One hundred years ago this month, Albert Einstein redefined what gravity is, overthrowing his own hero Isaac Newton.
Newton had imagined gravity to be a force like any other that pulls on things to get them going. But Einstein wove gravity into very fabric of space and time, molding an invisible landscape of hills and valleys through which objects move.
But physicists have good reason to be grumpy about general relativity, despite its success. It doesn’t get along with quantum mechanics, which governs the smallest scales of reality. And it includes a fudge factor that troubled Einstein himself, who added it to account for the accelerating expansion of the universe. But here in our own solar system, general relativity has proven itself time and time again.
source:http://www.popsci.com/100-years-general-relativity-why-einstein-still-stands
