# What happens when a raindrop hits a puddle?

Have you ever taken a walk through the rain on a warm spring day and seen that perfect puddle? You know, the one where the raindrops seem to touch down at just the right pace, causing a dance of vanishing circles?

# Math shows how DNA twists, turns and unzips

If you’ve ever seen a picture of a DNA molecule, you probably saw it in its famous B-form: two strands coiling around each other in a right-handed fashion to form a double helix. But did you know that DNA can change its shape?

# The great mystery of mathematics is its lack of mystery

In one sense, there’s less mystery in mathematics than there is in any other human endeavour. In math, we can really understand things, in a deeper way than we ever understand anything else. (When I was younger, I used to reassure myself during suspense movies by silently reciting the proof of some theorem: here, at least, was a certainty that the movie couldn’t touch.) So how is it that many people, notably including mathematicians, feel that there’s something ‘mysterious’ about this least mysterious of subjects? What do they mean?

# Nothing matters: how the invention of zero helped create modern mathematics

A small dot on an old piece of birch bark marks one of the biggest events in the history of mathematics. The bark is actually part of an ancient Indian mathematical document known as the Bakhshali manuscript.

# Why Google wants to think more like you and less like a machine

What does this mean:

wht has Don Trm don nw?

You’ve probably decided the intended question is: “What has Donald Trump done now?”But how did you reach that conclusion? The word fragments could be part of many different words. You even expanded two almost identical fragments – “Don” and “don” – to different words – “Donald” and “done”.

# Maths: why many great discoveries would be impossible without it

Despite the fact that mathematics is often described as the underpinning science, it is often not given enough credit when scientific discoveries are presented. But the contribution of mathematics and statistics is essential and has transformed entire areas of research – many discoveries would not have been possible without it. In fact, as a mathematician, I have contributed to scientific discoveries and provided solutions to problems that biology was yet to solve.

On March 14, or 3/14, mathematicians and other obscure-holiday aficionados celebrate Pi Day, honoring π, the Greek symbol representing an irrational number that begins with 3.14. Pi, as schoolteachers everywhere repeat, represents the ratio of a circle’s circumference to its diameter.

# Mathematics is beautiful (no, really)

For many people, memories of maths lessons at school are anything but pretty. Yet “beautiful” is a word that I and other mathematicians often use to describe our subject. How on earth can maths be beautiful – and does it matter?

# What exactly does ‘instantaneous’ mean?

How short is an “instant”? Is it a second? A tenth of a second? A microsecond? You might think all of these qualify. What about 100 years? That certainly doesn’t seem like an instant, and to a human being, it isn’t, since we’d be lucky to have a lifespan that long. But to a giant sequoia, say, 100 years is no big deal. And in geological terms it’s practically nothing.

# How to crack British intelligence service’s devilish Christmas puzzle

Calling all aspiring spooks. Robert Hannigan, director of Britain’s security and intelligence organisation GCHQ, has included a rather tantalising puzzle with his Christmas card this year. He hopes that it will exercise your grey cells over the holiday period. If you can solve the puzzle, along with the others that it will lead to, you can email the solution to GCHQ (the Government communications headquarters) before January 31. A winner will be drawn from all the correct answers – and doubtless be named to much fanfare. So what do you need to do to be in with a chance?