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.

Flickr: B.S.Wise/YouTube
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Extremist ads and LGBT videos: do we want YouTube to be a censor, or not?

Is the video-sharing platform a morally irresponsible slacker for putting ads next to extremist content - or an evil, tyrannical censor for restricting access to LGBT videos?

YouTube is having a bad week. The Google-owned video-sharing platform has hit the headlines twice over complaints that it 1) is not censoring things enough, and 2) is censoring things too much.

On the one hand, big brands including Marks & Spencer, HSBC, and RBS have suspended their advertisements from the site after a Times investigation found ads from leading companies – and even the UK government – were shown alongside extremist videos. On the other, YouTubers are tweeting #YouTubeIsOverParty after it emerged that YouTube’s “restricted mode” (an opt-in setting that filters out “potentially objectionable content”) removes content with LGBT themes.

This isn’t the first time we’ve seen a social media giant be criticised for being a lax, morally irresponsible slacker and an evil, tyrannical censor and in the same week. Last month, Facebook were criticised for both failing to remove a group called “hot xxxx schoolgirls” and for removing a nude oil painting by an acclaimed artist.

That is not to say these things are equivalent. Quite obviously child abuse imagery is more troubling than a nude oil painting, and videos entitled “Jewish People Admit Organising White Genocide” are endlessly more problematic than those called “GAY flag and me petting my cat” (a highly important piece of content). I am not trying to claim that ~everything is relative~ and ~everyone deserves a voice~. Content that breaks the law must be removed and LGBT content must not. Yet these conflicting stories highlight the same underlying problem: it is a very bad idea to trust a large multibillion pound company to be the arbiter of what is or isn’t acceptable.

This isn’t because YouTube have some strange agenda where it can’t get enough of extremists and hate the LGBT community. In reality, the company’s “restricted mode” also affects Paul Joseph Watson, a controversial YouTuber whose pro-Trump conspiracy theory content includes videos titled “Islam is NOT a Religion of Peace” and “A Vote For Hillary is a Vote For World War 3”, as well as an interview entitled “Chuck Johnson: Muslim Migrants Will Cause Collapse of Europe”. The issue is that if YouTube did have this agenda, it would have complete control over what it wanted the world to see – and not only are we are willingly handing them this power, we are begging them to use it.

Moral panics are the most common justification for extreme censorship and surveillance methods. “Catching terrorists” and “stopping child abusers” are two of the greatest arguments for the dystopian surveillance measures in Theresa May’s Investigatory Powers Act and Digital Economy Bill. Yet in reality, last month the FBI let a child pornographer go free because they didn’t want to tell a court the surveillance methods they used to catch him. This begs the question: what is the surveillance really for? The same is true of censorship. When we insist that YouTube stop this and that, we are asking it to take complete control – why do we trust that this will reflect our own moral sensibilities? Why do we think it won't use this for its own benefit?

Obviously extremist content needs to be removed from YouTube, but why should YouTube be the one to do it? If a book publisher released A Very Racist Book For Racists, we wouldn’t trust them to pull it off the shelves themselves. We have laws (such as the Racial and Religious Hatred Act) that ban hate speech, and we have law enforcement bodies to impose them. On the whole, we don’t trust giant commercial companies to rule over what it is and isn’t acceptable to say, because oh, hello, yes, dystopia.

In the past, public speech was made up of hundreds of book publishers, TV stations, film-makers, and pamphleteers, and no one person or company had the power to censor everything. A book that didn’t fly at one publisher could go to another, and a documentary that the BBC didn’t like could find a home on Channel 4. Why are we happy for essentially two companies – Facebook and Google – to take this power? Why are we demanding that they use it? Why are we giving them justification to use it more, and more, and more?

In response to last week’s criticism about extremist videos on the YouTube, Google UK managing director Ronan Harris said that in 2016 Google removed nearly 2 billion ads, banned over 100,000 publishers, and prevented ads from showing on over 300 million YouTube videos. We are supposed to consider this a good thing. Why? We don't know what these adverts were for. We don't know if they were actually offensive. We don't know why they were banned. 

As it happens, YouTube has responded well to the criticism. In a statement yesterday, Google's EMEA President, Matt Brittin, apologised to advertisers and promised improvements, and in a blog this morning, Google said it is already "ramping up changes". A YouTube spokesperson also tweeted that the platform is "looking into" concerns about LGBT content being restricted. But people want more. The Guardian reported that Brittin declined three times to answer whether Google would go beyond allowing users to flag offensive material. Setting aside Brexit, wouldn't you rather it was up to us as a collective to flag offensive content and come together to make these decisions? Why is it preferable that one company takes a job that was previously trusted to the government? 

Editor’s Note, 22 March: This article has been updated to clarify Paul Joseph Watson’s YouTube content.

Amelia Tait is a technology and digital culture writer at the New Statesman.