It’s hard to stay upright. The lack of oxygen here, to 4,900 meters above sea level, grave like a pineapple that leaves you on the verge of knockout. But the site has its advantages, especially if we are talking about astrophysics and especially if it is a goal so ambitious that many believe it could lead to a Nobel Prize.
Is about verify, or perhaps discard, the current theory of the origin of the Universe, that of the Big Bang. The one that postulates that it all started 13.8 billion years ago from a great explosion of a point of very high density and temperature that, fractions of seconds later, produced a tremendous expansion, called “universal inflation” (nothing to do with Argentina), which ended up giving rise, 400 thousand years later , to space and time.
It turns out that, if the theory is like that, as it is formulated and is endorsed by the entire scientific community, that first great explosion and universal inflation should have left an “echo” in space, a relic of the origin of the Universe, in the form of background radiation (CMB for its acronym in English), some very low intensity microwaves with a special type of polarization (wave structure), which is known as “B-mode”.
The point is that the theory closes well on paper, but so far no one could verify it empirically, with an experiment, although there have been many attempts. Scientists know that, to validate the Big Bang, they have to be able to measure that background radiation with the polarization predicted by the same theory. Although they also know that another possibility opens up: not finding those polarized microwaves and that the theory should be revised.
And it is here where we return again to 4,900 meters above sea level, where the lack of oxygen knocks you down. We are in Altos Chorrillos, full highlands of Salta, about 20 kilometers past San Antonio de los Cobres, celebrated for its Train to the Clouds. A thousand meters higher than San Antonio, which is already quite high.
In addition to the dizziness caused by the site, the clarity of the sky, the temperature, the wind speed and the relative humidity of the air makes of this a prime location for deep space observations. And it is here where an international consortium -which involves 150 scientists and laboratories from France, Italy, the United Kingdom, Ireland, the USA and Argentina- has just put the Qubic telescope into operationthe first in the world with technology capable of detecting, or ruling out, the background microwave radiation from the Big Bang.
A hundred people, including scientists from different parts of the world, national and provincial officials and journalists attend, as they can, to the inauguration ceremony of the telescope. There will be words from ministers and mayors, many explanations from researchers. And four nurses with an oxygen tube giving vital support.
The Argentine astrophysicist Alberto Etchegoyen, director of the Institute of Detection Technologies and Astroparticles (ITeDA), says that in 2018 he was calm with his projects -among them running the Pierre Auger Cosmic Ray Observatory (in Malargüe, Mendoza)-, when they touched him the door from France to offer to take over the Argentine part of Qubic.
The reason is that this international consortium -which was formed 15 years ago- had detected that the highlands of Salta was the most appropriate place to locate the instrument they were developing. They needed the collaboration of the Argentine scientific community. Today from Qubic, the Institutes of the National Atomic Energy Commission (CNEA), CONICET, the National University of La Plata; the National Commission for Space Activities (CONAE), among other national organizations and those of the province of Salta.
The secret of the Qubic project (for its acronym in English: Q and U Bolometric Interferometer for Cosmology) is just your telescopewhat’s wrong with it a unique technology which was developed in France between 2008 and 2018. It is the first in the world that combines, within the same equipment, two instruments that until now were used separately and here work together: a bolometer What is it very sensible to measure very low energy radiation (and for that he works at very low temperatures, almost absolute 0 or -273 degrees), plus an interferometer, that gives a lot of securityIt is time to interpret what type of signal it is.
Bolometers are microsensors that, working at very low temperatures, heat up when detecting background radiation, thus changing the electrical resistance of the material and generating an electronic signal. The interferometer, for its part, measures the wavelength of the signal and analyzes the characteristics of radiation.
“That combination, the bolometric interferometry, helps us to elucidate if the signal is related to primordial radiation or not. So we have this great advantage, that by combining interferometry with bolometry, we are clearer about what we are measuring, if they are B modes of primordial radiation”, says Etchegoyen.
The Frenchman Jean-Christophe Hamilton, director of the Qubic project, adds that “the detectors are so cold because we are going to measure a signal from the first 10 to at least 35 seconds after the Big Bang. Truly the beginning of the Universe. Far away in time, that signal is very weak. And to measure such a weak signal we need very sensitive detectors. And to be very sensitive they need to be at very low temperatures”.
Developed in France, in July 2021 the telescope arrived in Argentina and was transferred to the CNEA Northwest Regional Integration Laboratory (specially built for this purpose) in Salta, where it was assembled, put into operation and tested at over a year. The installation of the instrument in its current place in Alto Chorrillos took several weeks, in which all the systems were integrated and tested and the telescope was placed on the observation mount.
QUBIC competes with several other observational cosmology projects investigating B-modes of background radiation: BICEP/KECK, CLASS, SPIDER from the United States, Ali-CPT from China, and the Japanese satellite project (with a major European contribution) LiteBIRD (planned for 2033). However, none of these telescopes combine bolometry with interferometry.
Like VAR, but in space
The very high sensitivity of Qubic will serve, say the scientists, to be able to distinguish that the signals they receive They are really from the beginning of the Universe and not other very similar signals from our galaxy. They say that, in various experiments, the background microwave radiation, polarized in B mode, had already been measured, it was believed that they were looking at the verification of the Big Bang theory, it was celebrated, but later they realized that It was a similar signal, but of another origin, such as elements of the Milky Way or other cosmic objects. Almost like a goal disallowed by VAR.
With Qubic, scientists they will be constantly measuring a sector of space, which they have identified as the one with the least stellar “contamination”. Engineer Manuel Platino, Qubic’s operational director, says that the instrument has three axes of movement.
“With these three movements from the primary control we scan the sky. We are going to aim for a small piece of heaven, permanently, over and over again. With the rotation we are going to compensate the movement of the Earth. The bolometers are going to be measuring and all the information is going to be stored in a central that is going to be managed from France and in our integration laboratory in Salta”.
If Qubic detects B-mode background radiation will be a direct proof of the inflation phase of the Big Bang theory, as well as an important result in cosmology and with profound consequences for particle physics. Of course, the final discovery of B-mode will have to be confirmed independently by various groups, as established by the procedures of science.
Etchegoyen estimates that, in about 3 and a half yearsapproximately, could have the first results. He says it half jokingly and half seriously, but claims that “If everything works and nature accompanies us we are to win the Nobel Prize.”
From Altos Chorrillos, Salta
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How is the telescope that, from Argentina, seeks to verify (or rule out) the Big Bang theory