from Hacker News

Astronomers Just Solved the Mystery of the Universe's Missing Matter

by guerrilla on 6/17/25, 6:44 PM with 22 comments

• by umeshunni on 6/17/25, 7:14 PM

  It's important to note that this isn't the same as Dark Matter.

• by arcastroe on 6/18/25, 9:15 AM

  I remember this being news two years ago [1]. What changed between then and now? Seems like dejavu reading about the same missing matter being found again.

  [1] https://www.astronomy.com/science/half-the-matter-in-the-cos...

• by GianFabien on 6/18/25, 1:59 AM

  Perhaps I'm missing something critical.

  As I understand it: when astronomers are looking at things a very long distance (measured in lightyears) away, they are looking at how things were that number of millions/billion(s) years ago.

  Based on my possible misunderstanding, shouldn't any such claims be made on the basis of how things were and with no indication as to how things may have changed since?

• by blacksmith_tb on 6/17/25, 7:26 PM

  Perhaps some local astrophysicists can chime in on how the gas could be characterized as "hot" - my naive assumption is that could only be relative?

• by gwbas1c on 6/17/25, 7:18 PM

  I wonder if we'll have to revise our current measurements of distances among stars and galaxies as a result?

• by andrewstuart on 6/17/25, 9:47 PM

  This sounds very certain, like it’s accepted fact.

• by ed_mercer on 6/18/25, 4:08 AM

  > By measuring this decrease in speed

  How do you measure the speed of a radio signal going away from you?