Are Orbits like this even POSSIBLE?!

hey crazies the earth orbits in a nearly perfect circle's it's simple regular and reliable but not all orbits are like that some of them can get really weird this episode was made possible by generous supporters on patreon ok let's start with the basics the word orbit is pretty broad it's defined as any path where gravity is the only influence like I said it's pretty broad wouldn't that make freefall in orbit umm yeah yes it would what I know it seems weird how can this be in orbit it's a straight line that starts and ends that last part is where I think most of our trouble comes from how can a path that ends be in orbit I think it'll help if we imagine what would happen if the earth didn't get in the way this is just a portion of a much larger path one that goes all the way through the earth if we dig a big tunnel and remove all the air then there's nothing in the way the squirrel will fall forever back and forth through the earth that feels a little more like an orbit doesn't it ok if you're still not convinced it'll be more obvious if we make a move sideways to say we launched the squirrel off a building using a slingshot introductory physics tells us the squirrels path will be a parabola but that's only approximately true let's zoom out and launch him way harder we can see now that his path is actually a small portion of a large ellipse an ellipse he would travel along if the earth didn't get in the way ellipses are very common orbit shapes parabolas happen to just not near the surface of the earth in fact using newton's laws on a pair of objects is called the two-body problem and there are only five types of solutions for those problems lines circles ellipses parabolas and hyperbolas that's it just five basic shapes lines are just free-fall like the squirrel in the tunnel circles and ellipses are what we expect for planets orbiting stars our moons orbiting planets even moons can have moons we call the moon moons parabolas and hyperbolas are the orbits of things that zip in and then zip right back out you know like that o Mulla Mulla object everyone was all excited about a couple years ago these five basic solutions are what we call the conic sections because they can be found when a plane cuts through a cone they're the solutions of the two-body problem actually those are very realistic Hughes's I know I know okay here's the deal there is really no such thing as an exact two-body problem we like to think the Earth's orbit is only affected by the Sun but it's also affected by the moon that makes it a three body problem this way it looks circular or at least elliptical but if I exaggerate things you can see these orbits aren't any of the conic sections they're kind of wavy gravity is still the only influence though so they're still considered orbits on the whole three body orbits tend to be chaotic and unstable many look like they have no pattern at all some will collapse together to form one big object others will throw an object into deep space and become a two-body system the vast majority of three-body solutions are like this but not all of them I mean the Sun Earth Moon system is stable and regular right there must be other stable examples and there are but some of them are kind of unexpectedly weird we call these freefall orbits because they act kind of like the squirrel falling through the earth each object moves along its own path but those paths are not Luke's they're segments they each have a beginning and an end will they do that forever sure well unless they get nudged by a fourth object freefall orbits are extremely sensitive they're like a tiny island of stability in a sea of chaos one little gravitational nudge and it's all over which brings me to my next point there's no such thing as an exact three-body problem either if we consider the entire solar system there's the Sun the eight planets a bunch of dwarf planets and countless asteroids and comets that's a many-body problem the early solar system was a very chaotic and unstable place things were moving all over running into each other being thrown out of the solar system the only reason it's stable now is because the big stuff that remains is pretty far apart those vast distances make each planet behave as if it forms a two-body system with the Sun and that means the conic sections work fairly well in the short term but in the long term we have to make some corrections the most well-known of those Corrections is orbital precession also known as the precession of the perihelion I know those are fancy names but but they're actually not that complicated in an elliptical orbit like this the perihelion is the point where the planet is closest to the Sun it's literally what the word perihelion means but we've already said that orbits are only that simple in a two-body problem the solar system is not a two-body problem even though they're really far apart the planets do tug on each other a little those tugs are gravitational so the path is still considered an orbit it just makes the orbit process the perihelion of the ellipse shifts around over long time periods the perception it's really that big four planets are wrong your losses are fine thanks for the reality check he's right as usual you'll only see a precession this large around a neutron star or black hole around a normal star the shift is much smaller you'd have to observe the planet for decades before you'd notice this precession happens with all of the planets in the solar system but none of them are as famous as Mercury's when we measure Mercury's precession the shift is 5,600 arc seconds every century Oh what's an arcsecond it's an itty-bitty tiny angle circles are divided into 360 degrees right well one sixtieth of a degree is called an arc minute and one sixtieth of an arc minute is called an arc second that makes Mercury's 5,600 arc seconds equivalent to a little over a degree and a half per century since 360 degrees would be one full cycle Mercury's perihelion won't come back to where it is now for twenty three thousand one hundred and forty-three years that's a long time we do have a minor problem though when we consider all the tugs with Newton's laws we only predict mercury processes by five thousand five hundred and fifty seven arc seconds every century the prediction is off by forty three arc seconds that might sound small but it means the prediction of the full cycle is off by a hundred and seventy-nine years it cannot be written off as a measurement error unfortunately we'd have to wait until 1915 Ferb Einstein and his friends to solve it we needed the general theory of relativity or just general relativity for short which says that gravity is actually space-time curvature I've got an entire playlist about it if you're interested but here's the basic idea gravity isn't actually a force that pulls things together gravity is just the name we give to the physical distortion of space and time we still call it gravity though so any paths curved by that distortion are still considered orbits it just tweaks the rules a little bit so we can fix some of the errors we were getting with Newton's laws you know like that missing 43 arc seconds of precession every century for Mercury those types of errors while important to fix are ordinarily pretty negligible 99% of the things in 99% of the universe obey Newton's laws to a high degree of accuracy but sometimes things aren't ordinary sometimes they're extraordinary the craziest example being a black hole which isn't actually a hole black holes are roughly spherical their balls space space-time is so curved around these things that some really weird happens the path that light takes can get bent too which leads to some very strange optics if that light is close enough to the black hole it can actually orbit on a closed loop or even fall in just like anything else a little further out even the orbits of massive objects can do unexpected things they can zoom in and then out whirling around as they go that's why we call orbits like this zoom whirl orbits actually this is really calming maybe I'll just let it hey what what what how what where was I right black holes all orbits up to this point have been planar that means each orbit stays in its own plane but almost all black holes are rotating and that does even weirder to the orbits planar orbits like this one are only possible in the equatorial plane of the black hole in that plane we can still find zoom whirl orbits outside of that plane all bets are off the space-time curvature pulls the orbit out of the plane and into three dimensions this is the weirdest looking orbit that I can think so how weird can orbits get pretty weird actually we like to think of orbits as simple conic sections circles ellipses parabolas are hyperbolas but that's only approximately true those shapes can process they could have some waviness to them they might look kinda like free fall they could zoom in whirl like this orbit around a black hole or they might even do whatever this is it all depends on how accurate you want to be and how extreme you want to get so were you surprised by any of these orbits let us know in the comments thanks for liking and sharing this video don't forget to subscribe if you'd like to keep up with us and until next time remember it's okay to be a little crazy to everyone overwhelmed by the last video yes I know it was a very niche topic but I started it over a year ago it was time to let it go so I can move on to bigger and better things hopefully today's video was more to your liking and thanks for watching

Channel: The Science Asylum

Views: 266,834

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Id: 2JZ9PORUR4A

Length: 11min 20sec (680 seconds)

Published: Sun May 31 2020