My other blog

04Nov10

I won’t be continuing this blog now that my thirty posts for assessment are done, but you can check out my other blog at http://spacegirlerin.wordpress.com.

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The last post

29Oct10

The dark energy controversy is unresolved, and will likely continue to be unresolved for a long while yet. While cosmologists do use the ΛCDM model to fit WMAP (cosmic microwave background probe) and SDSS/2dFGRS (galaxy redshift surveys) data, sometimes they vary the ‘cosmological equation of state’ parameter (w), which should be set at -1 for a cosmological constant; w=-1 fits better, but many papers concede that it’s just not possible yet to detect quintessence.

We’re at a stage where plenty of papers are coming out, whether fitting observational data to the ΛCDM model, reviewing the situation, presenting a new hypothesis or a new analysis, supporting quintessence or the cosmological constant or another theoretical alternative, discussing consequences for the fate of the universe with certain models… but the cosmological constant is still the best we’ve got as far as observations go. Some (few?) scientists simply accept this, but I have to agree with Rocky Kolb:

It would be a mistake to be satisfied with the cosmological constant just because it’s a simple explanation.

However, a possible new controversy may be rearing its head, this one over interpretations from cosmological probes (I read this somewhere about WMAP). If the interpretations aren’t correct, this could have severe implications for dark energy as a cosmological constant.

It seems to be that the dark energy controversy is just one of those things where the more you know, the more you realise just how little you know. Perhaps much of ‘normal science’ (Kuhn) is like this.

What we do know, though, is how important dark energy is as a puzzle: it will tell us the fate of our universe, it will allow us to understand our cosmos, and it will also add to our fundamental understanding of physics; it may even lead to a grand unified theory of general relativity and quantum mechanics. I assume that’s why dark energy now tops observational astrophysics priorities; they want this controversy, this crazy puzzle, solved ASAP.

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Presenting the controversy: communication

28Oct10

A difficulty with presenting dark energy, and indeed cosmology in general, to the public is that it’s so complex and long winded. Does this add to the controversy?

Reading reader comments on popular magazine articles, as I do, I sometimes find that there is a large amount of misunderstanding over dark energy, specifically which parts are confirmed and which are up in the air and why scientists have taken the route they have in trying to solve the puzzle.

However, at least in the early days of the controversy, the experts themselves have been writing most of the popular magazine articles, with dedicated science writers writing the others. This ensures the science is correct—that the public aren’t being fed rubbish like in other controversies, e.g. climate change—but it does open other possible issues, such as only certain opinions that the scientist believes in are given (I say again, it’s still a relatively subjective discipline), or the writing isn’t entirely suitable for the non-educated public.

Generally, though, in this controversy we don’t see information or scientists’ views being presented incorrectly in such a way as to influence people’s opinions a certain way or to attempt a balance of opinion. Balances of opinion are still given in popular dark energy articles—maybe not all of the different opinions, but a selection—but that’s because there are definite, strong differences of opinion, not, I’d say, because of journalistic tendencies.

While public opinion can affect this type of controversy through channels such as the NASA budget, I don’t believe that the dark energy controversy has been impacted in any significant way by the way it has been communicated.

As I said in my previous post, this controversy is stoked pretty much entirely by the information—the observations—and by the uncertainties inherent in the observations. 

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The experts

26Oct10

I’ve been putting off, all semester, writing about the experts…those warm, fuzzy cosmologists we don’t really know but perhaps still love because they’re adventurers exploring the big beyond and that’s pretty okay by us.

I read in Lerner that experts’ pronouncements are accepted on faith; he was upset about this because he thought it added to the religious-y nature of cosmology. But cosmology is science so removed from everyday life, someone like me has no experience to draw on when listening to the experts (unlike, perhaps, in medicine), so of course their pronouncements are accepted on faith… what could you possibly do otherwise? Lerner’s comment seemed extraordinarily silly to me.

Further, in a past blog post on dark energy, Ethan Siegel said that you should ‘choose your experts wisely’. There are still differences of opinion in this controversy, and some scientists who still ‘cling to past beliefs’ despite the overwhelming evidence for dark energy (of some form). If you have to accept experts’ pronouncements on faith, you need to know which experts to listen to!

We spoke a fair bit in class about experts and their role in controversies. In class, experts were defined as:

…individuals widely recognised as being especially knowledgeable on a given topic.

We also said there were two types of experts: experts about and experts at (doing something).

Cosmology is a mixed discipline, so you might find plenty of ‘experts about’ and then a bunch of ‘experts at’. Can a particle physicist make valid claims about cosmology? Can an astronomer? You could also find plenty of ‘experts’ about cosmology outside of the discipline. Can an intelligent designer be an expert in cosmology? Sure, why not—but that doesn’t mean they should be taken as an authority.

