Atoms are too small to be seen with the naked eye or even traditional microscopes because their size is far smaller than the wavelength of visible light. Although we know from the early experiments of J.J. Thomson that most of an atom’s mass is concentrated in a central nucleus which is surrounded by an orbit of electrons, we have no pictures of how individual atoms interact with their neighbors. Until now.
In a recent breakthrough, MIT researchers have captured the first-ever images of individual atoms interacting freely in space. These images confirm behaviors of atoms that were previously only predicted by theory – another spectacular example of the triumph of human thought.
Atoms can be bosons or fermions, depending on their total spin, which is determined by whether the total number of their protons, neutrons, and electrons is even or odd. In theory, bosons attract, whereas fermions repel. The new imaging technique shows for the first time that nature is exactly what the theory predicts. In the picture below, bosons are bunched up in space to form a wave. This characterizes the behavior of photons, first theorized by Erwin Schrodinger in the 1920s. At the right are atoms known as fermions captured in the act of pairing up in free space — a key mechanism that enables superconductivity.
To appreciate the magnitude of the new findings, recall that Heisenberg’s uncertainty principle poses a huge challenge to the visualization of quantum phenomena. This is because the principle states that it’s impossible to know both an atom’s exact position and its speed at the same time. Standard imaging techniques such as absorption images only provide a blurry view, showing atoms in a cloud but hiding the atoms themselves. To overcome this fundamental obstacle, the MIT team, led by Professor Martin Zwierlein (the lead author of the study) first allows a cloud of atoms to move and interact freely. They then turn on a lattice of light that briefly freezes the atoms in their tracks and apply finely tuned lasers to quickly illuminate the suspended atoms, creating a picture of their positions before the atoms dissipate.
