atom

The atomic nucleus isn't always round like a billiard ball. Some nuclei stretch out like a rugby ball, while others become pear-shaped — with one end thicker than the other.

In nuclear physics, a puzzle has long been nagging: why among elements lighter than bismuth, only technetium (No. 43) and promethium (No. 61) have no stable isotope at all? All their neighbors in the periodic table can boast at least one long-lived variant, but these two seem to fall out of the general pattern.

In 1905, Einstein showed that the chaotic motion of pollen in water results from the jostling of invisible molecules. A century later, physicists have learned not only to observe but also to control motion at the quantum level.

At first glance, the atomic nucleus is a cramped communal apartment where protons and neutrons (together called nucleons) live by strict rules. Each occupies its own orbit, like electrons in an atom, and on average everything looks orderly.

The atomic nucleus is not a solid ball but a dense swarm of tiny particles called quarks, glued together by a special glue (the strong force). In light nuclei, such as calcium, this swarm is simply arranged: the numbers of the two quark types, up and down, are almost equal, like the white and black keys in an octave.

A wafer-thin film of organic molecules was grown on a silicon substrate. In this film, as if on a sheet of graph paper, tiny "pens"—artificial atoms — were laid out with the tip of a scanning tunneling microscope.

Light usually pushes an atom straight ahead, like wind pushing a sail. But if the beam is twisted into a corkscrew, the picture changes: the atom can fly off to the side, as if caught by a spinning wheel. In the new work, physicists calculated that such a vortex photon can transfer almost all of its rotation to the atom — up to 100 percent.

In a molecule resembling chlorophyll and built from carbon, a metal atom at the center acts as a toggle. Shifting it by fractions of a nanometer can make the molecule glow, quench, or boost its brightness a hundredfold.

A chemical detective searches for life on other planets. Its tool is a mass spectrometer that identifies molecules by weight (the same device earthly forensic scientists use to analyze clues).

A crystal one atom thick is like a sheet of paper you can write on with electricity. Such a material promises to become the foundation for tiny, fast microchips. But before putting it into production, you need to know exactly what it's made of. And that's where the usual formula falls apart.

Neutrinos are the most elusive of all known particles. Every second, trillions of neutrinos from the Sun fly through your body, but you never notice: they barely interact with matter. To catch even one, physicists build giant detectors — pools of water or liquid argon deep underground.

Light consists of portions — photons. Max Planck was the first to understand that light is emitted in quanta. Today, we can guide single photons. When such a photon encounters a fast shutter, it cannot be sliced — half a photon doesn't exist. Instead, a quantum mixture of states with different photon numbers emerges: zero, one, two, three..

In a dark room, a laser beam draws a bright spot on the wall. Light seems warm and uncontrollable, but for three decades physicists have used it as a conductor's baton, making atoms dance in unison.