--- title: Black holes — a lesson of Mova's school · trees and pragmatics description: «Black holes», a lesson of the space course of Mova's primary school, sentence by sentence with dependency trees and pragmatics. It begins: A black hole is not a hole and not a cosmic vacuum cleaner: it is a huge amount of mass squeezed into a tiny space, so its gravity is so strong that not even li --- [Mova](https://md.mova.elamur.ai/free/en/) · [this page in HTML](https://mova.elamur.ai/free/en/corpora/school/space/25-black-holes/) [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/) / Black holes # Black holes Lesson 25 of the space 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/space/25-black-holes/). - [0](https://md.mova.elamur.ai/free/en/corpora/school/space/25-black-holes/0/) — A black hole is not a hole and not a cosmic vacuum cleaner: it is a huge amount of mass squeezed into a tiny space, so its gravity is so strong that not even light can get out. - [1](https://md.mova.elamur.ai/free/en/corpora/school/space/25-black-holes/1/) — Its edge is the event horizon, a point of no return: like a waterfall, you can paddle safely far upstream, but once you go over the edge you can never come back. - [2](https://md.mova.elamur.ai/free/en/corpora/school/space/25-black-holes/2/) — Squeeze the whole Earth down to the size of a marble, about 9 millimetres across, and it would become a black hole. - [3](https://md.mova.elamur.ai/free/en/corpora/school/space/25-black-holes/3/) — Far from a black hole its pull is just like that of any star of the same mass: if the Sun became a black hole, Earth would keep circling, only cold and dark. - [4](https://md.mova.elamur.ai/free/en/corpora/school/space/25-black-holes/4/) — We cannot see black holes directly, but we see what they do: stars racing round nothing visible, gas glowing as it falls in, and ripples in space when two of them crash. - [5](https://md.mova.elamur.ai/free/en/corpora/school/space/25-black-holes/5/) — A black hole is a place where so much mass is squeezed into a small space that its gravity lets nothing, not even light, escape. - [6](https://md.mova.elamur.ai/free/en/corpora/school/space/25-black-holes/6/) — The edge of a black hole is called the event horizon: anything that crosses it can never come back out. - [7](https://md.mova.elamur.ai/free/en/corpora/school/space/25-black-holes/7/) — Some very heavy stars collapse into black holes at the end of their lives, usually a few to a few dozen times the mass of the Sun; the Sun is far too light to become one and will end as a white dwarf. - [8](https://md.mova.elamur.ai/free/en/corpora/school/space/25-black-holes/8/) — The nearest known black holes are more than a thousand light years away, far too far to harm us. - [9](https://md.mova.elamur.ai/free/en/corpora/school/space/25-black-holes/9/) — Most large galaxies have a supermassive black hole at their centre, millions to billions of times the mass of the Sun. - [10](https://md.mova.elamur.ai/free/en/corpora/school/space/25-black-holes/10/) — In 2019 the Event Horizon Telescope published the first image of a black hole's shadow, M87\*, a dark centre in a glowing orange ring. - [11](https://md.mova.elamur.ai/free/en/corpora/school/space/25-black-holes/11/) — If the Sun were replaced by a black hole of the same mass, Earth would keep orbiting just as before, only in the cold and dark. - [12](https://md.mova.elamur.ai/free/en/corpora/school/space/25-black-holes/12/) — Falling feet-first towards a small black hole, the pull on your feet would be so much stronger than on your head that you would be stretched out like spaghetti. - [13](https://md.mova.elamur.ai/free/en/corpora/school/space/25-black-holes/13/) — To become a black hole, Earth would have to be squeezed to about 9 millimetres across, about the size of a marble. - [14](https://md.mova.elamur.ai/free/en/corpora/school/space/25-black-holes/14/) — In 2015 the LIGO detectors in the USA first caught gravitational waves, ripples in space from two black holes merging about 1.3 billion light years away. - [15](https://md.mova.elamur.ai/free/en/corpora/school/space/25-black-holes/15/) — Black holes cannot be seen directly, so astronomers find them by their effects: stars orbiting nothing visible, or hot gas glowing as it falls in. - [16](https://md.mova.elamur.ai/free/en/corpora/school/space/25-black-holes/16/) — Close to a black hole, time runs more slowly compared with far away, an effect predicted by Einstein. - [17](https://md.mova.elamur.ai/free/en/corpora/school/space/25-black-holes/17/) — In 1974 Stephen Hawking calculated that black holes should slowly leak tiny amounts of energy and, over unimaginably long times, evaporate. - [18](https://md.mova.elamur.ai/free/en/corpora/school/space/25-black-holes/18/) — Hawking's leaking, called Hawking radiation, has never been directly observed, because it is far too faint. - ← previous: [Galaxies and the Big Bang](https://md.mova.elamur.ai/free/en/corpora/school/space/24-galaxies-and-the-big-bang/) - next →: [Exoplanets and the search for life](https://md.mova.elamur.ai/free/en/corpora/school/space/26-exoplanets-and-the-search-for-life/) - ↑ back to [Space](https://md.mova.elamur.ai/free/en/corpora/school/space/)