Universe, Multiverse and Simulation
(A few remarks regarding the Multiverse)
CMAP (Centre de Mathématiques APpliquées) UMR CNRS 7641, École polytechnique, Institut Polytechnique de Paris, CNRS, France
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Keywords: Multiverse, Multivers.
Long ago, our ancestors believed that the Earth was stationary and at the center of the Universe.
This view was not at all ridiculous, as it was what our senses revealed to us (and still reveal today...),
in the absence of appropriate means of observation. This was geocentrism.
Even though before him, Aristarchus of Samos (~310-230 BC) and Hypatia of Alexandria (4th century AD) had intuited heliocentrism,
it wasn't until 1543 that Nicolaus Copernicus (in De revolutionibus orbium caelestium libri VI)
"placed" the Sun at the center of the Universe and made Earth a planet like the others.
As observational tools advanced, it was then the turn of our Sun to be "downgraded",
becoming just another star among its siblings at the heart of a single galaxy, the Milky Way.
New advancements later revealed, during the twentieth century,
that our galaxy was just one among hundreds of billions of others in a possibly infinite Universe...
What about today? Are we facing another demotion?
For a long time, there was hope to justify Earth's privileged position based on the Mathematical laws of Physics:
its optimal distance from the Sun (allowing water to be liquid),
the presence of a protective magnetic field (against solar or cosmic threats...),
the existence of a stabilizing satellite (the Moon), etc. Kepler attempted this by associating each of the five known planets with one of the Platonic solids.
Newton's laws, although allowing for precise calculations of the trajectories of the planets in the solar system,
required "initial conditions" (the positions of the bodies in space at a given moment) to be provided, and these could only be measured,
not deduced from the laws themselves.
Today, it is considered that Earth's fortunate position is the result of the conditions under which the Sun and its planetary system formed:
it is most likely a stroke of luck!
Since the discovery of the first exoplanet (51 Pegasi b) in 1995 by Michel Mayor (Nobel Prize in Physics 2019),
thousands of others have been identified, and it appears that most stars have such a planetary system.
However, it was also discovered simultaneously that the solar system might not be representative.
It seems that almost anything is possible: terrestrial planets (like Earth) close to or far from their star,
gas giants (like Jupiter) close to or far from their star, etc.
It is worth noting that the detection methods currently used (such as the so-called transit method,
where a planet passes in front of its star,
or observing the oscillations of a star caused by its potential planetary system) tend to favor giant planets with short orbital periods.
Thus, with the Universe appearing vast,
even infinite, there must be a number of favorable configurations,
with the solar system and Earth being just one of them: and we are here to make this observation!
Today, a similar question pertains to the Universe: it is described by about thirty parameters that are "finely tuned",
allowing for the existence of atoms, stars, planets, and life. So, why and how is such fine-tuning possible?
Could the answer to this question be of the same nature as that given above to explain Earth's privileged position?
Might there be a (quasi-)infinite number of Universes where nearly all combinations of fundamental parameter values are represented,
including ours? This collection of Universes would form a (the?) Multiverse...
It should be noted that this hypothesis is, on the one hand, contrary to Occam's Razor
on the other hand, logically implies the existence of a Multi-Multiverse, a Multi-Multi-Multiverse,
and so on ad infinitum...
Nevertheless, this metaphysical hypothesis emerges from a number of theories (which are not mutually exclusive!):
According to Karl Popper, a scientific theory must be falsifiable. In this context,
for example, the Big Bang model would not be considered scientific because it is not falsifiable
(it seems difficult to recreate the experiment!).
The current practice is to accept a model as long as some of its predictions are verified and others are not falsified
(this was the case with General Relativity concerning black holes and gravitational waves).
As it stands, Multiverse models have not made any predictions,
and we should await their further development,
particularly within the framework of Grand Unification (Quantum Mechanics and General Relativity)...
- [01]
Since 1905 and Albert Einstein's Special Relativity, we have known that the concept of simultaneity is relative.
This means that events A and B, which are any two events in spacetime, can be observed as simultaneous,
or A can be observed as occurring before B, or A after B, depending on the motion of a particular observer.
It is worth noting that in Quantum Mechanics, when a measurement is about to be made,
the possible outcomes {R1, R2, R3, ...}
can be calculated along with their respective probabilities {P1,P2,P3,...},
but the exact outcome Ri cannot be known in advance. This indeterminacy is quite troubling,
and many have sought a solution to this problem. In Hugh Everett's model, with each measurement,
the Universe bifurcates, duplicating itself into as many copies as necessary so that each branch of this branching structure corresponds to one of the outcomes Ri.
