have to reach very far so it would have to be very very long indeed it wouldn't have to have materials quite as strong for us so you would this elevator on earth but the space elevator on the earth would be shorter um I don't see that that's a problem Baragon um if you have the moon moving around the earth the point is the space elevator would be orbiting with it just like if we build a space elevator uh from the earth it's going around the sun just like the earth is going around so I don't see that as a big problem yeah that's that's good that's a good point Mike if you had the moon rotating faster the space elevator wouldn't have to be quite as long this yeah the space elevator okay it starts on the earth's surface but it extends into space I mean there was a yeah there was I don't see Clark's story but it was interesting obviously a rotating structure that actually came down to the earth on the other hand was way out beyond the geosynchronous orbit but um yeah it goes from the surface of the earth up to the geosynchronous orbit and it has a counterweight on the other side so it has to be like nearly twice as long as that so it would extend out to like 70,000 no not a few that's why I said if it's a geosynchronous orbit so you have the center of mass of this massive elevator would have to be at the geosynchronous in the geosynchronous orbit so it would be it would be it would be stationary with respect to the surface of the earth okay the moon is not now we're talking about something else there are two distinct things I'm talking about here one of them is that we're talking about the space elevator from the earth and that has nothing to do with the moon um then there's a space elevator from the moon space elevator for the moon like I said would have to be much oh an elevator to the moon I don't know how you would do that I I don't even I don't I don't even have a conception for how you would do that yeah connects earth to moon that would be pretty cool if you could do that but I'm talking about oh my voice is breaking up yeah I'm not sure what I can do about that um is it okay now but um okay yeah the uh I'm talking about two separate uh space elevators one from the surface of the earth and one from the surface of the moon and both of those are very useful because you can use the the counterweight at the far end of the elevator can be used to launch things into space because it's going faster than it needs to be going to stay in orbit so it can be used to launch uh ships this is a voice activated sure yeah that's true you could you could use yeah you wouldn't even need you would only need rockets to help you or you need engines to help you steer but most of the thrust would could come from the space elevator itself as you go beyond the geosynchronous point into that long counterweight as I've mentioned um you would be going faster than you need to stay in orbit and you could be flung outwards your ship could be flung outwards and that could help you go to the moon for example huh yes there are tidal uh effects on my voice okay would be scary tied affected my voice all day um not today I have a bit of a sore throat so I couldn't talk all day today but I could certainly talk for longer if necessary I'm afraid of what you have in mind it's a lunatic yes uh yeah what do you call a clock on the moon a lunatic yeah they're pretty terrible those jokes are pretty terrible okay mike bon appetit or as we say here buen provecho here too thank you shantel so what should I do with the screen should I just leave it here or you add you add it to a collection yeah thanks shantel yeah I did read or that briefly it seems a little bit convoluted why you'd need a bi planetary bi lunar hypothesis to explain things but it came out of somewhere so I suppose there are some observational experimental details that require yes I know how to take it back I'm just if you want to uh someone else wants to keep it they can do that too so I already have a copy in my inventory a view of me from behind yes I can I can email you that I can email you a pdf file or I didn't do this in powerpoint I did this in Libre office that's free I can give it to you in Libre office if you like yeah okay an amalgam um there was supposedly a third body involved but as I said before one possibility is that that interaction destroyed all the body and or destroyed the two and if it destroyed the two then basically homogenize the whole the whole system so yeah I'll uh I'll have a pdf version of the talk as well as the uh as well as uh the Libre office version as well um okay the cataclysmic event okay okay let's produce the chiksulub crater and cause the um the massive extinction at the end of the cretaceous period that was um that was not a particularly large body um it was I believe something like 10 kilometers across and uh so it wouldn't have had a strong effect on the moon other than um creating a large impact crater so it wouldn't have a big effect on the moon it's it's not that large as far as uh planets or moons are concerned um yeah that's a good question I think there are there's trace gases and they're talking about let's see pico bars of pressure and our earth's what is it for the earth it's like one bar or something so it's yeah it's many orders of magnitude down in pressure from the earth you can cook anywhere just you just eat a little stove and you can cook anywhere but I know what you mean yes our bodies would cook on the moon if we uh we're on the direct sun without a protective suit um yeah there's a documentary series on national geographic it was uh called one's one strange rock and will smith as the narrator it was an interesting uh series of documentaries so it was on netflix as a matter of fact and it talks about how the what life would be like if we didn't have the atmosphere protecting us okay yeah that's true I mean um I'm not sure if the grinding yeah the grinding would give you a greater homogenization of material without necessarily having as big an impact on the other hand it becomes a little more complicated when you have more bodies involved yeah okay well as someone says that we've never been to the moon yeah okay well I mean there there's um if you believe that I mean people like that tend not to be very logical um they can be extremely intelligent there's no question you can find people like that are very intelligent who have weird views but you know they believe what they want because they cherry pick the data um is there evidence I mean scientists here can prove that uh the human beings have gone to the moon because there have been uh corner uh corner reflectors on the moon moon that reflect back laser beams and we can we can see that and the corner reflectors had to get there somehow been there unless it's done with a robotic mission but it would have been obvious too collisions are common in space no they're not that common in space actually that's even in the asteroid belt which uh there aren't that many collisions that often for example on the moon if you look at the moon how often do we see um impacts on the moon when they do occur I mean they're common in the sense that you can have micrometeorites happening but not not that common in the sense that they would be visible to the naked eye because you have the occasional impact on the moon where you see a flash of light on the moon that has happened and uh last time that something like that was visible I believe was like a few centuries ago so the collisions are common in the sense that if you have tiny particles like sand grains you can see meteors coming into the Earth's atmosphere and these are size of sand grains yeah um those are fairly common but major collisions where you have bodies that are meters in size that's those aren't very common yes I noticed that in the uh in the green waves above my avatar that uh my voice stopped hi sr yes that's a good point or by colliding not grinding um yeah that's a good question I don't know if the if the uh the impacts would be more common on the far side than on the near side I don't think so I don't see any reason why that would be a good question I'm hoping that climate change won't destroy our civilization and if it doesn't then maybe within the next couple decades we'll have we'll have settlements on the moon yeah on our side of the moon yeah I don't know if there would be any higher rate of collisions on the far side than the near side I think it would be about the same by cas yeah I think I should uh oh I'm glad the recording went well I should probably check it out see yeah and see see my avatar facing the wrong way I was a long time ago thanks for the correction okay thanks for coming and look forward to seeing you again