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Current time:0:00Total duration:7:12

Video transcript

when you look at footage or photographs of astronauts in space it doesn't look like there's any gravity at work here the everything is not falling and down in one direction in fact it's not even clear what up or down is everything just floats around if I were to push off of this wall I would just float in that direction so it does it look like there's this there's this overarching influence like gravity that's trying to pull everything down but the question is is that these astronauts are still not too far away from a supermassive body in fact the Space Shuttle Space Shuttle gets up a cup only a couple of hundred miles above the surface of the earth so the Space Shuttle if I were to draw it to scale would probably be right about there and we know we know that the force of gravity between two objects is equal to big G the gravitational constant times the mass of the first object times the mass of the second object over the distance between the two objects squared and if the Space Shuttle is right here only a few hundred miles above the surface of the earth this R isn't that difference it's a little bit low it's a little bit further than if you were at the surface of the earth remember that R is measured from wherever you are to the center from the center of the earth or really the center of the object to the center of the earth the center of the the earth represents most of the distance here so if I'm at the surface of the earth or if I'm just a few hundred miles above the surface of the earth it's not going to change our that dramatically especially in terms of percentage so when you look at it this way it seems pretty clear that the force of gravity for someone who is in in space only a few hundred miles above the earth should not be that different than the force of gravity for someone who is on the surface of the earth so my question to you is what gives if there should be gravity in space how can we see all these pictures of people floating around like this and the answer is is that there is gravity in space and that these people actually are falling they're just moving fast enough relative to the earth that they keep missing it and let me show you what I'm talking about there so if I were to take a if I were to if I were to let's say I'm sitting here in Africa and I were to shoot something if maybe I have a really good slingshot and I were to sling something super fast at maybe a 45 degree angle it might take off a little bit and eventually hit another point and this would actually already be a super-duper slingshot I just made it travel a couple of thousand miles or at least over a thousand miles if I make it go a little bit faster if I put a little bit more force on if I just propel the projectile a little bit faster I'll it might go a little bit further but it'll eventually fall back to the earth let's try to propel it a little bit faster than that then it'll still fall to the earth let's propel it even faster than that well then it's still eventually going to follow the earth I think you might see where this is going let's go even faster than that so if we go even faster than that eventually it'll fall to the earth even faster than that so if you if you were to throw an object even faster than that it would then go really far and then follow the earth but I think you see what's happening every time you go faster and faster you you throw this projectile faster and faster gets further and further up to some some velocity that you release this projectile and every time and whenever it's trying to fall to the earth it's going so fast that it keeps missing the earth so it'll keep going round and round and round the earth and a projectile like that would essentially be in orbit so what's happening is if there was no gravity for that projectile if there was no gravity the projectile would just would just go straight at good to go straight away into space but because there's gravity it's constantly pulling it towards the center of the earth or the center of that projectile and the center of the earth are being pulled towards each other I guess is a better way to think about it the force of gravity is doing that and so it's curving its path and if it's going fast enough if the if the projectile or whatever object we're talking about is going fast enough it'll just keep going round and round the earth and since there is almost pretty much for for most purposes no air at if you go high enough especially the altitude that the Space Shuttle at is no noticeable drag this thing can just keep on going for a substantial amount of time although there is just a little bit of drag and that's why over time you do have satellites slowed down because there is just a little bit of air resistance so the answer to this conundrum is that there actually is gravity it's not it's not a gravity-free environment it's just that the astronauts and the space shuttle and everything else that's in the space shuttle it's all falling but it's moving fast enough that it never hits the earth it keeps missing the earth it keeps it keeps going round and round and round but it is completely under the influence of gravity if they were to just slow themselves down if they were to just break relative to the earth and if they were to just you know they put their their brakes on right over there they would all just plummet to the earth so there's nothing special about going three or four hundred miles up into space that all of a sudden gravity disappears the influence of gravity actually on some level it just keeps going you can't it might become unnoticeably small at some point but definitely for only a couple hundred miles up in the air there is definitely gravity there it's just there in orbit there going fast enough so if they just keep falling they're never going to hit the earth and if you want to simulate gravity and this is actually how NASA does simulate gravity is that they will put people in a plane and they call it the vomit rocket because it's known to make people sick and they'll make them go in a projectile motion so if this is the ground in a projectile path or a parabolic path I should say so the plane will take off and it will it will do a it will do a path exactly the same as something in freefall or in a parabolic path and so anyone who's sitting in that plane will experience freefall so if you've ever been in if you've ever you know right when you jump off of it if you if you've ever bungee jumped or sky dived or even the the feeling when a roller coaster is going right over the top and it's just pulling you down and your stomach feels a little ill that feeling of freefall that's the exact same feeling that these astronauts feel because they're in a constant state of freefall but that is an indistinguishable feeling from if you were just in deep space and you weren't anywhere close any No a mass that is that is an identical feeling that you would feel to having no gravity gravitational force around you so hopefully that clarifies things a little bit to someone who is just sitting in the Space Shuttle and if they had no windows there's no way of them knowing whether they are close to a massive object and they're just in freefall around it they're in orbit or whether they're just completely far away from any massive object and they really are in a state of or in a place where there's very little gravity