Albert Einstein, whose general theory of relativity is still fueling new work. Photo: -/AFP/Getty Images
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What’s up with gravity?

Cheer the discovery of the gravitational wave when it happens. But don’t be fooled: gravity will remain our greatest mystery for a long time yet.

Get ready for a lot of Einstein love. This year marks the centenary of Einstein’s general theory of relativity, which describes how gravity works. Sort of.

It does enough, for instance, to predict the existence of gravitational waves – ripples in space caused by objects moving within it. Not that we have ever seen one. US scientists have just celebrated the completion of their latest gravitational wave detector, which will turn on later this year. They hope to use them to spot the shaking caused by cataclysmic events, such as the collision of two black holes or a supernova explosion.

No one doubts that the waves do exist. Whether our detectors will prove sensitive enough to see them is another matter. Even if they do, it will be a hollow victory. General relativity will have ticked another box but it won’t advance our basic understanding of how gravity works. The truth is that this remains a mystery.

What we do know is that when you throw a ball up in the air, it returns to earth. That’s because the ball and the earth possess a quality called mass: a way of quantifying how difficult it is to accelerate something, to get that ball moving, or to change its path, or stop it. We can describe how something that has mass will move under the influence of something else with mass by calculating the geometry of the object’s gravitational field using Einstein’s mathematics.

Put simply, anything with mass warps the space (and time) around it, and an object travelling through this warped space follows a curved path. In the case of the ball, that means falling back down to earth. In the case of the earth moving past the sun, it means moving in an elliptical orbit rather than a line. After this, we’re hand-waving. Yes, we can do calculations and we can make predictions of phenomena that this warping of space and time will create. But gravity remains our least-understood force – by a very long way.

Take its weakness. The ball falls to earth, but a fridge magnet doesn’t fall off the fridge, even with the mass of the whole planet pulling on it. That’s seven million billion billion kilos losing out to a magnet the size of a coin. If you want to write down how much stronger than gravity the electromagnetic force is, you’ll need a 1 and 40 zeroes.

What’s more, our theory of magnets is much more complete than our theory of gravity. Gravity aside, we can describe all the forces using a mathematical description known as quantum field theory – a framework that lays out how energy, mass, space and time work together to create the forces we see in the universe. According to this theory, particles borrow energy thanks to the “uncertainty principle” of quantum mechanics, using it to create particles that pop in and out of existence. This is no flight of fancy: these “virtual” particles have been found for all the forces. They are the photon, the gluon and the W, Z and Higgs particles.

But we haven’t come close to finding anything that would constitute the “graviton”. Although we can understand the basic electromagnetic and nuclear forces that give us atoms, chemistry and all our electronic gadgets, we don’t have a bottom-up understanding of why a ball falls back to earth.

So cheer the discovery of the gravitational wave when it happens. But don’t be fooled: gravity will remain our greatest mystery for a long time yet.

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.

This article first appeared in the 27 May 2015 issue of the New Statesman, Saying the Unsayable

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Move objects with your mind – telekinesis is coming to a human brain near you

If a user puts on the Neurable headset, they can move virtual objects with their thoughts. 

On 30 July, a blog post on Medium by Michael Thompson, the vice-president of Boston-based start-up Neurable, said his company had perfected a kind of technology which would be “redrawing the boundaries of human experience”. 

Neurable had just fulfilled the pipe dreams of science fiction enthusiasts and video game fanboys, according to Thompson – it had created a telekinetic EEG strap. In plain English, if a user puts on the Neurable headset, and plays a specially-designed virtual reality video game, they can move virtual objects with their thoughts. 

Madrid-based gaming company eStudioFuture collaborated with Neurable to create the game, Awakening. In it, the user breaks out of a government lab, battles robots and interacts with objects around them, all hands-free with Neurable's headset. Awakening debuted at SIGGRAPH, a computer graphics conference in Boston, where it was well received by consumers and investors alike.

The strap (or peripheral, as it’s referred to) works by modifying the industry standard headset of oversized goggles. Neurable's addition has a comb-like structure that reaches past your hair to make contact with the scalp, then detects brain activity via electroencephalogram (EEG) sensors. These detect specific kinds of neural signals. Thanks to a combination of machine-learning software and eye-tracking technology, all the user of the headset has to do is think the word “grab”, and that object will move – for example, throwing a box at the robot trying to stop you from breaking out of a government lab. 

The current conversation around virtual reality, and technologies like it, lurches between optimism and cynicism. Critics have highlighted the narrow range of uses that the current technology is aimed at (think fun facial filters on Snapchat). But after the debut of virtual reality headsets Oculus Rift and HTC Vive at 2016’s Game Developers conference, entrepreneurs are increasingly taking notice of virtual reality's potential to make everyday life more convenient.

Tech giants such as Microsoft, Facebook and Google have all been in on the game since as far back as 2014, when Facebook bought Oculus (of Oculus Rift). Then, in 2016, Nintendo and Niantic (an off-shoot from Google) launched Pokémon Go. One of Microsoft’s leading technical fellows, Alex Kipman, told Polygon that distinctions between virtual reality, augmented reality and mixed reality were arbitrary: "At the end of the day, it’s all on a continuum." 

Oculus’s Jason Rubin has emphasised the potential that VR has to make human life that much more interesting or efficient. Say that you're undergoing a home renovation – potentially, with VR technology, you could pop on your headset and see a hologram of your living room. You could move your virtual furniture around with minimal effort, and then do exactly the same in reality – in half the time and effort. IKEA already offers a similar service in store – imagine being able to do it yourself.

Any kind of experience that is in part virtual reality – from video games to online tours of holiday destinations to interactive displays at museums – will become much more immersive.

Microsoft’s Hololens is already being trialled at University College London Hospital, where students can study detailed holograms of organs, and patients can get an in-depth look at their insides projected in front of them (Hololens won’t be commercially available for a while.) Neurable's ambitions go beyond video games – its headset was designed by neuroscientists who had spent years working in neurotechnology. It offers the potential for important scientific and technological breakthroughs in areas such as prosthetic limbs. 

Whether it was a childhood obsession with Star Wars or out of sheer laziness, as a society, we remain fascinated by the thought of being able to move objects with our minds. But in actual realityVR and similar technologies bring with them a set of prickly questions.

Will students at well-funded schools be able to get a more in-depth look at topography in a geography lesson through VR headsets than their counterparts elsewhere? Would companies be able to maintain a grip on what people do in virtual reality, or would people eventually start to make their own (there are already plenty of DIY tutorials on the internet)? Will governments be able to regulate and monitor the use of insidious technology like augmented reality or mixed reality, and make sure that it doesn't become potentially harmful to minors or infringe on privacy rights? 

Worldwide spending on items such as virtual reality headsets and games is forecast to double every year until 2021, according to recent figures. Industry experts and innovators tend to agree that it remains extremely unlikely you’ll walk into someone examining a hologram on the street. All the same, VR technology like Neurable’s is slowly creeping into the fabric of our lived environment.