The idea of a multiverse is based on three key assertions:
(1) there are an infinite number of universes;
(2) everything that could possibly happen, does happen, in some universe;
(3) within the multiverse, there must be many (or infinite) universes very similar to our own, many (or infinite) versions of earth, and many (or infinite) versions of each person on earth;
This set of ideas makes for good fictional stories, in movies and television series, in which there are multiple versions of each character among the many or infinite number of earths in the multiverse. But the idea is faulty, unscientific, and essentially unprovable.
1. Are there an infinite number of universes?
No evidence has been presented to support the claim that infinite universes exist. This claim is unproven conjecture that cannot possibly have any proof, and so it is not science. What would constitute proof, even hypothetically, that an infinite number of universes exist? It is not possible to visit infinite place, nor obtain an infinite number of samples of evidence, and we are not even able to visit places in other galaxies in this universe. Yet the idea is sometimes presented as if it were a legitimate theory, rather than an unprovable conjecture.
A related hypothesis is that some of these other universes may “bump” into our universe, and this bump might cause some effect in our universe that could be detected. No such effect has been found. And how would any proposed effect be proven to be from no possible cause within our universe? Then even if we grant as a premise that a bump occurred, this would not prove an infinite number of other universes. It would not even prove that other universes are many.
But we should also notice that this claim that one universe can effect another, by bumping into it, makes it seem that the other “universe” is simply part of this universe. And in no way, in any case, does such a bump provide any evidence that the other universe is a different version of this universe, with a different version of this earth. These proposed, not yet detected, bumps could not possibly contain enough information to determine the whether any such universe is just a different version of our own, which is the main premise of the multiverse.
Also, there would be no basis, if, hypothetically, other universes were detected, for scientists to conclude that an infinite number must exist. If ten million other universes were detected, that is not an infinite number. There exists not even a single proposed hypothetical proof for determining if an infinite number of universes or earths exist. And we know of no other universe but our own.
The visible universe is currently believed to be about 46 billion light years in radius, extending from earth in every direction. But what scientists see with advanced telescopes (like Hubble and the new James Web Space Telescope) is actually in the distant past. They cannot see what the “visible universe” looks like billions of light years away in the present. How large our universe may be is not clear at all, as scientists cannot determine what might be beyond the visible universe. So it is mere speculation to claim that other universes exist, when we do not even know the size or extent of this universe.
Now there may be very many galaxies beyond our visible universe, but that is not another universe. The existence of a vast number of other galaxies, even in addition to the number visible from earth, does not imply or suggest that there must exist different versions of earth, meaning earths that are very similar in civilization, history, and individual human persons. No matter how many earth-like habitable planets our universe may have, that is not a multiverse.
Some have speculated that a different universe might have entirely different principles of physics. But then a different physics in a different universe, an idea that is sometimes discussed, could not have a similar earth, with a similar civilization, history, and persons. The multiverse is not merely the claim that over universes exist, but that many very similar universes exist, that are closely related to our own universe, mainly in the things that are of interest to this society, in this civilization, on this planet — and generally ignoring the effects of such a multiverse on the entire rest of this galaxy and universe. It is a rather self-centered theory.
Fictional works in this vein often propose travel to other earths in the multiverse. Within these types of shows, this is presented as proof of the multiverse. If scientists could travel to even one other version of earth — with the same human civilization, society, and very similar individual human persons — this would seem like a confirmation of the theory. But in fact it would not confirm infinite universes, other similar earths, nor any particular principle for how such a similar earth could exist.
But if there were actually an infinite number of universes, with an infinite number of universes with a version of earth, then opening a “portal” to another universe would also find an infinite number of universes without an earth. There would even be, accepting the other claims of this theory at face value, an infinite number of universes, within the overall infinite set, which have no life at all in them. The infinite series of positive integers (1, 2, 3, ….) contains within it the infinite set of even numbered positive integers and the entirely separate set of odd numbered positive integers. So any attempt to prove the multiverse by finding another version of earth, supposing one exists, would face the problem of an infinite number of universes lacking an earth, if the hypothesis were true.
But why would this alleged principle, that infinity includes everything, only include everything interesting? It would not. So the odds of finding another earth containing variations on our civilization, history, and human population, would be essentially zero. This rules out travel to another version of earth as a proof. You would be figuratively rolling a dice with an infinite number of sides. In that case, you’ll never roll a seven.
