The most famous, and arguably greatest, contribution that Niels Bohr made to science was in helping us to better understand the structure of the atom. His work was mostly theoretical, and he used math and the work of experimental physicists to understand how electrons could circle the nucleus of an atom without losing energy and collapsing.Bohr described each electron as having a specific amount of energy and being set at a specific distance from the nucleus. If an electron absorbs just the right amount of energy, it can jump up to a higher level. If it jumps down to a lower level, it will release, or radiate, a certain amount of energy.Imagine the energy levels of an atom as the rungs on a ladder. The lowest rung has the least amount of energy and energy increases as you go up to higher rungs. Imagine climbing that ladder. You're tired and you can't quite get your foot up to the next rung. Can you place it somewhere in between two rungs? Not really. You will just drop back down to the lower rung. An electron is the same. It needs the right amount of energy to make it up to the next level, or rung of the ladder. This is what Bohr discovered and what won him that Nobel Prize. Today we refer to his description of the atom as the Bohr Model.