Artist's drawing of black hole Cygnus X-1 - Credits: NASA/CXC/M.Weiss
Black Hole Friday
Other Scottish Country Dances for this Day
Today's Musings, History & Folklore
“Time is a wave or a black hole could not bend it; humanity rides the crest of an infinite number of waves that are perceived as linear in their limited frame of reference.”
~ Ken Poirot
In the US, if the thought of Black Friday shopping (allegedly the biggest shopping day of the year) is not your cup of tea, why not contemplate the mysteries of the universe instead - particularly black holes! A black hole is a region of spacetime where gravity is so strong that nothing - no particles nor even electromagnetic radiation such as light - can escape from it. The boundary of the region from which no escape is possible is called the event horizon. In recent news, astronomers have for the first time observed clumps of gas orbiting dangerously close to the giant black hole that lies at the heart of our Milky Way galaxy named Sagittarius A*. Recent observations of this area show that clumps of gas are orbiting at about 30 percent of the speed of light on a circular path just outside the black hole's event horizon! Watch out! ☀️ ☀ ⚫ 🔭
The Black Hole
The day after Thanksgiving in the United States is traditionally called "Black Friday" because so many people go out to shop that it can cause traffic accidents and other mayhem!
First coined in 1966 by the Philadelphia Police Department, today retailers use this term "Black Friday" in a positive way to advertise special sales.
Playing off this name, scientists at NASA (The National Aeronautic and Space Administration) humorously call this same Friday "Black Hole Friday" and hold mini-events for public education and outreach to engage and interest people in astronomy in general, and black holes in particular.
A black hole is a region of spacetime exhibiting such strong gravitational effects that nothing - not even particles nor electromagnetic radiation such as light - can escape from inside it. Einstein's theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole.
The first use of the term "black hole" in print was by a science journalist in a 1964 article titled "'Black Holes' in Space." In December 1967, a student reportedly suggested the phrase "black hole" at a lecture by John Wheeler. Wheeler adopted the term for its brevity and it quickly caught on.
Early 2016 saw first confirmation of evidence for gravitational waves, coming from two black holes, 30 times as massive as the sun, located 1.3 billion light years from earth, that orbited one another, spiraled inward and smashed together.
For a simulation of a model for the orbiting black holes, click the image of the supermassive black hole at the core of supergiant elliptical galaxy Messier 87, with a mass ~7 billion times the Sun's, as depicted in the first image released by the Event Horizon Telescope (10 April 2019).