Gravitational Lenses

At the close of the previous chapter I mentioned Charlie Chaplin and his magnum opus Modern Times, a movie first shown in 1936. In the same year Albert Einstein published a short note in the journal Science concerning how starlight might be focused by gravitational fields. The gist of his paper was as follows. Consider again Figure 4-1 and imagine the light beams being extended to the right until they meet. Then you could think of the Sun as having acted as a lens a gravitational lens. Light...

Lunar Eclipses

That question may be answered by considering lunar eclipses. First, note that the frequency of lunar eclipses is not the same as the frequency of solar eclipses. Although the Earth is bigger than the Moon, so that it casts a larger shadow, the Moon is a smaller target for that shadow to hit and so, overall, lunar eclipses are not so numerous. There are on average 238 solar eclipses per century, but only 154 lunar eclipses. Despite their comparative infrequency, for an observer restricted to one...

By The Rivers Of Babylon

Much of the eclipse and calendar knowledge spreading from the Middle East to Greece and Rome and thence the rest of Europe stemmed from understandings developed in Mesopotamia between 3000 and 500 B.C. Mesopotamia is strictly the region between the Tigris and Euphrates rivers. In ancient times it was a bountiful shallow valley, the home of several distinct civilizations over the last three millennia B.C. Babylon itself was on the Euphrates, about 60 miles south of modern-day Baghdad. The...

S

Sabbath, 28, 29, 85, 365 Sabbatical, 28 Santa Fe railroad, 200 Saros, saronic cycle, 411-413, 414422 Babylonians on, 46, 85-86, 89 definition of, 46, 439 1878 eclipse and, 199-200 1999 eclipse and, 346 2017 eclipse and, 346 Halley on, 89, 90-91, 92-93, 94, 161 Hipparchus on, 88 latitude and, 227 leap years and, 46, 393, 411 Metonic cycle and, 79 predictions from, 49-51, 66 recording of, 86-87 total solar eclipses in, 65, 433 Satellite(s). See also specific satellites artificial, 301 artificial...

The Durations Of Eclipses

Although a small fraction last for as long as seven minutes, most present a period of totality lasting only two or three minutes. The partial phase of such an eclipse lasts for much longer, some hours. Refer back to Figure 2-3, and imagine that you are waiting somewhere on the track that the spot of totality will eventually cross, blanking out the Sun for a couple of minutes. The radius of the footprint delineating the penumbra is about 2,000 miles, and it sweeps...

Picture Credits

The following sources are gratefully acknowledged. All other diagrams and photographs are by the author. Figure 1-1 National Solar Observatory Sacramento Peak, Sunspot, New Mexico. Figure 1-2 John Walker, Fourmilab, Switzerland. Figure 1-3 High Altitude Observatory, National Center for Atmospheric Research, Boulder, Colorado. Figures 1-4, 13-3, and 13-4 G.F. Chambers, Handbook of Descriptive Astronomy (Clarendon Press, Oxford, 1877). Figure 1-5 SOHO Extreme Ultraviolet Imaging Telescope...

Eclipses of the Third Kind

Bad light planets too distant pestered with comets feeble contrivance could make a better myself. So far we've looked at two basic types of eclipse solar and lunar. Our Sun is not the only star whose face the Moon can pass across though. Every month the Moon, in its passage around the Earth, blocks out the light from some millions of stars in the Milky Way, and many extragalactic objects, too, each reappearing about an hour later behind the trailing limb of the Moon. Most...

The Importance Of Knowing The Suns Size

Total Eclipse Actual Path

No area of science has made recourse to historical information more often than astronomy, and Halley's 1715 eclipse compendium is a wonderful example, as we shall see. First, though, I must sketch in a little of the background. Halley was only 19 years old when he first made observations of sunspots, publishing the results in his second scientific paper. FIGURE 7-2. The actual total eclipse track observed in 1715, as assembled by Edmond Halley from eyewitness reports, along with his predicted...

The Distribution Of Eclipses

The average numbers of eclipses per century were mentioned in Chapter 2. The figures used were based on a monumental work by the nineteenth-century Viennese astronomer Theodor von Oppolzer, published posthumously in 1887. Using detailed theories for the orbits of the Sun and Moon, Oppolzer calculated by hand the circumstances for all eclipses between 1208 B.C. and A.D. 2161, a total of 3,368 years providing in all 8,000 solar and 5,200 lunar eclipses. From this compendium are derived the...

The First Voyage Of Lieutenant James Cook

The explorations of James Cook in the Pacific are well known, but the primary purpose of his first voyage, from 1768 to 1771, is not so extensively recognized. That purpose was to observe the anticipated transit of Venus on June 3, 1769, from Tahiti. In fact there had been a transit in 1761, as noted earlier, and the peculiar tale of that event will be told a little later in the book. For the time being, we pick up the story with Cook having been dispatched to the South Seas on board a small...

Ingress And Egress

Ingress and egress are the terms usually employed for the phases when Mercury or Venus are entering and leaving, respectively, the solar disk. Such terminology may also be used for eclipses and occultations, along with their synonyms immersion (or entrance) and emersion (or emergence). The different contact points for a transit are shown in Figure 13-2. Ingress lasts from when the planet meets the solar limb (contact I) until the instant at which the planetary disk is totally encompassed...

Fuzzy Occultation By Mars

William Herschel was mentioned earlier he was the German-British astronomer who discovered Uranus in 1781. His sister Caroline found many comets using her brother's telescopes, both from the city of Bath, where they had been living, and also from Slough, where they later moved. (Slough is near where London's main airport, Heathrow, was much later built.) The Herschel family had moved closer to the capital under the patronage of King George III. Nowadays the idea that major astronomical...

