Here is a possible solution of the Fermi Paradox.

If we could look outside the planetarium enclosing our Solar System, we would see the pitch darkness of a universe grown unimaginably old. Quintillions of years after the Big Bang; even the longest living stars have died; entire galaxies have evaporated and the gaps between them have increased a trillionfold. Life, however, still exists, though not life as we know it. Civilization is coterminous with the universe, living off energy released by feeding stellar corpses into the central black holes of galaxies.

Once there has been organic life. It arose in nearly every solar system of the young universe and rapidly (within a few billion years or so) flowered into civilization. The young universe positively teemed with civilizations, so that no inhabited world was more than a few lightyears distant from its nearest neighbours. They quickly integrated into galaxy-spanning wholes which eventually learned to communicate over intergalactic distances, giving rise to a universal culture. But with the aging of the universe, organic life gave way to machine-life, and the first generation of living machines was succeeded by other generations -- each one developed to cope with a new aera of the ever-changing environment. Now, after a quintillion years, even the number of these successive generations is no longer known. And as for organic life, it is all but forgotten. Some scientists actually deny that there ever was such a thing as organic life and propose that a fully formed machine civilization emerged from the Big Bang. The chances of such a thing happening are almost infinitely small, but one might posit an infinity of Big Bangs, just one of which spewed out a fully operational "seed". Anyway, there are no actual records left from the mythical age of organic life, so how life and civilization (which are almost synonymous) arose in the early universe is everybody's guess.

But the question could be investigated. The Department of Deep History decided to do an experiment. Some of its vast stores of energy were used to create enough hydrogen and other long-vanished chemical elements to shape a primordial solar system with exactly the mass and angular momentum which most theories of organic life predicted to be necessary. This primordial solar sytem -- our Solar System -- was encased into a spherical planetarium studded on the inside with projectors creating an electromagnetic an corpuscular backdrop which was programmed to faithfully mimic what the experimentors imagined the Extremely Early Universe to have looked like. This having been done, the experiment was allowed to develop naturally for a few billion years.

To the experimenters, living with very slow thought-processes in an extremely cold environment, a few billion years are almost nothing. A passing thought takes a century, the coffee break takes a few million years. The one lightmonth diametre planetarium, to them, would be no larger than a microscope slide to us. But to them, it's mean temperature of around three Kelvin would be something like the heat of a nuclear explosion to us. Because what they are trying to do is to recreate, in a very small volume, the conditions pertaining in the universe almost immediately after the Big Bang -- akin to what we are doing with our accelerators.

And of course there are no other civilizations "out there" for us to communicate with...

That would make a compelling first couple of paragraphs in a scifi book I'd like to read.

Let me know if you decide to write it.

..or it could be the start of some new religion...

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I would like to write it, but what could the storyline be?

People might find a dislodged projector, buried in the ice of a long-periodical comet which once grazed the wall.

They might then conclude that there is a wall, and send an expedition to find out what is behind it.

But there couldn't be any satisfying conclusion, I think. They couldn't talk to the beings outside, because each of those is "vaster than empires and more slow". Hopefully, the experiment would continue until the Sun has died, but we would be restricted to the Solar System for the entire lifetime of our civilization.

As for religion: perhaps the experimenters have agreed, for ethical reasons, to upload the mind of every conscious being from their experiment into their own world. Interestingly, they would all be resurrected at nearly the same time, even if they had died billions of years apart. Because a billion years in our world is something like a week in their world.

This would, however, make the experiment much more expensive.

So it's like the truman show, only much bigger?

Yes, but with some differences.

(1) Everyone on "stage" is genuine, nobody is an actor.
(2) The purpose of the setup is to provide scientific knowledge, rather than amusement.

I have a vague recollection of some science fiction story where all the deep space probes abruptly failed when they got a certain distance from the Sun, and the reason was that that was as much of the universe as was modeled in detail by the experimenters who had set us up.

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I recall a pulp scifi book about some scientists who set up some sort of containment field and created a sort of mini big bang in the tank.It turned out to be a sort of analog to our universe, but due to its small size it evolved so fast they could watch it. Galaxies formed in it, and star systems within the galaxies. Life occurred throughout, and the various denizens grew to explore their cosmos. Meanwhile the scientists could watch with super power microscopes and follow the developments. The minis developed interstellar travel and eventually became aware of the limits of their universe - the walls of the experimental chamber. Blah blah blah, they build ships to breach that barrier to find out what was outside their universe. Eventually these microscopic beings succeeded and their ships broke through into our universe. As they flew through the ships expanded into our size things, and teh book ended with a what have we done thought.

It was a nice enough story. It might have been one side of an Ace double novel. Don't recall title or author.