--- title: The Moon, the planets and the pull that holds them — a lesson of Mova's school · trees and pragmatics description: «The Moon, the planets and the pull that holds them», a lesson of the physics course of Mova's primary school, sentence by sentence with dependency trees and pragmatics. It begins: Swing a ball on a string round your head: the string keeps pulling the ball towards your hand and bends its path into a --- [Mova](https://md.mova.elamur.ai/free/en/) · [this page in HTML](https://mova.elamur.ai/free/en/corpora/school/physics/2-the-moon-the-planets-and-the-pull/) [home](https://md.mova.elamur.ai/free/en/) / [corpora](https://md.mova.elamur.ai/free/en/corpora/) / [school](https://md.mova.elamur.ai/free/en/corpora/school/) / [Physics](https://md.mova.elamur.ai/free/en/corpora/school/physics/) / The Moon, the planets and the pull tha… # The Moon, the planets and the pull that holds them Lesson 2 of the physics course of Mova's primary school: 19 sentences, each with its syntax tree and pragmatics. The lessons are written for Mova, and their agreed trees are part of Mova corpus 0.4 (CC BY-SA 4.0). How Mova does on its tests: [the lesson at school](https://md.mova.elamur.ai/free/en/school-run/physics/2-the-moon-the-planets-and-the-pull/). - [0](https://md.mova.elamur.ai/free/en/corpora/school/physics/2-the-moon-the-planets-and-the-pull/0/) — Swing a ball on a string round your head: the string keeps pulling the ball towards your hand and bends its path into a circle. - [1](https://md.mova.elamur.ai/free/en/corpora/school/physics/2-the-moon-the-planets-and-the-pull/1/) — The Moon is like that ball, and the Earth's gravity is the string: the Moon is falling towards us all the time, but it moves sideways so fast that it keeps missing. - [2](https://md.mova.elamur.ai/free/en/corpora/school/physics/2-the-moon-the-planets-and-the-pull/2/) — The same pull that drops an apple holds the Moon round the Earth and the Earth round the Sun; Isaac Newton was the first to show it is one and the same pull. - [3](https://md.mova.elamur.ai/free/en/corpora/school/physics/2-the-moon-the-planets-and-the-pull/3/) — Astronauts float in the space station not because gravity is gone, but because the station and everyone in it are falling round the Earth together. - [4](https://md.mova.elamur.ai/free/en/corpora/school/physics/2-the-moon-the-planets-and-the-pull/4/) — Your weight is how hard a planet pulls you, so on the small Moon you would weigh about one sixth as much, while your amount of stuff, your mass, stays the same. - [5](https://md.mova.elamur.ai/free/en/corpora/school/physics/2-the-moon-the-planets-and-the-pull/5/) — The Moon is falling towards the Earth all the time, but its sideways speed carries it past, so its path bends round the Earth. - [6](https://md.mova.elamur.ai/free/en/corpora/school/physics/2-the-moon-the-planets-and-the-pull/6/) — If the Earth's gravity switched off, the Moon would fly away in a straight line. - [7](https://md.mova.elamur.ai/free/en/corpora/school/physics/2-the-moon-the-planets-and-the-pull/7/) — Let go of a ball swung on a string and it flies off in a straight line, not in a curve. - [8](https://md.mova.elamur.ai/free/en/corpora/school/physics/2-the-moon-the-planets-and-the-pull/8/) — Up at the space station, gravity is still almost as strong as on the ground. - [9](https://md.mova.elamur.ai/free/en/corpora/school/physics/2-the-moon-the-planets-and-the-pull/9/) — Astronauts float because they and the station are falling round the Earth together, so nothing presses on the floor. - [10](https://md.mova.elamur.ai/free/en/corpora/school/physics/2-the-moon-the-planets-and-the-pull/10/) — On the Moon you would weigh about one sixth of your weight on Earth, and on Jupiter more than twice as much. - [11](https://md.mova.elamur.ai/free/en/corpora/school/physics/2-the-moon-the-planets-and-the-pull/11/) — Weight is how hard a planet pulls you; mass is how much stuff you are made of, and it does not change from planet to planet. - [12](https://md.mova.elamur.ai/free/en/corpora/school/physics/2-the-moon-the-planets-and-the-pull/12/) — Bathroom scales measure how hard you press on them: the spring inside squashes more when you press harder. - [13](https://md.mova.elamur.ai/free/en/corpora/school/physics/2-the-moon-the-planets-and-the-pull/13/) — In a lift that starts to go up, scales show more for a moment; in one that starts to go down, they show less. - [14](https://md.mova.elamur.ai/free/en/corpora/school/physics/2-the-moon-the-planets-and-the-pull/14/) — The Sun's gravity holds the Earth, and the Earth's sideways speed keeps it from falling into the Sun. - [15](https://md.mova.elamur.ai/free/en/corpora/school/physics/2-the-moon-the-planets-and-the-pull/15/) — Satellites that tell your phone where you are fall round the Earth like little moons, high above the air, with no engine needed; if one slows down too much, it drops into the air and burns up. - [16](https://md.mova.elamur.ai/free/en/corpora/school/physics/2-the-moon-the-planets-and-the-pull/16/) — A shooting star is not a star: it is a bit of space rock, often no bigger than a grain of sand, glowing as it rushes into the air, because the air in front of it gets squashed and very hot. - [17](https://md.mova.elamur.ai/free/en/corpora/school/physics/2-the-moon-the-planets-and-the-pull/17/) — Water stays in a bucket swung fast over your head because the bucket's bottom keeps pushing it round the circle. - [18](https://md.mova.elamur.ai/free/en/corpora/school/physics/2-the-moon-the-planets-and-the-pull/18/) — A roller coaster car stays on the track upside down in a loop because it is going fast enough that the track has to keep pushing it round. - ← previous: [Why things fall: the apple and the pull of the Earth](https://md.mova.elamur.ai/free/en/corpora/school/physics/1-why-things-fall/) - next →: [Parachutes, skydivers and falling safely](https://md.mova.elamur.ai/free/en/corpora/school/physics/3-parachutes-and-falling-safely/) - ↑ back to [Physics](https://md.mova.elamur.ai/free/en/corpora/school/physics/)