Research These physicists want to ditch dark energy (Sabine Hossenfelder)

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https://nautil.us/these-physicists-want-...6380166603

EXCERPTS: It is this model, the Lambda cold dark matter model, that requires dark energy to accelerate the expansion of the universe. [...] But strictly speaking, we already know that this model is, of course, wrong. Galaxies and galaxy clusters are not uniformly distributed. Instead ... It has patches with many galaxies in them—such as the one that we find ourselves in—but then there are big voids in between.

This is what the authors of the new paper looked at, a universe that is a patchwork of matter-filled regions like our own and voids. And all these regions interact, pushing and pulling on each other. Now not only do we have an expanding sponge that’s some dozens billion light-years wide, we have a sponge that doesn’t expand at the same rate everywhere.

[...] While I am sympathetic to the idea .. and think it has a lot of potential, I also think it is too early to declare the end of dark energy. Analyses like the one in the new paper, depend a lot on their assumptions (priors) and the data used, and I would not be surprised if another group soon claims that Lambda cold dark matter is superior after all. Questions like this one take time to settle.

[...] As they say, all models are wrong, but some are useful, and whatever your misgivings about dark energy, it certainly has proved to be useful for explaining many observations, such as the features of the cosmic microwave background and the growth of galactic structures. It will take a lot more than one paper to convince astrophysicists that dark energy should be declared dead... (MORE - details)

[Zinjanthropos]

Dark matter for Dummies:

Is void a term for absence of matter? Why can’t dark matter be light? Photons I assume are everywhere, so would they be present in the dark voids also? The space that’s expanding, do we know what it’s made of, if anything?

If space is expanding, is there a measurable pressure that causes it to stretch? I can imagine the universe like a flattened, dried up, crinkled balloon that’s unraveling as the pressure mounts. According to Google AI: The ratio of stars being born to stars dying in the Milky Way is about 7 stars per year being born for every 2 high-mass stars that go supernova each century, and 1 low-mass star that forms a planetary nebula each year. Would that mean much more light is created every second in the universe? Where do the photons from new or exploding stars go? What if there’s not enough room for them all?

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Dark matter for Dummies:

Is void a term for absence of matter?

Voids aren't completely empty, they're just less populated by highly visible, denser aggregations of matter.

Why can’t dark matter be light? Photons I assume are everywhere, so would they be present in the dark voids also? The space that’s expanding, do we know what it’s made of, if anything? [...] Where do the photons from new or exploding stars go? What if there’s not enough room for them all?

The role of dark matter is different from that of dark energy. The former contributes to the rotational stability of galaxies, and shapes and holds together large scale structures (like galaxy clusters).

Photons are mediators of the electromagnetic field that already pervades the entire universe, including voids (along with at least 23 other quantum fields). Photons lack mass, and they have visible effects on the eyes and equipment and interact with regular matter, in contrast to the purely gravitational influence of dark matter.

Black holes are able to swallow photons because they still have to follow the curvature of space -- a warping that is caused by the mass of non-boson or fermionic matter.