The paradox of **Schrödinger's cat** it is one of the strongest pillars of quantum physics. Now, thanks to a group of scientists, including Matteo Carlesso from the Department of Physics of the University of Trieste, a revisitation of the Schrödinger equation has been proposed, which has found space in the journal Journal of High Energy Physics.

To understand what we are talking about, it is appropriate to briefly review both the concepts of quantum mechanics and that of general relativity, still today considered mostly incompatible even if, approaching the question with a broader vision, in reality we realize that more the link between the quantum world and the world of the General Theory of Relativity is explored further **problems emerge **which unfold on different levels. To use a technical term, and this brings us back to the work of physicists, with the revisiting of Schrödinger's paradox we want to “quantize the universe”.

## What is Schrödinger's Cat paradox

Without going into too much detail, physics is based on quantum mechanics and the general theory of relativity. The first delves into the **subatomic world**investigating the intricacies of particles and waves, while the General Theory of Relativity explains gravity by introducing the idea of space-time as something curved and dynamic whose geometries vary continuously.

To be clearer: the General Theory of Relativity describes the gravitational phenomena concerning celestial bodies, quantum mechanics describes the **interactions between particles**, the subatomic world, the microscopic parts of matter. This generates a problem: celestial bodies are subject to gravitational logic (domain of the General Theory of Relativity) and are in any case made of atoms, a domain of quantum mechanics.

The Austrian physicist Erwin Schrödinger, in 1935, wanted to explain quantum systems using the rhetorical figure of the cat **most famous in physics**. The simple explanation is this: a cat is locked in a box along with a device that could kill it. Any radioactive decay of a substance would break a test tube with poison and prove lethal for the feline.

Until the box is opened, the cat remains in one **superposition of states** (it can be alive or dead) and, to dispel any doubt, it is necessary to measure the system, that is, it is necessary to open the box and see firsthand whether the cat is deceased or not.

The possibility that the cat is alive therefore depends on radioactive decay, a topic that belongs to the world of quantum mechanics, of the infinitely small.

## Reconciling the subatomic world with the infinitely large

The work carried out by physicists was illustrated by Carlesso, interviewed by Wired Italy. A **new paradigm **much needed by physics and its evolution because there is still much to discover and, to use the words of the American physicist Richard Feynman: “who says they understand quantum mechanics he doesn't understand quantum mechanics.”

The group of physicists wanted to bring the laws of the very small closer to those of the infinitely large. The idea is to study the universe assuming it began as **quantum entity**that is, in a superposition of different states (just as the cat is, at the same time, both alive and dead).

So the study focused on the superposition hypothesis **different geometries** of space-time and understand how and when one of these prevailed over the others. Carlesso and colleagues wanted to treat the entire universe like Schrödinger's Cat.

Inspired by an attempt at quantization of the general theory of relativity theorized in 1967 by physicists John Archibald Wheeler and Bruce DeWitt, the working group of which Carlesso is a member reliably theorized – with room for improvement – that the universe was born in a quantum state, for **then collapse** in the state we know today.

However, **supporting tests** they are quite complex to carry out because, says Carlesso, “copying” the universe and making measurements is impossible.

In any case, theories like these can be developed thanks to current technologies, which allow us to go where – just a few decades ago – it was impossible to reach.