![]() ![]() Anyone who’s ever stuck their arm out of the window of a moving car can attest that there is more air resistance the faster the car is moving (air is technically a fluid). The faster one layer slides over another, the more resistance there is, and the slower one layer slides over another, the less resistance there is. The friction arises because a flowing liquid is essentially a series of layers sliding past one another. One of those properties is viscosity, loosely defined as how much friction/resistance there is to flow in a given substance. Isaac Newton first delineated the properties of what he deemed an “ideal liquid,” of which water is the best example. Let me borrow a few paragraphs from my 2012 post on "oobleck" for context. Honey is an example of a non-Newtonian fluid – a fluid that changes its behavior when under stress or strain. In fact, there have been several attempts at modeling the behavior of honey as it drips over the last eight years, and a team of French scientists think they may have finally cracked the case with a new paper in Physical Review Letters. Physicists have been puzzling over why this might be the case ever since. The breaking up into droplets is delayed significantly, so much so that a single strand can stretch as much as 10 meters before it snaps. ![]() ![]() It's called the Rayleigh-Plateau instability.īut honey - also a kind of fluid - doesn't behave like that it is much more stable. They attributed this to surface tension, which amplifies the effects of small fluctuations, or waves, that develop naturally in a column of liquid as gravity pulls it down, eventually forming drops. Seriously, it might seem trivial, but it's a theoretical question that dates back to the late 19th century, when Lord Rayleigh and a Belgian physicist named Joseph Plateau studied the behavior of fluids, particularly how a column of water, for example, will fragment into discrete drops after just 10 centimeters. Inquiring minds want to know! Although if you're the sort who thinks all science has to have an application, it could help improve industrial processes like fabricating optical fibers, which involves pulling long strands of viscous fluids (like molten glass) into long thin strands. Forget Big Questions like dark matter, dark energy, supersymmetry, and the quest for a grand unified theory for a moment - what we really need physicists to focus on is the mystery of why strands of sweet, sticky honey can get so long and thin as they drip without actually breaking. ![]()
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