Skywatch for the week of July 19, 2021
Mon Jul 19, 2021 ROBERT HOOKE
Robert Hooke was born on July 18, 1635. He’s best known for his pioneering work in analyzing insects, plants, all manner of things in nature, using a microscope. He made a lot of sketches, and first described the cell-like structure of living organisms. He was also a mortal enemy of Isaac Newton. In fiction, Sherlock Holmes had to combat Professor Moriarty; Superman had to fight Lex Luthor; and Batman had to deal with the Joker. For Isaac Newton, it was this guy – Robert Hooke. Newton had just been made a member of the Royal Society, a group of English and European philosophers and scientists. Newton had built a small reflecting telescope, the first of its kind, and he was persuaded to share his experiments on how the eye sees light. Hooke, who had done some work in this area, strongly criticized Newton, and Newton didn’t like it. Hooke also claimed to have worked out the laws of gravity long before Newton’s published work, Principia. Thus began a life-long battle between the two.
Tue Jul 20, 2021 APOLLO 11 LANDING ANNIVERSARY
Fifty-two years ago today, astronauts Neil Armstrong, Buzz Aldrin and Mike Collins were orbiting the moon. They were not its first visitors: six men had preceded them, in Apollo’s 8 and 10; but those astronauts never landed. When the lunar lander Eagle separated from the Apollo command ship Columbia, Aldrin and Armstrong piloted it down to the moon’s surface, and on July 20th, 1969, at 4:18 pm they landed on the southern edge of Mare Tranquilitatis, the Sea of Tranquility – a huge lava flow of dark basaltic rock. At 10:56 pm, Neil Armstrong stepped onto the lunar surface, followed by Buzz Aldrin about ten minutes later. They were outside for two-and-a-half hours, setting up several lunar science experiments and collecting about fifty pounds of moon rocks. Shortly before 2 pm Eastern Daylight Time, their lunar lander Eagle blasted off from the moon and rejoined Command module pilot Mike Collins who was on board the Columbia in orbit. All three returned to earth on July 24th, 1969.
Wed Jul 21, 2021 LOOK-BACK TIME
If you can manage to live for a full century, go outside at night on your 101st birthday and look at the star at the end of the handle of the Big Dipper, in the northwest this evening. The light from that star, Alkaid, left there the day you were born (This calculation comes from data collected by the Hipparcos satellite; some of my colleagues insist that Alkaid is really 104 light years away, so you may want to hang on a few more years just in case.) Now go farther out: in the south is the star Antares, 500 light years away. If it went supernova today, we wouldn’t know about it for another 500 years. It takes light time to travel across the Universe. This phenomenon, Look Back Time, means that the farther something is from us, the older it is. So when we look at the Andromeda Galaxy, 2.5 million light years away, it’s what that galaxy looked like 2 and a half million years ago. What does it look like now? Not sure, but I’ll know, in about 2 and a half million years!
Thu Jul 22, 2021 FULL MOON HANGS LOW
All full moons rise at sunset and set at sunrise. So full moons are at their highest around the midnight hour (or 1 am, if you throw in daylight savings time.) But even though it’s at its highest then, July’s full moon isn’t very high. You see, full moons are directly opposite the sun. So they occupy the part of the sky where the sun will be found six months later. Half a year from now it will be winter, and the sun’s path in winter is very low; even at noon it’s not far off the south horizon. In summer the full moon is at the spot where the sun is in winter. So the summer’s full moon mimics the sun’s wintertime path. This also means that full moons in winter can reach the top of the sky at midnight, mimicking the sun’s path in summertime. So this month’s full moon won’t get very far above the horizon, and will be at a convenient altitude for us to admire it, just above the treetops, low in the southern sky at the midnight hour. Check out the full moon this weekend.
Fri Jul 23, 2021 JULY FULL MOON
The moon is full this weekend. Because thunderstorms are common in July, this full moon is often called the Thunder moon. According to the Sioux Indians, this is the Moon When the Wild Cherries Are Ripe. To the Winnebago, it is the Corn-Ripening Moon, and to the Kiowas, it is the Moon of Deer Horns Dropping Off. To the Omaha Indians, however, this is the Moon When the Buffalo Bellow. In ancient China, this was the Hungry Ghost Moon, named for departed souls who had left no descendants, and who according to legend caused drought, famine, fire or other disasters. In medieval times this was the Hay Moon or the Mead Moon, named for the elixir from the meadows of Briton and Europe. After this full moon came the first harvests from the fields and the pagan festival of Lughnasaid. Lughnasaid was later adopted by early Christians and became the celebration of Lammas, or “loaf mass,” in thanksgiving for the first fruits of the farmer’s labor.