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.
1 Special Relativity was developed by Hendrik Lorentz, Henri PoincarÃ©, and Hermann Minkowski, and Albert Einstein.  General Relativity (GR) is a theory which explains the laws of motion as viewed from accelerating reference frames and includes a geometric explanation for gravity. This theory was developed by David Hilbert and Albert Einstein as a generalization of the postulates of Special Relativity. A dramatic but later discredited claim by Sir Arthur Eddington of experimental proof of General Relativity in 1919 made Einstein a household name.