Dark Matter: The Situation has Changed
Why Hacker News recommends it
Recommended as an accessible, curious-undergraduate-level overview of dark matter and its alternatives.
What it is
Sabine Hossenfelder explains how her opinion on dark matter has shifted, weighing the evidence for and against it and the case for modified gravity. It runs through what dark matter is and why it has not been detected.
Recommended by 2 HN commenters across 2 different months, 2021 to 2023.
What Hacker News said
Recommends keithnz · 2021-05 · on “New dark matter map reveals cosmic mystery”
Sabine is a great science (physics) communicator to the "masses", she recently did an update on dark matter. [this video]
Recommends tlholaday · 2023-02 · on “Dark energy from supermassive black holes? Physicists spar over radical idea”
> correct me if I’m wrong … I think you’re oversimplifying, like seeing a forest and overlooking that it’s Prototaxites, not Malus domestica. Here’s Sabine Hossenfelder’s curious-undergraduate-level history of Dark Matter theories: [this video] Proper nouns include Renzo’s Rule and Baryonic Tully Fisher Relation.
Cites raz32dust · 2021-05 · on “Astronomers have created the largest ever map of dark matter”
I am not an expert. My understanding - (1) The quantity of rocks that would be needed to explain such a gigantic gap in mass is bound to be observed - if they are dark, then at least we should be able to see them when they block light. You have to remember we need dark matter to be around 80% of total mass of the universe. So they either need to be super dense, like tiny black holes [1], or there needs to be so much of it that there is no way we won't see them. (2) Dark matter is too spread out. If they were rocks or any of the known matter types, they should have coalesced on their own. So they have to be such that dark matter doesn't interact with itself. Edit: This is a nice intro: [LINK]
Cites astrange · 2022-03 · on “Four years on, new experiment sees no sign of ‘cosmic dawn’”
They're "actually" what QFT says they are, but the rest isn't wrong either. It's not wrong to say "a house exists" because it's actually a pile of bricks in the shape of a house. Dark matter must be "matter" if it exists, because there's not a category of things that aren't matter. [this video]