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See Inside May 2010

Readers Respond on "Looking for Life in the Multiverse"

Letters to the editor from the January 2010 issue of Scientific American

Life, the Multiverse and Everything
In “Looking for Life in the Multiverse,” Alejandro Jenkins and Gilad Perez say that life would be possible in a universe without the weak nuclear force. But they fail to note that the weak force is unique in treating matter and antimatter asymmetrically. Only because of this asymmetry did matter slightly outweigh antimatter before nearly all antimatter annihilated with an equal amount of matter, within the first seconds after the big bang. Everything we see—including stars, which are essential to life—is composed of that slight excess of matter. A universe without the asymmetric weak force would have virtually no normal matter and hence no life in any form we might recognize.
Robert L. Piccioni
The writer is author of Everyone’s Guide to Atoms, Einstein, and the Universe

THE AUTHORS REPLY: By itself, the weak nuclear force cannot distinguish between matter and antimatter, because it preserves what physicists call charge-parity (CP) symmetry, meaning that it treats a particle in the same way as the mirror image of the corresponding antiparticle. As Piccioni points out, however, it is possible to combine the weak force with other interactions in such a way that this CP symmetry is broken.

Today we know that CP asymmetry is way too small to account for the fact that our universe contains as much matter as it does, but no antimatter. Some new physical interactions at high energies, as yet undetected, are needed to resolve this fascinating puzzle. These other interactions could also produce an excess of matter over antimatter in a weakless universe. We did not cover this interesting point in our Scientific American article because of space limitations.

That information about “Life, the Universe, and Everything” could be found on none other than page 42 of this issue was ironic, given that this number had been specified in 1979 as the “Answer to the Ultimate Question” in Douglas Adams’s classic text, The Hitchhiker’s Guide to the Galaxy. For those of us who can barely get around the monoverse we find ourselves living in, it is a comfort to know that Scientific American has provided additional evidence that a convergence of multiverses arises from this locus, 42, as predicted by Adams.
William D. Brown
Seekonk, Mass.

Proceeding, with Care
In “Big Need for a Little Testing” [Perspectives], the editors write that “many companies are hesitant to invest in nanotechnology R&D, fearing the exposure to legal action that could result if one day a technology is deemed dangerous. Procter & Gamble, for example, is not pursuing nanotechnology because of the long-term risk of litigation.”

Contrary to what was stated, P&G is interested in nanotechnology, and we are actively pursuing the benefits it can deliver. We believe it holds great potential to bring exciting new levels of performance to products people use everyday. Nanotechnology opens up many possibilities to boost performance, reduce environmental impact and improve sustainability in virtually every consumer product category. As with any new technology, however, the potential for adverse effects must be understood, and the technology should advance only as fast as our ability to thoroughly evaluate it. We are taking an appropriately cautious approach with nanotechnology. In addition to our own research programs, we are also working together with others in the industry, with university labs and with government scientists to ensure the right tools are in place for the responsible development of this promising technology.
Mark Lafranconi
Section Head, Central Product Safety
Procter & Gamble

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