Episode 70 of SfS — The Crisis in Cosmology: What is the Hubble Tension? — is now live!
This week’s episode deals with a rather pressing matter for astronomers and cosmologists. Shortly after Einstein revealed his Theory of General Relativity in 1916, scientists began pondering how it predicted that the Universe was either expanding or contracting. The debate was settled when Georges Lemaitre and Edwin Hubble confirmed that it was expanding (in 1927 and 1929, respectively). In honor of their accomplishments, the rate at which the cosmos is expanding was named the “Hubble-Lemaitre Constant” (or more commonly, the “Hubble Constant”).
As the field of astronomy expanded and telescopes improved, scientists were able to make distance measurements for objects located farther and farther away. However, these observations were restricted to objects within 4 billion light-years due to the way Earth’s atmosphere distorts light. Depending on the distances involved, astronomers relied on different methods, which came to be known as the “Cosmic Distance Ladder.” In addition to determining the age and size of the Universe, these measurements allowed astronomers to refine their estimates of the Constant.
The Hubble Space Telescope revolutionized astronomy by gradually pushing the boundaries of the “observable Universe” to less than 1 billion years after the Big Bang (13 billion light years!) That’s when scientists noticed some discrepancies. Not only did they learn that the rate of expansion had accelerated over time, but distance measurements to objects located 13 billion light-years away (the earliest galaxies) yielded different values than local measurements. This came to be known as the “Hubble Tension” or the “Crisis in Cosmology.”
While it was hoped that the James Webb Space Telescope would resolve this crisis, its observations have only confirmed that Hubble was right on the money! The crisis endures, and scientists are seeking answers. Is Einstein’s Theory of General Relativity, which is foundational to our cosmological models, wrong? Or are there additional physics/forces at work that we haven’t yet accounted for? Once we know that, we’ll know how just about everything in the Universe works!
Check out the episode below.
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Originally published at http://storiesbywilliams.com on April 12, 2024.
