Is there anything else out there, or is our universe all there is? Is the
multiverse, which includes all possible universes, just one big collection
of them?
What would they be like if there are other universes? Could they support
life?
Although it may seem like conjecture on top of theory, this is not as
absurd as you might believe.
My coworkers and I have been investigating the potential existence of
additional regions of the multiverse, as well as what these fictitious
adjacent universes might have to teach us about the prerequisites for life
and how they form.
What-if scenarios
Some scientists
assert that the existence of a multiverse is inescapable because of inflation, a
burst of fast expansion that occurred at the cosmological beginning. In
reality, our universe would only be one of many.
According to this theory, every new universe emerges from the roiling
inflationary backdrop bearing a distinct set of physical rules.
We can understand these other worlds if they follow physical rules
comparable to our own. At the very least in principle.
Physics in our universe is controlled by laws that specify how things
should interact with one another and laws of nature that specify the
intensity of interactions, such as the speed of light.
We can therefore create hypothetical "what-if" worlds in which we alter
these characteristics and investigate the results using mathematical
equations.
Although it may seem straightforward, the universe is fundamentally
composed of the principles we play with. What would happen to stars,
planets, and even life if we imagined a world where, say, the atom is a
hundred times heavier than in our universe?
What is required for life?
In a recent set of articles, we addressed this issue by looking at
habitability across the multiverse. Of course, habitability is a complicated
idea, but we believe that for life to begin, a few prime components are
needed.
One of those elements is complexity. The intricacy of life on Earth is
derived from the periodic table's elements, which can be combined and
organized to form a wide variety of molecules. We are chemical engines that
are alive.
However, a steady atmosphere and an uninterrupted supply of electricity are
also necessary. It is not surprising that the origin of life on Earth
occurred on a rocky world with a rich chemical composition and in the light
of a long-lived steady star.
modifying the underlying factors
Do comparable environments persist throughout the multiverse's full extent?
We began our theory investigation by taking the wealth of
chemical components
into account.
Except for the initial hydrogen and helium created during the Big Bang, all
elements in our universe are created during the lifetimes of stars. They are
either produced by nuclear fusion in stellar centers or by the most violent
explosions known as supernovae, which occur when a massive star rips itself
apart at the end of its existence.
The four fundamental forces of the cosmos control each of these activities.
The stellar center is squeezed by gravity, which raises its warmth and
density to incredible levels. Atomic nuclei are attempted to be forced apart
by electromagnetic forces, but if they can get near enough, the powerful
nuclear force can bind them together to form a new element. The star fire is
ignited by the weak nuclear force, which has the power to change a proton
into a neutron.
The masses of the basic elements, like quarks and electrons, can also be
extremely important.
We can turn a lot of knobs in order to investigate these hypothetical
worlds. The remainder of physics is affected by the modifications to the
fundamental world.
Carbon-oxygen equilibrium
We divided the different physics components—stars and atmospheres,
planets and plate tectonics, the
origins of life, and more—into manageable parts in order to address the enormous intricacy
of this issue. Then, using the individual pieces, we pieced together a
larger narrative about habitability in the universe.
Emerging is a complicated image. The habitability of a world can be
significantly influenced by a few variables.
For instance, the ratio of carbon to oxygen, which is determined by a
specific series of nuclear processes in the star's core, seems to be
especially significant.
It would be very difficult for life to appear and flourish in settings that
stray too far from the balance in our universe, where there are
approximately equal quantities of the two elements.
However, it seems that the excess of other elements is less significant.
They can be important building elements for existence as long as they are
secure, which depends on the harmony of the basic factors.
discover more complexity
We have only been able to sample the space of options in very small,
discrete stages in order to uncover habitability across the universe.
Furthermore, we had to use a number of theoretical heuristics and estimates
in order to handle the issue. As a result, our knowledge of the
prerequisites for existence throughout the universe is still in its
infancy.
The complete complexity of alternate physics in other worlds needs to be
taken into account in the following stages. It will be necessary to
extrapolate from our understanding of the small-scale effects of the basic
forces to the formation of stars and ultimately planets on a larger
scale.
One piece of advice
The concept of a multiverse is still just a conjecture that hasn't been put
to the test. Actually, we're not sure if it's a hypothesis that can be
evaluated just yet.
And if the physical rules are distinct across the multiverse, we don't know
how much different they might be.
We may be embarking on a voyage that will eventually disclose where we
ultimately belong within infinity, or we may be moving in the wrong
direction in terms of science.
Geraint Lewis, Professor of Astrophysics,
University of Sydney