If we now consider not one measurement but two, A and B, in what temporal order must the Universe duplicate itself:
first A then B, or first B then A, or in some other (a priori undetermined) way? Finally, since bifurcations are unconditional,
the probabilities Pi, which are generally not equal, play no role, which is contrary to the very foundations of Quantum Mechanics...
- [02]
The question of whether we are inside a video game or whether our Reality is "simulated" is poorly framed.
Indeed, the notion of "simulation" emerged with computers and advances in mathematical and digital techniques.
Today, everything is "information" and "bit".
A so-called "digital" simulation consists of replacing "real"
experiments with calculations based on the formulation of the physical systems being studied.
This is how, for example, one can study the solar system.
These techniques are also found in learning or again gaming environments,
allowing one to virtually drive a Formula 1 car on a circuit or engage a fighter jet in an aerial battle.
It is important to note that the system being simulated is generally a subset of familiar reality.
However, it is entirely different when we question our Reality.
Indeed, consider R1 as the "master" Reality that would "host" the "simulation"
of our Reality R2 (limiting ourselves to a two-level hierarchy to start with).
Many people implicitly assume that R1 and R2
are somehow of the same nature. However, in general,
there is absolutely no reason for R1 to be described and understood using the specific,
local concepts of R2. These concepts are:
- OUR Mathematics,
- The "atoms" (space and time) and the laws of OUR Physics (Quantum Mechanics, Special and General Relativity),
- OUR computing,
- being,
- consciousness, which we still cannot define,
- morality,
- religion(s),
- ...
If it exists, Reality R1 is, a priori, not accessible to us, and even if it were,
it would most certainly be incomprehensible to us. Indeed, there is no reason to assume that the most fundamental notions of R2,
such as time, space, or even numbers, exist in R1
or have counterparts there (it is obviously hard for us to imagine being able to do without them to understand,
act, and, of course, simulate R2...). The question of whether our Reality is "simulated" is certainly legitimate,
but there are questions and assertions that are not, sometimes having no meaning based on the above, such as:
- Is the debate on the discrete nature of R2
(within the framework of research on the unification of Quantum Mechanics and General Relativity)
relevant to answering the question,
given that the word simulation in R1 is strongly linked to that of discretization?
- At the risk of creating an unsolvable paradox, it is not possible to question the inclusion of R1 within R2
- Is R3, Conway's Game of Life,
to R2 what R2 is to R1? Perhaps,
since R3 exists, by definition, only thanks to the Mathematics and computers of R2!
- Questioning the computational capacities required in R1 to simulate R2 makes no sense,
as the nature of R1 completely eludes us.
- When observing anomalies in R2, is this proof of a programming bug in R1,
and thus of the simulated nature of R2,
as John Barrow argues? In general, no, because our science (that of R2) is based on the belief,
through induction, in the existence and stability of underlying laws. But what is the "reality"?
For example, if we observe a planet suddenly changing its trajectory, is this a bug in R1
or a sign of the incompleteness of our gravitational models?
Additionally, it is important to remember that Physics in R2 is not always deterministic:
this is particularly true for Quantum Mechanics during the act of measurement...
- The beings responsible in R1 for the simulation of R2,
"what" and "who" are they, and can we question their motivations?
To imagine that they act for purposes of research in Physics, Psychology, Sociology,... or even "to play",
while possibly behaving "ethically", is clearly an unmistakable case of anthropocentrism!
- Possible solutions to the Fermi Paradox
do not indicate that we are alone in the Universe (R2),
but only that the encounter with other beings is highly improbable, primarily due to "spatio-temporal" reasons.
Thus, the underlying observations of this paradox ("we don't see extraterrestrials")
cannot be used to deduce that this is a simplification made in R1 to simplify the "process"...
It seems that the question "Is our Reality simulated?" should be generalized to "Was our Reality created?"
or even "Does God exist?".
One cannot avoid the "recursive" question: "Who created the creator?"
(It is worth noting that the question "Who simulates the simulator?" is unnecessary,
as "simulation" and "creation" are not on the same level or of the same nature...).
Thus, to escape this diabolical trap, there may be no other recourse than to apply
Occam's Razor and assert "God does not exist!",
leaving the question "Was our Reality created?" unanswered. And if it was not created, does it mean that it is eternal?
Copyright © Jean-François COLONNA, 2024-2024.
Copyright © CMAP (Centre de Mathématiques APpliquées) UMR CNRS 7641 / École polytechnique, Institut Polytechnique de Paris, 2024-2024.
