The Einstein Connection

The intellectual foundations for modern cosmology are found in Einstein's general theory of relativity. The twin connections between matter density and the geometry of spacetime, and between the geometry and motion of objects, lead to predictions about the behavior of spacetime itself—known as the world model or the world map, depending on the frame of reference chosen. In making this connection, one employs Weyl's postulate. Simply put, this is the notion that galaxies (or clusters of galaxies, or some other tracer of interest) have no peculiar motions of their own with respect to the expanding cosmological framework (which is to say that the comoving coordinates of any one of these remain constant). The postulate says that the paths of galaxies through the four-dimensional spacetime of relativity do not intersect and that these paths are orthogonal to the spatial coordinates (which is to say, the galaxies don't move in space).

0 0

Post a comment