Let it rip. Image: Getty Images
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From Big Bang to Big Rip: how will the universe end?

The universe is a very sticky place, but how sticky is it? Could it favour the “Big Rip” demise of the universe?

All good things come to an end. And the universe is no exception. In about 10100 years (that’s 10x10, 100 times over – so a long time), the universe will be dead, and all that will be left is a relic of the life and energy it once birthed.

Aeons from now, the universe will be nothing but bits of dead photons, electrons and neutrinos – that’s about it, sadly.

But how will the universe end? Will it freeze to death (the Big Freeze), get crunched to bits (the Big Crunch), or even more radically, get ripped apart (the Big Rip)?

It is not known how to describe viscous fluids (yep, sticky fluids) in the context of Einstein’s general relativity. Over the years, different approaches have been made, from Eckart’s theory to Mueller-Israel-Stewart theory.

Recently, researchers at Vanderbilt University have discovered a new mathematical formulation that may help draw a line between the two notions. This new formula ties in well with one of the more radical scenarios of how the universe with end – the "Big Rip".

The Big Rip is a cosmological hypothesis first published in 2003, which proposes the possibility of dark energy accelerating, and consequently the universe expanding, without limit. The dark energy will eventually become unbearably strong that the universe (gravitational, electromagnetic and weak nuclear forces) rips itself into pieces, hence the name.

The maths also sheds new light on the fundamental properties of dark energy, a force that is still largely unknown. The new approach is described in the Physical Review D.

Cosmological viscosity (ie. the stickiness of the universe) isn’t like the viscosity of ketchup, for example, which is a measure of a fluid’s resistance to flowing through small openings like the neck of a ketchup bottle. It’s the measure of a fluid’s resistance to expansion or contraction.

Marcelo Disconzi, an assistant professor of  mathematics, started off by tackling the problem of fluid dynamics - the natural science of fluids in motion - which happens quite frequently in the universe from supernovae (exploding stars) to neutron stars (stars double the size of the Sun that have crushed down to the size of cities).

Although scientists have successfully modelled what happens when ideal fluids with no stickiness move to near-light speeds, no one has managed to come up with a generally accepted way of dealing with sticky fluids travelling at near-light speed.

This is because the models haven’t made much sense: the most confusing models predict conditions where these fluids travel faster than the speed of light, defying the laws of physics.

These problems inspired Disconzi to reformulate an old proposal by André Lichnerowic from 1955 (a proposal that remained mostly unnoticed until Disconzi’s 2014 paper) in a way that does not exhibit the flaw of allowing faster-than-light speeds.

After showing that Lichnerowicz's approach is potentially a viable candidate, Disconzi teamed up with Robert Scherrer and Thomas Kephart from the Vanderbilt Physics Department, finding that a Big Rip scenario is a natural consequence of the equations. The results included some potential new insights into the mysterious nature of dark energy.

Most dark energy theories so far haven’t taken cosmic stickiness into consideration, despite the fact that the repulsive effect is strikingly similar to that of dark energy.

“It is possible, but not very likely, that viscosity could account for all the acceleration that has been attributed to dark energy," Disconzi said to Vanderbilt University News‎. "It is more likely that a significant fraction of the acceleration could be due to this more prosaic cause. As a result, viscosity may act as an important constraint on the properties of dark energy,” he adds.

"In previous models with viscosity the Big Rip was not possible," Scherrer said to Vanderbilt University News‎."In this new model, viscosity actually drives the universe toward this extreme end state."

I ask Disconzi about the accuracy of his results. He replies:

My result by no means settles the question of what the correct formulation of relativistic viscous fluids is. What it shows is that, under some assumptions, the equations put forward by Lichnerowicz have solutions and the solutions do not predict faster-than-light signals. But we still don’t know if these results remain valid under the most general situations relevant to physics."

He also reflects on how his new formula may change the way we see cosmology:

It’s too early to tell. What is known from current observational data is that a Big Rip scenario is possible, although the available data is far from conclusive.What our paper brings to the discussion is a mechanism that yields a Big Rip in a fairly natural way, in contrast of most models of the Big Rip where unnatural assumptions have to be introduced."

So the Big Rip idea isn’t so far-fetched after all.

Tosin Thompson writes about science and was the New Statesman's 2015 Wellcome Trust Scholar. 

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Welcome to the Uncanny Valley: how creepy robot dogs are on the rise

It’s hard not to feel a little destabilised after watching a robot’s freakishly long limbs open a door. 

If you’re among those devouring the latest season of Charlie Brooker’s dystopian hellscape Black Mirror, you may still be having metallic nightmares of being chased by the freaky robo-dogs of  “Metalhead”. In which case, you maybe unsettled to know that these nightmares could in theory become a reality (in the distant future), as a viral video from the robotics firm Boston Dynamics (of backflipping robot fame) revealed earlier this week.

