Is there a center of the universe?

Smattering of distant galaxies imaged in Hubble's Ultra Deep Field Project.

A smattering of distant galaxies imaged in the Ultraviolet Coverage of the Hubble Ultra Deep Field Project.
NASA, ESA, H. Teplitz and M. Rafelski (IPAC/Caltech), A. Koekemoer (STScI), R. Windhorst (Arizona State University), and Z. Levay (STScI)

In a word, no. The universe began as a singularity (an infinitely tiny point with infinite density) that started expanding at the moment of the Big Bang. However, the Big Bang wasn’t a normal explosion starting from a single point in space. Rather, space itself was expanding, with everything in the universe moving away from everything else. Today we observe a universe that appears fairly isotropic; that is to say, it looks basically the same in every direction. In general, the galaxies along any line of sight from Earth are distributed in the same way. There is no “preferred” direction in the universe, which indicates that there is no inherent center of the universe.

The observable universe is a somewhat different story. The observable universe is the region of the universe we can observe, defined by how far light has traveled since the Big Bang 13.8 billion years ago. But this does not mean that Earth is the center of the universe. If you were to move to another star 10 billion light years away, you would still be the center of your own, significantly different observable universe.

Keep up with the expanding universe with our July 2014 and September 2014 issues of Sky & Telescope, where we discuss recent controversial cosmology results.

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