The kinetic energy formula, m*v2/2, was confusing to me. Since velocity is a relative value that depends on the observer, how can the value of energy change depending on the observer? What I’m realizing is that quite often, people talk about energy as if it has an absolute value, but in reality, we shouldn’t care too much about the absolute value of energy. What we care about is the difference between energetic states—that’s what’s important.
Sometimes people say, “The ocean has so much thermal energy, and if we lower the temperature of the ocean by 0.1°C, we can harvest such and such amount of energy,” which is a misleading point of view. They might also say, “This is useful energy, and that is useless,” usually referring to energy dissipated as heat. But we have plenty of heat machines—internal combustion engines (ICE) are a common example—that use heat energy effectively. So how can heat energy be considered useless?
But if we shift our perspective and forget about the absolute value of energy, focusing on the difference instead, the difference is what makes energy useful. It doesn’t matter how fast an object is moving; what matters is that you can decelerate the object to extract energy.