How did the Moon form? | 5 things we learnt from the Apollo Moon Landings

so I am currently holding a rock from outer space if you couldn't tell it this is me geeking out this is been geeking out so this rock actually comes from the asteroid belt so the pop space between like Mars and Jupiter where a lot of asteroids come from compare that to this little sample over here which is a Martian meteorite I'm actually holding a piece of Mars right now so this will have been created when another rock hit into the surface of Mars throwing up a lot of fragments one of those fragments ended up falling to earth and you can get the same thing happening from the moon as well so that you also get lunar meteorites now unfortunately the Oxford Natural History Museum where I am at the minute doesn't have any Luna meteorites you know sometimes but if you're wondering well how do we tell what's the difference between something that's coming from the asteroid belts I mean it's come from Mars and something it's come from the moon in part it's all thanks to the moon rocks that were returned by the Apollo moon landings now it's the 50th anniversary of the very first moon landing on Saturday the 20th of july 2019 and while that was one giant leap for mankind I think it's the scientific legacy of the Apollo missions that really were their crowning glory so the experiments the astronauts did on the surface of the Moon itself and then all the experiments we did from the moon rocks and soil samples that were brought back to earth after the missions that have really pushed the boundaries of humanity's knowledge of our place in the universe so all the news stories you're gonna hear in the next week are gonna be about that incredible achievement of Apollo 11 being the first mission to put humans on the moon Neil Armstrong Buzz Aldrin taking those first steps while Michael Collins still pilots the command module in orbit around the moon and yeah that was an incredible achievement but I really want to talk about this science that was done off the back of the Apollo missions so I've got five things for you that we didn't know before the moon landings to Apollo 11 14 and 15 all left laser retroreflectors on the surface of the moon so that we could fire a laser at the moon it would bounce back to us and then from the time it took we'd be able to calculate the distance now people often refer to this as they left a mirror on the surface of the Moon but that's not quite right because the way a mirror reflects light is very different to how a retroreflector reflects light example if I point this laser at an angle at this mirror it looks like the lasers going straight through but in reality what's happening it's is being reflected over the other side it's reflected at the same angle as the angle I'm pointing at the mirror not ideal for leaving something on the surface of the moon instead to get a reflection back I have to point it directly at it and apparently give myself a laser mustache in the process if instead I pointed this laser at a retroreflector a bike reflector you'll see that whatever angle I point the laser out it always gives me a reflection back in the direction it came and that is ideal for leaving on the moon to put it into perspective though of every hundred million billion photons in the lasers pointed at the retroreflectors left on the surface of the moon only one makes it back to earth so this is really precision science here so you'd never be able to see the laser coming back with the naked eye unfortunately but what it's allowed us to do is actually measure that the moon is moving away from us every single year by about 3.8 centimeters which is intriguing to say the least and this is all happening because of the time the difference in the force of gravity on the earth and the moon which is causing sort of like a drag force which is slowing down the rotation rate of the earth but about like two milliseconds a century or something and then at the same time causing a moon to move away from the earth so the rate that it's moving away from the earth and the distance that it currently is that kind of gives you an age on the moon if you sort of wind back time it gives you an age of about one and a half billion years and yet the oldest rock we've ever found on the moon is over four billion years old so we think that it's actually faster now than it was in the past but we'll come back to that later so the two and a half hours or so that Neil and Buzz walked on the surface of the Moon during the Apollo 11 mission they placed a seismometer on the surface ie device that could detect seismic waves ie moon quakes the same as we have seismometers on earth to detect earthquakes and that was to enable us to figure out what the interior of the moon was actually like and they did that by using seismometers that were placed by later Apollo missions in different locations on the moon's surface which sort of joined together to make this network to pinpoint the distance and location inside the moon that these moon quakes were coming from and you can do that because seismic waves travel deeper through the interior the further away they've come from and so you essentially get a time delay on your network depending on which direction or how deep a moonquake has come from also these waves get refracted when they move from liquid to solid as well and so some of the first results in this experiment suggested the moon's interior could actually be liquid and have this molten magma interior just like the earth did which wasn't really expected at all because the moon is a very static object we've never really seen it change at all and so it was thought to be a very solid lump of rock not only that but the seismometer experiments reveal that the moon also had an iron core just like the earth however that iron core in the moon was only about 25% of its radius compared with the earth sighing core which is about 54% of its