Does dark matter exist?

After 80 years of agreement about the dark stuff, opinions may be changing.

The peasants are revolting. Last night the Flamsteed Astronomical Society met at the National Maritime Museum to hear a debate on the existence (or not) of dark matter. In a vote at the end, the audience decided it probably doesn’t exist.

The idea of dark matter has been around since 1933, when a Swiss astronomer called Fritz Zwicky found that centrifugal forces should have been tearing spinning galaxy clusters apart – but weren’t. The answer, he suggested, was that there was extra stuff in there, whose gravitational pull was holding everything together.
Astronomers now believe this stuff makes up around a quarter of the universe, if you take into account all the mass and energy in the cosmos. Ignore the pure energy, and dark matter accounts for 80 per cent of the universe’s mass. Which makes it a little embarrassing that we have never seen any.

Neither do we know what it looks like. We’ve been groping around for dark matter since about 1970. Various predictions have been made: in 1980, astronomer Vera Rubin said it would be found within 10 years. In 1990, astronomer royal Martin Rees said the dark matter mystery would be solved by the turn of the century. In 1999 Rees was aware he had been too hasty, and said we would know what dark matter is by 2004. Last January, CERN theoretical physicist and Gandalf lookalike John Ellis gave the physicists another decade.
But patience is starting to wear thin. At last night’s debate, Oxford physicist and co-presenter of The Sky at Night Chris Lintott made the case for dark matter; astronomy writer Stuart Clark argued that a modification to the laws of gravity, which are dictated by Einstein’s general relativity theory, held more promise for explaining the (apparently) missing mass. At the end of the evening, the audience sided with Clark and modifying gravity.
That’s not going to have dark matter astronomers quaking in their boots. But it is nonetheless indicative of a change of mood. Take what went on at the Cosmic Variance blog last week. Sean Carroll, the blog’s host, has always been bullishly pro dark matter. But it seems he has started to hedge a bit.
In a fascinating post, he published the trialogue he had been conducting with astronomer Stacey McGaugh, the original proponent of the modified gravity idea (it’s called MOND: modified Newtonian Dynamics) and German astrophysicist Rainer Plaga. Right at the top, Carroll concedes that “it may very well turn out that the behavior of gravity on large scales does not precisely match the prediction of ordinary general relativity”. In other words, he is saying, we might well have to modify gravity.
It’s worth pointing out a couple more reasons it’s OK to harbour doubts about the dark stuff. Last September, Durham astronomer Carlos Frenk admitted he was “losing sleep” over the results of his own computer simulations. His work had showed that the way simulated dwarf galaxies – mainly composed of dark matter – form in a halo around our own galaxy doesn’t tally with what we observe. His conclusion was that the standard theory of dark matter is almost certainly wrong, adding that searches for the stuff at the LHC in Geneva would therefore prove fruitless.
Then last month two groups of astronomers announced that dark matter wasn’t where it should be. The sun is meant to be surrounded by a halo of dark matter, and it isn’t.
If there really is no dark matter, that won’t be a mainstream view for decades to come. Once it’s got some momentum, it takes a lot of effort to change direction in science. But it does seem that, after 80 years, someone’s found the handbrake on the dark matter juggernaut.

Images of giant galaxy clusters, said to be mainly made up of dark matter. Photograph: Nasa/Getty Images

Michael Brooks holds a PhD in quantum physics. He writes a weekly science column for the New Statesman, and his most recent book is At the Edge of Uncertainty: 11 Discoveries Taking Science by Surprise.

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The answer to the antibiotics crisis might be inside your nose

The medical weapons we have equipped ourselves with are losing their power. But scientists scent an answer. 

They say there’s a hero in everyone. It turns out that actually, it resides within only about ten percent of us. Staphylococcus lugdunensis may be the species of bacteria that we arguably don’t deserve, but it is the one that we need.

Recently, experts have cautioned that we may be on the cusp of a post-antibiotic era. In fact, less than a month ago, the US Centres for Disease Control and Prevention released a report on a woman who died from a "pan-resistant" disease – one that survived the use of all available antibiotics. Back in 1945, the discoverer of penicillin, Alexander Fleming, warned during his Nobel Prize acceptance speech against the misuse of antibiotics. More recently, Britain's Chief Medical Officer Professor Dame Sally Davies has referred to anti-microbial resistance as “the greatest future threat to our civilisation”.

However, hope has appeared in the form of "lugdunin", a compound secreted by a species of bacteria found in a rather unlikely location – the human nose.

Governments and health campaigners alike may be assisted by a discovery by researchers at the University of Tubingen in Germany. According to a study published in Nature, the researchers had been studying Staphylococcus aureus. This is the bacteria which is responsible for so-called "superbug": MRSA. A strain of MRSA bacteria is not particularly virulent, but crucially, it is not susceptible to common antibiotics. This means that MRSA spreads quickly from crowded locations where residents have weaker immune systems, such as hospitals, before becoming endemic in the wider local community. In the UK, MRSA is a factor in hundreds of deaths a year. 

The researchers in question were investigating why S. aureus is not present in the noses of some people. They discovered that another bacteria, S. lugdunensis, was especially effective at wiping out its opposition, even MRSA. The researchers named the compound created and released by the S. lugdunensis "lugdunin".

In the animal testing stage, the researchers observed that the presence of lugdunin was successful in radically reducing and sometimes purging the infection. The researchers subsequently collected nasal swabs from 187 hospital patients, and found S. aureus on roughly a third of the swabs, and S. lugdunensis on up to 10 per cent of them. In accordance with previous results, samples that contained both species saw an 80 per cent decrease of the S. aureus population, in comparison to those without lugdunin.

Most notably, the in vitro (laboratory) testing phase provided evidence that the new discovery is also useful in eliminating other kinds of superbugs, none of which seemed to develop resistance to the new compound. The authors of the study hypothesised that lugdunin had evolved  “for the purpose of bacterial elimination in the human organism, implying that it is optimised for efficacy and tolerance at its physiological site of action". How it works, though, is not fully understood. 

The discovery of lugdunin as a potential new treatment is a breakthrough on its own. But that is not the end of the story. It holds implications for “a new concept of finding antibiotics”, according to Andreas Peschel, one of the bacteriologists behind the discovery.

The development of antibiotics has drastically slowed in recent years. In the last 50 years, only two new classes of this category of medication have been released to the market. This is due to the fact almost all antibiotics in use are derived from soil bacteria. By contrast, the new findings record the first occurrence of a strain of bacteria that exists within human bodies. Some researchers now suggest that the more hostile the environment to bacterial growth, the more likely it may be for novel antibiotics to be found. This could open up a new list of potential areas in which antibiotic research may be carried out.

When it comes to beating MRSA, there is hope that lugdunin will be our next great weapon. Peschel and his fellow collaborators are in talks with various companies about developing a medical treatment that uses lugdunin.

Meanwhile, in September 2016, the United Nations committed itself to opposing the spread of antibiotic resistance. Of the many points to which the UN signatories have agreed, possibly the most significant is their commitment to “encourage innovative ways to develop new antibiotics”. 

The initiative has the scope to achieve a lot, or dissolve into box ticking exercise. The discovery of lugdunin may well be the spark that drives it forward. Nothing to sniff about that. 

Anjuli R. K. Shere is a 2016/17 Wellcome Scholar and science intern at the New Statesman