Primbon - Five planets were known to the ancients: Mercury, Venus, Mars, Jupiter and Saturn. Four of them are in plain view on many nights. But little Mercury is different. There’s a reason why it was named for the quick, mercurial messenger of the gods. It dashes back and forth between the sunrise and sunset sky, staying out of sight most of the time and usually hiding low in the twilight when it shows at all.
Ramalan Primbon - As a result, you may have never seen Mercury. This week, however, it stands in unusually plain view about as high and bright as it ever gets. What’s more, it has a brilliant companion practically hollering for you to come pay attention.
Look low in the west as twilight fades, and you’ll see not just one shining world, but two. The brilliant one is Venus. Mercury is the smaller, shyer partner just to Venus’s right or lower right, separated from it by about the width of two fingers at arm’s length.
Although they look close together, Venus is actually 50 percent farther away. It shines so much brighter, despite its greater distance, for three reasons. It’s about twice as big a planet as Mercury; it’s covered with brilliant white clouds, while Mercury is a bare world of dark gray rocks and dust; and Venus is also showing us more of its sunlit dayside right now.
The great Copernicus myth
Mercury’s elusive nature is legendary. And one of the best legends about it is false, yielding only now to a century of debunking.
In the late 1500s, the reclusive astronomer Nicolas Copernicus figured out two extraordinary things, that Earth is a planet like the ones in the sky and that all of them circle around the sun. He was the opposite of a glory seeker. He kept his secret largely to himself for many years, published it only in his dying days, and even then seemed to hedge it with qualifications and digressions. As a canon in the Catholic Church, perhaps he was afraid of the kind of harsh reaction that would later overtake Giordano Bruno and Galileo Galilei.
His theory took decades of work. The trick was to measure the positions of the planets on numerous dates — as seen on the apparent dome of the sky, like specks of paint on the inside of a huge hemisphere — and correctly interpret their complicated, puzzling motions.
Copernicus’s breakthrough was in realizing that their inexplicable loops, backtracks, and forward races on the starry sky-dome made sense if the planets were actually following simple orbits in three-dimensional space, centered on the sun — and if Earth was doing the same thing, too.
But getting it right required a large number of measurements. And each of these had to be processed with 3-D geometry and trigonometry when every calculation was done with pencil and paper. Copernicus relied mostly on measurements made by earlier astronomers. He made relatively few observations himself and spent most of his life indoors puzzling over the math.
Mercury was especially tough. It moves fast, it follows (we now know) an unusually elliptical orbit, and it spends a lot of time out of sight. A legend developed that on his deathbed, Copernicus lamented that he had never actually seen Mercury. In the 1840s, a popular German science book titled Kosmos, by the great naturalist and explorer Alexander von Humboldt, spread this legend far and wide. As a result, it became a fixture in popular science writing for more than a century.
It seemed plausible. Copernicus lived much of his life in what is now northern Poland, at a latitude where Mercury remains especially low. And he often complained about the Baltic mists and fogs blotting out his views.
But no. It is clear from Copernicus’s writings that what bothered him was his inability to measure Mercury’s position at times when the planet was especially near the horizon, leaving gaps in his data. By the 1890s, the deathbed tale had been debunked many times. But a good story is hard to kill. It was still being published when I was a kid learning astronomy in the 1960s.
Eventually, however, truth won out. You don’t run into the tale in the 2000s. It is good to know that sometimes it is possible to lay a popular falsehood to rest, though it may take more than a century.
Ramalan Primbon - As a result, you may have never seen Mercury. This week, however, it stands in unusually plain view about as high and bright as it ever gets. What’s more, it has a brilliant companion practically hollering for you to come pay attention.
Look low in the west as twilight fades, and you’ll see not just one shining world, but two. The brilliant one is Venus. Mercury is the smaller, shyer partner just to Venus’s right or lower right, separated from it by about the width of two fingers at arm’s length.
Although they look close together, Venus is actually 50 percent farther away. It shines so much brighter, despite its greater distance, for three reasons. It’s about twice as big a planet as Mercury; it’s covered with brilliant white clouds, while Mercury is a bare world of dark gray rocks and dust; and Venus is also showing us more of its sunlit dayside right now.
The great Copernicus myth
Mercury’s elusive nature is legendary. And one of the best legends about it is false, yielding only now to a century of debunking.
In the late 1500s, the reclusive astronomer Nicolas Copernicus figured out two extraordinary things, that Earth is a planet like the ones in the sky and that all of them circle around the sun. He was the opposite of a glory seeker. He kept his secret largely to himself for many years, published it only in his dying days, and even then seemed to hedge it with qualifications and digressions. As a canon in the Catholic Church, perhaps he was afraid of the kind of harsh reaction that would later overtake Giordano Bruno and Galileo Galilei.
His theory took decades of work. The trick was to measure the positions of the planets on numerous dates — as seen on the apparent dome of the sky, like specks of paint on the inside of a huge hemisphere — and correctly interpret their complicated, puzzling motions.
Copernicus’s breakthrough was in realizing that their inexplicable loops, backtracks, and forward races on the starry sky-dome made sense if the planets were actually following simple orbits in three-dimensional space, centered on the sun — and if Earth was doing the same thing, too.
But getting it right required a large number of measurements. And each of these had to be processed with 3-D geometry and trigonometry when every calculation was done with pencil and paper. Copernicus relied mostly on measurements made by earlier astronomers. He made relatively few observations himself and spent most of his life indoors puzzling over the math.
Mercury was especially tough. It moves fast, it follows (we now know) an unusually elliptical orbit, and it spends a lot of time out of sight. A legend developed that on his deathbed, Copernicus lamented that he had never actually seen Mercury. In the 1840s, a popular German science book titled Kosmos, by the great naturalist and explorer Alexander von Humboldt, spread this legend far and wide. As a result, it became a fixture in popular science writing for more than a century.
It seemed plausible. Copernicus lived much of his life in what is now northern Poland, at a latitude where Mercury remains especially low. And he often complained about the Baltic mists and fogs blotting out his views.
But no. It is clear from Copernicus’s writings that what bothered him was his inability to measure Mercury’s position at times when the planet was especially near the horizon, leaving gaps in his data. By the 1890s, the deathbed tale had been debunked many times. But a good story is hard to kill. It was still being published when I was a kid learning astronomy in the 1960s.
Eventually, however, truth won out. You don’t run into the tale in the 2000s. It is good to know that sometimes it is possible to lay a popular falsehood to rest, though it may take more than a century.
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