radius the earth actually is the densest planet in the solar system because of that because it's iron core is so big again this was a weird result that people didn't really know how to explain so another experiment carried by Apollo 11 was the solar wind composition experiment and you might have seen this in the background of a lot of the photos from the Apollo 11 mission and wondered what it was it was called the Swiss flag and it was essentially a big sheet of aluminium foil that was left exposed to space to collect solar wind particles so solar wind comes in the Sun it's extremely high-energy particles that are released in the interior when the Sun gets a little bit too active now on earth were shielded by those high-energy schools because of our magnetic field some of them do get funneled down to the poles and we get the beautiful Aurora the northern and the southern lights the moon doesn't have a magnetic field so it's completely unprotected which means we can get a really pure sample of the particles in the solar wind now it's really important we understand this because these geomagnetic storms can essentially create a huge shockwave on the magnetic field of Earth which can put out electrical grids communication networks satellites all of which can have an impact on day-to-day life here on earth so it's something we have to understand in order to be able to mitigate for so while that experiment did allow us to better understand the solar wind the other thing it allowed us to do was to measure the total density of all normal matter in the universe which is a pretty big deal for a short backyard hop to the moon and the reason they could do that was they were able to measure the ratio of deuterium to hydrogen in the solar wind ie in the Sun itself you know deuterium is something we call heavy hydrogen and a normal hydrogen atom you just have one proton in the center of the atom but in deuterium you also have a neutron as well but there's no Astrophysical process that we know can create deuterium it's actually destroyed in stars in order to make helium the only time we ever know that deuterium was actually produced was during the Big Bang so then if you can measure the amount you find today in stars you can put a lower limit on the amount that was actually created in the Big Bang but that amount of deuterium is then directly correlated with all the normal matter you make in the Big Bang so if you can measure the abundance of deuterium now then you can infer the total density of all normal matter in the universe and so the solar wind composition experiment of Apollo 11 gave a value for that of 3 times 10 to the minus 31 grams per centimeter cubed compare that with a more recent measurement this from 2001 which is galaxies to probe it we found 4 times 10 to the minus 31 grams per centimeter cubed the agreement between the different methods is excellent it's actually within 30 percent for all the known methods to measure this and the solar wind composition experiment from Apollo 11 is one of them so not just stuff about the moon Apollo 11 but stuff about the entire universe as well the lasting legacy of the Apollo missions though is definitely the amount of moon rocks and lunar soil samples they brought back to earth with them 382 kilograms in total and I cannot stress enough how valuable they are because they provide this window into like geological time where you've had no effects of weather or erosion might you do on earth so you can really pro the very early days of the solar system the oldest rocks we've ever found on earth are in the range 3.8 to about 4.2 billion years but some of the rocks and the Highlands found on the moon from summer later missions have been dated at 4.4 billion years nearly every moon rock is older than nearly every earth rock the other big surprise was that most of the moon's surface was made of igneous rocks these are rocks made of big crystalline structures that form when lava cools and solidifies which tells us that the moon was once molten so as well as carbon dating the rocks to get an age you can also measure something called the oxygen isotope ratio an isotope is essentially a normal atom that you've added extra neutrons to the center up to make it a bit heavier and that is often then unstable as well as the radioactively decay eventually back into a normal oxygen atom and when they measured the oxygen isotope ratio in moon rocks compared with in Earth rocks they found they were exactly the same and completely different from any other rock in the solar system an asteroid meteorite or a Mars meteorite so there was a lot of people scratching their heads over this but the final piece of the puzzle came from the Apollo 15 mission in the discovery of a mineral called olivine on the surface of the Moon this is olivine it's a mineral made out of iron and magnesium and you will notice that it is green and this is not the first time that I've held olivine because it's also found on the surface of the earth as well and in particular in Hawaii so I got to go to Hawaii as part of my PhD I was sent to observe some galaxies using the telescope's on the top of the mountain they're mounted keigher and once I'd done all my night shifts and I got back down to see I decided to go snorkeling so in amongst all the turtles and the fishes I got very excited when I spotted some green sand just like this sample here sand essentially made of olivine and the reason you find olivine in Hawaii like that is because essentially the entire Big Island of Hawaii is one huge giant volcano and olivine is one of the most common minerals found in the Earth's magma ocean underneath it's cross so anywhere you've got a volcano or tectonic plates meeting you can dredge up a lot of that olivine to the surface that's really the only time you ever see it so you can imagine the Apollo 15 astronauts surprise when they're just casually driving the lunar rover and they spark a