We present a centennial review of the history of the term known as the cosmological constant. First introduced to the general theory of relativity by Einstein in 1917 in order to describe a universe that was assumed to be static, the term fell from favour in the wake of the discovery of the expanding universe, only to make a dramatic return in recent times. We consider historical and philosophical aspects of the cosmological constant over four main epochs; (i) the use of the term in static cosmologies (both Newtonian and relativistic): (ii) the marginalization of the term following the discovery of cosmic expansion: (iii) the use of the term to address specific cosmic puzzles such as the timespan of expansion, the formation of galaxies and the redshifts of the quasars: (iv) the re-emergence of the term in today’s Λ-CDM cosmology. We find that the cosmological constant was never truly banished from theoretical models of the universe, but was marginalized by astronomers for reasons of convenience. We also find that the return of the term to the forefront of modern cosmology did not occur as an abrupt paradigm shift due to one particular set of observations, but as the result of a number of empirical advances such as the measurement of present cosmic expansion using the Hubble Space Telescope, the measurement of past expansion using type SN Ia supernovae as standard candles, and the measurement of perturbations in the cosmic microwave background by balloon and satellite. We give a brief overview of contemporary interpretations of the physics underlying the cosmic constant and conclude with a synopsis of the famous cosmological constant problem.

中文翻译：

---

一百年的宇宙常数：从“多余的特技”到暗能量

我们对这个被称为宇宙常数的术语的历史进行了百年回顾。爱因斯坦于1917年首次将广义相对论介绍给人们，目的是描述一个被认为是静态的宇宙，该词因发现膨胀的宇宙而受到青睐，但在近代才获得了戏剧性的回报。 。我们考虑四个主要时期的宇宙常数的历史和哲学方面。（i）在静态宇宙学中（牛顿和相对论）使用该术语：（ii）在发现宇宙膨胀之后将该术语边缘化：（iii）使用该术语来解决特定的宇宙难题，例如时间跨度膨胀，星系的形成和类星体的红移：（iv）当今Λ-CDM宇宙学中该术语的重新出现。我们发现，宇宙常数从未真正从宇宙的理论模型中消失过，而是由于方便的原因而被天文学家所边缘化。我们还发现，由于一组特定的观察结果，该术语返回现代宇宙学的前沿并没有发生突然的范式转变，而是由于许多经验上的进步，例如使用当前的宇宙膨胀来测量的结果。哈勃太空望远镜，使用SN Ia型超新星作为标准蜡烛测量过去的膨胀，并通过气球和卫星测量宇宙微波背景中的摄动。我们简要概述了当代对宇宙常数基础的物理学的解释，并以著名的摘要作为结论宇宙学常数问题。