Episode 60 of Stories from Space — The Dark Universe — is now Live!
This week was a bit of a treat for me personally since I got to delve into something really astrophysical and theoretical! To break it down, in 1916, Einstein placed the finishing touches on his Theory of General Relativity (GR), which explained how gravity alters the curvature of spacetime, matter and energy are equivalent, and time and space are one. His theory was confirmed almost immediately, but by the 1950s and 60s, astronomers finally had the telescopes they needed to really test GR!
Ah, but there was a snag! When observing massive galaxies, astronomers noticed that their rotational curves suggested there was a lot more mass out there than what they could see. This led to the speculation that the Universe was filled with a mysterious invisible mass (“Dark Matter”) that interacted with “normal matter” only through gravity. The existence of this mass was needed for GR to be correct, which had been confirmed nine ways from Sunday by this point.
In the 1990s, the Hubble Space Telescope provided the most breathtaking and deep images of the cosmos. The primary mission of this observatory was to test Hubble’s Law — i.e., that the Universe is in a state of expansion. When looking back through space and time upwards of 10 billion light-years (or more), astronomers hit another snag. Essentially, the rate at which the cosmos was expanding (the Hubble Metric) was speeding up over time!
This led to speculation that Einstein’s theory about a force that “held back gravity” — the Cosmological Constant, which he described as the “biggest blunder of his career” — was actually correct. This unknown force, “Dark Energy,” became another mysterious phenomenon scientists needed to include in their cosmological models. To this day, neither has been confirmed directly. But next-generation telescopes are coming that could resolve this mystery.
Where to Listen:
Originally published at http://storiesbywilliams.com on December 4, 2023.
