A  Science and Technology Odyssey In Cyberspace-Time 
20000 BC to 1800 AD
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Title Page

20000BC-301BC

300BC-1499AD

1500 - 1699

1700 - 1800

Back to Timeline 300 B.C. thru 1499 A.D

Magnetic Compasses

"By the time of the T'ang dynasty (7-8th century CE) , Chinese scholars had devised a way to magnetize iron needles, by rubbing them with magnetite, and then suspending them in water (early 11th century). They also had observed that needles cooled from red heat and held in the north-south orientation (the earth's axis) would become magnetic. These more refined needle compasses could then be floated in water (wet compass), placed upon a pointed shaft (dry compass) or suspended from a silk thread. Consequently, they were much more useful for navigation purposes since they were now much more portable (and smaller). During the Sung dynasty (1000 CE) many trading ships were then able to sail as far as Saudi Arabia without getting lost." From Compass, China, 220 BCE.

Marie Curie's Search for Radium (Science...

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