--- title: Distances and light years — a lesson of Mova's school · trees and pragmatics description: «Distances and light years», a lesson of the space course of Mova's primary school, sentence by sentence with dependency trees and pragmatics. It begins: Space is so big that kilometres stop being useful, so astronomers measure it by how far light travels, the fastest thing there is. --- [Mova](https://md.mova.elamur.ai/free/en/) · [this page in HTML](https://mova.elamur.ai/free/en/corpora/school/space/22-distances-and-light-years/) [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/) / [Space](https://md.mova.elamur.ai/free/en/corpora/school/space/) / Distances and light years # Distances and light years Lesson 22 of the space course of Mova's primary school: 14 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/space/22-distances-and-light-years/). - [0](https://md.mova.elamur.ai/free/en/corpora/school/space/22-distances-and-light-years/0/) — Space is so big that kilometres stop being useful, so astronomers measure it by how far light travels, the fastest thing there is. - [1](https://md.mova.elamur.ai/free/en/corpora/school/space/22-distances-and-light-years/1/) — A light year sounds like a time, but it is a distance: how far light goes in one year, about 9.5 trillion kilometres. - [2](https://md.mova.elamur.ai/free/en/corpora/school/space/22-distances-and-light-years/2/) — Light is fast but not instant: sunlight that warms your face on the beach left the Sun about 8 minutes 20 seconds ago. - [3](https://md.mova.elamur.ai/free/en/corpora/school/space/22-distances-and-light-years/3/) — So when you look at a star you see old light, like getting a postcard posted long ago: you see the star as it was, not as it is now. - [6](https://md.mova.elamur.ai/free/en/corpora/school/space/22-distances-and-light-years/6/) — Light from the Moon takes about 1.3 seconds to reach us, and radio signals travel just as fast, so a call to astronauts on the Moon has a short delay, and sunlight takes about 8 minutes 20 seconds. - [7](https://md.mova.elamur.ai/free/en/corpora/school/space/22-distances-and-light-years/7/) — Astronomers measure the solar system in astronomical units, where 1 AU is Earth's average distance from the Sun, about 150 million km. - [8](https://md.mova.elamur.ai/free/en/corpora/school/space/22-distances-and-light-years/8/) — The nearest star after the Sun is Proxima Centauri, about 4.2 light years away, or about 40 trillion km. - [9](https://md.mova.elamur.ai/free/en/corpora/school/space/22-distances-and-light-years/9/) — Voyager 1, launched in 1977, is the farthest human-made object, and it is due to reach about one light-day from Earth, about 26 billion km, around late 2026. - [10](https://md.mova.elamur.ai/free/en/corpora/school/space/22-distances-and-light-years/10/) — Even at Voyager's speed, a journey to Proxima Centauri would take about 75,000 years. - [11](https://md.mova.elamur.ai/free/en/corpora/school/space/22-distances-and-light-years/11/) — When you look at a star, you see light that left it long ago, so you see the star as it was, not as it is now. - [12](https://md.mova.elamur.ai/free/en/corpora/school/space/22-distances-and-light-years/12/) — If the Sun were a football in the middle of a pitch, Earth would be a peppercorn about 25 metres away, and the nearest star another football thousands of kilometres away. - [13](https://md.mova.elamur.ai/free/en/corpora/school/space/22-distances-and-light-years/13/) — Professional astronomers often use the parsec, about 3.26 light years, a unit based on how stars seem to shift as Earth orbits the Sun. - [14](https://md.mova.elamur.ai/free/en/corpora/school/space/22-distances-and-light-years/14/) — Bright stars are at very different distances: Sirius is about 8.6 light years away, Vega about 25, Polaris about 430, and Deneb probably more than 1,500. - [15](https://md.mova.elamur.ai/free/en/corpora/school/space/22-distances-and-light-years/15/) — The Moon is moving away from Earth by about 3.8 centimetres a year, about as fast as fingernails grow. - ← previous: [The night sky in summer and autumn, and the southern sky](https://md.mova.elamur.ai/free/en/corpora/school/space/21-the-night-sky-in-summer-and-autumn-and-the-southern-sky/) - next →: [The Milky Way](https://md.mova.elamur.ai/free/en/corpora/school/space/23-the-milky-way/) - ↑ back to [Space](https://md.mova.elamur.ai/free/en/corpora/school/space/)