“Sure, black holes can kill us, and in a variety of interesting and gruesome ways. But, all in all, we may owe our very existence to them”*…
If you want to see a black hole tonight, just look in the direction of Sagittarius, the constellation. That’s the center of the Milky Way Galaxy and there’s a raging black hole at the very center of that constellation that holds the galaxy together.
– Michio Kaku
So, which came first: the galaxies spread through the universe, of the black holes that hold them together? Ethan Siegel answers and explains.
* Philip Plait, Death from the Skies!: These Are the Ways the World Will End…
As we raise our eyes, we might send star-struck birthday greetings to Johann Rudolf Wolf; he was born on this date in 1816. A distinguished astronomer and mathematician, Wolf wrote on prime number theory, geometry, probability, and statistics; but he is best remembered for his work on sunspots. Working from Heinrich Schwabe’s suggestion that sunspot activity was cyclical, Wolf calculated the period of the cycle at 11.1 years; he was among the first to establish the connection of sunspot activity to geomagnetic activity on Earth; and he developed a way of quantifying sunspot activity– the Wolf number, as it is known– that remains in use.