Prices of a stock will move throughout the day. Investors generally buy a stock they feel is undervalued, and sell a stock they feel is overvalued. For instance, if the price of AAPL is $600 dollars, it means the cost to purchase one share of Apple is $600 dollars.
Einstein quickly realized (or had known all along) that his new theory of gravity was really a theory of the cosmos. In 1917, he wrote a famous paper applying general relativity to the universe as a whole. Today that paper stands as the foundation for modern cosmology.
Special Relativity theory says that time and space are intertwined. On the other hand, General Relativity theory treats gravity as a curvature in space and time. It says that the curvature is actually caused by matter. The argument presented in General Theory also points to the curvature of the earth.