Dark Matter and Dark Energy

The 4% Universe by Richard Panek
From our garden, on a clear moonless night, you can easily see the Milky Way as a broad arc across the sky. With a pair of binoculars thousands more stars are visible. For millennia mankind has gazed at the stars, but it was only in 1923 that Edwin Hubble confirmed that there were galaxies outside our own Milky Way.


Edwin Hubble

Hubble, in 1929, also confirmed by measuring the redshifts of other galaxies, and using Cepheid variables in these galaxies to determine their distance, that the more distant a galaxy is, the faster it is receding from us.

It has been known for a long time that a very large proportion of the stuff of the universe is invisible.  Fritz Zwicky in 1933 first observed that the visible matter in galaxies in the Coma cluster was not enough to account for the speed with which they were moving towards each other, that would require them to be four hundred times heavier! These highly significant facts were, however, generally set aside whilst astronomers got on with proving that Einstein’s Theory of General Relativity was correct, to ever smaller margins of error, and physicists were doing the same with Quantum Mechanics, whilst also finding more and more sub-atomic particles.

Amongst academics in 1964, cosmology was almost a disreputable field of study, somewhat akin to metaphysics. At the time there was an absence of data and of theories leading to testable predictions. Meanwhile, in the fourth form at school, as 15 year olds, we had discovered relativity, which was creating quite a buzz. This was totally independent from anything our teachers were doing and they didn’t really want to talk about it!  A year later I was a supporter of Fred Hoyle’s Steady State Theory, which postulated a form of continuous creation of matter in interstellar space to drive the expansion of the universe.

The detection of cosmic microwave background radiation left over from the Big Bang by Penzias and Wilson in 1965 put paid to the Steady State Theory.  When the news finally reached me at university a few years later I found it philosophically hard to accept. How could a whole universe just appear from a singularity?  If there was a Big Bang, surely an oscillating universe that contained enough mass to finally slow down, and start collapsing, before exploding yet again, was more intellectually satisfying, at least to an atheist like me.


Distant galaxies photographed by the Hubble Space Telescope - click to enlarge
Read more on NASA's Hubble mission pages

Eventually in the late sixties and early seventies astronomers and theorists came back to the question of Dark Matter and the associated ultimate fate of the universe. By looking for, and finding supernovae, in ever more distant galaxies, and applying corrections to the growth and decay of their measured brightness, the Supernova Cosmology Project and the High-z team were able to use them as a form of calibrated “Standard Candle” to determine their distance and plot it against their redshift. After many years of observations they were in a position to answer the question “were distant galaxies slowing down, maintaining a steady -just right- velocity, or even possibly speeding up?”

The story of this phase of scientific discovery is the subject of Richard Panek’s latest book “The 4% Universe”. He has interviewed the majority of the actors in this search and he tells the story by including many anecdotes and details in a colourful and lively account, which places you, the reader, at the centre of the action.  I wish, however, that he had included some diagrams.  A few equations would also have helped here and there, but it’s a very good read for an enthusiastic amateur like me.

Current research indicates that the universe is expanding at an increasingly greater rate, driven by the presence of 72.8% Dark Energy, which is enough to overcome the combined gravitational effect of 22.7% Dark Matter and 4.5% visible matter.  At present, nobody has a clue what Dark Energy and Dark Matter actually are, and I suspect that will still be true for many years to come. The many published speculative papers have not so far been confirmed or denied by experiment.  It is, it must be said, very difficult to devise a method of observing the unobservable, although some are being tried! They are briefly discussed in Richard Panek's book.


NGC 1300 a barred spiral galaxy - click to enlarge

In this video Patricia Burchat explains the evidence for Dark Matter and Dark Energy in plain language.



So if I was still around in a few billion year’s time, and I have avoided being assimilated by the Borg, I could look out from my refuge in the Alpha Quadrant, on the unfashionable Western Spiral Arm of the Milky Way, onto a sky containing many fewer distant galaxies than it does now!  I would probably also be using Dark Energy to power the infinite improbability drive of my interstellar cruiser as well as to cool my "synth-wine with white grape flavonols and polyphenols"!  Chardonnay of course!

The Trouble with Physics



Lee Smolin

 I bought myself a book for Christmas called the “Trouble with Physics” by Lee Smolin. He calls into question the physics research of the last thirty years by taking a layman, like myself, on a tour of the five great unanswered problems in physics (**see below), from its inability so far to unify general relativity and quantum theory, to the need to explain dark matter and dark energy.

In fact he starts by representing the lack of fundamental theoretical breakthroughs in the last thirty years as a failure and goes on to undermine much of the current research in physics by describing it as being based on unsound foundations.  He consequently attracts criticism even "flaming” for his challenging views from certain physicists who, in the direction of their research, are committed to what amounts to the new orthodoxy of String Theory.

Perhaps this extract below concerning supersymmetry will help explain why he is sometimes considered controversial.

"In supersymmetry-theory convention, the superpartners of fermions begin with an “s,” like the selectron, while the superpartners of bosons end in “ino.” .........
First of all a theory cannot be partly supersymmetric. If one particle has a superpartner, they all must. Thus, each quark comes with a bosonic partner, a squark. The photon is partnered with a new fermion, the photino. ..........
Not only are there squarks and sleptons and photinos, there are also sneutrinos to partner the neutrinos, Higgsinos with the Higgs, and gravitinos to go with the gravitons. Two by two, a regular Noah’s ark of particles. Sooner or later, tangled in the web of new snames and naminos, you begin to feel like Sbozo the clown. Or Bozo the clownino, or swhatever."

Within the context of a comprehensive review of recent research, he paints a picture of a large highly cohesive group of earnest string theorists unquestioningly following their leaders and excluding alternative views or fields of research. Whilst doing so they are ignoring the basic requirement of a scientific theory, which is to make predictions that are testable by observation and experiment. (Otherwise it is all just metaphysics - my comment not his!)
Towards the end of the book he comments on the sociological aspects of the organisation of scientific research in physics and finds many elements of the same sort of "groupthink" that has unfortunately been seen in twentieth century politics.  In addition he makes the case that academic recruitment to physics research posts in the USA is structured in such a way that the likelihood of scientific visionary thinkers obtaining a post is extremely limited, whilst those researchers committed to extending the work of more senior scientists in the current orthodoxies are most likely to be appointed or given tenure. He implies that without a change in the support made available to visionary theorists the US physics academy will continue to stagnate in terms of a lack of fundamental and testable theoretical breakthroughs. 
The irony is, as he also points out, that the psychology and sociology of these self sustaining groupthink situations, which undermine performance or lead to disastrous consequences, is well understood, particulary by US academics in other disciplines and even in businesses.

I found it surprisingly soothing over the Christmas and New Year holidays after I had had a wisdom tooth removed and whilst I was surrounded by family chit-chat in French.

Here is Lee in entertain and amaze mode!


**1. Combine general relavity and quantum theory into a single theory that can claim to be the complete theory pf nature.  This is called quantum gravity.
2. Resolve the problems in the foundations of quantum mechanics, either by making sense of the theory as it stands or by inventing a new theory which does makes sense.
3. Determine whether or not the various particles and forces can be unified in a theory that explains them all as manifestations of a single fundamental entity.  The unification of the particles and forces.
4. Explain how the free constants in the standard model of particle physics are chosen in nature.
5. Explain Dark Matter and Dark Energy.  Or if they don't exist determine how and why gravity is modified on large scales.  More generally, explain why the constants of the standard model of cosmology, including the dark energy, have the values they do.