So what makes a person an expert on cosmology to whom the public should listen? Well, I’d say that they’d have to actually be a cosmologist, and should be both types of expert—they should be an expert about the field, but also be an expert at observing or data fitting or analysis. Is there an issue here with how somebody could be an expert about something so far removed? Maybe not, but I do feel like there may be an issue about how somebody could be an expert at interpretation. If things are slightly more subjective—making an interpretation based on your experience, your knowledge, and your beliefs—couldn’t just about anyone be an expert at interpretation? This feeds into what I called that controversial nature of cosmology, the result of it being based purely on observation and interpretation.

But, in general, the experts don’t really feed the controversy—information and uncertainty do. As noted by my classmates, experts really only come into play in public controversies, which the dark energy controversy certainly is not.

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Presenting the controversy: themes

24Oct10

While for obvious reasons dark energy hasn’t appeared often in the mainstream news, I had a look at 14 articles written in the New York Times between 1998 and 2001. The progression of themes went something like this:

• Report on the discovery –> universe a ‘mess’
• Pondering a theory to match observations à fudge factor back to haunt cosmology
• Ultimate theory
• New finding support –> growing evidence, age of universe
• Flat universe –> desperately looking for a theory à philosophical arguments
• Possible theory – other universe ‘pulling’ –> mystical nature of modern cosmology
• Λ as one of ten fundamentally important question in physics
• Describing the new universe

This is generally indicative of the major themes in which dark energy and the surrounding controversy has been presented, both in the popular media and even in journals like Nature and Science.

For example:

• Perhaps the most popular theme is that of the fate of the universe – whether it will recollapse, expand forever, or reach a plateau; these futures are intricately connected to acceleration and flatness and hence, dark energy in all of its uncertainty
• Then there’s the theme of solving cosmology, of putting new pieces into the puzzle
• Many articles, perhaps more so in popular magazines and Science and Nature, throw light on the bad aspects of dark energy – that it may be an illusion, that scientists have many doubts and disagree with each other, it makes the cosmological model messy, that it’s hard to believe, and some even go as far as to say it appears more mystical rather than a solid scientific theory
• On the other end of the spectrum, there are just as many, if not more, articles reporting on further evidence and confirmations of dark energy
• And, of course, articles focussing on alternative models; predominant in both journals and popular media

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Presenting the controversy: dark energy everywhere

23Oct10

Since 1998, articles about dark energy in journals and magazines have become very common. The diagram, taken from Horvath, who argues for a Kuhnian paradigm shift in modern cosmology (Dark Matter, Dark Energy and Modern Cosmology: The Case for a Kuhnian Paradigm Shift, by Horvath, in Cosmos and History: The Journal of Natural and Social Philosophy, vol. 5, no. 2, 2009), shows the number of journal papers containing certain terms in their titles from 1998 to 2005: red is the cosmological constant, blue is quintessence, a leading class of alternative dark energy models, and black is dark energy itself.

  

If we were to extrapolate out to 2010, I’m confident that we’d continue to see the exponential increase in articles about dark energy, with the increasing number of scientists jumping on the bandwagon in an attempt to reconcile the controversy. I wouldn’t be surprised if we saw a similar pattern in popular magazines; articles on dark energy are common, probably because of the increasing realisation of its importance to fundamental physics.

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Dark Energy Controversy: Part 3

21Oct10

The third aspect of what makes dark energy a controversy is sort of a cumulation of some of the issues I’ve raised in past posts. There is a clear aversion to a dark universe and to a cosmological constant; some scientists are so unhappy with the situation that they actually hope that they’ve got it all wrong.

Here’s a selection of rather despairing quotes from both popular magazine articles and journal articles that I’ve pulled out from the hundreds that I’ve gone through (so I’m sorry that I can’t pinpoint the reference right now, although I’ve noted the scientist I think it came from for a couple):

▪   It smells wrong

▪   At some point you can’t patch a theory too much before it gets too ugly to accept

▪   We could be wrong about cosmology for the next thousand years; deeply wrong

▪   The standard model is horribly ugly, but the data support it

▪   For every complicated physical phenomenon there is a simple, wrong explanation

▪   This is the biggest embarrassment in theoretical physics

▪   My own reaction is somewhere between amazement and horror (Brian Schmidt)

▪   It’s crazy, who needs all this stuff in the universe? (Rocky Kolb)

Kuhn does say that one of the indicators of a pre-paradigm shift period (as is what may be happening here) is despair, but overall, Kuhn’s controversy as a scientific revolution framework doesn’t fit here. Instead, Joseph Gusfield proposes a framework for scientific controversy based on moral orders (seen in Gross, A. (2005) Scientific and technical controversy: three frameworks for analysis. Argumentation and Advocacy, vol. 42, 43-47). He talks about decisions based on feeling overpowering reason and rationality; the aversion to dark energy and a cosmological constant based on perceived ugliness screams of a clash of moral orders.

