Written by Kevin Jennings
The more pedantic among you are likely already screaming at your monitors based on the title of this post, so let’s first address nomenclature and popular misconceptions about science. The list of scientific theories that can’t be proven true is extremely long, because no scientific theory can ever be proven. Theories are tested, and either repeatable results support that theory to the point that it is generally accepted as fact, or contradictory results disprove the theory.
By its very nature, science doesn’t seek to prove things in the same way one might perform a mathematical proof, because to regard a theory as proven means that there’s no room for it to be wrong. The theory of gravity has been accepted as fact, and with good cause. Our understanding of gravity is provably consistent both here on Earth and on a massive, cosmological scale.
However, our understanding of gravity is also incomplete and at some point may need revision. To definitively refer to the theory as proven would make such revisions far more difficult should a time come when some need to be made.
Before a theory is a theory, it is a hypothesis. For a hypothesis to become a theory, it needs to be testable, and more importantly there needs to be a test that could disprove it if the results are not in line with what the theory predicted. But not every hypothesis can be tested. Despite this, some of these untestable hypotheses have been elevated to the levels of scientific theory, at least in the public consciousness, due to their popularity among scientists.
There are a lot of variations on the multiverse theory, but the general principle is the same: our universe is just one of many, and many of those universes are similar to our own. The most common version of this is the “many worlds” theory, which posits that everything that could ever happen did. Any time there is more than one possible outcome for an event, the universe branches into separate universes, one for each possible outcome.
Another possibility for the multiverse is that our universe contains multiple distinct universes within it. Space is unimaginably large, and there are places in the universe that will never be possible to observe due to their distance away from us and the universe’s constantly accelerating expansion. It is out there, in the depths of unobservable space, where matter formed into a galaxy with the exact same configuration as ours which then spawned intelligent life on its own version of Earth.
The idea of a multiverse is compelling from a story telling perspective. If there are infinite universes in which everything that could ever happen did happen, the ability to travel between them would create infinite narrative possibilities. It can also be a comforting thought for people that even if things aren’t great here, somewhere there is a universe where they are supreme, unquestioned ruler of the entire planet, or even the entire universe.
Despite being such a common trope that multiverse theory has almost been imbedded in everyone’s mind as scientific fact, we have no way to know whether any of this is true. There are lots of different types of multiverses, with some physicists having even created a hierarchy of four layers of multiverses, each layer incorporating all of the previous ones. However, all of these different types of multiverses proposed share one very important detail with one another: there is absolutely no way to test for them.
In the theory where the multiverse is all contained within our universe, it is at a distance that will never be possible for humans to observe. Theories involving completely separate alternate universes are obviously untestable as there is no way we could ever travel to them, and they would not be interacting with our universe in any detectable way.
To many scientists, the idea of a multiverse is more a philosophical thought experiment than anything resembling actual science. To others, it is an obvious progression of how reality would function. Since both sides of the argument agree that there’s no way to test for other universes let alone travel to them, it’s up to you to decide whether this theory has a basis in science or whether it is just a tool of science fiction authors to create more interesting settings for their stories.
There are a few constants throughout all of human history. People enjoy games, people enjoy learning about the past, and people will do basically anything, no matter how seemingly nonsensical, just to prove that it can be done.
In 1972, the game Pong was released. It was a simulation of ping pong, and it looked terrible. Its mere existence was impressive enough for the time, but it was hardly a complex or visually stunning game. Now take a look at how far games have come in only 50 years. Graphics are far more realistic. Characters and items are rendered as 3D objects rather than just a 2D collection of oversized pixels. And instead of just a single screen with a couple moving parts, computers can render a massive, 3D landscape.
Sure, your average game still utilizes transitions and loading zones to avoid needing to render an entire planet all at once, but for a time span of only 50 years the improvement is incredible. Now let’s assume that technology continues to progress in such a fashion. How advanced will our technology be in another 50 years, or perhaps in 500 years?
The actual time frame is unimportant. What matters is that, eventually, technology will reach a point where it is possible to run a simulation of an entire planet, referred to as an ancestor simulation. The practical benefits or other rationale behind creating such a simulation are irrelevant, because once it is technologically possible somebody will do it just to say they did; humans have been operating that way for thousands of years so there’s no reason to suspect all of human nature would change.
The ancestor simulation itself would be exactly like the real world. It would simulate every plant, animal, bacteria, and rock perfectly. Each person within the simulation would have a form of digital consciousness, essentially believing that they are human. The simulation is then left to run its course.
As the simulated civilization plays through the course of history, they invent video games and simulations, which become increasingly more advanced. Eventually, they too reach the point where they are capable of creating an ancestor simulation. This loop can take place an infinite number of times, with simulations inside of simulations inside of simulations. With a potentially infinite number of nested simulations, the probability that we are living in base reality rather than in a simulation is essentially zero.
