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 best Instagram accounts to follow if you love space

As new space findings hit the news on an almost daily basis, the app offers an alternative window onto the universe.

If there’s anything that can break us away from the humdrum monotony of modern life, it’s space. It renders us awe-struck and captures our imagination with its vastness and surreal imagery, and as astronomy-related research expands, cosmic mysteries continue to unfold.

Whether it’s the occurrence of rare celestial events, the discovery of exoplanets that could potentially harbour life, or the confirmation of gravitational waves that ripple through the space-time continuum, it seems that there are new findings propelled onto our newsfeeds daily.  

Yet one of the best ways of keeping up to date with the latest research and projects at the frontier of space is on Instagram, the social media platform. Here are some of the accounts you should be following to get the greatest insight into space:

1. SpaceX (@spacex)

The aerospace company SpaceX designs spacecrafts and reusable rockets in the hope that their technology can one day make human life multi-planetary. Spearheaded be CEO Elon Musk, the company has the lofty ambition of one day colonising Mars. Below is a spectacular image of the company’s Falcon 9 rocket in its first-stage entry:


Photographer unexpectedly captures Falcon 9 second stage burn and first stage entry @slowcountrylife

A photo posted by SpaceX (@spacex) on


2. International Space Station (@iss)

The International Space Station, a habitable satellite whirling around the Earth approximately 16 times per day in low orbit, has an Instagram feed displaying the equipment on board as well as stunning pictures of the Earth from a distance. Here’s a picture from the station 250 miles above earth depicting the Earth as an azure blue marble:


The blue of the #bahamas can't be mistaken, even from 250 miles above. #YearInSpace #nasa #space #spacestation : @stationcdrkelly

A photo posted by International Space Station (@iss) on


3. Tim Peake (@astro_timpeake)

Currently aboard the International Space Station is Tim Peake, a British astronaut. As he has carried out his work on Expedition 46/47 on the station, he has shared a range of photos of Earth that he has shot with his Nikon D4 from the vantage point of space, from reefs off the coast of Mozambique to the glint of sun highlighting Vancouver Island. Here we have a clear image of the Pacific “Ring of Fire”:


3/3: The Pacific ‘Ring of Fire’ clear to see amongst the volcanoes of Kamchatka, Russia

A photo posted by Tim Peake (@astro_timpeake) on


4. Scott Kelly (@stationcdrkelly)

Scott Kelly is an engineer and a retired American astronaut who recently spent a year commanding the International Space Station, travelling 143,846,525 miles around our globe in the process. A quick scroll through his profile will demonstrate just how profound his experience must have been at the shores of space, and includes a host of images of the aurora borealis:


#GoodMorning #aurora and the Pacific Northwest! #YearInSpace #northernlights #beautiful #morning #space #spacestation #iss

A photo posted by Scott Kelly (@stationcdrkelly) on


5. Nasa Goddard (@nasagoddard)

Nasa’s Goddard Space Flight Centre was the company’s very first flight centre. It’s the largest of its kind, and the official Instagram account for the centre serves as a highlight reel for everything NASA is working on. There are behind-the-scenes looks at the James Webb Space Telescope under construction, computer-simulated images of supermassive black holes, and clear views of distant galaxies captured by the Hubble Space Telescope:


Observations by the NASA/ESA Hubble Space Telescope have taken advantage of gravitational lensing to reveal the largest sample of the faintest and earliest known galaxies in the universe. Some of these galaxies formed just 600 million years after the big bang and are fainter than any other galaxy yet uncovered by Hubble. The team has determined for the first time with some confidence that these small galaxies were vital to creating the universe that we see today. An international team of astronomers, led by Hakim Atek of the Ecole Polytechnique Fédérale de Lausanne, Switzerland, has discovered over 250 tiny galaxies that existed only 600-900 million years after the big bang— one of the largest samples of dwarf galaxies yet to be discovered at these epochs. The light from these galaxies took over 12 billion years to reach the telescope, allowing the astronomers to look back in time when the universe was still very young. Although impressive, the number of galaxies found at this early epoch is not the team’s only remarkable breakthrough, as Johan Richard from the Observatoire de Lyon, France, points out. “The faintest galaxies detected in these Hubble observations are fainter than any other yet uncovered in the deepest Hubble observations.” By looking at the light coming from the galaxies the team discovered that the accumulated light emitted by these galaxies could have played a major role in one of the most mysterious periods of the universe’s early history — the epoch of reionization. Reionization started when the thick fog of hydrogen gas that cloaked the early universe began to clear. Ultraviolet light was now able to travel over larger distances without being blocked and thus the universe became transparent to ultraviolet light. Credit: NASA/ESA #nasagoddard #Hubble #HST #space #galaxy

A photo posted by NASA Goddard (@nasagoddard) on


6. Roscosmos (@roscosmosofficial)

Roscosmos is the Russian Federal Space Agency at the heart of all space endeavours in Russia. The agency is involved in the maintenance and progression of the International Space Station, and is working on its own research projects such as a planned robotic mission to one of Mars’s moons.  Here’s the launch of a rocket from the Vostochny Cosmodrome which is under construction:


7. Nasa (@nasa)

Over the years, Nasa has firmly committed to pushing the boundaries of space exploration, and, as its 12.3m Instagram acolytes would agree, it has been successful. As part of the Frontier Fields campaign investigating galaxy clusters, a recent deep field image from the Hubble revealed bounds of galaxies in the constellation of Leo:


Nearly as deep as the Hubble Ultra Deep Field, which contains approximately 10,000 galaxies, this incredible image from the Hubble Space Telescope reveals thousands of colorful galaxies in the constellation of Leo (The Lion). This vibrant view of the early universe was captured as part of the Frontier Fields campaign, which aims to investigate galaxy clusters in more detail than ever before, and to explore some of the most distant galaxies in the universe. Galaxy clusters are massive. They can have a tremendous impact on their surroundings, with their immense gravity warping and amplifying the light from more distant objects. This phenomenon, known as gravitational lensing, can help astronomers to see galaxies that would otherwise be too faint, aiding our hunt for residents of the primordial universe. Image credit: ESA/Hubble & NASA, Acknowledgement: Judy Schmidt #nasa #hubble #astronomy #science #space #galaxy #galaxies

A photo posted by NASA (@nasa) on