Power is a measure of our ability to make reality conform to our intentions.
Engineers and scientists calculate power as the redistribution of energy from one form to another, and ultimately into the disordered state of heat. Initially, energy is generated in the sun through nuclear fusion. For human purposes, by far the greatest portion of that energy (roughly 99.99999995%) is cast uselessly into space, where it eventually warms interstellar and intergalactic gas. However, some of it arrives on earth, where most simply warms the surface. Plants use a portion of it to manage the flow of materials across their cell membranes, feeding chemical factories that build complex molecules out of air, water and minerals. Ecologies thrive on the basis of that process, culminating with homo sapiens sapiens. At every stage, energy is lost to heat. At some level, that loss is good: Jupiter's moon Titan is a model of what the Earth would be like if heat was not generated. In other circumstances, such as on a long desert walk, heat can be dangerous, if not deadly.
The power of physical processes, as we might gather from the numbers regarding the sun's output, dwarf human capacities. We did not win the evolutionary struggle because of our innate physical prowess, we won because we know how to store and organize power. A spear focuses energy generated in the shaft to a small cutting edge at a substantial distance from the wielder. The sharp edge makes a local wound, but through blood loss and tissue damage, creates a physical shock that weakens a more powerful animal. The distance at which energy is focused creates a measure of safety - although the unskilled or unwary can still be overwhelmed through the speed and strength of a more powerful animal.