Friction friction and wear in so-called self-lubricating materials. Fluid friction occurs between fluid layers that are moving relative to each other. This internal resistance to flow is named "viscosity". In everyday terms, the viscosity of a fluid is described as its "thickness". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity. The less viscous the fluid, the greater its ease of deformation or movement. All real fluids (except superfluids) offer some resistance to shearing and therefore are viscous. For teaching and explanatory purposes it is helpful to use the concept of an inviscid fluid
Brief Answers to the Big Questions at your feet ... Try to make sense of what you see, and wonder about what makes the universe exist ... It matters that you don't give up. Unleash your imagination. Shape the future." Physicist Marcelo Gleiser, reviewing the book for NPR, writes: "Stephen Hawking is one of those rare luminaries whose life symbolizes the best humanity has to offer ... [his book is one] every thinking person worried about humanity's future should read ... If there is a unifying theme across the book, it is Hawking's deep faith in science's ability to solve humanity's biggest problems ... His answers