Posts Tagged ‘galaxies’
“Look up at the stars and not down at your feet. Try to make sense of what you see, and wonder about what makes the universe exist.”*…
Our environment…
This map shows a slice of our Universe. It was created from astronomical data taken night after night over a period of 15 years using a telescope in New Mexico, USA. We are located at the bottom. At the top is the actual edge of the observable Universe. In between, we see about 200,000 galaxies.
Each tiny dot is a galaxy. About 200,000 are shown with their actual position and color. Each galaxy contains billions of stars and planets. We are located at the bottom. Our galaxy, the Milky Way, is just a dot. Looking up, we see that space is filled with galaxies forming a global filamentary structure. Far away from us (higher up in the map), the filaments become harder to see…
For a (much crisper, more vivid, and interactive) version: “The Map of the Observable Universe.”
* Stephen Hawking
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As we explore, we might recall that it was on this date in 1616 that The Minutes of the Roman Inquisition recorded the conclusion that Galileo’s writings in support of Copernicus’ heliocentric view of the solar system were “foolish and absurd in philosophy, and formally heretical since it explicitly contradicts in many places the sense of Holy Scripture.” The next day, Galileo was called before Cardinal Bellarmine, who (on Pope Paul V’s instruction) ordered Galileo to abandon the teaching. Shortly thereafter, Copernicus’s De Revolutionibus and other heliocentric works were banned (entered onto the Index Librorum Prohibitorum) “until correction.”
Sixteen years later, Galileo “published” Dialogue Concerning the Two Chief World Systems (Dialogo sopra i due massimi sistemi del mondo)– that’s to say, he presented the first copy to his patron, Ferdinando II de’ Medici, Grand Duke of Tuscany. Dialogue, which compared the heliocentric Copernican and the traditional geo-centric Ptolemaic systems, was an immediate best-seller.
While there was no copyright available to Galileo, his book was printed and distributed under a license from the Inquisition. Still, the following year it was deemed heretical– and he joined Copernicus on the Index Librorum Prohibitorum: the publication of anything else Galileo had written or ever might write was also banned… a ban that remained in effect until 1835.
“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…
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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.
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