Physics! That great Science. The sublime description of the Cosmos, from the smallest subnuclear particles to the Universe as a whole. Physics is, and always has been a thrilling enterprise. It has not been a single decade without a new challenge or surprising discovery. Today, are we living the n-th golden age of Physics?
At the end of the 19th century, some great physicists, among them the great Lord Kelvin (in the image), believed that all the laws of Nature were almost discovered. There were only a couple of small problems, and a few experimental improvements to calculate some parameters, but after that, nothing would remain to be discovered. Solving those small problems led to the birth of Quantum Mechanics and Relativity, which are at the basis of most of the Physics and technology of the 20th century. Right after the talk where Lord Kelvin made that claim Science witnessed one of the most exciting periods of Physics.
Where are we now? Well, we have confirmed all of Einstein's predictions (being the latest the direct observation of gravitational waves), we have confirmed the Standard Model of elementary particle and found the Higgs boson, that explains some of the open questions of this model, we are using the weird properties of Quantum Mechanics, such as entanglement and superposition, in our commercial technology. But we have huge questions to answer, such as: what are dark matter and dark energy?
After the discovery of the Higgs boson, most physicists pointed that the LHC particle accelerator was ready to discover new Physics, to detect new particles or interactions to guide us to answer open questions and find unexpected Physics.
Indeed, a few weeks ago some researchers, analyzing data from LHC, claimed they had found a clear sign of a new Force of Nature. For more than sixty years we have been counting with four fundamental forces: gravity, electromagnetism, strong nuclear and weak nuclear. A fifth force has been postulated and gone several times in the last sixty years. But this time all was pointing to no doubt experimental result.
Well, ..., last week, other analysis pointed out that those measurements were not consistent enough with that conclusion. Not yet time for a fifth force.
Another of the open questions that has been concerning Physicists for the last few years has to do with the elusive neutrino. Fortunately, since 2010 we have the Ice-Cube Neutrino Observatory, in Antarctica. It is a huge (one cubic kilometer) neutrino detector. It is the biggest on the planet and highly interesting research is been carried on in it for the last five years.
The neutrino was postulated by Wolfgang Pauli in the 1930s to solve some observations that suggested that energy could not be conserved. Pauli himself thought that we would not be able to detect neutrinos (extremely light, neutral particle) as it interacts extremely weakly with other particles. Trillions of neutrinos go through your body every second and none of them will interact with your atoms. It took 25 years but it was finally detected. Now, we have even observed neutrinos coming from the center of the Sun. The image at the right is a picture of the core of the sun taken with neutrinos (not with photons).
Neutrinos come in three families (electron, muon and tau) and they change their flavor as they travel through space. This is what the Standard Model allows and what has been found in observations. But some scientists have postulated that there could be four families of neutrinos. This fourth neutrino would be a 'sterile' neutrino. It would be even much harder to detect than the other three. This sterile neutrino would be detected by catching it when transforming into another type of neutrino. The existence of the sterile neutrino would help explain the mass of the neutrinos, and it would also help understand dark matter. But it would open big questions on the validity/limitations of the Standard Model.
This week the journal Physical Review Letters publishes a paper by the IceCube collaboration pointing that there is no room for the sterile neutrino in the observations. The neutrinos observed are generated through collisions from cosmic rays in the higher atmosphere. They go though the Earth and reach IceCube at the other end (see picture below, from PRL). In their brief travel though the planet they can transform into another type of neutrino and be observed at the detector. With a confidence of 99%, the experimenters claim that there is no sterile neutrino.
It seems that the New Physics is been coaxed, but for sure it will come sooner than later.
Physicist, working in quantum optics and nonlinear dynamics in optical systems. Loves to communicate science.