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11.
Waltham D 《Astrobiology》2004,4(4):460-468
This paper investigates whether anthropic selection explains the unusually large size of our Moon. It is shown that obliquity stability of the Earth is possible across a wide range of different starting conditions for the Earth-Moon system. However, the lunar mass and angular momentum from the actual Earth-Moon system are remarkable in that they very nearly produce an unstable obliquity. This may be because the particular properties of our Earth-Moon system simultaneously allow a stable obliquity and a slow rotation rate. A slow rotation rate may have been anthropically selected because it minimizes the equator-pole temperature difference, thus minimizing climatic fluctuations. The great merit of this idea is that it can be tested using extrasolar planet search programs planned for the near future. If correct, such anthropic selection predicts that most extrasolar planetary systems will have significantly larger perturbation frequencies than our own Solar System. 相似文献
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Howard G Levine Ken Anderson April Boody Dave Cox Oleg A Kuznetsov Karl H Hasenstein 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2003,31(10):2261-2268
This experiment was conducted as part of a risk mitigation payload aboard the Space Shuttle Atlantis on STS-101. The objectives were to test a newly developed water delivery system, and to determine the optimal combination of water volume and substrate for the imbibition and germination of flax (Linum usitatissimum) seeds in space. Two different combinations of germination paper were tested for their ability to absorb, distribute, and retain water in microgravity. A single layer of thick germination paper was compared with one layer of thin germination paper under a layer of thick paper. Paper strips were cut to fit snugly into seed cassettes, and seeds were glued to them with the micropyle ends pointing outward. Water was delivered in small increments that traveled through the paper via capillary action. Three water delivery volumes were tested, with the largest (480 microliters) outperforming the 400 microliters and 320 microliters volumes for percent germination (90.6%) and root growth (mean=4.1 mm) during the 34-hour spaceflight experiment. The ground control experiment yielded similar results, but with lower rates of germination (84.4%) and shorter root lengths (mean=2.8 mm). It is not clear if the roots emerged more quickly in microgravity and/or grew faster than the ground controls. The single layer of thick germination paper generally exhibited better overall growth than the two layered option. Significant seed position effects were observed in both the flight and ground control experiments. Overall, the design of the water delivery system, seed cassettes and the germination paper strip concept was validated as an effective method for promoting seed germination and root growth under microgravity conditions. 相似文献
13.
The conference began with The Charles Martin Lecture, given this year by George Abbey, formerly Director of the NASA Johnson Spaceflight Center. George spoke of the significant contribution of British scientists and engineers to the early days of NASA. He was followed by an ebullient tour d’horizon from the admirable Dr David Southwood, Head of Science at ESA. Lucie Green from Mullard Space Science Laboratory (MSSL), who is leading the outreach component of the International Heliophysical Year, then brought the first session to a close. The conference then split into three parallels. 相似文献
14.
The UK government appears to be taking space more seriously, even if funding for the sector remains limited. Speeches and attendees at the conference confirm this trend, with a particular emphasis on innovation and a general sense that prospects for the UK space industry are good. The various themes and highlights of the conference are discussed. 相似文献
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