Your article "Can We Find Another Earth?" [March] is a wonderful discussion of the remarkable science sponsored by NASA that may soon allow us to find a new Earth. However, the last paragraph of the article implies that the end point of the program is finding out whether life exists on some other Earth-like planet. Human curiosity about the possibility of life elsewhere is a side issue that should not in any way distract from the goal of survival of Earth's miraculous life system. We must focus on how we can carry elements of Earth's life to a new Earth and thus double its chances of survival in the universe.
William J. Sauber
Gulf Shores, Alabama
In Your Dreams
The interview with Bill Domhoff [Discover Dialogue, March], in which he questions whether dreams have a function or a purpose, left me feeling annoyed. Dreaming, like sleep, is a necessity for developing the part of our brain that deals with intuitive awareness and knowledge. Man does not develop his intuitive sense as animals do. Repetitive dreams are telling us to pay attention to something; aggressive dreams are related to our society and should be addressed. As a surgeon, I have diagnosed serious illnesses from patients' dreams. They contain information about not only the body but also the future and the past. Freud and Jung may not have been perfect, but what makes Domhoff think he has all the answers?
Bernie Siegel, M.D.
Bill Domhoff responds: Based on solid empirical studies concerning (1) the neural network that makes dreaming possible, (2) the development of dreaming in children, and (3) the everyday content of thousands of laboratory dream reports, it is unlikely that dreaming is a "necessity" or that any clinical theory of dreams has any value beyond that dreams contain some psychological information. The future therefore lies with neurocognitive theories of dreams. The idea that any illness can be diagnosed with dreams is anecdotal bunkum unsupported by research, and that a surgeon would use dreams in this way is a scary thought.
I'm 50, and all my life nuclear scientists have been predicting working fusion power in 10 years ["Still Dreaming of Star Power," Future Tech, March]. That old chestnut about "virtually pollution-free" power is a pile of atomic debris. Fusion may generate several times the volume of radioactive debris that fission reactors do. Scientists write this off as "clean" because the debris radiates mostly alpha particles. Although human skin stops alpha particles just fine, they're killers if ingested. And to dispose of this alpha-emitting trash, scientists want to bury it, where it can get into the environment, the water table, living things. Yeah, that's clean. I'll take gamma-spitting, smoking-hot spent fuel rods over alpha emitters any day.
You're right, of course, that fusion researchers have a miserable track record of meeting their goals. Yet our government still spends a lot of money on this research, and many engineers still believe in its potential. The current plan for fusion reactor design would use graphite shielding to absorb the stray neutrons. As you say, this shielding would become radioactive and consequently a waste product. Unlike the waste from fission reactors, however, the radioactive by-products would pose no proliferation risk, and their half-life is quite shorta couple of decades rather than 25,000 years for plutonium-239.
I object to the wording of a headline on the cover of your March issue. I quote: "Who were the first men to ride horses?" Nothing in the article leads me to believe that the first riders had to be men. These riders could have been women. Unlikely, perhaps, but possible.
In "Can We Find Another Earth?" (March), we should have stated that Wesley Traub is affiliated with the Smithsonian Astrophysical Observatory, a member of the Harvard-Smithsonian Center for Astrophysics. The bridge tower pictured on page 83 of the same issue is about one-eighth of a mile high, not half a mile. Finally, we did not mean to imply that the Paleozoic fossils (page 27, Works in Progress, March) used as beads by the Neanderthals were created by their wearers.