Astrophysicist Explains How Earth’s Moon Was Created - Dr David Kipping

talking about large impacts can we talk about the importance of the Moon and its creation and stuff yeah the the moon's a puzzle that we still wonder about today despite the fact it seems like it's a a sealed story we think the moon formed from a huge impact it's thought that there was a mars-sized planet which smashed into the Proto Earth billions of years ago for just after the solar system formed so the Earth would have been actually been larger then had this impact not had occurred it would have been maybe 50% more massive than it is today maybe twice as massive and this impactor came along smashed into the Earth it knocked off a huge amount of material and it's thought that impactor which we normally give it the name Thea would have been almost completely obliterated in this and vaporized in this in this collision and then some chunk of the Earth was knocked off and that chunk of the earth is ultimately what formed the Moon or maybe even multiple moons that then coales later into a single Moon so there there's a huge amount of interest about why why you might come up with a speculative idea and and still people are challenging this idea the thing we know for sure is that the the moon rocks that were collected by the apoll Apollo Astronauts have almost the exact same isotropic ratio of oxygen 18 to oxygen 17 I think it is as Earth rocks do and this is thought to be a fingerprint that the rocks formed in the exact same place around the sun we look at rocks from Mars we look at rocks from Venus these are basically meteorites we've collected that land in on the earth they have distinct isotropic ratios but the Moon and the Earth have exactly the same so that tells us that they formed from the same inherent clump of material that's challenging with this impactor with the impactor if this thing really did have its own unique origin this impact to Thea Why didn't it contaminate that then and have its own distinct signature that gets mixed in so that has been a challenge one idea that has been suggested to cter this is called cestia I think I'm pronouncing that right cestia and that's when the impact happened it was so uh extreme that it Formed basically one giant donut-shaped planet for a while so the Earth and the moon would have smashed together formed basically a ball of lava essentially that was shaped like a almost a donut in space spinning very rapidly because of all the anle momentum from the impact and then gradually have peeled off and formed a moon and the earth separately from this giant impact the reason why this is attractive because it allows for this material to mix in come thoroughly so so this impact to whatever it was Thea and the Earth completely mix into one single object and then it separates out into the Earth and the moon separately that seems to uh explain some of the Mysteries but not everybody accepts that idea and there still a lot of controversy about the moon like the moon's Far Side has a very different appearance and thickness to the near side if you ever seen a picture of The Far Side of the Moon it looks radically different to the near side the near side has these Maria these beautiful lava flows that happen millions of billions of years ago that kind of smooth it out and then it has these more crated uh areas whereas The Far Side is almost completely crated there's very very few Maria that's because the crust the actual lithosphere of the moon is much thicker on The Far Side than the near side and again that's weird like why why should that be why is there a dichotomy like that and so once one idea of there is that actually Two Moons formed in this process and then one kind of pancak onto the back of the the moon today and that is that pancaking that then formed like a thicker shell on The Far Side of the Moon so there's it's like I wish we had a time machine because this would have been like the greatest fireworks shown in in the universe to have seen the formation of the Moon and again it raises so many questions like how how unique was that does that happen in other exoplant systems are we special that this happened here we don't really have any observational evidence either way but obviously my team and I one of the things we've been trying to do over the last few years is to try and detect moons around other planets to try and ultimately answer this question because at the end of the day the moon has a huge influence on our planet it stabilizes the obliquity of the earth it gives us the tides gives us you know the the rise and the fall of the tides which potentially are a useful thing for life they create Rock pools on the on the on the coastlines especially when the moon was closer in it would have formed o you know continent covering Tides basically the entire continent would have been covered in a massive tide that would have formed all these Rock pools all over the place um it also uh potentially stripped off the upper mantle the upper lithosphere of the earth and that could so basically the crust so the crust may have been much thicker of the earth when it first formed and then the impact could have ripped off some of that thick crust and had that not had happened the crust may have been too thick to have allowed for plate tectonics so plate tectonics we think are absolutely crucial for life as light light Life as we have it on the earth because they allow for something called the carbon cycle so when an animal dies in the bottom of the ocean its carbon is locked up in its bones and its shell whatever it is and it settles down to the bottom of the ocean just stays there and if there was no if that was just the way it was the the world would run out of carbon basically and there'd be no way for animals to grow on the surface anymore because there be no carbon left but instead what happens is these these plates subduct and they go under each other and so that carbon recycles it comes back out in CO2 in volcanoes and that allows access for photosynthesis to to happen in plants for instance so without the carbon cycle it's difficult to imagine how we'd have the biosphere we have today and the Moon may actually be the reason why we have a carbon cycle for if it had not stripped off that upper uh that Upper Crust the crust would have been so thick that would have formed what we call a stagnant lid a stagnant lid is what we is seems to be the case with Venus Venus seems to have a very thick uh lithosphere which basically prevents plate tectonics as we have them on the earth so yeah very intriguing like you look at all the things the moon does and you think wow are we are we a product of the Moon the idea of plate tectonics kind of tilling like doing Global tilling uh is so so fascinating and yeah I I mean the Moon being tily locked or rotationally locked what's that what's that called yeah tily locked yeah tily locked yes so we only ever see how rare is that to have something that doesn't rotate at all that seems bizarre that's pretty that's actually pretty common so a lot yeah a lot of meons that's true of because there and we think we understand why this should happen whenever you