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Agriculture on a large scale:
Crops had to be planted and harvested in the right season. Floods were a recurrent phenomenon in the river valleys, for which it was essential to be prepared beforehand. The observation of sun and stars to fix the length of a year became so precise that already in 2700 B.C., the Egyptians were able to fix it at 365.2422 days! Sumerians and their successors in Mesopotamia adjusted t'he solar (sun-based) and lunar (moon-based) calendars through accurate observations. They invented the sexagesimal system of 360 degrees in a circle (near enough to the days in a year), 60 minutes in an hour, 60 seconds in a minute. The exercises were carried out using mathematical tables and ied to algebra and arithmetic of the later epochs. Another occupation that came to be very prestigious with the growth of cities was that of medicine. Although the practice of medicine was limited to treating wounds, dislocations, fractures etc., the practitioners could successfully diagnose many diseases. They could compare cases with one another, notice different diseases and record them. From such descriptions, orally passed on to later generations, arose the sciences of anatomy and physiology. Practitioners of medicine also had the knowledge of plants and mineral substances to prepare drugs for various diseases. They grew plants and herbs for this purpose. It is from this source that the science of botany arose later. The basis for chemistry was laid in the observations and practices of jewellers, metal- workers and potters. They knew about at least nine chemical elements-gold, silver, copper, tin, lead, mercury, iron, sulphur and carbon, and also about a variety of dry and liquid reagents. The process of smelting ores, of purifying metals, of colouring them, of adding enamel%-all involve complex chemical reactions that were learnt by many trials and experiments. However, chemistry never rose to the rank of a recognised science in the 'Bronze Age.
Solar energy: The energy we get today from the fossil fuels like coal, is in reality sun's energy, trapped in them millions of years ago. Plants make their food and grow bec
In the following table state how gymnosperms are adapted for living on land with respects to each of the following aspects Aspect Adaptation for living on land Alternation of Gener
Why do organisms need water? Organisms need water for the following reasons: (i) All cellular processes need water as a medium. Usually, the reactions that take place in our
Blood - Abnormal Constituent of Urine In acute inflammation and trauma, blood may be present in the urine. This condition is known as haematuria. Blood may be present in cancer
Define the visual area of the Cerebrum The visual area lies behind the parieto-occipital sulcus and includes greater part of occipital lobes. Optic nerve passes from eyes to th
Obesity : Generally, fat people think that their overweight is due to their constitution and for heredity. It could be true in some cases. But have you ever come across a fat labou
Driving a boat by surface tension Secure some gum camphor at the drug shop. Cut two or three boats from stiff paper, every about 2.5 cm in length. Cut a notch in the stern larg
Define pus - abnormal constituent of urine Pus: Pus cells are found in the urine in infections of urinary tract. Pus is actually a viscous, yellowish-white fluid formed in infe
how do the currents produced by a 1.5V flashlight cell and a 12 V car battery compare if the resistance is the same?
If the Quabbin Reservoir Watershed is 100 km2, the average precipitation in New England is 130 cm/year, and the volume of the reservoir is 1.5 x 1012 liters, what is the residence
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