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Unformatted text preview: 1300 PERSPECTIVES progress at the Parkes, Green Bank, and Arecibo observatories, and it is expected that even more relativistic binary pulsars will be found. With the advent of the Square Kilometer Array, a huge sample of relativistic binaries will be available ( 13 ). At the same time, VLBI techniques are rapidly evolving, which will provide an accurate location of these clocks within the Galaxy. A rich array of perfectly clocked shrinking binary sys- tems, exactly located in different zones of the Galaxy, will be available, constituting a pow- erful gravity probe. As the present uncertain- ties in the gravitational potential of the Galaxy would be averaged by such an array, orbital decays and other non-Newtonian effects would be estimated with better accu- racy, thus providing an unprecedented test of relativistic gravity. It would then pose chal- lenging questions to those alternative theories of gravity. References 1. A. T. Deller, M. Bailes, S. J. Tingay, Science 323 , 1327 (2009); published online 5 February 2009 (10.1126/ science.1167969). 2. LIGO Scientific Collaboration: B. Abbott et al. , http://arxiv.org/abs/0711.3041v1 (2007). 3. A. Giazotto, S. Braccini, in Proceedings of the 14th SIGRAV Conference on General Relativity and Gravitational Physics , Genova, Italy, September 2000, (Springer, Berlin, 2002), pp. 111–119. 4. D. R. Lorimer, Living Rev. Relativity 11 , 8 (2008). 5. R. A. Hulse, J. H. Taylor, Astrophys. J . 195 , L51 (1975). 6. I. Ciufolini, J. A. Wheeler, Gravitation and Inertia (Princeton Univ. Press, Princeton, NJ, 1996). 7. S. Dodelson, M. Liguori, Phys. Rev. Lett. 97 , 231301 (2006). 8. T. Damour, G. Esposito-Farese, Phys Rev. D 54 , 1474 (1996). 9. N. Yunes, D. N. Spergel, http://arxiv.org/abs/0810.5541v1 (2008). 10. M. Burgay et al. , Nature 426 , 531 (2003). 11. A. G. Lyne et al. , Science 303 , 1153 (2004). 12. R. P. Breton et al ., Science 321 , 104 (2008). 13. R. Smits et al. , Astron. Astrophys. 493 , 1161 (2009). 10.1126/science.1170936 H uman changes to the global environ- ment have long been known to affect organisms, for example by altering their physiology, range, or longevity ( 1 , 2 ). However, responses vary widely across species, making it difficult to predict how entire ecosystems will respond in the future ( 3 ). A key problem is that species do not respond to extrinsic drivers (such as climate) in isolation. Rather, species responses may be determined to a greater or lesser extent by other species with which they interact. On page 1347 of this issue, Harmon et al. elucidate one such interac- tion in a study of pea aphids and two of their ladybird predator species ( 4 ). Early population models showed that interactions among species could weaken or strengthen within-species responses to envi- ronmental change ( 5 ). More recently, empiri- cal evidence has demonstrated that species interactions can reverse the response of indi- vidual grassland species to climate change and subsequently alter their community tra-...
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This note was uploaded on 07/19/2011 for the course EVS 101 taught by Professor Varsolosunio during the Winter '10 term at American Intl. University.
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