Physics Lover

The kinetic energy that water gains when it falls (and can therefore be converted into electricity by a hydroelectric plant) comes ultimately from sunlight and not from gravity. As a force, no energy can be extracted from gravity itself. Public Domain Image, source: Christopher S. Baird. No, gravity can not be used as an infinite energy source. In fact, strictly speaking, gravity itself can not be used as an energy source at all. You are confusing forces with energy, which are very different things.  Energy  is a property of objects, such as balls, atoms, light beams, or batteries. In contrast,  forces  describe the  interaction  between objects. Forces are the way that energy is transferred from one object to another when they interact, but forces are not the energy itself. Gravity is a force, so it just provides one way for objects to exchange and transform energy to different states. If I lift a bowling ball to the top of a hill and let it go, the ball f...

The kinetic energy that water gains when it falls (and can therefore be converted into electricity by a hydroelectric plant) comes ultimately from sunlight and not from gravity. As a force, no energy can be extracted from gravity itself. Public Domain Image, source: Christopher S. Baird. No, gravity can not be used as an infinite energy source. In fact, strictly speaking, gravity itself can not be used as an energy source at all. You are confusing forces with energy, which are very different things.  Energy  is a property of objects, such as balls, atoms, light beams, or batteries. In contrast,  forces  describe the  interaction  between objects. Forces are the way that energy is transferred from one object to another when they interact, but forces are not the energy itself. Gravity is a force, so it just provides one way for objects to exchange and transform energy to different states. If I lift a bowling ball to the top of a hill and let it go, ...

Walking on Caltech's campus, research engineer Chris Roh (MS '13, Ph.D. '17) happened to see a bee stuck in the water of Millikan Pond. Although it was a common-enough sight, it led Roh and his advisor, Mory Gharib (Ph.D. '83), to a discovery about the potentially unique way that bees navigate the interface between water and air. Roh spied the bee during California's years-long drought, when the pond's fountain was turned off and the  water  was still. The incident occurred around noon, so the overhead sun cast the shadows of the bee—and, more importantly, the waves churned by the flailing bee's efforts—directly onto the bottom of the pool. As the bee struggled to make its way to the edge of the pond, Roh noticed that the shadows on the pool's bottom showed the amplitude of the waves generated by the bee's wings, as well as the interference pattern created as the waves from each individual wing crashed into each other. "I was very excited to see...

Walking on Caltech's campus, research engineer Chris Roh (MS '13, Ph.D. '17) happened to see a bee stuck in the water of Millikan Pond. Although it was a common-enough sight, it led Roh and his advisor, Mory Gharib (Ph.D. '83), to a discovery about the potentially unique way that bees navigate the interface between water and air. Roh spied the bee during California's years-long drought, when the pond's fountain was turned off and the  water  was still. The incident occurred around noon, so the overhead sun cast the shadows of the bee—and, more importantly, the waves churned by the flailing bee's efforts—directly onto the bottom of the pool. As the bee struggled to make its way to the edge of the pond, Roh noticed that the shadows on the pool's bottom showed the amplitude of the waves generated by the bee's wings, as well as the interference pattern created as the waves from each individual wing crashed into each other. "I was very exc...