Letters to the editor

Ethics of humanized mice
The recent stories “Human cells rev up mouse brains” (SN: 4/6/13, p. 16) and “Of mice and man” (SN: 3/23/13, p. 22) drove home to me that human-animal hybrids are now reality. In science fiction stories with such hybrids, a big part of the plot is the resultant ethical gray area: There are certain standards for animal research, and much stricter standards for human research. What standards apply to animals that have a significant payload of human cells? Brain research has the most obvious ethical implications, but what makes a “human” is complex and probably involves other parts such as the immune system. (I would be interested if mice with humanized immune systems showed changes in learning ability.)
Virginia Brock, Rock Island, Ill.

Flu facts
The graph of influenza and humidity (“Damping down flu,” SN: 4/6/13, p. 4) was most interesting. I would refer you to the February 28, 1948, edition of Science News Letter and the article “Humidity Kills Germs.” It seems we are rediscovering the past. Why flu is more prevalent in winter and how to slow its spread has been known for 65 years. Yet we continue to build the heating systems of hospitals, schools, stores, et cetera with little or no consideration for humidity.
Mark Davidsaver, via e-mail

Randomness not so random
The article on the Planck view of the microwave background (SN: 4/20/13, p. 5) contains an excellent picture of the distribution of temperatures of the microwave background radiation. As one who has spent a lot of time pondering microscopic images of distributions of one phase in another, I can’t help but wonder if we’re just seeing randomness in this picture. After all, random images of particulate materials in a clear matrix look very much like this picture, as do random number tables and packages of multicolored jelly beans. Random distributions are not spatially perfect, but strongly clustered.  In fact, today we recognize clustering as an attribute of randomness, rather than a disproof of it.
Lou Floyd, via e-mail

The reader makes a good point about randomness. It’s not surprising that fluctuations in the cosmic microwave background radiation cluster together in spots. In fact, these localized clusters led to the clumping of matter into stars and galaxies. But it is surprising and maybe not random that when scientists zoom out and look at the whole universe, there are clear differences between one half of the sky and the other. —Andrew Grant