On Columbus ' first voyage , he independently discovered the Americas and magnetic declination that Shen Kuo discovered 400 years earlier .
On his first voyage , he independently discovered the Americas and magnetic declinationShen Kuo discovered 400 years earlier , in Asia , the concept of true north in terms of magnetic declination towards the north pole , with experimentation of suspended magnetic needles and `` the improved meridian determined by Shen 's [ astronomical ] measurement of the distance between the polestar and true north '' .
Christopher Columbus