在1990年代，天文學家利用被稱為「標準燭光」的Ia型超新星來測量宇宙的距離與膨脹歷史。亞當·里斯及其團隊在觀測這些遙遠的爆炸恆星時，意外發現宇宙的膨脹速度並沒有如預期般因引力而減緩，反而在不斷加速。這項驚人的發現促使了暗能量概念的提出，並讓科學家們獲得了諾貝爾物理學獎。

為了解釋這項發現與其他宇宙現象，科學家建立了Lambda-CDM標準宇宙模型。該模型指出，宇宙的組成中約有4%是常規物質，26%是暗物質，而高達70%是推動宇宙加速膨脹的暗能量。儘管我們對暗物質和暗能量的本質仍不清楚，但這個模型成功地精確預測了宇宙微波背景輻射等多種觀測結果，成為過去二十多年來的核心理論。

然而，隨著觀測技術的進步，現代宇宙學面臨著被稱為「哈伯張力」的重大挑戰。天文學家利用鄰近宇宙的超新星所測量出的當前宇宙膨脹速率（哈伯常數），與透過早期宇宙微波背景輻射和標準模型所預測的數值產生了顯著的落差。這種無法忽視的差異暗示了標準模型可能存在缺陷，迫使科學家期待藉由新一代太空望遠鏡的觀測數據來解開這個未解之謎。

In the 1990s, astronomers utilized Type Ia supernovae, known as "standard candles," to measure cosmic distances and the universe's expansion history. While observing these distant exploding stars, Adam Riess and his team unexpectedly discovered that the universe's expansion was not slowing down due to gravity as anticipated, but was instead accelerating. This astonishing finding led to the proposal of the dark energy concept and earned the scientists the Nobel Prize in Physics.

To explain this discovery along with other cosmic phenomena, scientists established the Lambda-CDM standard cosmological model. This model posits that the universe is composed of approximately 4% normal matter, 26% dark matter, and a staggering 70% dark energy, which drives the accelerated expansion. Although the true nature of dark matter and dark energy remains unknown, this model has successfully and precisely predicted various observations, such as the cosmic microwave background, serving as the core theoretical framework for over two decades.

However, with advancements in observational techniques, modern cosmology is facing a major challenge known as the "Hubble tension." The present-day universe expansion rate (the Hubble constant) measured by astronomers using supernovae in the nearby universe shows a significant discrepancy with the value predicted using the early cosmic microwave background and the standard model. This unignorable difference suggests potential flaws in the standard model, compelling scientists to look forward to observational data from a new generation of space telescopes to solve this enduring mystery.