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Every science documentary I've watched tells me most physicists want to ditch "dark energy" because it's a placeholder term for something we still don't underst

Every science documentary I've watched tells me most physicists want to ditch "dark energy" because it's a placeholder term for something we still don't understand yet. Map-makers didn't actually believe there were dragons after all.

the__alchemist 2y ago
I've heard the same about Dark Matter, and that was previously my amateur mental model. This was naive; in practice it confidently refers to CDM (cold dark matter), which is matter that interacts gravitationally, but not electromagnetically, with normal matter.
- XorNot 2y ago
  That's literally what a placeholder is: it's a description of a suite of observed properties. Hot dark matter would be a black body emitter - we would see it. If it interacted electromagnetically then effects like the bullet cluster's gravitational lensing shouldn't happen. And if it didn't interact gravitationally then we should see normal galactic rotation curves.
  - andrewflnr 2y ago
    No, hot dark matter would not magically start interacting with the EM field to make black body radiation. I believe the hot/cold dark matter question is entirely about the velocities of the particles.
  - uoaei 2y ago
    > it's a description of a suite of observed properties "Looks like matter" is not a property, this interpretation already presupposes a theory that excludes many others that are heretofore still plausible. Physicists tend to ignore those other options, I believe, because of a combination of natural human linguistic biases and the desire for certainty in explanatory models that drives many of us into studying physics. Some get too confident too early and start making dogma their entire academic personality.
    - deleted 2y ago
      [deleted]
  - the__alchemist 2y ago
    I think we are on the same page. I was sloppy in my wording; my point is, "dark matter" is not a placeholder for discrepancies in Newtonian simulations of cosmological features with observation, but a placemholder for a type of gravitational-interacting bodies.
  - floxy 2y ago
    >Hot dark matter would be a black body emitter - we would see it. Hot dark matter would be stuff like neutrinos and axions which don't interact electromagnetically. https://en.wikipedia.org/wiki/Dark_matter#Warm_dark_matter https://en.wikipedia.org/wiki/Dark_matter#Warm_dark_matter

the__alchemist 2y ago

I've heard the same about Dark Matter, and that was previously my amateur mental model. This was naive; in practice it confidently refers to CDM (cold dark matter), which is matter that interacts gravitationally, but not electromagnetically, with normal matter.

XorNot 2y ago
That's literally what a placeholder is: it's a description of a suite of observed properties. Hot dark matter would be a black body emitter - we would see it. If it interacted electromagnetically then effects like the bullet cluster's gravitational lensing shouldn't happen. And if it didn't interact gravitationally then we should see normal galactic rotation curves.
- andrewflnr 2y ago
  No, hot dark matter would not magically start interacting with the EM field to make black body radiation. I believe the hot/cold dark matter question is entirely about the velocities of the particles.
- uoaei 2y ago
  > it's a description of a suite of observed properties "Looks like matter" is not a property, this interpretation already presupposes a theory that excludes many others that are heretofore still plausible. Physicists tend to ignore those other options, I believe, because of a combination of natural human linguistic biases and the desire for certainty in explanatory models that drives many of us into studying physics. Some get too confident too early and start making dogma their entire academic personality.
  - deleted 2y ago
    [deleted]
- the__alchemist 2y ago
  I think we are on the same page. I was sloppy in my wording; my point is, "dark matter" is not a placeholder for discrepancies in Newtonian simulations of cosmological features with observation, but a placemholder for a type of gravitational-interacting bodies.
- floxy 2y ago
  >Hot dark matter would be a black body emitter - we would see it. Hot dark matter would be stuff like neutrinos and axions which don't interact electromagnetically. https://en.wikipedia.org/wiki/Dark_matter#Warm_dark_matter https://en.wikipedia.org/wiki/Dark_matter#Warm_dark_matter