Ep 11. What If Dark Matter Is Just Black Holes?

In this episode of PBS Space Time, titled "What If Dark Matter Is Just Black Holes?", the hosts delve into one of the biggest mysteries in astrophysics: what exactly is dark matter? While scientists know that it exists, they have yet to directly detect or fully understand it. The hosts explore the idea that dark matter could actually be made up of black holes, and what that would mean for our understanding of the universe.

To start, the hosts explain what dark matter is and why it is so important. Dark matter makes up about 85% of the matter in the universe, but it does not interact with light or other forms of electromagnetic radiation, which makes it difficult to study. Scientists have come up with a variety of theoretical particles that could make up dark matter, but none have been directly observed.

The hosts then introduce the idea that dark matter could be made up of primordial black holes, which are black holes that were formed soon after the Big Bang. These black holes would be much smaller than the ones we typically study, with masses ranging from a few grams to tens of solar masses. The hosts discuss the different ways that primordial black holes could have formed, including through the collapse of small pockets of matter in the early universe.

The hosts then explore the possibility that dark matter is made up of black holes by looking at how they would affect the motion of stars in galaxies. Scientists have observed that the stars in galaxies move differently than they should based on the visible matter in the galaxy. This discrepancy is often attributed to the presence of dark matter, but the hosts explain that it could also be explained by the gravitational influence of a large number of small black holes.

Next, the hosts consider some of the implications of dark matter being made up of black holes. They explain that if this were true, it would mean that black holes are much more common in the universe than previously thought. It would also change the way that scientists think about galaxy formation and evolution, as well as the search for gravitational waves.

Throughout the episode, the hosts discuss some of the challenges that come with studying dark matter, including the difficulty of detecting black holes that are so small and the fact that they would be spread out across the universe. They also highlight some of the experiments that are currently underway to try and directly detect dark matter, including the Large Underground Xenon (LUX) experiment and the upcoming Dark Energy Survey.

Overall, "What If Dark Matter Is Just Black Holes?" is a fascinating look at one of the biggest mysteries in astrophysics. The hosts present the idea that dark matter could be made up of black holes in a clear and accessible way, while also exploring some of the implications of this idea for our understanding of the universe. Whether you are a casual fan of astronomy or a seasoned astrophysicist, this episode is sure to leave you thinking about the mysteries of the cosmos in a new way.