What Early Astronomers Did For Us (More Than You Think!)Early astronomers performed methodical observations of the night sky, and astronomical artefacts have been found from much earlier periods.
Astronomers of early civilisations carried out systematic observations of the night-time sky, and astronomical artefacts were discovered much earlier. We check out the most famous astronomers and scientific breakthroughs in history.
Thales and the Eclipse of 585 BC
Thales of Miletus was born around 625 BC. He is generally thought to be the first Greek mathematical scientist and mathematician and is seen by some as the possible inspiration of Pythagoras.
Thales of Miletus is said to have been the first to predict an eclipse of the Sun. He had announced that an eclipse would occur in 585 BC, and the Greek historian Herodotus chronicled that an eclipse occurred on that date. The mathematical basis of Thales's prediction is unknown, though it is believed that he used the Babylonian saros of 18 years, 10 days and 8 hours to do so.
Many modern scholars are sceptical about the historical accuracy of this saros, which the Babylonians understand. Thales only appears to have given a year and not an exact date for the eclipse. We know a total solar eclipse occurred on 28 May 585 BC.
Alhazen and the Effects of Atmospheric Refraction
The Earth's atmosphere's effects on astronomical bodies as they approach the horizon have long fascinated astronomers. A significant advance in understanding these effects happened in Cairo about 1000 years ago, when Alhazen (Ibn Al-Haitham), arguably the greatest Arabic experimental scientist of the Middle Ages, set himself to the questions.
Alhazen was once as much an optical physicist as an astronomer. He wanted to understand why the air first became bright when, from his measurements made with an astrolabe against the last fading stars at daybreak, the Sun was still 19° beneath the eastern horizon.
He concluded that the Earth's atmosphere refracted light coming to us from astronomical bodies, distorting their shapes and colours and even lifting their apparent images above the horizon when geometrically they were slightly under it.
Alhazen's remarkable analysis made the development of both experimental and mathematical optics conceivable.
Chinese Astronomers Observe the Crab Nebula Supernova
The Crab Nebula came to be seen by late 20th-century cosmologists as a laboratory within which they could study what happens when a star explodes. While Greek and Arab astronomers noted the bright new star in June 1054, Chinese astronomers left the complete narrative for the 'guest star essentially' in 5 separate texts.
The supernova was, in the beginning, as bright as Venus. It could even be seen in daylight for the first 23 days, then faded over the following two years. When 20th-century cosmologists realised the importance of the Chinese document, they could reconstruct from this dated event exactly how a supernova remnant behaves in each period. They could do this using photographic and radio techniques and extrapolating to the Chinese observations.
Observing the Summer and Winter Solstices in 1570
Astronomy hardly accommodates conveniently round numbers, and the formation of the calendar was no exception. The medieval Christian Church had issues in accurately fixing any year's movable date of Easter. Being a spring festival, the date of Easter is ruled by the appearance of the first full Moon following the spring equinox. Because of the precession of the equinoxes, however, this date slowly creeps back over the centuries.
In the 16th Century, several big Meridiana, or pinhole camera sundials, were laid out in the dark interiors of large Italian churches, such as San Petronio, Bologna. The pinhole projections of the Sun's disk, sometimes thrown back 60m in winter, now enabled the winter and summer solstice angles, equinoxes, and other solar orbital details to be measured so correctly that our modern Gregorian Calendar was made possible by 1582.
Galileo's First Telescopic Observations
It's easy to underestimate the importance of Galileo's telescopic observations; however, they were truly fantastic and changed astronomy for the time being. After his results had been announced in March 1610, the entire scale of astronomy changed, as scientists realised that there was a vast Universe out there that could not be seen by the naked eye.
Galileo did not invent the telescope, nor was he the first to use a telescope to look at astronomical bodies. Galileo was the first to recognise its enormous power to revolutionise concepts. Between December 1609 and February 1610, he discovered mountains on the Moon, the satellites of Jupiter, saw 32 stars in the Pleiades star cluster and would soon observe the phases of Venus and arguably the first to look at sunspots.
He used his new results to give an impressive spin to the Copernican theory. His observations opened a universe that those before could not have imagined. Galileo's observations changed man's place in the cosmos indelibly. Today, Galileo's telescopes are invaluable museum items.
