National Geographic : 1989 Sep
Members Forum Gravity Of particular interest in your outstanding discus sion of a very difficult subject (May 1989) was gravity's impact on spaceflight. The opportunity I had to talk with the author and photographer during their flight on the NASA KC-135 added to my enjoyment of the final product. As many observant readers have probably noted, the pic ture on page 583 shows me struggling with tooth paste, not jumping rope. This photograph captures the exhilaration of being free of the earth's pull as well as the difficulties that come with this freedom. KEN REIGHTLER, NASA Johnson Space Center Houston, Texas Yes, dozens of alert readers caught our slip. To answerone who asked what happenedafterward, the toothpaste, once squeezed, kept coming and when normal gravity resumed fell to the floor in a mess. Page 581 says that "gravity's pull is particularly strong" over the "Indian Ocean anomaly," causing satellites to drop. Page 583 says "grav ity is ... noticeably weaker in ... the Indian Ocean." Can this be explained more clearly? CHERYL SUE GATLING Syracuse, New York Gravity is generally weak in the Indian Ocean, but north of Madagascarit is stronger, hence an anomaly, illustrating earth's varying densities. The article overemphasized the possibility of a new fifth force. It should be stated clearly that independent research groups have not been able to reproduce precisely the results attributed to the existence of a fifth force. Moreover, the experiments that have reported positive fifth force (sixth-force) results appear to disagree with each other. It is difficult to understand why the article would say the null results obtained in the Galileo experiment of Niebauer and Faller and the torsion balance experiments of Adelberger and Stubbs, both of which have been repro duced, are "disappointing" or "empty." Quite the contrary, these results place interesting limits on Einstein's general theory of relativity even if the fifth-force conjecture fades. DR. T. M. NIEBAUER Max Planck Institute Garching, West Germany A match made in heaven: Tyler, age six, and his Canine CompanionSERVICE dog, Handy. What aDifference aDog Makes! Canine Companions for Independence is successfully training dogs to serve as arms, legs and ears for people who have physical disabilities. With Handy's assis tance and love, Tyler's life has changed dramatically. At the heart of sto ries like this are peo ple like you, whose membership dollars are the key to pro viding dogs like CCI SERVICE dogs pull wheel Handy for people chairs, retrieve items, and turn like Tyler. lights on and off for their masters. Your Canine Companions for Independence membership includes our quarterly newsletter, the Courier, and a special Canine Companions lapel pin. Give a gift of friendship, love and independence. ANIN For information, write OMPANION to Canine Companions for Independence, P.O. Box 446, Santa Rosa, CA ((FOR INDEPENDENCE) 95402-0446, or call (707) 528-0830.