Astronomy Cosmology Physics

At The Conversation: Why DO astronomers believe dark matter exists?

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3-D impression of dark matter via Hubble

Here are some interesting features of dark matter that are currently known:

Remarkably, our inability to see or detect dark matter provides clues as to how it behaves. It must have few interactions with itself and conventional matter apart from the force of gravity – otherwise we would have detected it emitting light and interacting with other particles. As dark matter mostly interacts via gravity alone, it has some curious properties. A cloud of hot gas in space can lose energy by emitting light, and thus cool down. A sufficiently massive and cold gas cloud can collapse under its own gravity to form stars. By contrast, dark matter cannot lose energy by emitting light. Thus, while conventional matter can collapse into dense objects like stars and planets, dark matter remains more diffuse. This explains an apparent contradiction. While dark matter may dominate the mass of the universe, we don’t think there is much of it in our Solar System. …

Most astronomers would say dark matter is the simplest and best explanation for many of the phenomena we see in the universe. While there are potential issues for simplest dark matter models, such as the number of small satellite galaxies, they are interesting problems rather than compelling flaws.

But the fact remains that we are yet to detect dark matter directly. This doesn’t particularly bother me, as physics has a history of particles that have taken decades to directly detect. If we haven’t detected it 20 years from now I may be concerned, but for now I’m betting that dark matter is the real deal.

Michael J. I. Brown, “Why do astronomers believe in dark matter?” at The Conversation


Is dark matter the Higgs boson, hard to find but eventually found, or the ether, once believed to pervade the universe? If twenty years pass with no dark matter, unfortunately, the needle will tilt a bit more toward the ether.


Discover: Even the best dark matter theories are crumbling

Researcher: The search for dark matter has become a “quagmire of confirmation bias” So many research areas in science today are hitting hard barriers that it is reasonable to think that we are missing something.

Physicists devise test to find out if dark matter really exists

Largest particle detector draws a blank on dark matter

What if dark matter just doesn’t stick to the rules?

A proposed dark matter solution makes gravity an illusion

and

Proposed dark matter solution: “Gravity is not a fundamental governance of our universe, but a reaction to the makeup of a given environment.”

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4 Replies to “At The Conversation: Why DO astronomers believe dark matter exists?

  1. 1
    Pearlman says:

    no required/predicted missing dark matter and / or energy and SCM-LCDM is falsified, leaving SPIRAL as the only viable cosmological model between the two.
    SPIRAL already has great advantage over SCM as it would predict the prevalent CR and overall increase of CR w/ distance rather than react to same. SPIRAL also aligns better w/ CMB than does SCM.
    reference ‘SPIRAL cosmological redshift (CR) hypothesis and model’ volume II of the YeC Moshe Emes series for Torah and science alignment
    how much longer do they need to look before they consider the scientific alt.?
    it reminds me of NDT still looking for the predicted missing links and vastly greater number of missing trial and error dead-ends before studying and fair consideration of the ID alt. to NDT (Neo-Darwin doctrine)..

  2. 2
    bornagain77 says:

    A rather important small detail that they left out of the article, a small detail that happens to be of great interest to Intelligent Design proponents, is that Dark matter is fine-tuned:

    Dark Matter Deniers
    Exploring a blasphemous alternative to one of modern physics’ most vexing enigmas.
    By Steve Nadis|Thursday, May 28, 2015
    Excerpt: If dark matter is responsible for such uniform rotation speeds, it would require an extraordinarily precise distribution of the invisible stuff – “fine-tuning in the extreme,” as Milgrom calls it. “It’s like taking 100 building blocks and throwing them on the floor, and lo and behold, I see a castle.
    http://discovermagazine.com/20.....er-deniers

    The Dark Matter ‘conspiracy’ – Apr 30, 2015
    Excerpt: One of the most surprising scientific discoveries of the 20th century was that spiral galaxies, such as our own Milky Way, rotate much faster than expected, powered by an extra gravitational force of invisible ‘dark matter’.
    Since this discovery 40 years ago, we have learned this mysterious substance, which is probably an exotic elementary particle, makes up about 85 per cent of the mass in the known Universe, leaving only 15 per cent to be the ordinary stuff encountered in our everyday lives.
    Dark matter is central to our understanding of how galaxies form and evolve and is ultimately one of the reasons for the existence of life on Earth – yet we know almost nothing about it.
    “One of the surprising findings of this study was that spiral galaxies maintain a remarkably constant rotation speed throughout their disks,” Dr Cappellari said. “This means stars and dark matter conspire to redistribute themselves to produce this effect, with stars dominating in the inner regions of the galaxies, and a gradual shift in the outer regions to dark matter dominance.”
    But the ‘conspiracy’ does not come out naturally from the models, and some fine-tuning is required to explain the observations.
    http://phys.org/news/2015-04-dark-conspiracy.html

  3. 3
    SmartAZ says:

    When 95% of the universe is something you can’t detect, observations are irrelevant.

  4. 4
    tjguy says:

    “Thus, while conventional matter can collapse into dense objects like stars and planets, …..”

    I take issue with this. I don’t think we an be sure that conventional matter can collapse into dense objects like stars and planets. I know that is what the hypothesis says to explain planet formation, but how in the world do particles start to stick together as opposed to bouncing off one another? What force/process is there that enables this to happen? Normally this does not happen so why do we think it did happen in this case?

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