7 major experiments that have not yet found the desired

Neutrino detector Super-Kamiokande

The experimenter is often an ungrateful profession. You read news about experiments that ended with great discoveries, but few have heard of attempts, often heroic, of experimenters who have yet to discover or observe what they were made for.

Some of the attempts have been dragging on for decades and see a change of generations of people, consider their man-hours and experience. However, the lack of results sometimes has the same scientific meaning as any advertised discovery: we learn about what the real world is not, or about what is not in it. On the other hand, getting some kind of positive response from any of these experiments would have far-reaching consequences for our understanding of the Universe and our place in it.
')
Your attention is invited to a list of the seven ongoing experiments that are still to be found. All of them are amazing in their genius and ambition. It is not surprising that they are trying to continue and maintain.

To shed light on dark matter, bury a container with liquid xenon in the ground.

Scientists have put forward the theory that the threads of dark matter form a kind of skeleton, on which all the galaxies we see hold. Each of them is surrounded by a dark matter halo, providing additional gravity, explaining how the stars revolve around galactic centers. But dark matter we still have to find directly. Although over the past few decades many attempts have been made to detect dark matter through extremely weak interactions with ordinary matter, they all failed.

Among the various forms that dark matter is capable of taking, so-called. Weakly Interacting Massive Particles (WIMPs) represent one of the most interesting possibilities for particle physics specialists. The LUX experiment, located more than a kilometer underground in a former mine in South Dakota, helped raise the bar of failure in detecting WIMPs very high. The equipment is a tank with 72,000 tons of high-purity water that filters out parasitic cosmic rays. Inside it is a third of a ton of liquid xenon, surrounded by sensors sensitive enough to detect light emitted as a result of a collision of dark matter with xenon atoms.

The failure of LUX to detect any traces of dark matter led to an LUX-Zeplin upgrade — an experiment in which almost 20 times more liquid xenon is used than in LUX. Whether a new experiment will find something where LUX could not do it will be shown in time. Apparently, nature likes to scoff at the hopes and expectations of scientists.

To actually see the gravitational waves left over from the Big Bang, study different frequencies

Gravitational waves (the gravitational analogue of electromagnetic radiation, or light) from the time of the Big Bang should have left a unique trace in the relic radiation observed by us in all directions and left after the explosion that created the observed Universe. It demonstrates tiny fluctuations in temperature and polarization, providing us with a photograph of the gravitational field at the same time — when the universe was 379,000 years old — when the first neutral hydrogen atoms were formed. This trace should be a rotating polarization pattern, the technical term for which is B-modes .

The joy caused by the announcement of the discovery of such B-mods made in 2014 by the BICEP / Keck group proved premature. What seemed to be primary gravitational waves turned out to be polarized dust particles at high galactic latitudes, capable of imitating the same rotating polarization pattern that gravitational waves should demonstrate.

Despite this, the BICEP group has been updated to a BICEP3 configuration consisting of an array of 2500 sensors (bolometers) designed to monitor the background radiation at much lower frequencies than its previous version. Ten years of observations using different versions of the BICEP telescope did not lead to the detection of B-modes of primary gravitational waves, but they are not going to stop the search - the competition for finding them first is only warming up.

To find out if strong nuclear and electroweak interactions combine, look for “supersonic cotton” near the light.

The standard model of particle physics is the culmination of decades of interaction between theory and experiment, from the birth of quantum mechanics to the assumption that weak nuclear interaction (responsible for certain types of radioactive decay) and electromagnetism are different aspects of the same "electroweak" interaction. Electromagnetic and weak interactions only seem to us to be different on the scale of a typical laboratory experiment, since the Higgs field — which imparts mass to the particles interacting with it — hides the symmetry inherent in these two interactions.

In the standard model, there is another, strong nuclear interaction, which should unite with the electroweak on energies one trillion times higher than what we can achieve at CERN, in the “Grand Unification”. One of his predictions is that the proton ceases to be stable and can decay into other particles — pions and positrons — although rarely enough, so that the half-life can be more than a hundred trillion trillion times than the current age of the Universe.

Super-Kamiokande - and the planned update, Hyper-Kamiokande - is located one kilometer below the mountain in the Kamioka laboratory in central Japan. This experiment is looking for, among other things, signs of such extremely rare proton decays in the unreal size of superpure water tanks. Scanning space in search of dim flashes of light, known as Cherenkov radiation — the optical equivalent of supersonic cotton — the Super-Kamiokande searches for particles with high energy into which a proton decays.


Cherenkov radiation in the core of an advanced test reactor in the Idaho National Laboratory

Nothing found yet. But Hyper-Kamiokande, whose planned sensitivity will be 10 times more, should start observations already in 2020.

To test supersymmetry, probe the neutron.

