Mon Jul 18, 2022 ROBERT HOOKE
Robert Hooke, born on July 18, 1635, is 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 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 19, 2022 STARS OF THE SUMMER TRIANGLE
The Summer Triangle is made up of three bright stars that are in our eastern sky after sunset at this time of the year. The highest star, Vega, is the brightest of the three, but the star Altair, below and a little to the south of Vega, is almost as bright. The third star, the northernmost one, is called Deneb, and it’s no match for the brightnesses of the other two. But that’s because, as you may have guessed, Deneb is much farther away from us, so its light is correspondingly dimmer. Altair is a mere seventeen light years away – that’s a little over a hundred trillion miles. Vega is a little farther away, twenty-five light years, but it’s an intrinsically brighter star, and that extra luminosity makes it brighter. But Deneb, which is the dimmest star, is also about a hundred times more distant; if Deneb were as close to us as the other two, it would be bright enough to cast shadows!
Wed Jul 20, 2022 APOLLO 11 LANDING ANNIVERSARY
Fifty-three years ago today, astronauts Neil Armstrong, Buzz Aldrin and Mike Collins were orbiting the moon. 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.
Thu Jul 21, 2022 THE MILKY WAY AND THE LOCAL GROUP
The Milky Way, part of it at least, can be seen tonight under clear dark skies. It spreads across the eastern sky, from Cassiopeia in the north to Sagittarius in the south. The Milky Way is our home galaxy; we live on a planet orbiting a star about two-thirds of the way out from its center. We have satellite galaxies, most notably the Large and Small Magellanic Clouds. And there’s a bigger spiral galaxy about 2 and a half million light years away: its catalog number is M31, but we know it best as the Andromeda Galaxy. Now besides the Milky Way and M31, there are about 30 other, smaller galaxies in the immediate neighborhood (and by “immediate neighborhood,” we mean anything that’s within a million parsecs of here.) This cluster of galaxies is called the Local Group. Most of them are fairly small and contain only a billion or so stars. M31 and the Milky Way are the Group’s gravitational “anchors”.
Fri Jul 22, 2022 LOOK-BACK TIME
If you can manage to live 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 distance measurement comes from the Hipparcos space satellite. 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!
