electron microscope

The laser beam in an optical tweezer is not just a spot of light but a force bag. A particle caught in it usually rolls toward the brightest point, like a ball into a dimple.

In a benzene molecule, electrons buzz around the nuclei like a swarm of bees around a hive. But this swarm doesn't just hum: it pulses: every 856 attoseconds, the electron cloud completes a full oscillation cycle. The hive itself, the carbon nuclei, rocks more slowly, with a period of 36 femtoseconds.

A dust grain hangs in the air, held by an invisible beam of light. Around it is ordinary air, but sometimes a tiny spark jumps across the grain. For the first time, scientists have observed such discharges up close and found that they are triggered not by the grain itself, but by invisible visitors from space and from the ground.

At night in a dark room, the human body emits a barely perceptible glow. This light is so faint that only highly sensitive detectors can catch it. Some researchers thought this glow from the head could tell us about brain activity — no scanners or wires needed. But when put to the test, the story changed.

You can't catch X-rays from stars with an ordinary mirror: they pass through glass like light through a window pane. To reflect them, you need a mirror almost parallel to the beam: then the X-rays skim along the surface like a flat stone skipping on water, only slightly changing direction.

Since Vera Rubin first convincingly showed that galaxies are surrounded by invisible matter, the quest to understand the nature of dark matter has remained one of physics' greatest challenges.

You can trap light in a cage smaller than a speck of dust. Photonic crystals are lattices that stop light from scattering and force it to run in circles. Previously, such structures were grown on a bulky substrate, making them too large for living cells.

Throw pebbles along a tight row of posts: they ricochet into a dense spray. Throw at an angle, and they scatter. Gamma rays in a crystal do the same: they spawn particle cascades that spread out unless the crystal’s atomic rows are perfectly aligned. Align them within a hair’s width, and the cascade sharpens into a tight beam. A small crystal then outperforms a large one.

In a dark room, you might notice a faint blue glow around some radiation sources. This is Cherenkov light: it appears when a charged particle travels through a medium faster than light can propagate in it. The result is a light shock wave, similar to the sonic boom from a supersonic jet, but made of photons.