cover of episode Is our model of the universe wrong?

Is our model of the universe wrong?

2024/12/17

Science Weekly

凯

凯瑟琳·海曼斯

播

播音员

主持著名true crime播客《Crime Junkie》的播音员和创始人。

播音员: 宇宙的膨胀速度，即哈勃常数，是确定宇宙年龄的关键。目前，通过观测晚期宇宙（恒星、星系和超新星）和早期宇宙（宇宙微波背景辐射）得到的哈勃常数数值存在显著差异（约72和67），这引发了宇宙学危机。这种差异可能源于测量方法的误差，也可能源于我们对宇宙模型（包括暗物质和暗能量）的理解存在偏差。詹姆斯·韦伯太空望远镜的观测结果证实了晚期宇宙观测结果的准确性，因此问题可能在于对宇宙的基本理解。哈勃常数的差异导致对宇宙年龄的估计差异巨大（138亿年 vs 126亿年）。宇宙学家们讨论了哈勃常数差异的可能原因：尘埃和磁场。詹姆斯·韦伯太空望远镜的红外观测排除了尘埃对哈勃常数测量的影响。宇宙早期可能存在的原始磁场可能是哈勃常数差异的原因之一。凯瑟琳·海曼斯: 解释了多普勒效应及其在测量星系远离速度中的应用（红移），以及如何使用标准烛光（造父变星和超新星）测量星系距离，从而计算哈勃常数。她认为，“早期暗能量”理论可能是解释哈勃常数差异的最佳理论，该理论可以解释詹姆斯·韦伯太空望远镜观测到的早期宇宙中巨大星系的形成。她作为观测宇宙学家，不进行理论预测，只关注观测结果。暗物质和暗能量理论虽然解释了很多宇宙现象，但随着观测数据的增加，该模型也暴露出一些问题。需要在理解暗区方面取得突破才能解决哈勃常数问题。

Deep Dive

Why is the Hubble constant a critical factor in understanding the age of the universe?

The Hubble constant, which measures the current rate of expansion of the universe, is crucial because it allows scientists to trace the universe's expansion backward in time to estimate its age. Different values of the Hubble constant lead to different ages of the universe, creating a significant discrepancy known as the Hubble tension.

Why do measurements of the Hubble constant from the late universe and the early universe differ?

Measurements from the late universe, using stars, galaxies, and supernovae, give a Hubble constant of about 72 km/s/Mpc, while measurements from the early universe, using the cosmic microwave background, give a value of about 67 km/s/Mpc. This discrepancy, known as the Hubble tension, suggests either a problem with the measurements or a flaw in our model of the universe.

What role does the James Webb Space Telescope play in resolving the Hubble tension?

The James Webb Space Telescope (JWST) was expected to help resolve the Hubble tension by providing clearer, dust-free observations of standard candles like Cepheid stars. However, JWST's results have confirmed the Hubble Space Telescope's measurements, indicating that the discrepancy likely lies in our theoretical understanding of the universe rather than in the measurements themselves.

What is the early dark energy model and how does it address the Hubble tension?

The early dark energy model proposes an additional component of dark energy that was active very early in the universe, giving it an initial 'kick' that could explain the discrepancy between the predicted and observed expansion rates. This model also helps explain the formation of massive galaxies much earlier than current models predict.

Why are cosmologists concerned about the implications of the Hubble tension?

The Hubble tension is concerning because it suggests that our current model of the universe, which includes dark matter and dark energy, might be incomplete or incorrect. This uncertainty impacts our understanding of the universe's age and the processes that govern its expansion and structure formation.

Shownotes Transcript

For the past 10 years cosmologists have been left scratching their heads over why two methods for measuring the universe’s rate of expansion provide totally different results. There are two possible solutions to the puzzle, known as the Hubble tension: either something is wrong with the measurements or something is wrong with our model of the universe. It was hoped that observations from the James Webb space telescope might shed some light on the problem, but instead results published last week have continued to muddy the waters. To understand why the expansion rate of the universe remains a mystery, and what might be needed to finally pin it down, Madeleine Finlay speaks to Catherine Heymans, the astronomer royal for Scotland and a professor of astrophysics at the University of Edinburgh. Help support our independent journalism at theguardian.com/sciencepod)