The standard model of particle physics predicts that a neutron - which, together with a proton, makes up the contents of the atomic nucleus - has an extremely small electric dipole moment (EDM), a fixed distance separating two opposite charges. It is because of its small size, most likely, it has not yet been discovered. But theories that supplement the Standard Model with supersymmetry - the hypothetical equivalence of interactions and matter - usually predict an EDM that is 100,000 times larger than the SM predicts.

By introducing restrictions on the value of the neutron EDM, one can check whether supersymmetry is present in nature in a more rigorous way than can be achieved by accelerating particles in colliders. The CryoEDM experiment is just trying to do this at the Laue-Langevin Institute in Grenoble, France. Observing the difference in the precession of the spin of very slow neutrons — that is, in changing the orientation of the axis of rotation — in the presence of magnetic and electric fields, one can accurately measure the neutron EDM, if it exists, since the rate of precession depends on its presence.

By the time CryoEDM reaches its calculated sensitivity, he will be able to eliminate or confirm the presence of supersymmetry. Observation of EDM will be a seductive proof of the presence of supersymmetry in nature, since the value predicted by the Standard Model is too small to be detected with current sensitivity of experiments.

To notice extra dimensions, look at gravity.

If additional dimensions exist, they can affect the operation of gravity at ultra-short distances. They not only imply the presence of deviations from the usual inverse square law of Newtonian gravity, but also imply the existence of new forces acting at short distances comparable to gravity, violating the so-called. equivalence principle. The principle postulates that all matter — the cannonball, the apple — falls equally in a given gravitational field. And the features of the extra dimensions are that the fields controlling the size of the extra dimensions imitate gravity, but only at very short distances, and at the same time they act differently on different types of matter.


Scientists have suggested that additional measurements may have the form of a 6-dimensional Calabi-Yau variety, which led to the emergence of the idea of ​​mirror symmetry

Although Einstein’s general theory of relativity has been thoroughly tested on scales from the solar system to the universe, researchers have only recently begun to test it on submillimeter scales.

Using precisely calibrated torsion scales , the Et-Wash collaboration] group (named after Baron von Atvös, who conducted the first such experiments at the beginning of the twentieth century and the city of Washington) from the University of Washington is looking for violations of the equivalence principle - in addition to inverse squares are on scales approaching 100,000th of a meter. So far, no modifications have been found for Newton's laws or the equivalence principle, which means that if there are additional dimensions, then they are much smaller in the collapsed state than a few tenths of a micron.

To observe cosmological “dark ages”, tune in to a weak radio signal.

In the history of the universe there was an epoch about which relatively little is known - these are the so-called dark ages. This is the era after recombination, after the first neutral hydrogen atoms had formed, and before the first stars began to shine.

The hydrogen atom itself does not emit anything special. But, like a planet orbiting around the Sun, also rotating around its axis, a single electron orbiting around a hydrogen nucleus “rotates” around its axis, which is directed in the same or in the opposite direction relative to its orbital motion. In the latter case, he has less energy.

A small part of neutral hydrogen, darkly lit by relic radiation, was excited and moved to a state with higher energy and the same directivity. And after the transition of these excited atoms to a state of low energy and multidirectional configuration, they emit a signal at a frequency of 1.4 GHz, corresponding to a very weak radio signal with a wavelength of 21 cm. Detection of 21-cm background radiation will allow us to look into the dark ages .

The Low Frequency Array ( LOFAR ) telescope is an array of 20,000 phase antennas located in Europe (mostly in the Netherlands) that have been looking into space since 2012, hoping to detect this weak signal. But the Earth, and the Galaxy in which it is located, are very noisy places, and so far we have not been able to detect a signal from the dark ages, overcoming local noise. Ambitious plans are being developed to create the international Square Kilometer Array ( SKA ), but so far the dark ages remain dark.

To find aliens, just stop listening.

The discovery of convincing evidence of the existence of a different intelligent life in the Universe will be a turning point in the life of our civilization. Collective efforts, consisting of a large number of experiments, were aimed at searching for extraterrestrial signals of reasonable civilizations almost as many as radio. The idea is that artificial radio signals can be distinguished from natural (astrophysical) sources, due to their narrow frequency range and repetitive nature, as is the case with human radio programs. A seductive candidate for such a signal was discovered in 1977, although it has not been seen since, and the possibility of its natural origin cannot be excluded.


Arecibo Observatory in Puerto Rico is involved in the search for extraterrestrial intelligence

The SETI (Search for Extra-Terrestrial Intelligence) experiment is being conducted using various radio telescopes, including the Allen Antenna , which was recently equipped with the technology commonly used to search for exoplanets. Scientists also set it up to search for possible alien megastructures , the existence of which was suggested by the physicist Freeman Dyson. Developed civilizations can build such structures for the direct collection of star energy. And despite the fact that for decades, nothing was found, the collective search for extraterrestrial intelligence is now better equipped than ever. They take action on the concern of Arthur Clark, expressed in the famous phrase: “There are two possibilities: either we are alone in the Universe or not. Both are equally frightening. ”