More than a kilometer underground, in an old gold mine in a small Australian town, a group of scientists is building a laboratory that aims to look where no one has been able to look before. Its name is \u00a0SABER South\u00a0, and its mission sounds simple but borders on the impossible: \u00a0detect the particles that make up dark matter\u00a0, that mysterious component whose existence, until now, we only intuited.<\/p>\n
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To understand how we got here, we have to travel back to \u00a01998\u00a0. That year, an experiment in the \u00a0Gran Sasso underground laboratory\u00a0 in Italy recorded a strange signal that some interpreted as a clue to dark matter. That observation, known as \u00a0DAMA\/NaI\u00a0, ignited a scientific career that has not stopped since.<\/p>\n
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Now, Australia enters that global race. According to ABC News Australia<\/a>, SABER South will be the \u00a0first dark matter detector in the southern hemisphere\u00a0 and will begin collecting data next year. Its director, physicist \u00a0Phillip Urquijo\u00a0, explains that the objective is to reproduce the Italian observations and check whether these signals are real or the product of interference from the environment. <\/p>\n <\/p>\n Currently, three other teams\u2014in Italy, \u00a0Spain\u00a0, and \u00a0South Korea\u00a0\u2014are still trying to replicate the original experiment. However, the Australian project has a unique advantage: its location in the southern hemisphere will allow the data to be compared with those from the north and rule out \u00a0seasonal or local effects\u00a0. <\/p>\n <\/p>\n Powered by the \u00a0University of Melbourne\u00a0 and the \u00a0ARC Center of Excellence for Dark Matter Particle Physics\u00a0, SABER South seeks to understand the nature of a substance that surrounds everything, but that no one has ever seen.<\/p>\n <\/p>\n The \u00a0Standard Model of physics\u00a0 accurately describes the particles and forces we know, but it still leaves too many gaps unfilled. One of the biggest is this: why don’t galaxies disintegrate? What holds them together if everything we see\u2014planets, stars, gas, dust\u2014barely adds up to \u00a05% of the universe\u00a0? The rest is hidden from view. The physicists estimate that around<\/a> \u00a027% would be dark matter\u00a0 and another \u00a068% would be dark energy\u00a0. Physicist \u00a0Elisabetta Barberio\u00a0, director of the ARC Center of Excellence for Dark Matter Particle Physics, puts it bluntly: “Between \u00a075% and 80% of the universe\u00a0 is made of something we can’t see or touch. This experiment brings us closer to discovering what most of the cosmos is really made of.”<\/p>\n <\/p>\n Therefore, if SABER South manages to detect \u00a0WIMPs\u00a0\u2014those hypothetical massive particles that interact weakly\u2014we would be facing a new form of matter and, perhaps, physics that goes beyond the \u00a0Standard Model\u00a0. Simply put: it would demonstrate that almost everything that exists has a tangible structure. And every time humanity has understood a new force or particle, technologies that previously seemed like science fiction have appeared: \u00a0semiconductors, lasers, or magnetic resonance\u00a0.<\/p>\n <\/p>\n The experiment is carried out at the \u00a0Stawell Underground Physics Laboratory (SUPL)\u00a0, excavated \u00a01,025 meters deep\u00a0, a distance that is equivalent to a protection of almost three kilometers of water, enough to block cosmic rays and natural radiation that could interfere with the measurements.<\/p>\n <\/p>\n The laboratory is air-conditioned, has \u00a0filtered air\u00a0, and has data connections linking to the University of Melbourne. At its heart, a room-sized detector houses \u00a0ultrapure sodium iodide (NaI)\u00a0 crystals. When a WIMP particle collides with an atom in the crystal, it produces a tiny flash of light, so weak that it lasts just a few nanoseconds. These flashes are captured by \u00a0photomultiplier tubes (PMT)\u00a0, devices capable of transforming light into measurable electrical pulses.<\/p>\n <\/p>\n The crystals are submerged<\/a> in a scintillating liquid\u2014\u00a0linear alkylbenzene (LAB)\u00a0\u2014that acts as a \u201cveto\u201d: if the LAB detects light at the same time as the crystal, the event is discarded as background noise. The entire system is sealed inside a \u00a0low-radioactivity stainless steel tank\u00a0, surrounded by alternating layers of steel and polyethylene, and monitored from above by a \u00a0muon detector\u00a0.<\/p>\n <\/p>\n SABER South will operate \u00a0almost autonomously\u00a0. According to the technical reports of the project, the system records in real time the temperature, humidity, detector voltage, nitrogen gas flow, and even mine vibrations. If something goes out of normal values, it generates an \u00a0automatic alert\u00a0. In addition, human presence will be minimal: scientists will monitor the data remotely and will only access the laboratory for specific maintenance tasks.<\/p>\n <\/p>\n Even before its construction, the operation of the detector was simulated with the \u00a0GEANT4\u00a0 software, a tool also used by \u00a0NASA\u00a0 and \u00a0CERN\u00a0. These simulations allowed us to estimate the background radiation levels and optimize the sensitivity of the system. Each light pulse captured will be analyzed with programs designed to distinguish between noise and possible real signals.<\/p>\n <\/p>\n In a study by the \u00a0University of Ottawa\u00a0, physicist \u00a0Rajendra P. Gupta\u00a0 suggests that what we think we see as dark matter could be just a mathematical effect. Their model suggests that the fundamental constants of the universe could vary with time, and that the so-called \u201c\u00a0tired light\u00a0\u201d\u2014the loss of energy of photons as they travel through space\u2014would explain observations that until now we attribute to an invisible mass. <\/p>\n <\/p>\n For years to come, SABER South’s crystals will remain in the shadows of the mine, waiting for a flash so faint it could barely illuminate a speck of dust. If that signal is confirmed, it would be the \u00a0first direct trace of dark matter\u00a0, the invisible glue that holds galaxies together. But if it doesn’t appear, it will also be an answer: a sign that perhaps the universe works in a way we don’t yet understand.<\/p>\n <\/p>\n As detailed theoretical physicist Nicole Bell<\/a> from the University of Melbourne: \u201cThis project represents the \u00a0definitive quest\u00a0 to understand the world in which we live.\u201d And perhaps, in that tiny spark beneath the ground, humanity will find the answer to a question it has been pursuing for decades: \u00a0what is the universe actually made of?\u00a0<\/p>\nThe Enigma of the Invisible Universe<\/h2>\n
A Mine Converted Into a Cosmic Laboratory<\/h2>\n
A Machine That Listens to Itself<\/h2>\n
Some Are Not Optimistic<\/h2>\n
Waiting for the Flash<\/h2>\n