Book: Death by Black Hole: And Other Cosmic Quandaries
Quotes of Book: Death by Black Hole: And Other
Let's grant that the stars are scattered through space, hither and yon. But how hither, and how yon? To the unaided eye the brightest stars are more than a hundred times brighter than the dimmest. So the dim ones are obviously a hundred times farther away from Earth, aren't they?Nope.That simple argument boldly assumes that all stars are intrinsically equally luminous, automatically making the near ones brighter than the far ones. Stars, however, come in a staggering range of luminosities, spanning ten orders of magnitude ten powers of ten. So the brightest stars are not necessarily the ones closest to Earth. In fact, most of the stars you see in the night sky are of the highly luminous variety, and they lie extraordinarily far away.If most of the stars we see are highly luminous, then surely those stars are common throughout the galaxy.Nope again.High-luminosity stars are the rarest. In any given volume of space, they're outnumbered by the low-luminosity stars a thousand to one. It's the prodigious energy output of high-luminosity stars that enables you to see them across such large volumes of space. book-quotephysicsIn the twentieth century, astrophysicists in the United States discovered galaxies, the expanding of the universe, the nature of supernovas, quasars, black holes, gamma-ray bursts, the origin of the elements, the cosmic microwave background, and most of the known planets in orbit around solar systems other than our own. Although the Russians reached one or two places before us, we sent space probes to Mercury, Venus, Jupiter, Saturn, Uranus, and Neptune. American probes have also landed on Mars and on the asteroid Eros. And American astronauts have walked on the Moon. Nowadays most Americans take all this for granted, which is practically a working definition of culture: something everyone does or knows about, but no longer actively notices.While shopping at the supermarket, most Americans aren't surprised to find an entire aisle filled with sugar-loaded, ready-to-eat breakfast cereals. But foreigners notice this kind of thing immediately, just as traveling Americans notice that supermarkets in Italy display vast selections of pasta and that markets in China and Japan offer an astonishing variety of rice. The flip side of not noticing your own culture is one of the great pleasures of foreign travel: realizing what you hadn't noticed about your own country, and noticing what the people of other countries no longer realize about themselves. book-quote
