How it all started?
The first answer is that we have no idea; but there is another scientific from the 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 radiation –the “echo”– of that explosion with which the universe began that arrives from all directions in the galaxy...
And we continue to expand?
It's only been a decade since we've had enough computing power to simulate that big bang, and they tell us that at the beginning there was a quark soup, to gradually form particles and then electrons, protons, neutrons that gradually joined into atoms to form molecules. ...
Why does the broth become bodies?
Because when there is an explosion, space-time is generated that expands rapidly as it cools and densities increase and particles of primordial matter are formed that make up population III stars, the first to form.
Are they very different from our Sun?
They are thin, gigantic and, well, the truth is that we have not 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, thus, meanwhile, galaxies, clusters of galaxies and large-scale cosmic structures began to take shape. We are in one of those galaxies.
And can we look back – see the past – in the cosmic expanse?
We have been able to see galaxies that are very close to the time they formed, about 8 million light years from us...
Have you seen those galaxies?
Just a red dot from satellites...
Why do they look like that little red dot?
Because those galaxies are accelerating and moving away from us. But in reality they are not the ones that are moving away from us, it is the whole universe that is expanding. That's why from them they would see us as another little red dot...
And by calculating that speed, can we also date the age of the universe?
We have measured galaxies accelerating in the same direction and at the same speed since the big bang...
How fast?
To the Hubble constant and from type 1a supernovae. On July 1 we launched a satellite, the Euclid from ESA, to measure the Hubble constant for the speed of cosmic expansion and it is very relevant because it depends on the amount of matter it contains: it is the gravitational force...
Can't calculate yet?
It's just that the numbers don't come out: that speed is excessive for the amount of matter that we observe in the universe, so now the most refined instrument has been launched to measure this Hubble constant of cosmic expansion...
Why don't the numbers come out?
Because dark matter exists. We don't know anything about it except that it makes up 80% of the universe. Euclid will give clues...
And you investigate it?
I do research in high energy astrophysics: extreme objects, black holes, neutron stars...
What do you look for in them?
What kind of matter is in a black hole or a neutron star that is not protons or electrons but very dense matter, and I think it is fundamental, because all the technological discoveries of the last 100 years...
Of accelerated innovation.
...from 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 now?
In these regimes of extreme gravities, Einstein's general theory of relativity governs, which tells us that we have a general reference system on Earth with 4 axes: the three we learned in school: length, width and height, and... . time.
Space-time?
Because those axes are a dynamic reference system. If a person leaves a place, when he returns his time is not the same as that of the person who has stayed in it.
Does the one who stays get older?
And even more so if we were to travel to an extreme center of gravity, like a black hole, when we returned we would find those who had remained much older.
