" There are two questions we might ask about the particle in this wave packet: (1) Where is it, and (2) what is its momentum? Physicists discovered that you can ask one of these questions, but not both. For example, once you ask “Where is it?” and you fix a wave-particle in a location, it becomes a particle. If you ask “What is its momentum?” you have decided that movement is the critical factor; therefore you must be talking about a wave. So is this thing we are talking about, the “wave-particle,” a particle or a wave? It depends on which of the two questions we decide to ask. At any given moment, that wave-particle can be either a particle or a wave because we can’t know both the location and the momentum of the wave-particle. In fact, as it turns out, until we measure either its location or its momentum, it is both particle and wave simultaneously. This concept is known as the Heisenberg Uncertainty Principle, and it is one of the fundamental building blocks of modern physics. "

― Deepak Chopra , The Spontaneous Fulfillment of Desire: Harnessing the Infinite Power of Coincidence