The asteroid parable, the Pope's medical report and the versions from El Ventorro

An astronomer, a doctor and a politician walk into a bar and the bartender asks them: “What kind of truth do you want today?” I’ll let you imagine the punchline, because the interesting thing is to use the question to reflect on what has happened in recent days. The dangerous asteroid, the sick pope and the president of Schrödinger ( who was and wasn’t at Cecopi ): in all three cases, the version of what was known has changed, but in each circumstance the relationship with the truth was completely different. And it is important that we remember how the truths we consume daily crystallize in order to distinguish between high-purity cut crystals and plastic cups.

The asteroid 2024 YR4 was for a moment the most dangerous ever predicted , but in the end it has come to (practically) nothing. Every day, the world's astronomy looked through telescopes and recalculated the probability of the rock falling to Earth. And since every day was different, we wondered in the Science section of EL PAÍS what to do with the new data. It's one thing to keep people informed, but it's another thing to confuse them - in times of information overload - with changing figures about a minimal threat for the year 2032. But why this convoluted number of figures? Because that's how science and its predictive capacity work: observations are made that allow probabilities to be calculated and the more observations are made, the more refined this calculation becomes. As astronomer Julia de León explained in the first days: "If the complete orbit of this asteroid were like an athletics track, which measures 400 meters, for now we only know the first six." The space agencies were not lying or wrong when they published a risk of 1.2%, then 3.1% and then 0.0001% : the asteroid was the same, with the same parabola, but our knowledge was improving.

Every day we had the risk data from the asteroid and the medical report of Pope Francis , which sometimes forced us to prepare the obituary and other times it seemed that he was returning home safe and sound. These changing versions of the report give us another perspective of reality: the asteroid always had the same trajectory, but Bergoglio's body is not always as Catholic . It is not that doctors are inventing what is happening every day, it is that reality - the situation of the papal lungs - is changing. Medical science is not nearly as exact as the calculation of the trajectories of space bodies, among other reasons, because many more factors intervene and, in addition, they are unstable. Uncertainty is a value that we must always take into account in science - it is not impossible that YR4 hits us - but there are ways to mitigate it: scrutinizing the skies with better instruments, examining the patient with a CAT scan.

And finally, the versions about what the Valencian president Carlos Mazón did and where he was on the most terrible day. In his case, the reality is more similar to that of the asteroid than to that of the Pope. What happened on October 29th does not change: we were all where we were and did what we did. If the version published about the trajectory of the asteroid Mazón from the El Ventorro restaurant changes, it is not because the past has been altered, it is because we are told things that are more or less far from reality: what we colloquially call lies. And to prevent us from talking about the true orbit of Mazón, they wanted to cast doubt on the telescopes: when Alberto Núñez Feijóo went to Valencia to hint that the Aemet technicians had provided “inaccurate, improvable” information. On October 31st I had to make a hasty analysis in the newspaper's live broadcast and, surprisingly, it has aged well. I was asked how the alert system could be improved and I said two things: to foster confidence in scientific institutions, “not to question them”, and to send out more alerts, not less: “Citizens do not have enough information”. We now know that the majority of the 224 deaths caused by the flood in Valencia died before receiving the massive alert from the Generalitat.

The asteroid episode has allowed the world to see that the day we get a real scare, like in the film Don't Look Up , we will all find out all at once thanks to hundreds of astronomers who will seek the truth about its trajectory and its risk to humanity. It will not be a solitary Leonardo DiCaprio , as we have seen these days, and there will be no lack of information for citizens as long as we have data to generate it. To obtain it, astronomers need to scrutinize the sky from telescopes located in both hemispheres, because the planet is a sphere and the threat can come from any side. And when politicians hide the truth, we also need journalists and citizens scrutinizing them from both hemispheres , so that they cannot hide in the darkness of their space .