The circadian clock is in nearly every cell, and researchers have untangled many of its secrets. But sleep has been harder to pin down.

# Articles tagged Abstractions

### The Hidden Twist to Making a Möbius Strip

The simple Möbius strip illustrates a deep mathematical challenge that has long tormented the field of symplectic geometry.

### How Viruses May Have Led to Complex Life

Without viruses, we might never have evolved.

### Droplets That ‘Come to Life’

Life might have originated in droplets that behave surprisingly like living cells.

### Graph Isomorphism Vanquished — Again

Just five days after posting a retraction, László Babai announced that he had fixed the error in his landmark graph isomorphism algorithm.

### How Curvature Makes a Shape a Shape

The ancient study of an object’s curvature is guiding mathematicians toward a new understanding of simple equations.

### Complexity Theory Problem Strikes Back

The legendary graph isomorphism problem may be harder than a 2015 result seemed to suggest.

### Test Your Mathematical Sculpting Skills

Can you turn a two-dimensional fractal into a 3-D object? Break out your scissors and tape for a chance to win a 3-D printed sculpture.

### On the Moon’s Far Side, Clues to a Cataclysm?

A mission to collect samples from the far side of the moon could answer questions about a barrage of asteroids nearly 4 billion years ago.

### Quantum Gravity’s Time Problem

The effort to unify quantum mechanics and general relativity means reconciling totally different notions of time.