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.

Sam Pepper via YouTube
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The story of Sam Pepper: how a British YouTuber incurred the wrath of the internet

The Dapper Laughs of online pranks  has finally gone too far.

Last night, a Twitter user claiming to be "a voice" for hacker collective Anonymous sent out a series of angry tweets slamming a video featuring "violent abuse". The user wasn't referring to Isis, which is the subject of an ongoing campaign by the hacker group, but a young, turquoise-haired British man named Sam Pepper. 

Pepper is a YouTube star who came to fame after appearing in the 11th series of reality show Big Brother. He's known for his prank YouTube videos posted under the username "Sam", which have in the past involved such hilarious japes as wearing a prosthetic old man's face and climbing into bed with his own girlfriend. He now lives in LA, but is friends with other prominent British YouTubers, including, of course, Zoella. 

So on the face of it, it's a little surprising that @TheAnonMessage blasted out this tirade against the star last night as a series of tweets to his 170,000-odd followers:

We've been notified of a sick, disturbing video uploaded by @sampepper. Yet again, he uses violent abuse to garner subscribers.

This is something that we cannot stand for. This so-called prank should bring shame to the YouTube community for supporting this imbecile.

This video must be taken down. @SamPepper you have been warned. You have 24 hours or we will unleash fucking hell on you.

The video in question, "KILLING BEST FRIEND PRANK | Ft. Sam & Colby", was published on 29 November but already has over two million views. In it, Pepper teams up with another Sam, half of the YouTube duo Sam & Colby, to pretend to, er, kill him, and terrify Colby in the process.

Sam and Colby drive into shot, then both get out of the car to check the oil. A figure wearing a black balaclava grabs Colby, put a bag over his head, tapes up his hands and dumps him in the boot of the car, all with Sam's help. The pair take him to a rooftop, where the bag is removed, and Pepper - the masked attacker - shoots Colby in the head with a fake gun. The visual references to Isis are hard to ignore:  

Photo: Sam Pepper via YouTube

What follows is a genuinely disturbing thirty seconds in which Colby screams and cries, eventually drowned out and replaced in the video's edit by tinkly piano music. Finally, Sam stands up and reveals he isn't dead. 

YouTubers responded angrily to the prank. Commenters called it "cruel" and seemed genuinely distressed by Colby's experience. The video's approval ratings, represented by thumbs up and thumbs down, are a good indication of audience reaction: 

So what happens if Pepper doesn't remove the video within 24 hours? Gabriella Coleman, author of Hacker, Hoaxer, Whistleblower, Spy: The Many Faces of Anonymous told me that "[@TheAnonMessage] has earned the wrath of Anonymous for acting irresponsibly" in the past (most notably, the user launched an attack on the wrong Ferguson police officer), and isn't part of the main Anonymous group. However, this doesn't mean the user couldn't attack Sam's channel or website. Either way, @TheAnonMessage has leapt on the coattails of a controversy that seems to have caught the imagination of large swathes of social media.

From Pepper's own point of view, though, it's easy to see why the whole furore is a little mystifying. His entire empire is founded on pushing boundaries of acceptability, and no one involved in this particular prank is angry - the video includes an epilogue where he chats to Sam and Colby, and Sam grins and exclaims "that was crazy!".

There's a parallel with the comedian Daniel O'Reilly (also known by his persona Dapper Laughs) here: both are young male entertainers who built an online audience through pushing the envelope with humour and pranks, and are then a bit shocked when they cross an invisible line and are lambasted for behaviour not dissimilar to the actions that earned them followers in the first place. 

Pepper, like Dapper, has been accused of misogyny, and even sexual harassment in his videos - he removed one, "Fake Hand Pinch Prank", which involved grabbing women in public using a fake hand, following online outcry. Yet one of his most watched videos is "How to Make Out with Strangers”, in which he approaches random women in Miami, says things like “I’m seeing which beautiful girls would like to make out…with me,” and kisses them. The video received none of the same criticism, and earned him over 17 million views. You can see why he might not be getting the message. 

The difference between the two videos lies, of course, in consent, as Pepper at least pretends to ask the women's permission in the Miami video. Yet as YouTuber Laci Green gently points out in an open letter to Pepper written at the time: "You pressure women on camera to make out with you - again, many of whom are visibly uncool with it. Confused and caught off guard, they painfully follow through with your requests, clearly uncomfortable."

What's clear is that the internet is still trying to figure out what is acceptable in the realm of humour. Internet-friendly humour tends to be slapstick, brash, irrelevant, and involve making fun of gormless members of the public. But pushed to extremes - the extremes which can seem necessary to make a name for yourself in the saturated vlogger market - these gags can easily turn nasty. 

Barbara Speed is a technology and digital culture writer at the New Statesman and a staff writer at CityMetric.