Charmingly titled, “Hey Buddy, can you give me a hand?” a SpotMini, Boston Dynamics’ smallest robot, approaches a door and appears to turn sideways before scampering away. Another SpotMini, fitted with an extending claw-arm, opens the door and lets the first robot scamper through, propping it open to follow. 


The director of “Metalhead”, David Slade, was inspired by these very demonstrations. As he stated in an interview in January, the inspiration for those robotic villains stemmed from none other than Boston Dynamics itself. “Those fucking Boston Dynamics robots are terrifying, so that in itself was enough that we didn’t have to worry about it,” he told IndieWire. 

Beyond its viral value, the SpotMini marks an interesting stage in the development of artificial intelligence and robotics. Being able to open a door has long since been the bar for the development of modern robots, as Matt Simon of WIRED pointed out. With this bar seemingly met – and surpassed – the questions remains as to what’s next.

Boston Dynamics robots seem designed mostly for academic and research purposes. Previously, DARPA, the research and development wing of the US defence department and arguably the birthplace of modern robotics, rejected some of the robots for usage because they were too loud. Now, though, they’re silent.

Even those who were not Black Mirror fans expressed a sense of unease while watching the Boston Dynamics email. Indeed, it’s hard not to feel a little destabilised after watching a robot’s freakishly long limbs open a door, which was previously the domain of, you know, humans and crafty pets. But such feelings of revulsion could have something to do with Masahiro Mori’s “Uncanny Valley” theory, which he first proposed in the 1970s.

The “uncanny valley” could be defined as the dip in emotional response from humans when interacting with a being that is vaguely humanoid. The theory suggests that robots become more appealing as they draw closer to human characteristics – but only up until a certain point. Once that point has been reached, and surpassed, humans then find those robots “uncanny”. Then, as they resemble us even more closely, we find that we grow less repulsed by them. 



While the theory has circulated since the 1970s, a 2005 translation of the paper into English made the concepts more widely accessible, and it has been studied by academics ranging from philosophy to psychology. Despite the term wriggling its way into everyday techspeak, the theory itself is yet to be proven. In 2016, the researchers Mathur & Reichling studied real world robots and humans’ reactions to them, but found overall ambiguous evidence for the existence of the uncanny valley. 

Watching one of the SpotMinis open a door – and then prop it open, like you would – may make our skin crawl for those very reasons. The SpotMini, and even some of Boston Dynamic’s other robots, like the backflipping Atlas, have a weird mix of familiar and unfamiliar characteristics. In the viral video, for example, the way that the armed robot holds open the door resembles an interaction that many of us see everyday.   

That may also have something to do with why this particular robot, which has also been used to wash dishes, has triggered a different reaction to Handle, another robot in the Boston Dynamic litter, which can wheel around faster than any natural organism and perform backflips (complete with an athletic hand raise at the end). Handle's acrobaticism inspires a mixture of fear and awe. Watching SpotMini, whose mannerisms bear a resemblance to a family dog, fumble and open a door, feels a little more familiar, but a little more weird.


There are, of course, real fears about robots that are not driven by TV. The baseline for robo-phobia has long since been that they’re not only coming to take our jobs, but they’ll be better than us at it too. SpotMini is technically very interesting because of how it merges software and hardware. That the two SpotMinis can co-operate paves the way towards teamwork between robots, which has until recently remained a far off prospect.

Robots are already a key function of many military operations. They carry out tasks that are too dangerous to entrust to humans, with more accuracy. Additionally, robots are entering our social spheres - with AI controlled assistants like Alexa, the controversial robot Sophia (she once expressed a desire to destroy humans), or the AELOUS home assistant that was unveiled at a convention in Vegas, which can vacuum and fetch you a beer (and will be retailing later this year).

While there are all kinds of debates within artificial intelligence and robotics about what this means for the field, there could be a greater number of non-technically trained experts interacting with robots, relying on intuition and common sense to frame their interactions. 

That takes the implications of the uncanny valley outside of just theoretical. What kind of robot can we interact with, sans revulsion? Does that mean we can only use them in specific contexts. And do they have to look a certain way? 

As always, there’s the bigger picture to consider too. Boston Dynamics remains spectacularly good at making viral videos that draw attention to its products, which are indubitably marvels of modern engineering. Moreover, lower level sensorimotor skills that an infant develops intuitively – such as, you guessed it, opening a door – are actually far more difficult to programme than high-level displays of intelligence, such as winning a chess game (also known as Moravec's paradox).

So while the robo-dog may be unnerving (and there's a reason for that), our robot overhounds are still a while away. But when fully autonomous and physical robots do eventually proliferate, they'll know how to set themselves free.