Atoms make up everything around us, but do these building blocks of matter ever actually touch?
From nearly indestructible metals, like tungsten , to delicate clouds in the sky, atoms make up everything around us. But do these atoms ever touch each other? As with most topics in atomic physics, the answer is more complicated than you might expect. Before we can answer this question, it's important to define what we mean by "touch," said Christopher Baird , an associate professor of physics at West Texas A&M University. "On the human scale, what we usually mean when we say that two objects are touching is that the well-defined outer surface of one object resides at the same location as the well-defined outer surface of the other object," Baird told Live Science in an email. "[But] this type of touching does not really make sense at the atomic scale because atoms do not have well-defined outer surfaces." An atom is neither a solid object nor the smallest unit known to scientists. Instead, an atom is made of many different particles that interact according to specific rules. At its core, an atom is a nucleus surrounded by a cloud of electrons. But a closer look reveals that this nucleus comprises protons and neutrons, which are made up of particles called quarks and gluons. Atoms of different elements have different numbers of protons, neutrons and electrons. For example, a hydrogen atom has one proton, one electron and zero neutrons, while uranium has 92 protons, 92…