人又回到了宇宙中心吗?

地球在宇宙中心吗?这个问题似乎十分荒谬,然而上千年来,其答案却明白无误是肯定的。一些古希腊的先哲们认为地球绕着太阳转,可是任何傻瓜都能仰望天空,指出他们是错的。虽然几个世纪的科学思想已得出了相反的证明,尽管如此,有些具有哲学思维     

Spaced receiver observations of radio pulses

Preliminary observations have been carried out to look for radio signals associated with gravitational waves. Although inconclusive, the observations from five receivers in the British Isles suggest the value of pressing on with further experiments.     

万物之理——整个宇宙可用超弦解释

物理学家戴维·格劳斯坐在普林斯顿雅得文学院他办公室内硕大的写字台后面,一边侃侃而谈,一边不时神秘地微笑着,似乎他知道了别人尚不知晓的秘密。事实确是如此。格劳斯正在描述超弦,这些玩意儿是如此之小,以致由它们组成的夸克显得不可思议的庞大——夸克是最小的亚原子粒子,其存在已被证实。     

Evidence from three-dimensional seismic reflectivity images for enhanced melt supply beneath mid-ocean-ridge discontinuities

Quantifying the melt distribution and crustal structure across ridge-axis discontinuities is essential for understanding the relationship between magmatic, tectonic and petrologic segmentation of mid-ocean-ridge spreading centres. The geometry and continuity of magma bodies beneath features such as overlapping spreading centres can strongly influence the composition of erupted lavas and may give insight into the underlying pattern of mantle flow. Here we present three-dimensional images of seismic reflectivity beneath a mid-ocean ridge to investigate the nature of melt distribution across a ridge-axis discontinuity. Reflectivity slices through the 9 degrees 03' N overlapping spreading centre on East Pacific Rise suggest that it has a robust magma supply, with melt bodies underlying both limbs and ponding of melt beneath large areas of the overlap basin. The geometry of melt distribution beneath this offset is inconsistent with large-scale, crustal redistribution of melt away from centres of upwelling. The complex distribution of melt seems instead to be caused by a combination of vertical melt transport from the underlying mantle and subsequent focusing of melt beneath a magma freezing boundary in the mid-crust.