There seems to me to be a real cottage industry in proposing alternatives to Dark Matter and Dark Energy. I wonder why that might be. Why isn't there as much interest in alternatives to, say, Plate Tectonics or the Germ Theory?
Researcher proposes model replacing dark energy/matter to explain universe
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Re: Researcher proposes model replacing dark energy/matter to explain universe
#52There seems to me to be a real cottage industry in proposing alternatives to Dark Matter and Dark Energy. I wonder why that might be. Why isn't there as much interest in alternatives to, say, Plate Tectonics or the Germ Theory?
Because those are coherent theories, that don’t have massive gaps in them like dark matter.
Re: Researcher proposes model replacing dark energy/matter to explain universe
#53There seems to me to be a real cottage industry in proposing alternatives to Dark Matter and Dark Energy. I wonder why that might be. Why isn't there as much interest in alternatives to, say, Plate Tectonics or the Germ Theory?
Because those are coherent theories, that don’t have massive gaps in them like dark matter.
What massive gaps?
Re: Researcher proposes model replacing dark energy/matter to explain universe
#54I don't have access to the paper, but it seems to make zero testable predictions and is therefore just mathematical fiction. If it's not falsifiable, it's not science. EDIT: the last sentence is "Given sufficient redshift (or, equivalently, time) resolution effected by the redshift slicing, one might just find that the Hubble diagram exhibits jumps in the redshift distance relation, which would be very revealing." So…
All these papers miss the fact that our main evidence for dark matter (or something like it) is the cosmic microwave background. I see no mention on how this very convoluted model can reproduce it. The evidence is in the oscillations of the primordial plasma seen directly in the CMB. These come from the gravity pulling the plasma and pressure pushing back. Without DM they would be too shallow, DM helps by pulling the…
“ All these papers miss the fact that our main evidence for dark matter (or something like it) is the cosmic microwave background. ”
There is also the galactic rotation curve evidence. With Newtonian physics, the visible mass in galaxies should rotate faster toward the center and slower toward the edge. This is the rotation curve. We actually observe a very linear curve, where the outer stars and gases rotate at the same speed or even faster than the centers. A dark matter halo would provide the additional gravitational mass for cohesion.
Re: Researcher proposes model replacing dark energy/matter to explain universe
#55There seems to me to be a real cottage industry in proposing alternatives to Dark Matter and Dark Energy. I wonder why that might be. Why isn't there as much interest in alternatives to, say, Plate Tectonics or the Germ Theory?
There are- things like flat or hollow earth, antivax and HIV deniers, homeopaths etc.
Proponents of all of the above are looking for a grand unifying cosmology. Dark matter and dark energy are confusing and unknown, so people want to just simplify them away. Flat earthers want to simplify away the existence of other planets. Antivaxers want to simplify away medicine.
Because it's complicated astrophysics and largely unknown it is normal to put dark matter and energy theories into a non-fantastical category. The very large majority of physicists think MOND and similar are defunct theories. Dark matter and energy are very different, separate phenomena that just share a name. It does not make sense for them to have a shared explanation. There are also so, so many ways we observe dark matter that make it clear there is matter involved. Every new observation has completely overturned the predictions of every MOND or modified gravity theory, and they just come back with a totally different explanation to fit the new data.
Re: Researcher proposes model replacing dark energy/matter to explain universe
#56Earlier quoted context omitted.
Because those are coherent theories, that don’t have massive gaps in them like dark matter.
What massive gaps?
I am not a physicist, buy maybe the nature of dark matter and dark energy? What are their properties aside from their effect on the large scale structure of the universe?
Re: Researcher proposes model replacing dark energy/matter to explain universe
#57If you ask me, Inflation is far more problematic than the Dark Stuff. Nevertheless, so far it remains the best explanation we have for observed phenomena ¯\_(ツ)_/¯
Definitely more problematic. And Webb only made it more confusing :(
https://en.wikipedia.org/wiki/Cosmological_constant_problem
> Depending on the Planck energy cutoff and other factors, the quantum vacuum energy contribution to the effective cosmological constant is calculated to be between 50 and as many as 120 orders of magnitude greater than has actually been observed, a state of affairs described by physicists as "the largest discrepancy between theory and experiment in all of science" and "the worst theoretical prediction in the history of physics".
