Imagine that in our vast
universe, some brains are coming into existence right at this very
second. Everything in those brains is formed in this exact instant.
What’s even more interesting is that everything it “contains” is false: the memories of life up until
this moment, their origin, their ideas, their perspective of the universe... the brains came
with a ready-made set of memories and thoughts that never happened, and are therefore artificial!
Even so, these brains will perceive themselves to be real and everything they know to be real.
So, how would those brains know that their memories are artificial and their existence is
more like a hallucination? How would we be able to know that we aren’t those artificial brains?
This is the Boltzmann Brain paradox, the result of Ludwig Boltzmann’s many years of debate with other
scientists on his interpretation of entropy. To understand Boltzmann brains, we need to
revisit the laws of thermodynamics. The Second Law of Thermodynamics says that
the entropy or disorder of a system can either stay the same or increase, but never decrease.
To understand that, let’s look at a basic example. You've surely seen a glass shatter,
but have you ever seen that shattered glass return to its previous pristine state?
Entropy is the degree of randomness within a system.
Having high entropy means having a highly disturbed or randomly oriented system.
However, when Boltzmann applied his knowledge of statistical mechanics to the concept of entropy,
it spun scientists into a heated debate that has lasted for decades.
Boltzmann stated that the probability of the entropy of a system increasing or staying
the same is high. However, that doesn't mean the probability of the entropy decreasing is zero. It
is simply so small that for realistic systems, like a box of particles, it can be ignored.
However, what happens if you imagine an infinite system?
This question made scientists at the time pause and take a step back; debate quickly ensued.
Scientists realized that if a system has an infinite number of particles, there will be
at least one instance or one possibility out of those infinite possibilities that
the particles would make something structured, instead of arranging in a random orientation!
Basically, the seemingly impossible phenomenon of entropy reduction is still possible in an infinite
universe. So, in an infinite universe, we have only ONE possibility out of an
infinite number where entropy reduces and the particles come together to form a structure,
rather than randomly existing. Boltzmann said that, at some point,
all the randomly organized particles in an infinitely old universe must come together
to form a structured system, as that is what statistics say! Maybe this formation
of a structure would mean all these particles converging into one point—leading to a Big Bang!
This idea, which started with the concept of thermodynamics, obviously entered the
realm of astronomy. That’s when Sir Arthur Eddington, a very famous astronomer, physicist,
and mathematician of the time, entered the debate. He took this crazy and exciting train of thought a
step further, arguing that we don't even need a whole galaxy to validate the existence of
structure in a dead universe. We simply need one intelligent observer, like you and me!
This idea of intelligent observers was brought to the ultimate pinnacle by physicists and
cosmologists, Albrecht and Sorbo, who said that we would only need the body part necessary for
cognition and consciousness—the brain. This brain would randomly come into
existence out of nowhere in a dead universe, and would contain memories of an entire life.
It would be a life that never actually occurred and is as artificial as its thoughts.
This idea was called the Boltzmann Brain. Are you a Boltzmann brain?
When scientists came to understand the legitimacy of this paradox,
no one believed that they could ever be a Boltzmann brain. However,
a Boltzmann brain would similarly not know that its memories and existence were artificial.
This thought lit a fire and an existential crisis within the scientific community,
so people started researching the probability of being a Boltzmann brain.
They calculated that the possibility of the existence of a Boltzmann brain in an
infinite universe is infinitely higher than the probability of a human brain developing!
Statistically, that means we are more likely to be surrounded by Boltzmann brains and ARE
ourselves Boltzmann brains! Whereas, it's very unlikely that there is a “real” brain anywhere!
There is no way of knowing if we are a Boltzmann brain or not, but an infinitely
high probability says that we are! Scientists have studied the cosmological
models that exist for infinity that support the existence of Boltzmann brains. They concluded
that these models are very unstable and too self-undermining to be seriously considered.
Thus, they must be rejected, alongside the existence of these Boltzmann brains.
We now know that the model of an infinitely long-existing universe is a bust. Most scientists
and researchers instead believe that our universe has existed for a finite period of time, starting
from the Big Bang. So, for now, we all can rest easy knowing that our brains are, in fact, real.