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

Anna Leszkiewicz
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Why doesn't falling snow show up on your phone camera?

And while we're at it, why can't you take a good picture of the moon?

If snow falls on the ground and no one sees it on Instagram, did it really happen?

The answer to that question is a firm “No”, much to the chagrin of social media users around the United Kingdom today. There will be no flurry of Likes to accompany today’s flurry of snow, as one by one we each realise it is damned impossible to take a good picture of falling snow on our phone cameras.

 

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The question is, why?

“All photography is dependent on light irrespective of camera type,” says Matthew Hawkins, a senior lecturer in photography at The University of the Arts, London. “Snowflakes usually fall in times of low contrast and relatively low levels of light.

“This increases the duration of exposure which becomes too long to freeze the motion of an inherently translucent flake.”

So it seems that, provided you’re not trying to shoot on a Nokia 3310, it might not actually be your phone that is the problem. In recent years phone cameras have become incredibly advanced, and the World Photography Organisation even has awards for mobile phone photos.

That said, phone cameras are obviously less advanced than expensive, professional DSLRs, and a lot of digital cameras actually have a “snow mode”, designed to help with the lighting issues that occur when photographing bright, white snow. "Snow scenes generally tend to come out underexposed, so exposure compensation (adding more stops) is usually needed and the automatic settings within a phone camera don't compensate for this," says James Jones, a freelance photographer.

Lauren Winsor, a photography lecturer at Kingston University, adds: “The shutter simply isn’t quick enough to freeze the majority of falling snow. It’s therefore either lost to near invisible motion blur or rendered as inelegant white, out of focus blobs.”

Given that your iPhone is currently trying to catch up with a theatre mode, it’s no wonder that it’s not really designed for the complexities of snow.

But if – as Hawkins says – these problems occur with fancy cameras as well as your phone, then why are your snow photos so underwhelming?

The answer to the question might actually be the answer to life’s many questions: you’re just not very good.

 

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When I ask Lewis Bush, a photography lecturer (who is currently working on a project that uses satellite imagery for another perspective on the refugee crisis), why it’s so hard to capture a good picture of falling snow, he says it’s isn’t “if you know how”.

Multiple online guides have sprung up to help you get this knowledge, and Paul Moore, of iphonephotographyschool.com offers eight tips for the perfect wintery photo. “Depending on the light and the weather, snow can take on different color hues or even end up a dull gray color,” he writes, advising that it can instead be fixed in editing. A simple black and white filter or a photo editing app can change everything.

And while you’re here, what about nature’s other trickiest photography subject, the humble moon? Bush has advice for any amateur phone photographers looking to capture the big cheese. “The moon is hard, so shoot with manual exposure controls if your phone has them, you could also try using telephoto adaptors that clip on to your phone camera or even borrowing a telescope and shooting through it,” he says.

But if the snow continues to fall and you can't afford a swanky camera, what on earth should you do next?

“Shoot towards something dark,” says Bush. “White snow isn’t like to appear very well on a white background, and use a flash if it’s dark.

“Also, maybe question whether the world really needs more photographs of snow?”

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