(ORDO NEWS) — To observe certain astronomical phenomena, scientists need to place their observatories deep underground, in tunnels or abandoned mines. This is the so-called “underground astronomy”.
What do you think, what interest for an astrophysicist can be the details from long-sunken ships or, for example, railroad tracks from the beginning of the last century?
Everything is very simple: it is necessary that the experiment carried out by scientists is not subjected to the slightest radioactive contamination.
The fact is that the scientist is hunting for ghostly particles: the elusive neutrinos and the even more elusive and mysterious dark matter.
These particles are of a type that interact very weakly with ordinary matter. So small that, for example, a neutrino is able to break through a lead wall several hundred billion kilometers thick, as if it were ordinary air.
Or to put it another way: of the neutrinos produced by the nuclear reactions that take place inside the Sun, we detect only one in every 5,000 million passing through the Earth.
This difficulty in detecting them has forced physicists to make two decisions at the same time.
First, large detectors are needed, because the more mass you have, the more likely a neutrino will collide with an atom.
So, for example, in Japan there is a Super-Kamiokande detector (Super-Kamiokande), located in a Japanese laboratory at a depth of 1 km in the Kamioka zinc mine and containing 50,000 tons of water.
There is a second way – to bury the detector under tons of rock. The main goal is to protect the device from cosmic rays, which create background noise in the detector and interfere with neutrino detection.
Therefore, in order to “hear” the whisper of a neutrino, it is necessary to find a quiet place.
You might think that this is enough, but it is not. Everything around us is radioactive. This means that the rock and even the material involved in the experiment create a radiation background. Hence the interest of physicists in the old railway tracks or the lead wreckage of sunken ships.
For the most sensitive parts, iron and lead are primarily selected, used in such a way that they are melted down to the first radioactive emissions in the atmosphere and thus avoid further human contamination.
The older the material, the better. For example, the lead used contains the isotope lead-210, which has a half-life of 22 years.
This means that if we have one kilogram of this lead, half of it will decay in just over two decades. For example, lead cast during the Roman Empire is more “pure” than lead cast in 1900.
It turns out that in order to detect neutrinos coming from the sun or from other astronomical phenomena, such as supernova explosions, we have to keep telescopes under tons of rocks. What, in fact, do physicists in search of particles.
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