Without any conflict with the second law of thermodynamics, heat can flow from a cooler but constantly heated body to another thermally connected and constantly hotter body. This anomalous heat transfer has been demonstrated in a two-phase liquid-vapor system composed of a Rayleigh–Bénard convection (RBC) cell filled one-half with normal liquid helium and one-half with […]
Maples rely on wind, upward currents, and gusts to spread their seeds over long distances that can reach several kilometers. Maple seeds are able to autorotate because their center of gravity, determined by the position of the nut, is located at the base of the wing-shaped seed. It has been observed that, despite their small […]
During the last year, a longtime forgotten controversy was reactivated by a very interesting paper written by J. Polchinski and his collaborators, in which they questioned whether the so called black hole complementarity principle is a good solution to the apparent information paradox of quantum gravity. This is a question that attracted a lot of […]
Pele is the Hawaiian goddess of volcanoes. Pele’s hairs are thin strands of molten basaltic glass drawn out from lava, thrown into the air from lava fountains, lava cascades or vigorous lava flows, and spun out by the wind. Each hair-like strand has a diameter less than 0.5 millimeters and is as long as 2 […]
The lungs of birds move air in only one direction during both inspiration and expiration through a set of tubular gas-exchanging bronchi called parabronchi. On the other hand, in the lungs of mammals and other vertebrates, air moves tidally into and out of terminal gas-exchange structures, called alveoli (Figure 1). The work carried out by […]
It is well known that an accurate and energetic laser shot can melt, ionize and excite the material in which the light is focused, creating very bright plasmas after the interaction. Valuable information can be obtained from the light emitted by the plasma, such as the elemental composition of the material itself or the environment […]
“ Photonic crystals” is the name that was given to periodic arrangements of materials with different refractive indexes. This name derives from the analogy between the behavior of photons in these materials and the one of electrons in the periodic structure formed by atoms in an actual crystal. The technological side of the analogy suggests […]
Humans can build and use the most sophisticated tools. One of the reasons is the configuration of our hands, which enable us to hold items in a very convenient way. But further than that, we can actually grab items because of the friction coefficient that exists between the skin of our hands and the surface […]
Olfaction is one of the most important senses. It protects us from eating spoiled food, it helps animals to detect their relatives, it makes the perfume business quite successful and, in general, it connects us to the volatile chemicals surrounding us. These chemicals, usually called “odorants”, can be detected even if they are in a […]
Quantum field theory has been the paradigm of modern physics since it was formulated in the first half of the last century. It is based on the idea that everything in physics corresponds to the interaction of some fundamental fields that permeate all space and the excitations of which represent the particles we see in […]