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cover of episode Why Can’t Scientists Agree On The Age Of The Universe? with Wendy Freedman

Why Can’t Scientists Agree On The Age Of The Universe? with Wendy Freedman

2024/10/3
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Wendy Freedman: 我在几十年的研究生涯中致力于精确测量宇宙的膨胀速度,也就是哈勃常数。起初,我们对宇宙的年龄知之甚少,误差高达一倍。通过测量附近星系的距离和它们远离我们的速度,并利用宇宙学模型进行外推,我们可以估算宇宙的年龄。此外,我们还可以通过观测宇宙中最远处的可见光——宇宙大爆炸后最早的光——结合宇宙学模型来确定宇宙的年龄。这两种方法的测量结果存在差异,这可能意味着我们对物理学的理解存在错误,或者我们的标准模型中缺少某些东西,例如暗能量或暗物质。 近年来,我们利用哈勃太空望远镜和更先进的探测器,对哈勃常数进行了更精确的测量。然而,通过宇宙微波背景辐射测量的哈勃常数与我们通过直接测量得到的哈勃常数存在差异,这就是所谓的哈勃张力。这种差异可能意味着我们的测量存在错误,或者我们的标准模型存在问题。 最近,我们利用詹姆斯·韦伯太空望远镜对哈勃常数进行了新的测量。我们使用了三种不同的方法和两种不同类型的遥远天体来进行测量,以提高测量的可靠性。结果表明,其中两种方法的测量结果非常一致,而造父变星的测量结果与它们存在差异。这表明,我们对距离测量的理解可能存在问题,而不是标准模型存在问题。目前,我们还没有足够的证据来证明标准模型存在问题,但未来的研究可能会提供更多的证据。 总而言之,我对宇宙年龄的测量和哈勃常数的精确测定充满热情。尽管我们取得了很大的进展,但仍有许多未解之谜等待我们去探索。我希望在有生之年能够看到更多令人兴奋的发现,例如发现地外生命,并对暗能量和暗物质有更深入的理解。

Deep Dive

Key Insights

Why is determining the age of the universe so important?

The age of the universe is crucial because it affects our understanding of physics and the standard model. A discrepancy in measurements could indicate missing elements in our current understanding, potentially leading to new discoveries.

What is the Hubble constant and why is it significant?

The Hubble constant measures the rate of expansion of the universe. It is significant because it allows scientists to calculate the age and size of the universe, which is fundamental to cosmology.

How does the expansion of the universe differ from everyday experiences of expansion?

The universe's expansion involves space itself expanding, not objects expanding into something else. Unlike everyday experiences, space is being created as the universe expands.

What are the implications if the universe's expansion rate differs from predictions?

A discrepancy could mean there is something wrong with our standard model of physics, potentially pointing to missing elements or new fundamental physics that we haven't discovered yet.

How has the James Webb Space Telescope (JWST) contributed to resolving the Hubble tension?

JWST has allowed for more accurate measurements of the Hubble constant due to its larger mirror, better resolution, and higher sensitivity. These improvements bring us closer to resolving the discrepancy between different measurement methods.

What are some of the challenges in measuring the Hubble constant?

Challenges include accounting for dust, resolving crowded stars, and ensuring the accuracy of distance measurements. These factors can affect the precision of the Hubble constant calculations.

What is the significance of the Cepheid variable stars in measuring the Hubble constant?

Cepheid variable stars are used as distance indicators because their brightness correlates with their pulsation period. This allows astronomers to measure distances to galaxies and calculate the Hubble constant.

What is dark energy and why is it a mystery?

Dark energy is a form of energy causing the universe to expand at an accelerating rate. It is a mystery because there is no physical explanation for it, and its properties are not well understood.

What role does the cosmic microwave background play in measuring the age of the universe?

The cosmic microwave background provides information about the early universe. By studying its properties, scientists can estimate the age of the universe, which is currently calculated to be 13.8 billion years.

What are the potential outcomes of resolving the Hubble tension?

Resolving the Hubble tension could either confirm the standard model of physics or reveal missing elements, leading to new discoveries and a better understanding of the universe's composition and behavior.

Shownotes Transcript

How old is the universe—and how fast is it expanding? These are part of one of the biggest—and most contested—questions in science, and the answers could change our understanding of physics.

In this episode, we talk with renowned UChicago astronomer Wendy Freedman, who’s spent decades trying to solve these very questions. There are two ways to measure how fast the universe is expanding, also known as the Hubble constant; Freedman has done groundbreaking research to calculate this number using stars, but the problem is, her numbers don’t match up with scientists using a different method. And the implications of that difference are massive, because it could indicate that our Standard Model of physics could be broken.

Yet Freedman’s latest research, using the powerful James Webb Space Telescope, might finally give us a clearer answer. In our conversation, we explore the age of the universe, the mysteries of dark matter and what all this could mean for the future of physics—and maybe even the discovery of life beyond Earth.