宇宙視界及宇宙膨脹的探討

Abstract

大霹靂理論無疑是近代物理學中最迷人和最重要的理論之一。然而，在大霹靂理論中常被提及的空間膨脹，卻也是最易被誤解的物理概念之一。本文透過對宇宙學上三種視界—粒子視界、事件視界和哈伯半徑－之探討，試圖釐清各種不同的膨脹宇宙模型的樣貌。我們同時也討論常令人困惑的宇宙紅移與距離和速度的關係。最後，根據Harrison在1995年所提出「繫鏈星系」這個假想實驗的機制來鑽研宇宙膨脹的本質，以及空間膨脹在各種不同宇宙模型所造成的影響。

The big-bang theory is arguably one of the most fascinating and significant theories in modern physics. However, an expanding space－the major notion of the big-bang cosmology－is also one of the most confusing concepts in modern physics. In this thesis, we first explore various models of expanding universe by virtue of three cosmological horizons, i.e. the particle horizon, the event horizon, and the Hubble radius. We then discuss some of the most perplexing features of the big-bang cosmology, such as cosmological redshifts and the receding velocity of distant galaxies. Finally, based on the gedanken experiment of the “tethered galaxy” proposed by Harrison in 1995, we investigate the very nature of space expansion and its consequences in different cosmological models.