Another problem with the idea of somehow traveling to another version of earth in another universe is the movement of the earth through the universe. The earth spins, and also revolves around the sun. The sun is moving, with the whole solar system, through the Milky Way, revolving around the central supermassive black hole, and that revolution has an elliptical and also a wavy (up and down, relative to the plane of the ellipse) motion as well. Then the Milky Way is moving through the universe toward a location known as the Great Attractor. This gives the earth a wildly complex path of motion relative to the rest of the universe. To travel from one version of earth to another in a different universe would have to take account of such a complex motion, on both earths, requiring opening a portal to the exact right place and time, and keeping the two portals aligned. But the theory of the multiverse is essentially just fiction, so it is merely proposed that there is some way to overcome all these problems.
The same problem occurs with the idea of time travel. If you travel back in time within the same earth, it is in a different place in the galaxy and universe. So you have a similar problem of getting the exact location correct. This makes time travel, if hypothetically possible, rather useless as you would just end up in space somewhere, not on earth in the past or future. But fiction ignores all these problems, and so does the multiverse theory, which is essentially just fiction.
When all these points are considered, it seems there is not even a hypothetical way to prove that infinite universes exist.
Physicist Sabine Hossenfelder opines that the multiverse is religion, not science. Her position is that “science does not tell us anything about universes we cannot observe, therefore claiming they exist is not science.” She does not assert that other universes do not or cannot exist, but only that we have no evidence of other universes. Therefore, she says, the multiverse is a belief, not a scientific theory. Belief in the multiverse is similar to belief in a religion. Science does not prove or disprove religion, as religion is not science. You can believe if you want to, but don’t call it science. See Sabine’s most recent video on this topic here.
2. Does the idea of infinite universes imply that everything that could possibly happen, does happen, in some universe? Not at all. That is not what the concept of infinite means.
This second point is simply a misunderstanding of the word “infinite”. The term infinite does not mean every possibility. For example, the series of even positive integers (2, 4, 6, 8, etc.) is an infinite series. Yet it contains no odd numbers, no number zero, no negative numbers, no irrational numbers, no fractions, and no decimals. Then there are multiple sets of infinite numbers which do not intersect with the set of even positive integers: odd positive integers; decimals beginning with 1 (e.g. 1.1; 1.2; 1.3…1.12, etc.); decimals beginning with 2, etc.; negative even numbers; negative odd numbers; the digits in pi; the digits in other irrational numbers; etc. Therefore an infinite set, such as a proposed infinite set of universes, does not include every possible universe, nor every possible earth, nor every possible version of any person.
So the claim that infinite universes must include every possible version of earth and of each person on earth is patently absurd. The unproven premise that infinite universes exist in no way implies or suggests any such correlation between other universes and this universe, with its particular version of earth, civilization, history, and the individuals in our population. Suppose that every universe, for no apparent reason, has the same solar system and the same planet earth, and the beginnings of a human race as well. There would be an infinite number of versions of each of those earths that never produces a single person who is essentially the same as a person on this earth. The number of ways that history could unfold, so that there would be no one at all like you on any of those earths is infinite, making the odds of a similar population, extreme, and the possibility of an earth with a version of every person on this earth absurd. Any little difference in history would result in great differences generations later. And there is no principle that guides these other hypothetical earths along a path to reach this particular point in civilization and history, with a version of each of us on both earths. Infinity does not imply such a correlation, and instead the infinite number of other possibilities, nothing like this civilization and history and population makes such a correlation unlikely in the most extreme sense of the word. So claiming that infinity causes such a correlation is not based in reason or science.
Therefore, even if there were infinite universes, there might be no other universe with a planet closely resembling earth, on which evolved a human species, which then developed a civilization much like ours, with much the same history, and much the same population. Infinity does not imply that everything which could possibly happen, does happen! That assumption is a fundamental logical error, that many smart scientists overlook, perhaps because they have been influenced by the popularity of the idea of a multiverse. Science does not take place in a social vacuum. Scientists are people who are influenced by the society in which they live. That is why science sometimes goes astray from theories supported by evidence, into popular conjectures. They are influenced by the popularity of an idea.
3. Does quantum mechanics imply the existence of different versions of our universe?
Perhaps someone will reply that maybe the multiverse does include every possibility, not as a consequence of infinite universes, but rather as a result of the way that quantum mechanics works. This is the “many worlds” interpretation of the multiverse. In this interpretation, every time there is an event with more than one possible outcome, the universe branches into two versions, one with each outcome. This would seem to imply that this other universe, created by the mere possibility of a different possible outcome for the smallest of events, is entirely the same except for that one difference. This implies that a second universe somehow began, unfolded for 13.8 billion years in exactly the same way, particle for particle, until that single branching event.
