"They are all on the same level. They all move in the same direction ... that's perfect, you know. Is magnificent. It is almost inexplicable. "

Astronomer Geoffrey Marcy describes the solar system

How To Build A Universe

We don't need to get too excited about it: we will never be able to understand how tiny and insignificant a proton can be from a dimensional point of view. It's just too small.

The proton is an infinitesimal portion of an atom, which obviously is already a tiny object in itself. Protons are so small that a dot of ink like the one on an "i" can contain something like 500,000,000,000, that is, more than the number of seconds contained in half a million years. In short, protons are microscopic to excess, and it is still an understatement.

Imagine being able to shrink a proton down to one billionth of its normal size (obviously you can't) and force it into a space so small that its former dimensions seem enormous. Now, let's try to amass a scant thirty grams of matter in that tiny space.2 Done? Very good. We are now ready to build a universe.

I'm assuming we want to build an inflationary universe. If, on the other hand, we prefer to make an old style, the classic Big Bang type, then other materials would be needed. In truth, it would be necessary to collect everything around, every grain and particle of matter from creation to the present day, and compress it until it is reduced to a point so infinitesimal and compact that it has no dimensions: what is called a singularity. .

Either way, let's prepare for a huge explosion. Obviously, to enjoy the show, it would be better to take cover in a safe place. Too bad, however, that this safe place does not exist, since there is nothing else besides the singularity. When the universe begins to expand, it does not expand to fill a larger pre-existing void. The only existing space is, in fact, what the universe itself creates by expanding.

It is natural - but it is not correct - to imagine the singularity as a kind of fruitful point that floats in the darkness of an empty and unlimited space. Instead, there is no space, and there is no darkness. Around itself, the singularity has no surroundings. There is no space that it can occupy, it has no place to be. We can't even ask her how long she's been there; whether it has come into existence as an idea that comes into the mind, or whether it has always existed in the silent waiting for the right moment. Time does not exist. There is no past from which it can emerge.

And so, from nothing, our universe takes shape.

A single dazzling pulsation, a moment of glory too rapid and grandiose to be put into words: the singularity takes on celestial dimensions. An unimaginable space. The first second of life (a second to which many cosmologists will devote their careers, dissecting it into increasingly thin wafers) produces gravity and the other forces that govern physics. In less than a minute the diameter of the universe has already exceeded one million billion kilometers and is growing at great speed. There is enormous heat now, ten billion degrees, enough to trigger the nuclear reactions that generate the lightest elements, especially helium and hydrogen, with a little lithium (about one atom in a hundred million). In three minutes 98 percent of all matter that exists or will ever exist has been produced. We have a universe. It is a place of wonderful and rewarding potential. And it is also beautiful. Built in roughly the time it takes to make a sandwich.

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