Christopher Columbus And The Lunar Eclipse Of 1504

Columbus struck trouble in the Caribbean in 1503 when, having already needed to abandon two ships, his last pair of caravels also became riddled with marine worms. He was forced to lie up on the northern shore ofJamaica, at a small cove named Santa Gloria (now Saint Ann's Bay). The Jamaican indigenes were friendly when Columbus arrived, but their hospitality had begun to wane after six months of the prolonged Spanish stay, the stranded party repeatedly needing to request food and water in...

Bailys Beads Seen In 1780

One may or may not consider another outcome of the eclipse expedition to Maine in 1780 to be an embarrassment. In the opening chapter we met Francis Baily, the British astronomer who in 1836 gave a description of the luminous phenomenon seen just as totality begins and ends, universally known as Baily's beads. It so happened that Samuel Williams noticed these beads of light during the 1780 eclipse. If his account had been better known, then people would nowadays talk about spotting Williams's...

Coronium And Nebulium

This is not the end of the story of the coronal spectrum. As seen in Figure 5-7, there are myriad spectral lines, each of which may have its wavelength measured, and its elemental parentage perhaps allotted. Inspired by the discovery of Janssen and Lockyer in the previous year, astronomers flocked to observe the 1869 total eclipse in North America using their spectrometers, and the new methods of photography to record the spectra for later analysis. When the dust settled and all the easy...

The Effect Upon Eclipse Times

As it moves further away from us, the Moon takes longer to complete an orbit. Looking backwards in time, perhaps to 500 B.C., it was closer to us and so its orbital period was less. If the recession rate given above, an inch and a half per year, has continued throughout the intervening 2,500 years, this would imply that back then the Moon was about one-sixth of a mile closer, and the synodic month lasted for almost two seconds less than it does now. Without accurate clocks in ancient times, how...

The Rocky Mountain Eclipse of 1878

The mapping of the dark shadow, with its limitations of one hundred and sixteen miles, lay across the country from Montana, through Colorado, northern and eastern Texas, and entered the Gulf of Mexico between Galveston and New Orleans. This was the region of total eclipse. Looking along this dark strip on the map, each astronomer selected his bit of darkness on which to locate the light of science. Maria Mitchell, professor of astronomy at Vassar College, describing the eclipse of 1878 Several...

Eclipses And Their Effect On People

Wall Street, down near the southern tip of Manhattan, was not within the band of totality in 1925, and yet it may well have been affected. Analysts who study trends in stock market prices have suggested from time to time that surges and falls in share prices may be linked with eclipses. Apparently there is often a crash in prices within a few days of a lunar eclipse and within six weeks of a solar eclipse. It would be difficult to imagine any causal connection that could produce such a...

Maria Mitchell Nantuckets Great Astronomer

The quote concerning the eclipse of 1878 with which Chapter 9 began was from the writings of Maria Mitchell, who was Professor of Astronomy at Vassar College (in Poughkeepsie, New York) from 1865 until 1888. She died the following year in Lynn, Massachusetts, but she had been born in 1818 on Nantucket, and she is still strongly associated with the island. Mitchell was a woman famed around the world, with due cause. The list of her achievements is phenomenal, especially in the context of her...

Nantucket And Its Eclipses

The eclipses of 1925 and 2079 bring together two very different places New York City and Nantucket Island. Because we are familiar with major astronomical observatories being sited atop remote mountain peaks, it seems peculiar that Nantucket has so many connections with astronomy. But it does, as we have seen above. The next connection is through eclipses. That in January 1925 was well observed from Nantucket. It happens that the next total solar eclipse visible from there is also the next one...

The Eclipse Of 1780

Soon after its foundation in the seventeenth century, Harvard University instigated the study of physics. In 1726 a benefaction from FIGURE 8-1. This drawing of Christopher Columbus using the lunar eclipse of February 29, 1504, which appeared in Washington Irving's Life and Voyages of Christopher Columbus in 1892, gives a rather different impression to that shown in Figure 3-5, which is from a few decades earlier. This depiction shows Columbus in a more benevolent light, garbed in fine clothes...

The Selenelion Or Horizontal Lunar Eclipse

Selenelion

If you are interested in experiencing something that very few other eclipse watchers have seen, this event in 2003 may provide you with an opportunity. If you were in one of those zones where the eclipse is in progress at moonrise or moonset you have the peculiar chance to be able to see both the Sun and the eclipsed Moon in the sky at the same time, with a quick twist of the head. An eclipse occurs when the two celestial orbs are 180 degrees apart, with the Earth in between. The refraction (or...

The Track Edge Over Manhattan

In the year leading up to the 1925 eclipse astronomers knew that the border of the track would slice through New York City, but they were not sure precisely where. Looking just at Manhattan, it was clear that the track limit would pass near Central Park, but as to whether the absolute edge would be to the north or the south of it was another question. First, let us think about the orientation of the track. It approached the city in a broad arc from the extreme west of New York state, and so it...

Fooling The Natives

King Solomon Mines Eclipse

This tale of Columbus's deceptive use of an eclipse to fool a less scientific people has been echoed in various works of fiction. Quite likely the episode provided a direct inspiration for such writers for example, Washington Irving recounted Columbus's subterfuge in a best-selling book, making the story well-known. In 1889 Mark Twain published A Connecticut Yankee in King Arthur's Court, a novel that envisions life in sixth-century England. The author has Hank Morgan, the Yankee in the title...