Category Archives: Cosmology

Dark matter galaxy structure

Listening to episode 252 of Science sort of I came across this beautiful discussion of the evidence for dark matter and role it played in the formation of galaxies in the early universe. Here’s an excerpt where Ben Tippet is discussing dark matter in the computer modeling of galaxy evolution:

The galaxies wouldn’t evolve properly or in the correct timescale unless there was dark matter included in the simulations. And so, the modern description for how galaxies formed, in order for them to form in the timescale we see them forming using our telescopes, is if dark matter started out distributed everywhere. Dark matter was the first thing to collapse gravitationally, it formed a filamentary structure, in essence there are long strings of dense distributions of dark matter in the universe.

It collapsed first and then the regular, bosonic matter collapsed around the concentrations of the dark matter. The luminous galaxies we see collapsed around the pre-existing dark matter galaxies. So, there is a tremendous amount of both corroborative and direct evidence that dark matter exists.

Big Bang in 2D

This video at Big Think is an excellent description of the Big Bang. As much as I’ve read about it I’ve yet to come across a description this good and easy to understand. I’m trying it out on my family. Michelle Thaller does a fantastic job describing it. I’d previously heard it likened to a cinnamon roll expanding in an oven and I love cinnamon rolls so :nerd_face: But that description stops short of emphasizing, as she does in the video, the 2-D aspect, of only paying attention to the surface. New to my thinking.

Gravitational Waves Discovered

In case you missed it: LIGO announced the detection of Gravitational Waves

For the first time, scientists have observed ripples in the fabric of spacetime called gravitational waves. This confirms a major prediction of Albert Einstein’s 1915 general theory of relativity and opens an unprecedented window onto the cosmos.

Gravitational waves were detected by the two LIGO detectors in Hanford, Washington and Livingston, Louisiana, United States, at 5:51 am EDT (0951 UTC). The waves were generated during the final moments of the merger of 2 black holes resulting in a single, massive, rotating black hole. Even though such a merger was predicted to happen, it was never observed before.

The merger of the two black holes happened more than 1 billion light-years away. (definition of a light-year, use this calculator to convert light-years to miles.)

Why is this discovery so important? Gravitational waves tell us a lot about their cataclysmic origins. They offer a unique way to look deep into the past and observe cosmic events that happened a very long time ago. Gravitational waves provide information about the nature of gravity that we wouldn’t be able to get any other way. With this observation, LIGO opens a new window through which we can study the cosmos.

A lot more at LIGO’s Detection Portal.