Carl Sagan explains how the ancient Greeks knew the Earth was round and calculated its circumference over 2,000 years ago. Eratosthenes' method involved measuring the shortest shadow cast by the sun in Alexandria on the same day that there was no shadow at noon in Syene. He also hired a man to pace the distance between the two cities, which he determined to be 5,000 stadia, or about 800 kilometers. Eratosthenes then used simple proportions to calculate the Earth's circumference: 7.2 degrees is 1

Awesome Solar storms in Minimum & Maximum Cycle || You never seen this phenomena video before || Solar storms and their related phenomena all wax and wane with the Sun’s 11-year cycle of activity. Such events are more common during solar maximum (or peak of the solar cycle) but are less frequent during solar minimum (or low point of the cycle). Sunspots, or dark “blemishes” on the Sun, also increase during solar maximum and mark magnetically active regions on the Sun, which give rise to solar er