There’s no way to prove any of this, of course. If we are living in a simulation, then by design it would be indistinguishable from base reality. We would also have no way to interact with or prove the existence of a higher reality, be it base reality or another simulation, so there’s no way to test this theory. Fortunately, it doesn’t really matter. If everything is a simulation but there’s no way to tell the difference, it has no actual impact on our lives.
Albert Einstein is one of the most prominent scientific minds of the modern era, to the point that he was even named Time Magazine’s Man of the Century. Einstein is the man behind the theories of both special and general relativity, and his work remains as important today as it was during his lifetime. He also had some issues with quantum mechanics.
Einstein is often reported to have hated the idea of quantum mechanics, which is a bit of a misrepresentation of things. His famous quote that “[God] does not play dice with the universe” was not meant to say that quantum mechanics was all made up nonsense, just that it was incomplete. He believed in a completely deterministic universe, and the probabilistic outcomes of quantum mechanics do not fit into that view. He did think that quantum mechanics was a good start, but he could not condone notions like quantum entanglement, something he referred to as “spooky action at a distance.” Experiments have repeatedly shown that Einstein was wrong about this and that quantum entanglement is real, but that doesn’t suddenly make everything Einstein said incorrect.
Relativity is still an important part of physics, but it is complicated by the fact that relativity and quantum mechanics don’t seem to be able to coexist, at least not with our current understanding of things. Relativity is great for describing the universe on a large scale, and quantum mechanics does a good job of explaining it on the smallest scales possible. However, the principles of the two theories aren’t compatible with one another. There are many theories to try to reconcile relativity with quantum mechanics, the most famous of which is string theory.
Sting theory, also referred to as a “theory of everything”, is far too complex to adequately explain in this post. It’s so complicated that doing string theory math requires ten dimensions, rather than the normal three dimensions for space plus the time dimension. The simplest explanation is that string theory proposes all particles in the universe are made up of one-dimensional vibrating strings rather than individual points. The strings are indistinguishable from an ordinary particle when viewed on a larger scale.
In theory, string theory should be testable, but theory and practice can vary greatly. Thus far, we have not found a way to test string theory. The theory has yet to produce any sufficiently testable predictions, and we don’t know how to change that. One of the main issues is that these one dimensional strings would be the absolute smallest things in the universe, which would make them incredible difficult to observe or measure.
Though many scientists remain hopeful that string theory could be confirmed, the outlook isn’t great. Perhaps with a hadron collider large enough and powerful enough some evidence of string theory could be found, but we aren’t even close.
The End of the Universe
There are certain hurdles that can make a hypothesis impossible to test. In the case of string theory, the scale is too small to the point of being undetectable. With the section of multiverse theory pertaining to other universes within our same universe, the scale is too big. Should these objects exist, they are too far away to ever be observed. As for the ultimate fate of the universe, the problem is that the scale is too long. Well, that’s one problem; the other problem is that even if happened tomorrow, we’d all be dead so it would be too late to test anything.
Numerous theories exist about the end of the universe, such as the Big Bounce, Big Rip, and Big Freeze. If the universe was birthed from the Big Bang, then obviously whatever ends it has to have the word “big” in its name as well.
Which theory is the most highly regarded changes over time, but currently the most popular theory for the death of the universe is the Big Freeze, also referred to as the heat death of the universe. By its very nature, the universe favors entropy, which is to say disorder. The second law of thermodynamics states that all closed systems tend to maximize entropy, so what happens when that is no longer possible?
It is suggested that the universe will reach a state where there is no longer any thermodynamic free energy and as such it will no longer be able to sustain any processes that increase entropy; in this state, the universe will have achieved thermodynamic equilibrium. What this all essentially means is that the universe wants to maximize entropy, and eventually it will.
Once this occurs, the entire universe will potentially approach absolute zero. It’s slightly more complicated depending on the topology of the universe and whether or not dark energy is real, but it is expected to either reach absolute zero or very close to it. In either situation, the universe would be done for.
The end of the universe is an existentially terrifying proposition, but when exactly is the Big Freeze supposed to occur? Current estimates say that we are a mere 1.7 × 10^106 years. That is 1.7 googol years times a million, and it is many, many orders of magnitude longer than the current age of the universe.
Regardless of which theory for the end of the universe we want to subscribe to, they all use similarly impossible seeming lengths of time. This means there will never be any way to test which is true. That’s probably for the best anyway. There are enough problems here on Earth; the last thing we need is to definitively prove how the universe will end, only to waste time and energy trying to prevent something that won’t happen until long after humanity has ceased to exist.