2006年诺贝尔物理学奖——宇宙微波背景辐射的黑体谱和各向异性

NOBEL PRIZE IN PHYSICS 2006—— BLACKBODY SPECTRUM AND ANISOTROPY OF MICROWAVE BACKGROUND RADIATION IN THE UNIVERSE

相传约137亿年前我们的宇宙起源于“盘古开天地式的大爆炸”,能量密度和温度均超高无比,却绝无什么特殊的“爆炸”中心,在足够大的尺度上均匀且各向同性,一直持续膨胀至今.刚开始的时候,随着宇宙温度的迅速降低,若干基本粒子物质相继浮现,宇宙早期的核合成过程制备形成了宇宙时空中第一代恒星形成之前的大致原初元素丰度分布.宇宙“大爆炸”发端时空中的能量场应当有量子涨落;耦合演化到后来呈现的物质场中,这些微弱而此起彼伏的涨落逐渐被引力在各种不同层次上放大,从而最终形成宇宙时空中不同尺度的物质结构系统(包括超星系团、星系团、星系、球状星团、恒星、行星等).伴随着宇宙膨胀,有一个温度不断下降的热电磁辐射场被“捂”在物质场中;大约在389000年以后,这个热电磁辐射场基本不再与物质相互耦合作用,但它依然带有早期物质场中各处涨落的信息烙印.基于Einstein创立发展的广义相对论(1915年),Einstein(1917年)、Friedmann(1922年)、Lematre(1927年)、deSitter(1932年)开辟了近代理论宇宙学的先河.Hubble(1929年)公布了遥远的星系退行速度正比于它们到我们的距离的划时代观测事实.基于宇宙元素丰度和核合成物理,Gamow,Alpher和Herman于1940-1950年大胆设想了宇宙“大爆炸”的物理框架图像.Penzias和Wilson(1964年)在贝尔试验室从事微波天线研究时意外地发现了2.7K宇宙微波背景辐射.经过多年的精心设计和准备,Mather和Smoot(1989—1994年)领导的“宇宙背景探索器”(COBE)空间试验精确地测量宇宙微波背景辐射的黑体谱和微弱的各向异性涨落;他们俩因此荣获2006年度的物理诺贝尔奖.90年来,科学家们众说纷纭,唇枪舌战,搜索证据,编造理论.随着地面、高空和空间综合试验及理论研究的持续迅速发展,精确宇宙学的时代已经到来.

As the folklore goes that our universe started about 13.7 billion years ago in a manner of a Big Bang as the mythical Hero PanGu cleft the sky from the Earth, the energy density and temperature were extremely high at the beginning yet without a particular point of explosion center, everything was uniform and isotropic on sufficiently large scales of spacetime, and the Universe continues to expand up to now. Soon after the very beginning, the temperature of our Universe dropped rapidly, several types of fundamental particles emerged in succession, processes of thermal nuclear synthesis in the early Universe largely determined the primordial element abundance distribution prior to the formation of first-generation stars in the Universe. At the onset of Big Bang of our Universe, there should exist quantum fluctuations in the energy field; such weak yet ubiquitous fluctuations carried over to the matter field emerged later were gradually amplified hierarchically by gravity, leading to the formation of material structural systems on various scales in cosmological spacetime （including superclusters of galaxies, clusters of galaxies, galaxies, globular clusters, stars, and planets and so forth）. As the Universe expands, the temperature of a thermal electromagnetic radiation field trapped inside materials decreases; about 389 thousand years after the Big Bang, this thermal electromagnetic radiation field no longer interacts with matter but still carries the indelible imprint of earlier matter fluctuations. Based on the general theory of relativity created and formulated by Einstein （1915）, Einstein himself （1917）, Friedmann （1922）, Lemaitre （1927）, de Sitter （1932） initiated the theoretical exploration of modern cosmology. Hubble （1929） published the ep ochal observational fact that the receding speed of galaxies is proportional to their distances away from us. Based on cosmic elemental abundance and the physics of nuclear synthesis, Gamow, Alpher and Herman boldly conceived the physical framework scenario for a Big Bang Universe during 1940s to 1950s. While conducting microwave antenna research at Bell Laboratories, Penzias and Wilson （1964） unexpectedly discovered the remnant 2.7K cosmic microwave background radiation. After years of careful design and preparation, Mather and Smoot （from 1989 to 1994） led the COsmic Background Explorer （COBE） satellite experiment to accurately measure the blackbody spectrum and the anisotropy of feeble fluctuations; in recognizing their groundbreaking contributions, they were awarded the Nobel Prize in Physics of year 2006. During past 90 years, scientists voiced various opinions in competition, fighting each other fiercely, collecting relevant evidence, and creating various theories. Along with the persistent and comprehensive development of experiments on ground, at high altitudes and in space as well as the theoretical research, we are entering the era of precision cosmology.