Dark days can also be created by events outside the Earth's atmosphere.
During a central solar eclipse, for a few minutes, the Moon completely hides the face of the Sun. However, there is never complete darkness, as the Sun's outer atmosphere, the corona, provides some light. How much light there is depends on the extent of the corona, which varies during the solar activity cycle. Observers at a total eclipse on July 28, 1851 in Norway said that the darkness was not similar to that of night. Mountains 15 miles away were faintly visible, and large print could just be read. The effect was still awe-inspiring. One astronomer wrote; "The awful appearance of the terribly black cloudy portions of the sky, and the intensely gloomy look of the remaining portion, cannot easily be forgotten." One old Norwegian woman was, however, unimpressed. During totality, she lit a candle and continued with her work. During the total eclipse of April 22, 1715, in London, three planets and several stars were visible. The astronomer De Louville grumbled, "it was a piece of good fortune at this time to have found in London an interval of clear sky."
Theoretically, an asteroid might pass close enough to the Earth to eclipse the Sun for a few seconds. It is not known if this has ever actually happened.
There seems little doubt that on June 30, 1861, a great comet did obscure the Sun as the Earth passed through its tail two-thirds of its length from the nucleus. E. J. Lowe, in England, recorded that "the sky had a yellow, auroral, glare-like look, and the sun, though shining, gave but a feeble light." There was "a singular yellow phosphorescent glare, very like diffused Aurora Borealis, yet being daylight such Aurora would scarcely be noticeable." On February 12, 1106, according to Erman and J. R. Hind, there was a "sun-darkening" which was accompanied by meteors. A few days earlier, on February 5, a great comet had been seen near the Sun.
There are a few accounts of dark days, outside solar eclipses, in which the stars were seen. Whatever the cause might have been on these occasions, it must have originated outside our atmosphere, otherwise the stars would have been obscured with the Sun. In AD 542, according to Hector Boetius, "The sun appeared about noondays, all wholly of a bloody colour. The element appeared full of bright stars to every man's sight, continually, for the space of two days together." On April 23, 1547, in England, France and Germany, "the Sun appeared for three days as if it were suffused by blood while at the same time many stars were visible at noon." The famous astronomer Kepler thought this must have been due to "the wide diffusion of some cometary matter". Others said it was a Hohenrauch (high smoke), "notwithstanding the visibility of stars".
There are some accounts of dark days which are so peculiar, or which have so few details, that it is impossible to say what their cause was. In AD 934, according to a Portuguese historian, the Sun lost its ordinary light for several months. Then "an opening in the sky seemed to take place, with many flashes of lightning, and the full blaze of sunshine was suddenly restored." This last sounds like a description of the end of a total eclipse; but, of course, eclipses do not last for months. On September 29, 1091, Schnurrer says that "there was a darkening of the Sun which lasted three hours, and after which it had a peculiar colour which occasioned great alarm." According to a Notes and Queries correspondent of 1857, a total darkness at noon which lasted for hours enveloped Amsterdam on a summer day about 1800. The day was fine, the air was calm, and there was no fog. Many people were drowned by falling into the canals. The most mysterious dark day must be the one described with irritating brevity by Charles Fort. At Pernambuco, Brazil, on April 11, 1860, about noon in a cloudless sky, "suddenly the light of the Sun was diminished". The darkness increased, and the planet Venus shone brilliantly. A corona appeared round the Sun. (This may have been a diffraction corona, not the solar corona). The darkness lasted several minutes. Total eclipses for 1860 were January 23 and July 18.