green rock in amongst all of the grey on the surface of the Moon so that really confirmed the moon did have a magma ocean just like the seismic experiments have been suggesting and that was because olivine essentially is so much heavier than any of the igneous rock you get at the surface that it sinks to the bottom of that magma ocean and so the purity of the olivine you then get at the surface is there any related to how deep your magma ocean is and on the moon we find the magma ocean is 600 miles deep which is essentially half of the moon's radius to have a magma ocean that large it means the moon has to have formed incredibly quickly and at one point been entirely molten rock now the fact that you find both olivine on the surface of the earth and the surface of the Moon formed by the exact same processes suggest that the moon and the earth actually have a common origin so before the Apollo missions there was a couple of theories floating around for how the moon might have formed it could be that it was a captured asteroid just like we saw in Phobos and Deimos Mars is moons or it could be that the moon and the earth had formed from the same material at the same time around the Sun and then there was a pretty old theory that said the moon could have formed after a huge impact of something with the earth and the very early solar system but people had sort of dismissed that theory for being well kind of too obvious sort of too coincidental a bit of a just-so story with all the findings of the Apollo mission that the moon is slowly moving away from us that it was once molten and now has a cross made of solidified lava that it has a magma ocean still underneath that cross with an iron core that's much smaller than Earth's the fact that it has the same oxygen isotope ratio as Earth and that we find olivine there and even that the Moon and Earth are spinning in the same direction and then the earth has this massive tilt that causes our seasons every single one of those results piled up and up in favor of this giant impact hypothesis first proposed by Reginald Alworth daily in 1946 and finally then revisited by Hartman and Davis in 75 and Cameron award in 76 it would finally become the accepted front-running theory for how the moon informed after a conference in 1984 in Kona in Hawaii where the participants met to discuss what was the accepted theory now post Apollo and there's reports of people walking around shell-shocked because they couldn't quite believe that the giant impact hypothesis had come out on top the general idea is that a mars-sized planet that we called Theia collided with the very early Earth in the early days of the solar system that liquefied the entire Earth and the entirety of fear throughout all this molten rock into space which was gradually brought back into orbit around Earth that coalesced to form the moon in a very short space of times of less than a hundred years then it cooled and solidified and ever since then it's been gradually moving away from us so Apollo itself has an incredible scientific legacy along with all the people that it inspired to do PhDs in engineering physics computer sciences and it's those people that are now leading the missions where we send probes to elsewhere in the solar system as well now there's talk from many countries about sending people back to the moon but one thing's for sure is that the Apollo landing sites should be preserved as culturally significant landmarks that shouldn't be disturbed and instead preserved for all future generations of space tourists to come now if you want more historical and scientific background on how we figured out the giant impact hypothesis was the leading theory for the formation of the moon I cannot recommend this book enough it's called the big splat this by Dana Mackenzie and it is the book that convinced me to be a scientist I couldn't believe how incredible it was that the pieces of the puzzle would all come together from every single little person's contribution to the field it was like reading sort of a murder mystery or a crime novel about how scientists uncovered the evidence and uncovered the truth and I guess that's the biggest hope that I have for my book that comes out in September as well is that someone one day will also say that it was the book that inspired them to be a scientist who did you all know if I won an award as well well it was for my youtube channel it was the University of Oxford Vice Chancellors public engagement with research Awards which I wouldn't have won if all of you weren't watching my videos so this one's for all of you thank you so so much I am forever in your debt and this cold star trophy that I got is amazing I kind of want to make it into a necklace but I think it would be a little bit excessive so maybe I shouldn't speaking of necklaces did you spot my my crescent moon necklace which I thought was very appropriate for this video absolutely obsessed with this necklace at the minute it's from purely I'll link it down below absolutely gorgeous Neil Armstrong Buzz Aldrin taking their first steps on the moon while markable Markel my name is Michael Collins you're getting on well with Nick this one's my favorite so go I didn't behold it the other day it's amazing you need to Hoover the dinosaurs and it might interrupt filming you

Channel: Dr. Becky

Views: 91,685

Rating: 4.9036503 out of 5

Keywords: apollo50, astronomy, space, astrophysics, moon, moon landings, apollo 11, apollo 12, apollo 13, apollo 14, apollo 15, apollo 16, apollo 17, neil armstrong, buzz aldrin, michael collins, asteroid belt meteorite, martian meteorite, moon rock, moon quakes, seismometer, laser retroreflector, olivine, giant impact hypothesis, baryonic density of the universe, universe, space exploration, #apollo50, big splat, dr becky, dr becky smethurst, rebecca smethurst, becky smethurst

Id: At17Klp_pRI

Length: 17min 23sec (1043 seconds)

Published: Wed Jul 17 2019