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Dark Energy Controversy: Kuhn

20Oct10

Kuhn sure knew what he was talking about. The dark energy controversy, the major elements of it that I’ve discussed in the previous two posts, are perfectly Kuhnian.

Recall that Kuhn says that controversies can arise when observations turn up anomalies in the theory; that is, when “nature has somehow violated the paradigm-induced expectations”.

When anomalies occur, Kuhn believes that there are two ways for them to be “made sense of” within a paradigm: the anomaly can be rejected or excused, otherwise the paradigm must be revised or reconsidered; the latter leads to moments of crisis within a paradigm.

Here, we’ve got anomalies arising from major discrepancies between observation and theory or expectation: the expansion acceleration anomaly, the enormous difference in calculated and observed values of the cosmological constant, and the coincidence problem. Attempts were made to reject the expansion acceleration anomaly through thorough flaw checking in the supernovae results and making many additional independent measurements, but the anomaly remained.

There are then three ways to resolve the crisis: putting it in the ‘too hard’ basket, dealing with it and retaining the paradigm, or adopting a new paradigm.

A new paradigm—Lambda-CDM—emerged from the expansion acceleration result, which resolved one crisis but introduced the crisis concerning the cosmological constant.

These two anomalies (the enormous difference in calculated and observed values of the cosmological constant and the coincidence problem) are interesting; some scientists appear to have, for whatever reason, found themselves able to reject or excuse them in order to maintain the Lambda-CDM model. But in general, I think that they’ve been put in the ‘too hard’ basket; it’s simply not yet possible to determine if one of the other proposed models is consistent with observation.

Win for Kuhn!

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Dark Energy Controversy: Part 2

19Oct10

But it was not the end of the controversy.

There are three major problems with the cosmological constant that have caused the dark energy controversy to continue. The cosmological constant is controversial because:

1. It’s often been used in the past as a fudge factor, only to be gotten rid of after more information has been gathered
2. When calculated theoretically using quantum mechanics, scientists get a value for it that’s 10^122 times LARGER than observed! OUCH!
3. The density of dark energy as a cosmological constant is currently in the same order of magnitude as dark matter; this is an extraordinary coincidence; it means that we are in a special period of time at which we’re actually able to detect the accelerating effects of dark energy, which is frowned upon because we are scientists of Copernicus, who said we’re not special in space or time (this is now known as the cosmological principle).

Scientists have really gone the extra mile in the search for alternative explanations…

…even to the point of risking comparison with the Queen in Alice Through the looking-glass who practiced believing “as many as six impossible things before breakfast”.

(quote from article in the New York Times on May 5, 1998, by John Noble Wilford: Cosmologists Ponder ‘Missing Energy’ of the Universe)

Broadly, there are three other possible explanations for acceleration: it could be that dark energy evolves in time; that we don’t understand gravity correctly and don’t actually need dark energy to explain acceleration; or that we must do away with the cosmological principle (which is probably the least popular option). There are many theoretical models out there based on each of these.

However, because observations fit the Lambda-CDM model so well, cosmologists stick with the cosmological constant. It’s the easiest model to ‘take aim at’ at the present time, although some appear to firmly believe it’s more than that; that the three strikes brought against the cosmological constant can be ignored based on the observations, even though scientists have not yet determined how to distinguish the cosmological constant from some other possible models in observations.

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Dark Energy Controversy: Part 1

18Oct10

In 1998, two separate teams, using different type Ia supernova data, went out to show that the universal expansion was slowing down due to gravity, but instead found just the opposite, that the universal expansion was accelerating. This was very controversial and very unexpected; in fact, it was so different to the accepted theory that scientists simply assumed they could quickly downplay the results.

Scientists were committed to ensuring that the supernovae results did indeed point towards an accelerating universe: potential flaws in the observations were analysed and over the next few years independent measures were taken that all supported the conclusion. The fact that it was two separate sets of data that original showed the acceleration result probably helped to win scientists over so quickly; within a few years, most scientists were convinced that the universe’s expansion was accelerating, perhaps due to some kind of dark energy. Ethan Siegel from Starts With A Bang says:

It suddenly occurred to me that if you wanted to eliminate this one thing, dark energy, it would take a minimum of six separate observations to be overturned. And that was it; it was suddenly unreasonable to me that I would reject dark energy.

While there was really no dispute over the acceleration result after checks and additional confirmations, scientists had really very little idea about what the dark energy actually could be. Despite this, scientists were quick to point out that the cosmological constant fitted the acceleration result; it’s exactly what you’d expect to see if a cosmological constant made up about 70% of the critical density. So, dark energy was introduced into the standard model in this way, which is known as the Lambda-cold dark matter model. This could have been the end of the controversy…

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