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Life on Mars. August 6, 1996.

In August 6, 1996 a team of researchers announced that the meteorite ALH84001, discovered in the Allan Hills of Antarctica, may contain evidence of life on Mars, but further tests were inconclusive. To date, no proof has been found of past or present life on Mars. Cumulative evidence shows that during the ancient Noachian time period, the surface environment of Mars had liquid water and may have been habitable for microorganisms. The existence of habitable conditions does not necessarily indicate the presence of life. Scientific searches for evidence of life began in the 19th century, and continue today via telescopic investigations and deployed probes. While early work focused on phenomenology and bordered on fantasy, the modern scientific inquiry has emphasized the search for water, chem...

Halley´s approach. April 10, 1910.

Comet Halley, officially designated 1P/Halley, is a short-period comet visible from Earth every 75–76 years. Halley is the only known short-period comet that is regularly visible to the naked eye from Earth, and the only naked-eye comet that might appear twice in a human lifetime. Halley last appeared in the inner parts of the Solar System in 1986 and will next appear in mid-2061 to 2062. Halley’s returns to the inner Solar System have been observed and recorded by astronomers since at least 240 BC. Clear records of the comet’s appearances were made by Chinese, Babylonian, and medieval European chroniclers, but, at those times, were not recognized as reappearances of the same object. The comet’s periodicity was first determined in 1705 by English astronomer Edmond Halley,...

The Vision of Constantine. October 27, 312.

Constantine was the son of Constantius, who had served as a Caesar (a junior emperor) of the Western Roman Empire under Maximian before succeeding Maximian as Augustus (senior emperor) in 305. Constantius’ death in 306 sparked a conflict over who would succeed him. Though Constantine had the support of his father’s army, he allowed Severus, his father’s Caesar, to become Augustus. Maxentius, the son of Maximian, was angered that he was passed over and declared himself Augustus. He defeated the Severus and Galerius, the Augustus of the East, in 306 and 307. In 311, Maxentius declared war on Constantine, the greatest threat to his power. In the spring of 312, Constantine led his army toward Maxentius in in Rome. After routing Maxentius’ forces in northern Italy, Constantine approached Rome i...

The Eclipse of Thales. May 28, 585 BC.

The Eclipse of Thales was a solar eclipse that, according to The Histories of Herodotus, was accurately predicted by the Greek philosopher Thales of Miletus. If Herodotus’s account is accurate, this eclipse is the earliest recorded as being known in advance of its occurrence. Many historians believe that the predicted eclipse was the solar eclipse of 28 May 585 BC. How exactly Thales predicted the eclipse remains uncertain; some scholars assert the eclipse was never predicted at all. Others have argued for different dates, but only the eclipse of 28 May 585 BC matches the conditions of visibility necessary to explain the historical event. According to Herodotus, the appearance of the eclipse was interpreted as an omen, and interrupted a battle in a long-standing war between the Medes...

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