And what happens next? I don’t know of any version of this theory that even answers the question. Do the two universes, which now differ only in that one event with two possible outcomes, continue to be otherwise the same? Or do they suddenly lose this uncanny correlation? And where does the energy and matter come from to create a second version of the universe that is the same except for that one outcome?
This version of the multiverse is even less reasonable than the “infinity includes everything” claim. For it implies that every one of the the smallest of events, at the level considered in quantum mechanics (usually individual particles/waves), and at every moment throughout our exceedingly vast universe for billions of years, that each of these smallest events causes the creation of an entirely new version of that vast universe (with all the stars, planets, black holes, neutron stars, etc.) just to give every possibility its own universe. Why would this happen? The theory of quantum mechanics implies no such thing. To even construct such a theory, in a legitimate version (rather than the mere conjecture and fantasy version that we are presented), there would need to be at least a proposed mechanism for such a vast effect from the most minor of causes. There is not one. This is mere conjecture, which cannot answer any of the questions that the theory necessarily provokes.
Now how many such events, which would cause this branching, occur in any given second? Are these “branching events” only caused by the decisions of human persons? No, for quantum mechanics does not depend upon the decisions of people — which some scientists consider to be not due to free will. So a vast number of such events, that supposedly each create a new universe, occur throughout the galaxy and in every galaxy in our universe, and between galaxies as well. The implication is that new universes are being created in vast numbers every second of every day, and have been for the last nearly 13.8 billion years. And that is contrary to reason, contrary to science, and absolutely unsupported and unproven. It is absurd to propose an entire new universe for each trivial difference in possibilities, with no observations or evidence to support such a conjecture. Nothing in quantum mechanics even suggests that every possible outcome has its own universe.
4. Conflicts between the multiverse and Christian teaching
In the 1920’s, scientists believed that the universe was infinite and that it always existed. Such beliefs were contrary to the teachings of Christianity, especially Catholicism, which teach that God created the universe, before where nothing existed but God. And this understanding of Creation has always been finite, not infinite like God.
Then, in the early 1930’s, Jesuit priest and scientist George Lemaitre proposed the big bang theory, in which the universe had a beginning in time and place, and would therefore not be infinite, and would not have always existed. The theory was adopted rather quickly, and became the prevalent view for many years. (However, today many scientists are considering other possibilities.) This theory by Lemaitre is compatible with Catholic teaching, as it could be merely the means that God used to create the universe.
How does the multiverse compare to Christian teaching? It is entirely incompatible with Christian and Catholic Christian teaching.
A. If every possibility exists, then there is no morality. For each act of a human person, said to be a choice of free will subject to moral evaluation, would merely be a requirement that every possible outcome occur. Free will does not exist in the many worlds interpretation of the multiverse, as every possible decision occurs. In one universe you consider robbing a bank and do not do so, and in another universe, you do rob the bank. This removes, seemingly, the culpability — if it were actually true that events fulfill every possibility, rather than there being a real choice of free will. With free will and moral choice, you choose to do good and not evil, so that said evil never exists. A universe where every possibility exists has every possible evil, and would not be created by a good God. Allowing created persons free will is a good gift with many good possible ends. But creating a universe in which every possible evil exists, for no reason than to fulfill a principle that every outcome must occur, is not a good thing, and not something a good God would do.
B. Salvation is problematic if there are infinite versions of each human person, who differ from one another in every possible way. Instead of each person being held accountable before God for their lives, a multiverse with every possibility sends an infinite number of persons just like you to Hell, and another infinite number of persons just like you to Heaven. How can two infinite sets be derived from one infinite set? The set of positive whole numbers is infinite (1, 2, 3, 4, …) contains the infinite set of positive whole odd numbers and the other infinite set of positive whole even numbers.
C. To have a civilization, society, and population that is closely correlated to our own, there would need to be a Christianity in every version of earth. And this would require a Christ in every version, an infinite number of earths supposedly so much like our own. For without Christianity, dear scientists!, society would be vastly different, and civilization might never have progressed to this point. Yet Christ did not become incarnate an infinite number of times on infinite similar earths, as His salvific death on the Cross is once for all, not an infinite number of times for each set of persons on each version of earth.
Then, in Christianity, each human person is a unique creation by God. The soul is directly created by God, and each unique person is known and loved by God. But in the godless multiverse hypothesis, there are an infinite number of each person, fulfilling an infinite set of possibilities, with no regard for free will, love, or the plan of God. And how can God have a plan, if His Creation merely fulfills every possibility, rather than being guided by God to fulfill His divine plan?
So the multiverse theory is incompatible with Christianity, and, if you ask me, also incompatible with reason and science.
Ronald L. Conte Jr.