evolution of science:prehistoric period:part I

Evolution of science:

As humans evolved so do science, ofcourse we didnt know E=mC^2 out of the blue, science evolve by trial and error method.there were times when we thought earth is on top of a gaint turtle, and lunar eclipse is nothing but a wolf swallowing the moon.

we made our mistake, learned from it and now we are colonizing in mars.

scientific curiousity started when humans looked up in the sky and wondered the workings of it.

Ancient Chinese astrologers, by 2300 BC, already had sophisticated observatory buildings and as early as 2650 BC, Li Shu was writing about astronomy. Observing total solar eclipses was a major element of forecasting the future health and successes of the Emperor, and astrologers were left with the onerous task of trying to anticipate when these events might occur. Failure to get the prediction right, in at least one recorded instance in 2300 BC resulted in the beheading of two astrologers. Since the pattern of total solar eclipses is a very erratic one in time at a specific geographic location, many astrologers no doubt lost their heads. By about 20 BC, surviving documents show that Chinese astrologers understood what caused eclipses, and by 8 BC some predictions of total solar eclipse were made using the 135-month reoccurrence period. By 206 AD they could predict solar eclipses by analyzing the motion of the moon itself.


While Chinese, Babylonian and Greek astrologers dominated the astronomical knowledge of the 'Old World', half way across the globe, Maya observers were also working on calendars, and recording celestial observations to their own ends. The Dresden Codex records several tables which are widely thought to be lunar eclipse tables. As many civilizations had before them in other parts of the world, the Mayas used records of historical lunar eclipses to identify how often they occur over a 405 month period. There is no mention of recorded total solar eclipses, or discussions in the Codex for how to predict these events. After the conquest by the Spanish Conquistadors and the intentional destruction of nearly all native written records by the Missionaries by the 1600s, little survives today to tell us whether the Mayas, Incas or Aztecs had achieved a deeper understanding of solar eclipses and their forecasting.

Why the interest in eclipses?

One of the first things that civilizations must do to insure a coherent society, and the harvesting and planting of crops, is to establish an accurate calendar. Most of the early calendars were lunar 'monthly' calendars, but since the time between like lunar phases is 29.5 days, this only leads to 12.38 months during a solar ( seasonal) year, so that every year, the lunar calendar slips by 11 days relative to the seasonal 'planting' year. While establishing an accurate luni-solar calendar, ancient peoples observed the moon quite regularly, and over time would discover evenings when the moon was eclipsed by the Earth's shadow. Because the Earth's shadow is so vast, lunar eclipses were the first major celestial events that ancient astrologers would learn how to predict by using local historical observational records.

Why no solar eclipse predictions?

The diameter of the Earth's shadow at the distance of the Moon is over 12,000 kilometers across. This makes predicting lunar eclipses a very forgiving enterprise even when you do not know the precise details of the orbit of the Moon. For total solar eclipses, however, the shadow of the Moon upon the Earth's surface is only about 300 km across. At the distance of the Moon's orbit, this subtends an angle of less than 1/20 of a degree of arc. To forecast a solar eclipse, you would need to know the details of the lunar orbit to at least this degree of accuracy. With the exception of the ancient Chinese and Greeks, there are no written records that suggest that the Moon, stars or planets were routinely measured with this degree of accuracy. Some have proposed that many ancient civilizations kept track of when total solar eclipses occurred, and that from these local historical records, numerical patterns allowed ancient astrologers to make total solar eclipse forecasts. This also seems not to be possible.

                                                                                               ----THE PHYSICIST