Chris Lintott’s Universe

It may surprise you to know that the disparate, motley, collection of individuals that make up the professional astronomical community are as subject to the swings and roundabouts of fashion as anyone else, but nevertheless it’s true. Fashions can change the way we think about our research (can that pet project be pitched as vital for cosmology, or as contributing to ‘astrobiology’?), and infect the language that we use to talk about ideas.

There comes a time, however, when it is necessary to draw a line in the sand and defend it against all who dare to try to cross. In this spirit, I’m declaring war on all those - scientists, press officers and journalists - who use the word ‘dark’ to describe a new discovery.

First, we had ‘dark matter’. Astronomers discovered that pretty much wherever they looked, from galaxies to galaxy clusters, the stuff we can see can’t possibly be all there is. In order to hold objects together, we need stuff which has gravity - and thus can help keep galaxies in one piece - but doesn’t shine. In other words, we need matter which is dark, and we can chatter happily about ‘dark matter’ without raising my blood pressure.

Second, along came ‘dark energy’. Observations of distant supernovae revealed that the expansion of the Universe is accelerating, not slowing down under the influence of gravity as it should do. While the cause remains unknown, most researchers believe we are seeing the effects of a fifth fundamental force (to add to the traditional four : the strong and weak nuclear forces, electromagnetism and gravity). Such a force must be associated with energy, so I’ll concede the second word. But why, oh why, oh why (etc) do we have to call it ‘dark’ energy? Is gravity ‘dark’? What would it mean to have a light or dark weak nuclear force? It’s arrant nonsense, it’s confusing (as it encourages lumping in with dark matter, almost certainly a completely separate problem) and it makes my blood boil.

Nonetheless, probably because I didn’t have a blog at the time, ‘dark energy’ has become a standard term. This should strengthen our arms for the fight ahead, though, because looming into view is the monstrosity that is the ‘dark flow’. The result is interesting, although I haven’t had time to read the papers and am still somewhat sceptical. Taken at face value, a new analysis seems to suggest that hundreds of galaxy clusters are being carried along at roughly 2 million miles an hour, pulled by matter beyond our observable Universe.

As I said, interesting enough. But the press release and the papers, although mercifully not the titles of the papers, call this a ‘dark flow’. What does that even mean? How would a ‘light flow’ appear? Surely here we can all agree that using the word ‘dark’ doesn’t help us understand what’s going on - it’s just confusing.

Something must be done. I’m not sure what, so let’s just call it the dark campaign for now. Whatever it is, it starts here.

You now don’t have to listen to my attempt to parse Sean Carroll’s talk, but can go and read his take on the research at Cosmic Variance.

In commenting here, Sean said

I was mostly trying to make the point that, although multiverse ideas are very new and underdeveloped, it is certainly imaginable that someday when we understand them better we will be able to make concrete predictions. The new CMB paper is interesting mostly as an investigation into conventional inflation, but there might be some connection to the pre-inflationary universe, which is certainly intriguing. But it’s all quite speculative at this point.

I’d hoped I’d made clear in my piece for the BBC how speculative this was. What made me want to write the story in the first place, though, was exactly what Sean said above - to an outsider to the field the idea that it is even imaginable that we might be able to make concrete predictions from ideas about multiverses which have haunted the pages of New Scientist and its ilk for decades is stunning. That’s what I wanted to get across.

At any conference there’s one talk that changes the way you think about something, or crystalizes thoughts that you’ve had anyway. In the last few months I’d been thinking carefully about the answer to the question ‘but what happened before the Big Bang’, and a talk by Cosmic Variance blogger Sean Carroll crystalized some of those thoughts. He was clear that he was on the edge of speculation at times, but you can read the short version of my thoughts at the BBC website.

I’ll write more about my thoughts here over the weekend, so watch this space.

Update : Woo! Number 1 most emailed article…