Samplings: September 2007

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Lawrence M. Krauss

The universe is expanding, and many cosmologists think the expansion will continue forever. Paradoxically, though, a new analysis shows, billions of years from now—if anyone is around to care—the evidence for both the expansion and the big bang will vanish and the universe will appear deceptively static. Lawrence M. Krauss of Case Western Reserve University and Robert J. Scherrer of Vanderbilt University base their remarkable conclusions in part on Hubble’s law, the strongest case for universal expansion. The law summarizes the observation that the greater the distance between Earth and a faraway galaxy, the faster they are moving apart. Krauss and Scherrer calculate that during the next 100 billion years, the expansion will take galaxies beyond our local cluster so far away that they will be separating from the Milky Way faster than the speed of light. In effect, the more distant galaxies will become invisible—taking with them perhaps the most straightforward evidence for expansion. What about the cosmic background radiation, a relic of the big bang and another key piece of evidence for universal expansion? Nope, its wavelength will increase beyond detectability as the universe expands. Tongue slightly in cheek, Krauss and Scherrer point out how lucky today’s astronomers are to live in an era—admittedly a long one—when evidence of the true nature of the universe is still out there for us to see. (Journal of Relativity and Gravitation)