Curiouser and curiouser

In his book review "The Curious Energy of the Void" [2/03], Donald Goldsmith states: "As the universe expands, ... more space continuously comes into being, and so the total amount of dark energy also increases proportionately" In effect, energy is continuously created--an assertion that, for me, is quite counterintuitive.

Later he writes, "The amount of radiation generated by the universe in the earliest years of its expansion varies in different directions in space" But that seems to contradict a reference to "the pervasiveness and uniformity of the radiation throughout the universe" made elsewhere in the same issue ("At the Museum").

Howard J. Naftzger
Kensington, California

DONALD GOLDSMITH REPLIES: Howard Naftzger raises two excellent and appropriate questions. He is right to find it counterintuitive that new energy appears as space expands--not to mention that it's a violation of just about every physical rule in the books. That is one reason (and there are more!) conservative cosmologists have been slow to accept the existence of dark energy.

Nevertheless, new results from the Wilkinson Microwave Anisotropy Probe (WMAP) satellite seem to confirm almost beyond a doubt that space does teem with dark energy. Cosmologists like to call the new energy "the ultimate free lunch." If it's any help, according to our conception of physics, the universe as a whole does not have to obey the same rules as a closed, localized system does.

As for the uniformity of the cosmic background radiation, there are two salient facts. First, the background is amazingly uniform, arriving in the same amounts and with the same spectrum from all directions. Second, astronomers have now detected extremely small deviations from uniformity--the so-called anisotropies of the cosmic background radiation [see "Sharper Focus," by Charles Liu, page 70]. The anisotropies, small as they are, carry large amounts of information about the universe as it existed when the radiation was first set loose, a few hundred thousand years after the big bang.

By measuring the anisotropies on various angular scales, cosmologists can (amazingly) hope to determine the curvature of the universe, which amounts to determining the total quantity of all kinds of matter and energy. My book The Runaway Universe deals to some degree with these not-so-simple subjects.

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