Re: Researcher proposes model replacing dark energy/matter to explain universe
#58Earlier quoted context omitted.
What massive gaps?
I am not a physicist, buy maybe the nature of dark matter and dark energy? What are their properties aside from their effect on the large scale structure of the universe?
FWIW (which is not much), I was an astrophysicist whose research was Dark Energy, though I arrogate to myself no authority on this topic as frankly a lot of knowledge I used to possess on the topic has been replaced by knowledge of tedious programming APIs (meh...it's a living). My sense was that, perhaps owning to their colorful (colorless?) names, and because they diffused into popular culture more than other equally-important theories in other fields, Dark Matter and Dark Energy were presented to and apprehended by laypeople as "exotic". This invited speculation about these theories and even an urge to overturn them, especially where "exotic" was equated with "tendentious." But, by my lights these theories aren't very exotic. Dark Matter especially seems to me to be very consistent with the history of particle physics. Rutherford first proposed the existence of the neutron in 1920, but it wasn't observed directly until 1932. Pauli first proposed the existence of the neutrino in 1930, but it wasn't observed directly until 1956. Both are forms of "dark matter" and neutrinos were once a candidate for explaining flat rotation curves in galaxies and the "missing mass problem", until they were later excluded by observations of large scale structure. Dark Matter interacts with gravity strongly enough that its effects on astronomical and cosmological scales are pronounced, but it interacts with the other forces weakly enough that so far it hasn't been observed directly. So what?
"the nature of dark matter and dark energy"
I don't know anything about "the nature" of things. That sounds very philosophical to me.
"What are [the properties of Dark Matter and Dark Energy] aside from their effect on the large scale structure of the universe?"
I don't know. I also don't know why you're excluding (in the case of Dark Matter) its gravimetric effect on the large scale structure of the Universe. That seems like a pretty important property to me.
Re: Researcher proposes model replacing dark energy/matter to explain universe
#59Earlier quoted context omitted.
All these papers miss the fact that our main evidence for dark matter (or something like it) is the cosmic microwave background. I see no mention on how this very convoluted model can reproduce it. The evidence is in the oscillations of the primordial plasma seen directly in the CMB. These come from the gravity pulling the plasma and pressure pushing back. Without DM they would be too shallow, DM helps by pulling the…
“ All these papers miss the fact that our main evidence for dark matter (or something like it) is the cosmic microwave background. ” There is also the galactic rotation curve evidence. With Newtonian physics, the visible mass in galaxies should rotate faster toward the center and slower toward the edge. This is the rotation curve. We actually observe a very linear curve, where the outer stars and gases rotate at the…
"A dark matter halo"
Could this mass or gravitational impact be outside the expanding bubble of spacetime? If we are in a hole inside a block of swiss cheese, is there a way to determine if we are seeing the effects of the surrounding "cheese"?
Imagine our expanding universe to be inside a black hole. Could the "dark matter halo" be energy/matter dumped into our universe from an external source? Is the expansion of the universe actually our universe growing due to consuming its surroundings?
Re: Researcher proposes model replacing dark energy/matter to explain universe
#60Earlier quoted context omitted.
I’ve never really understood how just adding extra invisible stuff to make the equations work is justified either? It seems more likely there is simply something wrong with the equations.
The neutrino was also a particle that nobody could observe at the time when Pauli proposed it. It was just a manifestation of the energy and spin conservation. The Higgs is the same. It is not needed, but it solves the mass problem of the weak force. It is the only scalar field so far that we have observed and it was not clear whether it would exist at all. Quintessence and sterile neutrinos are also just pieces that…
"Measure first, discover later" can be a perfectly valid application of the scientific method. It's all about refining the resolution on reality.
The problem with dark matter/energy is that we're not guaranteed to discover anything. It might just be wrong. The neutrinos and Higgs just happened to match their initial theory, so that's a survivorship bias. We can't just assume the same will play out for dark matter. It might just be pure mathematical fiction, reflecting our ignorance and/or limitations to measurement rather than something "real" that we can zoom in on.