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

Lifestage
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Everything that is wrong with the app Facebook doesn't want over 21s to download

Facebook's new teen-only offering, Lifestage, is just like your mum: it's trying too hard to relate and it doesn't care for your privacy.

Do you know the exact moment Facebook became uncool? Designed as a site to connect college students in 2004, the social network enjoyed nearly a decade of rapid, unrivalled growth before one day your mum – yes, your mum – using the same AOL email address she’s had since her dial-up days, logged on. And then she posted a Minion meme about drinking wine.

Facebook knows it’s uncool. It had a decline in active users in 2014, and in 2015 a survey of 4,485 teens discovered it came seventh in a ranking of ten social apps in terms of coolness. In fact, only 8 per cent of its users are aged between 13 and 19. This is the main reason the corporation have now created Lifestage, an app specifically for under-21s to “share a visual profile of who [they] are with [their] school network”.

Here’s how it works. After signing up and selecting their school, users are prompted to create a series of short videos – of their facial expressions, things they like, and things they dislike – that make up their profile. Once 20 people from any school sign up, that school is unlocked, meaning everyone within it can access one another’s profiles as well as those from nearby schools. Unlike Snapchat (and truly, this is the only thing that is unlike Snapchat) there is no chat function, but teens can put in their phone number and Instagram handles in order to talk. Don’t worry, though, there are still vomit-rainbows.

But with this new development, rather than hosting your mum, Facebook has become her. Lifestage is not only an embarrassing attempt to be Down With The Kids via the medium of poop emoji, it is also an invasive attempt to pry into their personal lives. Who’s your best friend? What do you like? What’s not cool? These are all questions the app wants teens to answer, in its madcap attempt to both appeal to children and analyse them.

“Post what you are into right now – and replace the video in that field whenever you want,” reads the app description on the iTunes store. “It's not just about the happy moments – build a video profile of the things you like, but also things you don’t like.” They might as well have written: “Tell us what’s cool. Please.”

Yet this is more than an innocent endeavour to hashtag relate, and is a very real attempt, like Facebook’s many others, to collect as much data on users as possible. Teens – no matter how many hot pink splashes and cartoon toilet rolls are used to infantilise them – are smart enough to have figured this out, with one of the 16 reviews of the app on the iTunes store titled “Kinda Sorta Creepy”, and another, by a user called Lolzeka, reading:

“I don't like how much information you have to give out. I don't want my phone number to be known nor do I want everyone to know my Instagram and Snapchat. I could not figure out how to take a picture or why my school was needed. Like I said, I don't want all my information out there.”

But Facebook already knows everything about everyone ever, and it’s not this data-mining that is the most concerning element of the app. It is the fact that – on an app specifically designed for children as young as 13 to share videos of themselves – there is no user verification process. “We can't confirm that people who claim to go to a certain school actually go to that school,” Facebook readily admits.

Although the USP of this app is that those over the age of 21 can only create a profile and aren’t allowed to view others, there isn’t a failsafe way to determine a user’s age. There is nothing to stop anyone faking both their age and the school they go to in order to view videos of, and connect with, teens.

Yet even without anyone suspicious lurking in the shadows, the app’s privacy settings have already come under scrutiny. The disclaimer says all videos uploaded to Lifestage are “fully public content” and “there is no way to limit the audience of your videos”. Despite the fact it is designed to connect users within schools, videos can be seen anyone, regardless of their school, and are “viewable by everyone”.

Of course none of this matters if teens don’t actually bother to use the app, which is currently only available in the US. Lifestage’s creator, 19-year-old Michael Sayman, designed it as a “way to take Facebook from 2004 and bring it to 2016”. Although he has the successful app 4Snaps under his belt, there is no guarantee Lifestage will succeed where Facebook’s other app attempts (Notify, Facebook Gifts, Poke) have not.

There are a few tricks Facebook has put in place to prompt the app to succeed, including the fact that users are ranked by how active they are, and those who don’t post enough updates will be labelled with a frowning or (here we go again) poop emoji. Still, this hardly seems enough for an app whose distinguishing feature is “Privacy? Nah.” 

Only time will tell whether the app will appeal to teens, but one thing is certain: if it does, your mum is totally downloading it.

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