文章与日志

依据后面的文献总结一下哈勃空间望远镜(HST)近15年来的主要结果.

睁开眼睛的哈勃

接受航天飞机维护的哈勃

重12.5吨,发射于1990年4月.
轨道高度607公里,轨道周期90分钟.
空间角分辨率0.05弧秒;感光上限到波长1150埃;在紫外区域其敏感性是此前望远镜的100到1000倍.
1.太阳系
从1994年7月16日开始,SL-9彗星被木星引力潮汐撕碎而成的20多块碎片,开始陆续撞击木星,使得拥有现代科学观测工具的人类第一次活生生地看到了引力作用下天体的吞噬过程.
HST用足够清晰的照片验证了如下一些撞击力学描述:

无限是数学里面第一个锻炼人的形式抽象能力的概念,最近美国几位大学数学教师做了一个有意思的心理调查(Notices of AMS, August 2004),以了解对无限的不同理解.

他们给出如下几个具体的包含了一般所谓无限概念的问题:

1.古老的乌龟和健将Achilles赛跑的故事:如果乌龟的起跑点在Achilles的起跑点前面1米,那么Achilles不管能够跑多快都永远赶不上乌龟,因为当Achilles赶到乌龟起跑点时,乌龟肯定已经爬到该点前面一段距离的位置,等Achilles再赶到该位置时,乌龟在这段时间内还是向前爬了一段距离,如此反复下去,乌龟将永远在Achilles前面.
2.为什么一个变量的微分dx既可以被看成是一个大于0的数而对它进行计算，又常常可以当成0一样被忽略？

在宇宙空间,碟子状结构是最常见的力学结构,大约1半的恒星都位于碟子状螺旋星系当中,而象太阳系这样有行星的碟子状恒星结构,也越来越有迹象表明是普遍存在的.另外碟子的构型也出现在很多其他地方,如白矮星和黑洞,因此碟子一定引力的常见力学结果.

用红外眼睛朝银河系中心望去:

CREDIT: IPAC/CALTECH/2MASS/NASA

如果有可能在远处俯视银河这个大盘子:

CREDIT: CHRIS BUTLER
宇宙可见结构的演化,最主要的研究方法是计算机模拟.

可以肯定的是坊间流传的洗髓经不会早于宋明,不过其理路尚可,用于补足作为动功的易筋经是堪任的.
下面我剔除无用累赘之语,径直述说其理路,或有益于时人.
洗髓经属于所谓静功范畴,即:心象的建立-驱动生理功能构建-心象的泯灭-基于新生理功能的心象建立.这么一个循环的进步过程.
因此作为静功的入门,即腾出心力来专事于把握自体的心象之建立,也就是所谓放松与安静的实质.
但平常人的心力总是消耗或者说系绊在日常心理上,常用的两种解脱方式是:
1.替代法,即用本质仍然属于日常心理范畴的操作,例如数息,念诀,行气之类,来强制替代日常心理流,而该操作能够引导到心象的建立.
2.智慧法,集中运用人的思维,或者笼统地说智慧的能力,令人走上自我反省观照之路,以求截断日常心理之根源.

Cosmological Parameters from Eigenmode Analysis of Sloan Digital Sky Survey Galaxy Redshifts

原文

We present estimates of cosmological parameters from the application of the Karhunen-Loève transform to the analysis of the 3D power spectrum of density fluctuations using Sloan Digital Sky Survey galaxy redshifts. We use mh and fb = b/m to describe the shape of the power spectrum, 8gL" align="middle"> for the (linearly extrapolated) normalization, and to parametrize linear theory redshift space distortions. On scales k 0.16hMpc–1, our maximum likelihood values are mh = 0.264 ± 0.043, fb = 0.286 ± 0.065, 8gL" align="middle"> = 0.966 ± 0.048, and = 0.45 ± 0.12. When we take a prior on b from WMAP, we find mh = 0.207 ± 0.030, which is in excellent agreement with WMAP and 2dF. This indicates that we have reasonably measured the gross shape of the power spectrum but we have difficulty breaking the degeneracy between mh and fb because the baryon oscillations are not resolved in the current spectroscopic survey window function. ©2004 American Institute of Physics

Brane Inflation: From Superstring to Cosmic Strings

S.-H. Henry Tye
Laboratory for Elementary Particle Physics, Cornell University, Ithaca, NY 14853

Brane inflation, where branes move towards each other in the brane world, has been shown to be quite natural in superstring theory. Inflation ends when branes collide and heat the universe, initiating the hot big bang. Cosmic strings (but not domain walls or monopoles) are copiously produced during the brane collision. Using the COBE data on the temperature anisotropy in the cosmic microwave background, the cosmic string tension µ is estimated to be around 10 –6 > Gµ > 10–11, while the present observational bound is 7 × 10 –7 > Gµ. This implies that the anisotropy that seeds structure formation comes mostly from inflation, but with a small component (< 10%) from cosmic string effects. This cosmic string effect should be testable in the near future via gravitational lensing, the cosmic microwave background radiation, and/or gravitational wave detectors like LIGO II/VIRGO. ©2004 American Institute of Physics