--- title: Thinking like an astronomer — a lesson of Mova's school · trees and pragmatics description: «Thinking like an astronomer», a lesson of the world course of Mova's primary school, sentence by sentence with dependency trees and pragmatics. It begins: The Moon turns around its own axis exactly once while it goes around the Earth once, so it always keeps the same face towards us: walk around a --- [Mova](https://md.mova.elamur.ai/free/en/) · [this page in HTML](https://mova.elamur.ai/free/en/corpora/school/world/10-reasoning-about-space/) [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/) / [World](https://md.mova.elamur.ai/free/en/corpora/school/world/) / Thinking like an astronomer # Thinking like an astronomer Lesson 10 of the world course of Mova's primary school: 16 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/world/10-reasoning-about-space/). - [0](https://md.mova.elamur.ai/free/en/corpora/school/world/10-reasoning-about-space/0/) — The Moon turns around its own axis exactly once while it goes around the Earth once, so it always keeps the same face towards us: walk around a chair while always facing it, and you will find you have turned around once yourself. - [1](https://md.mova.elamur.ai/free/en/corpora/school/world/10-reasoning-about-space/1/) — Your mass, the amount of you, is the same everywhere, but your weight is the pull of gravity on you; the Moon has much less mass than the Earth, so it pulls about six times more weakly, and a child of 30 kilograms would weigh as much as 5 kilograms do on the Earth. - [2](https://md.mova.elamur.ai/free/en/corpora/school/world/10-reasoning-about-space/2/) — The night sky is dark although there are countless stars, because the universe had a beginning: light from very distant stars has not had time to reach us, and so in most directions our sight runs out into darkness before it meets a star. - [3](https://md.mova.elamur.ai/free/en/corpora/school/world/10-reasoning-about-space/3/) — The sky is blue by day because the air scatters the blue part of sunlight all over the sky; on the Moon, with no air, the sky is black even at noon and the stars can be seen beside the Sun. - [4](https://md.mova.elamur.ai/free/en/corpora/school/world/10-reasoning-about-space/4/) — An astronomer cannot travel to the stars, so he reasons from what he sees: shadows, shapes, timings and the rules of light and gravity. - [5](https://md.mova.elamur.ai/free/en/corpora/school/world/10-reasoning-about-space/5/) — The Moon turns once on its axis in the same time it takes to go once around the Earth. - [6](https://md.mova.elamur.ai/free/en/corpora/school/world/10-reasoning-about-space/6/) — Because of this, we always see the same side of the Moon from the Earth. - [7](https://md.mova.elamur.ai/free/en/corpora/school/world/10-reasoning-about-space/7/) — The far side of the Moon gets sunlight too; it is not always dark. - [8](https://md.mova.elamur.ai/free/en/corpora/school/world/10-reasoning-about-space/8/) — Mass is the amount of matter in an object, and it is the same everywhere. - [9](https://md.mova.elamur.ai/free/en/corpora/school/world/10-reasoning-about-space/9/) — Weight is the pull of gravity on an object, and it changes from place to place. - [10](https://md.mova.elamur.ai/free/en/corpora/school/world/10-reasoning-about-space/10/) — The Moon's gravity is about one sixth of the Earth's gravity. - [12](https://md.mova.elamur.ai/free/en/corpora/school/world/10-reasoning-about-space/12/) — The Moon has no air, so its sky is black even in the daytime. - [13](https://md.mova.elamur.ai/free/en/corpora/school/world/10-reasoning-about-space/13/) — The Earth's sky is blue because air scatters blue sunlight in all directions. - [14](https://md.mova.elamur.ai/free/en/corpora/school/world/10-reasoning-about-space/14/) — The night sky is dark partly because light from very far stars has not yet had time to reach us. - [15](https://md.mova.elamur.ai/free/en/corpora/school/world/10-reasoning-about-space/15/) — Stars are spread out very thinly, with huge empty spaces between them. - [16](https://md.mova.elamur.ai/free/en/corpora/school/world/10-reasoning-about-space/16/) — On the Moon there is no wind or rain, so astronauts' footprints can last for millions of years. - ← previous: [Time zones and the calendar](https://md.mova.elamur.ai/free/en/corpora/school/world/9-time-zones-and-the-calendar/) - next →: [Solids, liquids and gases](https://md.mova.elamur.ai/free/en/corpora/school/world/11-solids-liquids-gases/) - ↑ back to [World](https://md.mova.elamur.ai/free/en/corpora/school/world/)