--- title: How the Solar System was born — a lesson of Mova's school · trees and pragmatics description: «How the Solar System was born», a lesson of the space course of Mova's primary school, sentence by sentence with dependency trees and pragmatics. It begins: About 4.6 billion years ago there was no Sun and no Earth, only a huge, cold cloud of gas and dust called the solar nebula. --- [Mova](https://md.mova.elamur.ai/free/en/) · [this page in HTML](https://mova.elamur.ai/free/en/corpora/school/space/2-how-the-solar-system-was-born/) [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/) / How the Solar System was born # How the Solar System was born Lesson 2 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/2-how-the-solar-system-was-born/). - [0](https://md.mova.elamur.ai/free/en/corpora/school/space/2-how-the-solar-system-was-born/0/) — About 4.6 billion years ago there was no Sun and no Earth, only a huge, cold cloud of gas and dust called the solar nebula. - [2](https://md.mova.elamur.ai/free/en/corpora/school/space/2-how-the-solar-system-was-born/2/) — Most of the gas fell into the middle, which got so hot and squashed that fusion switched on: the Sun was born. - [3](https://md.mova.elamur.ai/free/en/corpora/school/space/2-how-the-solar-system-was-born/3/) — In the disc, dust stuck into pebbles, pebbles into rocks, rocks into small worlds, rolling bigger like a snowball, and these crashed and merged into planets. - [4](https://md.mova.elamur.ai/free/en/corpora/school/space/2-how-the-solar-system-was-born/4/) — Near the hot young Sun only rock and metal stayed solid, so the inner planets are small and rocky; further out ice could form too, and the outer planets grew into giants. - [5](https://md.mova.elamur.ai/free/en/corpora/school/space/2-how-the-solar-system-was-born/5/) — The Solar System formed about 4.6 billion years ago from a huge cloud of gas and dust called the solar nebula, which collapsed under its own gravity. - [7](https://md.mova.elamur.ai/free/en/corpora/school/space/2-how-the-solar-system-was-born/7/) — All eight planets go round the Sun in the same direction, the same way the Sun itself spins. - [8](https://md.mova.elamur.ai/free/en/corpora/school/space/2-how-the-solar-system-was-born/8/) — Most of the gas fell to the centre, and when it became hot and dense enough, fusion switched on and the Sun was born. - [9](https://md.mova.elamur.ai/free/en/corpora/school/space/2-how-the-solar-system-was-born/9/) — In the disc, dust grains stuck together into pebbles, then rocks, then bodies kilometres wide called planetesimals, which crashed and merged into planets. - [10](https://md.mova.elamur.ai/free/en/corpora/school/space/2-how-the-solar-system-was-born/10/) — Close to the Sun only rock and metal could stay solid, but beyond the frost line, around where the asteroid belt is now, ice could form too, so the outer planets grew much bigger. - [11](https://md.mova.elamur.ai/free/en/corpora/school/space/2-how-the-solar-system-was-born/11/) — Jupiter and Saturn grew solid cores about ten times the Earth's mass, then quickly pulled in vast amounts of hydrogen and helium gas. - [12](https://md.mova.elamur.ai/free/en/corpora/school/space/2-how-the-solar-system-was-born/12/) — Scientists think the Moon formed when a Mars-sized body, nicknamed Theia, smashed into the young Earth and threw out debris that gathered into the Moon; this is the leading idea, not proven beyond doubt. - [13](https://md.mova.elamur.ai/free/en/corpora/school/space/2-how-the-solar-system-was-born/13/) — The giant planets probably moved their orbits after they formed, scattering many small icy bodies inward and outward. - [15](https://md.mova.elamur.ai/free/en/corpora/school/space/2-how-the-solar-system-was-born/15/) — Astronomers have found more than 6,000 planets around other stars. - [16](https://md.mova.elamur.ai/free/en/corpora/school/space/2-how-the-solar-system-was-born/16/) — Telescopes such as ALMA in Chile have photographed dusty discs around young stars where new planets are forming right now. - ← previous: [The Sun, our star](https://md.mova.elamur.ai/free/en/corpora/school/space/1-the-sun-our-star/) - next →: [Mercury](https://md.mova.elamur.ai/free/en/corpora/school/space/3-mercury/) - ↑ back to [Space](https://md.mova.elamur.ai/free/en/corpora/school/space/)