Category archives: Physics

At low temperatures, the resistivity of a metal (the inverse of its conductivity) is nearly constant. As the temperature of a material is lowered and as we approach absolute zero the resistivity should approach a constant value. Many metals, known as normal metals, behave in this way. The behaviour of another class of metals and […]

Achieving room temperature superconductivity is among the most pursued but elusive goals of scientists. A paper uploaded to the arXiv in December 2014 claims to have observed superconductivity as high as 190 K in hydrogen sulfide at high pressure, breaking all the records thus far. If this observation is confirmed, cuprates will be knocked from […]

There are some concepts in physics difficult to grasp. Mainly because we have no direct evidence of them and, in orther to get some understanding, we rely on analogies that are not strictly correct. One of these difficult concepts is the spin of the electron. The analogy for the spin usually goes this way: Imagine […]

One of the greatest inventions of the 20th century, if not the greatest, was the transistor. It revolutionized the electronics industry and changed the way people around the world lived, learned, worked, and played. Its invention marked the beginning of solid state electronics which quickly reduced the size and power requirements of existing electronic tube […]

In lay people’s minds, railway lines are composed by rails and wooden sleepers on a bed of stones. These medium-sized stones are called ballast, and it is true that they are the most common material to lay the track on; at least when you are not building it in a tunnel or a bridge, where […]

Color patterns are important features of lots of animals, having key functions in protection against UV irradiation, camouflage, shoaling or sexual selection. Color patterns in birds and mammals are generated by a particular type of cell called melanocyte which produces melanin and transfers it to the tissues of fur or plumage. In fish, amphibia and […]

There are people that have the feeling that if they get to know what something is made of automatically thay have learned something. This attitude is called reductionism. But take water, for example: how knowing that water is composed of molecules and that each of these molecules is composed of two atoms of hydrogen and […]

Sunlight is the most important energy source of Earth. All earthlings live thanks to the ability of plants and bacteria to transform solar energy into chemical one. As sunlight is a free, and practically unlimited, energy source it is easy to understand the general interest in finding efficient ways of transforming it into electrical power […]

Although pretty much unknown for the public audience, Supergravity theories play an important role in modern Theoretical Physics, specially for the particle physics and (Super)String Theory communities . Loosely speaking, Supergravity is a theory that describes gravity along with other fundamental particles and interactions in such a way that the whole structure is symmetric under […]

Almost everyone with basic knowledge of physics have one clear concept, there is a minimum temperature and it is called ‘absolute zero’. This temperature corresponds to -273.15 degrees in the Celsius scale. In the Kelvin or absolute scale it is zero, by definition. Furthermore, there is another idea that is also widespread: absolute zero is […]