Cold Dark Matter

Given my current interest in the non-existence of dark matter, it was interesting to come across this recent (2nd November 2020) article on the BBC website:

Durham University Prof Carlos Frenk's prize a 'huge honour'

A cosmologist who helped shape understanding of dark matter and the structure of galaxies has been awarded a top physics prize. Prof Carlos Frenk has been awarded the 2020 Paul Dirac Medal and Prize for theoretical physics by the Institute of Physics (IoP). The Durham University researcher was one of the originators of the Cold Dark Matter (CDM) theory. It is the second year in a row a Durham professor has won the award. A university spokesman said research carried out by Prof Frenk and his Durham colleagues had "created an internationally-renowned capability for predicting the observable properties of galaxies in a CDM universe".

Following up on this mention of cold dark matter, I discovered that there are two other proposed forms of this elusive substance: hot dark matter and warm dark matter. I kid you not. Not only do some cosmologists postulate dark matter but they haggle over whether it is cold, warm or hot. Currently, most of the money is on cold dark matter (CDM). Reading the BBC article, you'd have no idea that there is a crisis in cosmology but then again if you read the BBC exclusively you'd have no idea about anything. It really is an execrable news outlet.

However, now I'm finding out more about the doubts surrounding dark matter, YouTube is throwing up some relevant links. Here is one that I came across today from Sabine Hossenfelder:

There are variations on even the CDM universe. For instance, this article postulates a Lambda-CDM model:

Dark matter and dark energy may really be one "dark fluid" with negative mass 

The Standard Model of particle physics is currently our best understanding of how the universe works – but it only describes about five percent of everything in it. The rest is made up of what we call dark matter and dark energy, which are so far only known through their gravitational interactions with regular matter. Now, an astrophysicist from Oxford has put forward a new theory that suggests that dark matter and dark energy are actually part of the same phenomenon: a "dark fluid" with negative mass that fills the universe.

In a way, dark matter and dark energy are both placeholder concepts, plugging holes between the Standard Model and what we actually observe. For instance, the observed movement and distribution of galaxies doesn't make sense if their mass is limited to the stuff we can see. Since the 1930s, this hidden extra mass has been dubbed dark matter.

Dark energy is a more recent concept. The observation that the expansion of the universe seems to be accelerating was only made in 1998, when it was discovered that more distant objects are moving away from us faster than those closer by. The mysterious force that drives this, which we still know very little about, is now referred to as dark energy.

Taken together, dark matter and dark energy form the basis of our current standard model of Big Bang cosmology, the Lambda-CDM model. The Lambda in that name denotes dark energy as a kind of cosmological constant, while CDM stands for "cold dark matter," which seems to be the most accurate theory of the stuff – it's "cold" because it moves relatively slowly and interacts fairly weakly with ordinary matter.

Dark matter and dark energy have always been treated as separate entities, but are they in fact two sides of the same coin? That's the core idea behind the new theory put forward by Oxford astrophysicist Jamie Farnes, which may expand on the Lambda-CDM model.

Well, cosmology is in an interesting state at the moment with several competing theories. I like the description of dark matter and dark energy as being both placeholder concepts, which is pretty much what they are. They've been put in place while we wait for something sensible to replace them. Now, in addition to dark matter and dark energy, we have dark fluid with negative mass (whatever that means). Things are getting sillier and sillier.

ADDENDUM: November 24th 2020

Just to emphasise the madness, the following article from Quanta Magazine begins:

The Search for Dark Matter Is Dramatically Expanding

Physicists plan to leave no stone unturned, checking whether dark matter
tickles different types of detectors, nudges starlight,
warms planetary cores or even lodges in rocks.

The following graphic from the article identifies the main suspects: