Over (to) The Moon: Crash Course Kids #13.2 - By Crash Course Kids
Transcript
00:09 | you know how many people have actually been on the | |
00:11 | moon ? 12 , that's all . But one day | |
00:14 | we may go back there , we have a lot | |
00:16 | more to learn about the moon and space in general | |
00:18 | . So someday , maybe in your lifetime we'll send | |
00:21 | astronauts out there to study and explore . Do you | |
00:24 | want to be one of them ? If you do | |
00:25 | let me give you some helpful tips about a little | |
00:27 | thing called gravity , because you're gonna need to know | |
00:30 | all about what gravity is and how it works . | |
00:32 | If you're going to escape the pull of Earth and | |
00:34 | fly to the moon . Now , you already know | |
00:36 | that astronauts can leave the Earth . But it takes | |
00:38 | a lot of effort to boldly go where few have | |
00:40 | gone before . But once astronauts reached the speed called | |
00:43 | escape velocity , they're able to overcome the force of | |
00:46 | Earth's gravity and get into orbit around our planet or | |
00:50 | head on over to the moon . So this brings | |
00:52 | up an interesting question . What happens when an object | |
00:54 | gets away from Earth's gravity but close to the moon's | |
00:57 | gravity . You already know that gravity is the force | |
01:03 | that keeps us from flying off the surface of the | |
01:06 | earth . And you know that gravity pulls things knocked | |
01:08 | down but towards the earth center . You also know | |
01:11 | that gravity exists between any objects that have mass and | |
01:14 | the greater and objects masses . The greater the effect | |
01:16 | of its gravity or pull on other objects is . | |
01:19 | But there's something more . Remember . Isaac Newton , | |
01:22 | the Apple Tree guy . He determined that the amount | |
01:24 | of gravitational force or pulled between two objects also depends | |
01:28 | on how far apart they are . So the farther | |
01:30 | away something is from the Earth . The letter will | |
01:32 | feel the pull of Earth's gravity and the closer it | |
01:34 | gets to the moon , the more it will feel | |
01:36 | the moon's gravity pulling on it . Let's do a | |
01:38 | little pretending to see what happens to something when it | |
01:41 | moves closer to an object that has a really large | |
01:43 | mass and therefore a really strong pull of gravity , | |
01:47 | mm If you've ever made a wish on a shooting | |
01:52 | star , you've seen the effect of Earth's gravity pulling | |
01:54 | on an object . Shooting stars which are actually Meteors | |
01:57 | occur when pieces of rock break off from a passing | |
02:00 | comet or asteroid and get too close to the Earth | |
02:03 | . For example , say this globe represents the Earth | |
02:05 | and the marble represents a piece of space rock that's | |
02:08 | flying by . You can see that there's a huge | |
02:10 | difference in size between the two objects and if we | |
02:13 | were to put them on a scale , we see | |
02:14 | that there's a big difference in their mass to our | |
02:17 | model , Earth has a larger mass . If the | |
02:19 | space rock is far away from the Earth , then | |
02:21 | it can go on its merry way , since it | |
02:23 | won't be affected by the Earth's gravity . But if | |
02:25 | it gets too close than it and the Earth engage | |
02:28 | in a bit of tug of war since both have | |
02:30 | gravity , they pull on one another . It's not | |
02:32 | much of a fight though . The more massive Earth | |
02:33 | has a much larger gravitational pull , so the rockets | |
02:36 | caught in Earth's gravity and most of the time it | |
02:39 | gives us a brilliant streak of light , we call | |
02:41 | a meteor . But what does this mean for our | |
02:42 | space travelers ? Well , when an astronaut ship takes | |
02:45 | off for the moon and moves away from the Earth | |
02:48 | , the farther from Earth it goes , the less | |
02:49 | it feels the pull of Earth's gravity , and as | |
02:52 | it gets closer to the moon , the spaceship begins | |
02:54 | to feel the tug of the moon's gravity more so | |
02:56 | even though the moon has a smaller mass than the | |
02:58 | Earth and has less of a pull on the ship | |
03:00 | than the Earth does . Once the ship gets closer | |
03:02 | to the moon than the Earth , the moon's gravity | |
03:04 | pulls the ship toward it and then the astronauts can | |
03:07 | make a safe landing so we can make the argument | |
03:13 | that two things affect the pull of gravity . First | |
03:16 | , the size of the object objects with a bigger | |
03:18 | mass have a stronger pull of gravity and second , | |
03:20 | the distance between objects , the farther apart objects are | |
03:24 | the weaker the pull of gravity between them and the | |
03:26 | closer together they are , the stronger the pull of | |
03:28 | gravity . All of this means that when the day | |
03:30 | comes that you're flying a spaceship to the moon , | |
03:32 | you just have to escape Earth's gravity and then get | |
03:34 | close enough to the moon to enter its gravity . | |
03:37 | Remember that when you're grown up and you're welcome if | |
03:39 | you want to thank me , you could just name | |
03:41 | a crater or something after me . When you get | |
03:42 | there |
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