„Save the date” is a series of articles that have been written to celebrate various unusual holidays. The authors of the presented materials are students, doctoral students and employees of the Faculty of Science and Technology of the University of Silesia.
On the occasion of Black Friday, we invite you to read a short article by Prof. Jan Sładkowski from August Chełkowski Institute of Physics about the most black phenomenon that humanity has discovered – not only on Friday.
Fot. Katarzyna Balin
Prof. Jan Sładkowski
Institute of Physics
Today we have the so-called Black Friday. Unfortunately, when someone falls into the vortex of promotional purchases, it is extremely difficult to get out of it! Physicists also know objects that can completely take over the observer. We refer to them by the term black holes. Roughly speaking, a black hole is a region of spacetime in which gravity is so strong that nothing – not even light – can leave it. The idea that a gravitational field could be strong enough to trap even light was born in the 18th century in the minds of (independently) John Mitchell (1784) and Pierre-Simon Laplace. In 1916, Karl Schwarzschild found a solution to Einstein’s equations that describes a region of spacetime having an interpretation of a black hole. Initially, they were considered a mathematical curiosity. Today we have many convincing observations that such objects do exist. For example, an imbalance between gravitational forces and nuclear reactions in a massive star can lead to it collapsing and creating a black hole. Here are some features of black holes:
- The commonly held belief that a black hole is very dense is incorrect. For example, the largest known supermassive black hole TON 618 (https://en.wikipedia.org/wiki/TON_618) has a density of around 4.5 g/m3! On the other hand, Sagittarius A* in the center of the Milky Way (https://en.wikipedia.org/wiki/Sagittarius_A) already has a density of about 10^6 kg /m3.
- Recently, the EHT collaboration published the first ‘photo’ of a black hole available at https://www.nasa.gov/mission_pages/chandra/news/black-hole-image-makes-history.
- You can find many simulations of black hole behavior on the Internet, for example https://www.nasa.gov/feature/goddard/2021/black-hole-simulations-provide-blueprint-for-future-observations or https://www.youtube.com/watch?v=hu6hIhW00Fk
Soon – on December 9, 2021 – we will move to August Chełkowski Institute of Physics, where an interdisciplinary conference will be held.
“Lem’s Physics: Yesterday’s Fiction, Today’s Science.”
Until then, to listen, to think!