Wilkinson D
Joseph Henry Laboratories, Princeton University, Princeton, NJ 08544, USA.
Proc Natl Acad Sci U S A. 1998 Jan 6;95(1):29-34. doi: 10.1073/pnas.95.1.29.
Most cosmologists now believe that we live in an evolving universe that has been expanding and cooling since its origin about 15 billion years ago. Strong evidence for this standard cosmological model comes from studies of the cosmic microwave background radiation (CMBR), the remnant heat from the initial fireball. The CMBR spectrum is blackbody, as predicted from the hot Big Bang model before the discovery of the remnant radiation in 1964. In 1992 the cosmic background explorer (COBE) satellite finally detected the anisotropy of the radiation-fingerprints left by tiny temperature fluctuations in the initial bang. Careful design of the COBE satellite, and a bit of luck, allowed the 30 microK fluctuations in the CMBR temperature (2.73 K) to be pulled out of instrument noise and spurious foreground emissions. Further advances in detector technology and experiment design are allowing current CMBR experiments to search for predicted features in the anisotropy power spectrum at angular scales of 1 degrees and smaller. If they exist, these features were formed at an important epoch in the evolution of the universe--the decoupling of matter and radiation at a temperature of about 4,000 K and a time about 300,000 years after the bang. CMBR anisotropy measurements probe directly some detailed physics of the early universe. Also, parameters of the cosmological model can be measured because the anisotropy power spectrum depends on constituent densities and the horizon scale at a known cosmological epoch. As sophisticated experiments on the ground and on balloons pursue these measurements, two CMBR anisotropy satellite missions are being prepared for launch early in the next century.
现在，大多数宇宙学家认为，我们生活在一个不断演化的宇宙中，自约150亿年前诞生以来，它一直在膨胀和冷却。这一标准宇宙学模型的有力证据来自对宇宙微波背景辐射（CMBR）的研究，即初始火球残留的热量。CMBR光谱是黑体光谱，正如1964年发现残留辐射之前，热大爆炸模型所预测的那样。1992年，宇宙背景探测器（COBE）卫星最终探测到了辐射的各向异性——初始爆炸中微小温度波动留下的指纹。精心设计的COBE卫星，再加上一点运气，使得能够从仪器噪声和虚假的前景辐射中提取出CMBR温度（2.73K）中30微开尔文的波动。探测器技术和实验设计的进一步发展，使得当前的CMBR实验能够在1度及更小的角尺度上搜索各向异性功率谱中的预测特征。如果这些特征存在，它们是在宇宙演化的一个重要时期形成的——物质与辐射在大约4000K的温度和大爆炸后约30万年的时间里脱耦。CMBR各向异性测量直接探测了早期宇宙的一些详细物理情况。此外，由于各向异性功率谱取决于已知宇宙学时期的成分密度和视界尺度，因此可以测量宇宙学模型的参数。随着地面和气球上的精密实验进行这些测量，两项CMBR各向异性卫星任务正准备在下个世纪初发射。
