How did it all start?
The first answer is that we have no idea; but there is another scientific one based on data and simulations...
That it all started with a big bang 13.7 billion years ago?
And we know this because the satellites of the European Space Station and of NASA have detected and continue to detect the radiations - the echo - of that explosion with which the universe began that arrive from all directions of the galaxy ...
And do we continue to expand?
It's only been a decade since we've had enough computing power to simulate this big bang, and we're told that in the beginning there was a pool of quarks, in which particles were formed and then electrons, protons, neutrons that gradually joined together in atoms to form molecules...
Why are bodies made of broth?
Because when there is an explosion, space-time is generated which expands in an accelerated way while it cools and the densities increase and particles of primordial matter are formed which constitute population III stars, the first to form.
Are they very different from our Sun?
They are not dense, they are giants and, well, the truth is that we haven't seen any yet. One of the missions of the James Webb Space Telescope is to be able to see some.
And meanwhile, the rest of the universe?
The universe has continued since the big bang to accelerate its expansion and cool down, so in the meantime galaxies, galaxy clusters and large-scale cosmic structures began to take shape. We are in one of these galaxies.
And can we look back – see the past – in the cosmic expansion?
We have been able to see galaxies that are very close to the time they formed, about 8 million light years away...
Have you seen these galaxies?
Just a red dot from satellites...
Why do they look like a red dot?
Because these galaxies are accelerating and seem to be moving away from us. But in reality they are not the ones moving away from us, it is the whole universe that is expanding. That's why from them they would see us as another red dot...
And by calculating this speed, can we also date the age of the universe?
We have measured the galaxies and they have been accelerating in the same direction and at the same speed since the big bang...
At what speed?
At the Hubble constant and from type 1a supernovae. On July 1, we launched a satellite, ESA's Euclid, to measure this Hubble constant of the rate of cosmic expansion, and it is very relevant, because it depends on the amount of matter it contains: it is the gravitational force...
Still can't figure it out?
It's just that the numbers don't add up: this speed is excessive for the amount of matter we observe in the universe, which is why the most refined instrument has now been launched to measure this Hubble constant of cosmic expansion.
Why aren't the numbers coming out?
Because there is dark matter. We know nothing about it except that it makes up 80% of the universe. Euclid will give clues...
And you investigate it?
I research high-energy astrophysics: extreme objects, black holes, neutron stars...
What are you looking for?
What kind of matter is in a black hole or a neutron star, which is not protons or electrons but very dense matter, and I think it's fundamental, because all the technological discoveries of the last 100 years...
Accelerated innovation.
...from the radio to mobile phones and their chips... derive from the understanding that matter reacts according to the forces of a magnetic field. And we believe that in these extreme conditions we will discover keys to new technologies.
What questions are you asking yourself now?
In these regimes of extreme gravities, Einstein's general theory of relativity governs, which tells us that we have a general system of reference to the Earth with four axes: the three we learned in school: long, wide and high, and... the weather.
Space-time?
Because these axes are a dynamic reference system. If a person leaves a place, when he returns there his time is not the same as that of the person who stayed in that place.
Does the one who stays get older?
And even more so if we traveled to an extreme center of gravity, like a black hole: when we return we would find that those who have stayed are much older.