get fairly close to a planet or a star the the gravitational effect obviously increases as you get closer and closer and it kind of locks in the the shape of that object to always have one side facing it so especially if you have some kind of uh fluids like the Earth does these Tides can be quite effective slowing things down um it happens for many moons around Jupiter Saturn so we think this is pretty common it's thought that uh this should be common for exoplanets as well which is interesting but again unproven but we think that there are some Stars which have very close in planets and those planets are so close that they should tily lock to their star and we've measured many of these hot Jupiters and we've watched them whiz around their star and we can even see basically re thermal Maps we can kind of re thermally map the distribution of energy on these planets and they look indeed like they are tidy locked as you would expect them to be so everything about exoplant seems to support this idea that tide locking should happen but there are also mysteries of title locking we don't really know exactly when it stops the theories of tidal theory that we use are fairly primitive to be honest they kind of parameterize things in a very basic way ideally you would just simulate an entire planet like every single atom but we just don't have computers powerful enough to simulate every single atom so we use these simplified models and we know these simplified models don't always work so for in for mercury it was predicted that mercury should be tidy locked to the Sun but it's not it's in a pseudos synchronous orbit and probably the reason why that's happening is is because of general relativity um because actually there's gen relativistic effects that come into play when you get close to a star as well so it's thought that um TI loocking should happen but in some instances it's more complicated than just a simple formula and you really need to like think about the composition of the star the composition of the planet what it's made out of does it have a core what what's its density profile like how how much general relativity kicking in here so the calculation is quite non-trivial but it does seem like it's common in the solar system and expected to be common elsewhere are there any other interesting rotations of planets in our solar system yeah I mean one of the things I think is interesting is Uranus uh is tilted on it side which is like kind of confusing so even though it's it's spin isn't particularly unusual it's somehow been knocked over so it's just spinning in a sideways config ation so that like it's rolling forward it's it's like it's just it's its axis in which it spins like the Earth's axis is basically pointed um orthogonal to its to its orbital plane so normal to its orbital plane pointing up if you like whereas for Uranus it's kind of tilted so its North Pole is pointed at the sun rolling like it's like it's rolling forward on a surface that doesn't exist yeah kind of yeah and and as it as it goes around what's kind of weird is that the moons I've also tilted over alongside it so this has been like Curious how we can imagine maybe the planet getting knocked over on its side but then why are all the moons also on its side as well we don't really understand what happened there so very strange to understand have Uranus and then one of the one of the cool things we're thinking about a lot of my team at the moment in my research group the cool words lab is the rotation of Jupiter and Saturn which are rotating pretty fast once every 10 hours and we think this is uh to be expected pretty much for all giant planets once you get far enough away from the Star so if the if Jupiter came too close to the Sun that tile locking thing would cook in and it would slow Jupiter down it put the brakes on Jupiter's Spin and slow it down to days rotation rate basically whatever orbit period was but Jupiter's far enough away that it still retains what we would call its primordial Spin and Jupiter and Saturn don't really have any way of getting rid of that spin for the sun it does loose spin it was probably spinning much faster when it was young and it's been losing it through its very strong magnetic fields Jupiter has magnetic fields but nowhere near strong enough that it can lose spin the same way that the sun does it's so far away from the Sun that it's not going to be slowed down by being closer yes correct so it doesn't really have any way to shed this spin that's interesting because we are now we have some observations coming up with the James web Space Telescope in October where we're going to basically measure a Jupiter analog so a planet an exoplanet around a different it's over a thousand light years away but we're going to measure very precisely its shadow as it passes in front of another star and we think that this planet should have simly a fast Spin and why that's interesting is that that fast spin causes Jupiter to bulge out at its equator more than its pole so it's actually 5% wider than it is tall and Saturn's 10% wider than it is tall through this spinning effect we think we can measure this it's never been measured before if we can measure it it will tell us basically what the plet is made out of how fast it's spinning and even its tilt angle so as I said Uranus is tilted right over Jupiter and Saturn are not very tilted compared to that but we should be able to actually measure that angle for the first time and really get a deeper insight as to how these plants are forming so I'm just excited that we might have access for the first time thanks to James web to a completely new observational technique learning about exoplant we have their Mass we have their radius but now we can get their spin their bulgin their their tilt angle and really just complete the picture as to how these things formed this episode is brought to you by element stop having coffee first thing in the morning your adenosine system that caffeine acts on isn't even active for the first 90 minutes of the day but your adrenal system is and salt act on your adrenal system element contains a sbed electrolyte ratio of sodium pottassium and magnesium with no sugar no gluten no coloring no artificial ingredients or any other BS it plays a critical role in reducing muscle cramps and fatigue while optimizing brain health regulating appetite and curbing Cravings the orange flavor in a cold glass of water is literally the best way to start your morning I've done it every single day for over three years now way before they were a partner on the show and I love it best of all there is a no BS no questions asked refund policy so you can buy absolutely risk-free and if you do not like it for any reason they will give you your money back and you don't even need to return the box right now you can get a free sample pack of all eight flavors with your first box by going to the link in the description below or heading to drink lnt.com slod wisdom that's drink LM nt.com modern wisdom thank you very much for tuning in if you enjoyed that clip you will love the ful length podcast in all its Glory which is available right here go on press it