It is important to remember the origins of the theories of "dark matter" and "dark energy". These are claimed to exist not based on their discovery, but rather solely as a curve fitting exercise using Newtonian dynamics (Keplerian) and the universal law of gravitation as applied to the velocity curves of galaxies and the estimated masses of the visible objects in those galaxies.
The most notable case is M31, the Andromeda galaxy. The light curve for Andromeda shows a central region (the bulge), a transitional region, a region containing the bulk of the galactic disk, and then the region beyond the seeming edge of the galaxy as viewed by human minds.
The central region behaves with a velocity curve that is linear with distance from the center. The transitional region includes a narrow band rotating retrograde to the rest of the galaxy. The main disk shows a velocity curve that looks like a superposition of a linear velocity with distance (with a much lower slope than the bulge) combined with a keplerian falloff with distance added on top of that. In other words, the inner half of the disk portion has a bulge somewhat faster than a linear relation would suggest. The region beyond the visible edge transitions to a velocity curve of near constant value for considerable distance that then falls off slowly with increasing distance. See page 617 of "Exploration of the Universe" by George Abell, 1969 edition for example.
More distant galaxies are harder to resolve their detailed velocity profiles. The inner details are entirely lost. Most often then, they show velocity curves that rise to a maximum value (disk region), then flatten for considerable distance before falling off.
This is not at all what would be expected from keplerian considerations.
It is these descrepancies that led to the postulation that there must be unseen "dark matter". As that theory was refined, it was realized that "dark matter" alone did not make the velocity curves fit keplerian requirements. Something seemed to be pushing the stars and objects faster. This led to the theory of "dark energy". Today, under the combination of these theories (cold dark matter or CDM), the vast majority of the "mass" of galaxies is proposed to be "dark energy". A minority of the "mass" is "cold dark matter", and a very small portion is the known actual mass of stars, nebulae, gas clouds, etc...
This theory though widely held and "studied" is pure speculation. No direct evidence of "dark matter" or "dark energy" has ever been found, despite intense efforts to find them. It is only inferred. What most scientists have not done is to consider that some other physical law or difference in physical laws are implied. Also, there is no basis at all in all of physics for a force exemplied by "dark energy", or for particles to support "dark matter", or the force of "dark energy". Adding these would break all of the theories of particle physics. Yet, rather than being taken as a fantasy theory, CDM is often taken as true none the less.
But that is not universally true. One group of scientists and researchers proposed modified Newtonian dynamics (MOND) to explain it all. MOND is likewise not a proven theory, and lacks an original explanation as well. However, tests of CDM versus MOND have not ruled either out. There are other theories as well. MOND does accurately predict the velocity curves of thousands of galaxies using a single parameter change in its theory compared to universal gravitation. CDM requires the a priori development of an inferred dark matte distribution for each galaxy to work. I.e. Curve fitting.
As theories go, MOND better fits the data with less fiddling. Occam's razor would suggest that of the two MOND is likely right. And MOND has the added benefit of fitting into existing theories. The background acceleration proposed in MOND may well be a measure of the stretching of space-time itself, or viewed differently as the growth of the universe, or ...., or as the integration constant in relativity, the C constant that Einstein added.
DF2 and DF4 are interesting low mass diffuse galaxies that put both theories to the test. And as it turns out, they don't rule either out.
https://arxiv.org/pdf/1804.04167.pdfhttps://www.physicsforums.com/threads/a-second-galaxy-with-no-dark-matter.964636/What none of the current theories explain is the rotational curves of M31 and our own Milky Way in the visible light region of the galaxies.
There is much more to be learned about how the universe actually works.
We humans repeatedly make the same errrors through time of assuming that we know everything important to know (to explain everything), and that we as individuals, we as a species, our home - the Earth, our sun, our galaxy, our theories, our philosophies, our deities are the center of everything, and that everything depends on us.
We assume too that we are the peak and end goal of the process that led to us, whatever that process is. On the one hand this is simply pure hubris. On another, it is pure arrogance, ignorance and stupidity. On yet another it is a complete failing to apply the things we know such as logic, physics, ... We never seem to generalize these lessons or to learn from them. We fall into the same holes time after time, not even understanding we have fallen into a hole, and utterly refusing to listen to people outside the hole trying to tell us we have fallen into a hole, even though it is they who are trying to help us extricate ourselves.
The application of that to human caused climate change and the disasters rapidly crashing in on us at accelerating speed is just one more exemplar. A large portion of humanity has fallen into their comfortable holes. They cannot see out. Worse, they do not want to see out. They like their cozy holes. As far as they are concerned, the people trying to warn them of the impending catastrophes are crazy. From their perspective in their cozy little holes, they both literally and figuratively cannot see the problem. Note here that seeing isn't just a matter of the optics of they eye, but is rather that plus the entire brain process that goes into building our internal map of what we think we "see". Much of what we "see" is a construct created in our brains. It is all too easy for a system built in this way to suffer aberrations in what we "see".
Sam
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but the interview is of course mainly about the arctic.
Actually, I love all the suggestions -- these are great. Let me tackle the first one first.
