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Mysterious Dark Matter Mapped In Finest Detail Yet (bbc.com) 34

According to the BBC, the Atacama Cosmology Telescope (ACT) in Chile has traced the distribution of dark matter "on a quarter of the sky and across almost 14 billion years of time." From the report: In the image [here], the colored areas are the portions of the sky studied by the telescope. Orange regions show where there is more mass, or matter, along the line of sight; purple where there is less. Typical features are hundreds of millions of light-years across. The grey/white areas show where contaminating light from dust in our Milky Way galaxy has obscured a deeper view. The distribution of matter agrees very well with scientific predictions.

ACT observations indicate that the "lumpiness" of the Universe and the rate at which it has been expanding after 14 billion years of evolution are just what you'd expect from the standard model of cosmology, which has Einstein's theory of gravity (general relativity) at its foundation. Recent measurements that used an alternative background light, one emitted from stars in galaxies rather than the CMB, had suggested the Universe lacked sufficient lumpiness.

Another tension concerns the rate at which the Universe is expanding - a number called the Hubble constant. When [the European Space Agency's Planck observatory] looked at temperature fluctuations across the CMB, it determined the rate to be about 67 kilometres per second per megaparsec (A megaparsec is 3.26 million light-years). Or put another way - the expansion increases by 67km per second for every 3.26 million light-years we look further out into space. A tension arises because measurements of the expansion in the nearby Universe, made using the recession from us of variable stars, clocks in at about 73km/s per megaparsec. It's a difference that can't easily be explained. ACT, employing its lensing technique to nail down the expansion rate, outputs a number similar to Planck's. "It's very close - about 68km/s per megaparsec," said Dr Mathew Madhavacheril from the the University of Pennsylvania.
ACT team-member Prof Blake Sherwin from Cambridge University, UK, added: "We and Planck and several other probes are coming in on the lower side. Obviously, you could have a scenario where both the measurements are right and there's some new physics that explains the discrepancy. But we're using independent techniques, and I think we're now starting to close the loophole where we could all be riding this new physics and one of the measurements has to be wrong."

Papers describing the new results have been submitted to The Astrophysical Journal and posted on the ACT website.
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Mysterious Dark Matter Mapped In Finest Detail Yet

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  • by Anonymous Coward

    This totally ought to go onto that "dark web" journos keep on yabbering about. Mysterious dark matter onto the mysterious dark web, already!

  • They've determined that "Dark Matter" is matter and know the mass of it?

    That would mean that "dark matter" is no longer a placeholder, and is just matter.

    No matter, it doesn't matter, no matter what is the matter.

    • Um no. It is dark matter because it has the properties that normal baryonic matter does not have. For example it does react with, absorb, or emit EM radiation.
      • I believe you meant "it does not react with, absorb, or emit EM radiation."
      • Re: (Score:2, Offtopic)

        by Ol Olsoc ( 1175323 )

        Um no. It is dark matter because it has the properties that normal baryonic matter does not have. For example it does react with, absorb, or emit EM radiation.

        Seems like it isn't matter then. No matter. Before we go too far, I'm just having a bit of light fun this morning.

        The Dark Matter Nursery Rhyme, by Ol Olsoc

        Oh dear, what can the matter be,

        Oh dear, universe ain't right to me

        Oh dear where can the matter be,

        Dark matter's the answer for me.

        It's 80 percent of all universe matter

        We can't see it though it should be on a platter,

        Enough to make physicists mad as a hatter,

        Dark matter's the answer for me.

        • by ceoyoyo ( 59147 )

          Might want to google what matter is.

          • Might want to google what matter is.

            Ah, ya might want to get a sense of humor, homie. Then again nahh, Show that guy what wrote the children's rhymes with your known facts.

            Anyhow, If you are going to be serious, let's have a line by line refutation of what I wrote, with peer reviewed citations showing the faults in a silly little joke. Then tell us exactly what the nature and composition of dark matter is. You know exactly what Dark matter is, amirite? So share it with the world.

            • by ceoyoyo ( 59147 )

              Seems like it isn't matter then.

              I was replying to this. I don't really care about your poetry.

              • Seems like it isn't matter then.

                I was replying to this. I don't really care about your poetry.

                Strange attributions, fo shizzle.

                Then as Slashdot's ranking cosmologist, What exactly is it? Don't say dark matter. Seems like most of the world doesn't know, and uses "dark matter as a placeholder, and have a number of candidates for this dark matter, which is apparently 85 percent of all the "matter" in the universe. That is a pretty big amount of unseen and unknown matter. I don't care about what you think about my nursery rhymes either - I want you to inform us exactly what dark matter is.

        • Tell me you do not understand basic physics without telling me you do not understand basic physics.
    • by fahrbot-bot ( 874524 ) on Wednesday April 12, 2023 @12:49PM (#63444458)

      They've determined that "Dark Matter" is matter and know the mass of it?

      About three seasons [wikipedia.org] :-)

      • They've determined that "Dark Matter" is matter and know the mass of it?

        About three seasons [wikipedia.org] :-)

        This is the best reply yet. I mean that. At least it is unambiguous! 8^)

        • They've determined that "Dark Matter" is matter and know the mass of it?

          About three seasons [wikipedia.org] :-)

          This is the best reply yet. I mean that. At least it is unambiguous! 8^)

          I would have enjoyed the show continuing, but (apparently) SyFy was going to cut either Dark Matter or Killjoys [wikipedia.org], for cost reasons, and I enjoyed Killjoys more so was okay with that decision. I'm also not sure where the story line was going in Dark Matter...

  • Interesting similarity to amorphous crystaline structures.

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