
Isn’t the FLRW metric way generic? It lays out the basic assumptions and tells us how the universe should behave, but it doesn’t say WHAT the universe is made of.

Isn’t the FLRW metric way generic? It lays out the basic assumptions and tells us how the universe should behave, but it doesn’t say WHAT the universe is made of.

Sometimes humans get ahead of ourselves. We embark on grand engineering experiments without really understanding what the long-term implications of such projects are. Climate change itself it a perfect example of that - no one in the early industrial revolution realized that, more than 100 years later, the emissions from their combustion engines would increase the overall global temperature and risk millions of people's lives and livelihoods, let alone the impact it would have on the species we share the world with. According to a new release from the Salata Institute at Harvard, we seem to be going down the same blind path with a different engineering challenge in this century - satellite megaconstellations.

The FLRW metric is a model. And you know the saying, all models are wrong, but some are useful.

In 2023, a subatomic particle called a neutrino crashed into Earth with such a high amount of energy that it should have been impossible. In fact, there are no known sources anywhere in the universe capable of producing such energy—100,000 times more than the highest-energy particle ever produced by the Large Hadron Collider, the world's most powerful particle accelerator. However, a team of physicists at the University of Massachusetts Amherst recently hypothesized that something like this could happen when a special kind of black hole, called a "quasi-extremal primordial black hole," explodes.

Astronomers have been collecting data for generations, and the sad fact is that not all of it has yet been fully analyzed. There are still discoveries hiding in the dark recesses of data archives strewn throughout the astronomical world. Some of them are harder to access than others, such as actual physical plates containing star positions from more than a hundred years ago. But as more and more of this data is archived, astronomers also keep coming up with ever more impressive tools to analyze it. A recent paper from Cyril Tasse of the Paris Observatory and his co-authors, published recently in Nature Astronomy describes an algorithm that analyzes hundreds of thousands of previously unknown data points in radio telescope archives - and they found some interesting features in it.

NASA’s Orion spacecraft, which will carry the Artemis II crew around the Moon, sits at the launch pad on Jan. 17, 2026, after rollout. It rests atop the SLS (Space Launch System) rocket. Orion can provide living space on missions for four astronauts for up to 21 days without docking to another spacecraft. Advances in technology […]

This is all based on the assumption that galaxies are receding away from us. And I actually cheated a little.