Good news. Sure. If it could actually happen. It’s sad to me that the sobering realities like climate change and mass extinction are always couched as “fixable”. They’re not. We’ve unwittingly started irreversible non-linear global ecosystem wide feedbacks that won’t stop anytime soon. Human culture at the scale we’re at currently is inherently unsustainable, degenerative and ecocidal. Among humans driven to breed and conspicuously consume ever more of everything (most of them), they’re not likely to choose to do otherwise until forced to, and by that time, the jig is up. We’re basically bacteria in a petri dish. Ravenously consuming all nutrients in our environment, population exploding until there are no nutrients left and population crashes. We’d do well to expect that population crash sooner than later. We’re not clever enough to get out of this intractable predicament we’ve wrought. The restoration of life on earth likely won’t happen on human timescales. Mass extinctions take eons to unfold.
Forces that can change the momentum of a droplet include the gradient of the pressure and gravity, as above. In addition, surface forces can deform the droplet. In the simplest case, a shear stress τ , exerted by a force parallel to the surface of the droplet, is proportional to the rate of deformation or strain rate . Such a shear stress occurs if the fluid has a velocity gradient because the fluid is moving faster on one side than another. If the speed in the x direction varies with z , the tangential force in direction x per unit area normal to the z direction is