Читать книгу String Theory For Dummies - Andrew Zimmerman Jones - Страница 36

Albert Einstein would revolutionize the way physicists see gravity. Instead of thinking of gravity as a force acting between objects, Einstein envisioned a universe in which each object’s mass caused a slight bending of space (actually space-time) around it. The movement of an object along the shortest distance in this space-time was the net effect of gravity. Instead of being a force, gravity was actually the result of the geometry of space-time itself.

Einstein proposed that motion in the universe could be explained in terms of a coordinate system with three space dimensions — up/down, left/right, and backward/forward, for example — and one time dimension. This 4-dimensional coordinate system, developed by Hermann Minkowski, Einstein’s former professor, was called space-time and came out of Einstein’s 1905 theory of special relativity.

As Einstein generalized this theory, creating the theory of general relativity in 1915, he was able to include gravity in his explanation of motion. In fact, the concept of space-time was crucial to it. The space-time coordinate system bent when matter was placed in it. As objects moved within space and time, they naturally tried to take the shortest path through the bent space-time.

We follow our orbit around the sun because it’s the shortest path (called a geodesic in mathematics) through the curved space-time around the sun.

Einstein’s relativity is covered in depth in Chapter 6, and the major implications of relativity to the evolution of the universe are covered in Chapter 9. The space-time dimensions are discussed in Chapter 15.