Why did the Big Bang take place? Is it now at the center of the universe?
THE TERM "Big Bang" might bring to mind an explosion from a centraldirections. In fact, scientists think that t h e Big Bang did not happen at a single location in space. It occurred everywhere at once. This is a challenging concept to grasp, but Arthur Eddington offered an analogy in his 1933 book The Expanding Universe: Imagine all the galaxies in the universe as points on the surface of an empty y balloon. A s the balloon expands, the galaxies all y balloon. A s the balloon expands, the galaxies all move a w a y from one another, but there is no single point on the surface that the galaxies are expanding away from. (Note that this analogy considers only the two-dimensional surface of the balloon, so the actual center of the balloon isn't part of the imagined universe) This may help explain how the universe can have no center and yet be expanding equally in all directions.
Peter Edmonds, Astrophysicist
Smithsonian Astrophysical Observatory