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Beyond the Boundaries of Science

The theological ramifications of aliens, time travel, and alternate universes

Jimmy Akin

Could there be intelligent aliens? Is time travel possible? What about parallel worlds with alternate versions of you and me?

These questions are interesting to ponder, and not just for science fiction writers. Scientists today take each of them seriously. And since they’re points where faith and science interact, Catholics have considered what their religious implications would be.

There’s a lot of room for discussion, because the Church doesn’t have official teachings in these areas. You may be a skeptic and think such things are unlikely or impossible, and you may be right!

Yet God’s mystery is infinite, and it’s reflected in aspects of his creation. In recent centuries, we’ve discovered creation is much bigger, stranger, and more complex than our ancestors imagined, and thus it reflects God’s mystery in even more ways.

That means it’s worth asking what would happen if our descendants discover creation is so big and strange it includes things currently found only in science fiction.

Let’s take a look at aliens, time travel, and parallel worlds and ask what’s possible and what the religious implications would be.

Alien life: what’s possible?

God is omnipotent, so he has the power to do anything that doesn’t involve a logical contradiction, such as making a four-sided triangle (Aquinas, Summa Theologiae I:7:2 ad 1, I:25:4).

Creating life doesn’t involve a logical contradiction, so God could create it any place he chooses, including on other planets.

We can even speculate about how common it might be and what forms it might take. It’s reasonable to suppose most life in our universe would have the same chemistry we find on Earth, using elements like carbon, hydrogen, and oxygen (i.e., “organic” life). These elements are common in the universe, and we see organic compounds all over the solar system.

Some have proposed life based on other elements, like silicon—this was the idea behind the Horta in the Star Trek episode “Devil in the Dark”—but there are problems that make these chemistries unlikely.

The most likely extraterrestrial life would be simple, single-celled organisms. These represent the vast majority of living things on Earth. They are at the bottom of the food chain that supports more complex life.

Because they’re simple, such creatures likely would be the first life to develop on a planet. On Earth—which appears to be 4.5 billion years old—single-celled organisms show up in the fossil record around 4 billion years ago, but complex life didn’t emerge until around 1 billion years ago, and intelligent life only emerged around 100,000 years ago (or less).

Given that, there might be lots of “germ worlds” with only single-cellular life, a few “animal and plant” worlds, and very few “intelligent life” worlds.

A huge discovery!

We seem to be the only intelligent life in our solar system, but one day we might find simpler creatures. Organic life could exist on Mars or in the oceans of moons in the outer solar system.

Upon finding it, we’d need to ask whether it came from Earth. Certain tiny organisms—called extremophiles—can survive very harsh conditions and could have come from Earth. They might have been blown by the solar wind from our upper atmosphere, hidden in rocks knocked off Earth’s surface that became meteorites, or been carried by space probes we’ve sent.

We’d need to see if newly discovered life matched any Earth species and genetics. If it didn’t, we’d know God had allowed life to develop elsewhere, which would be a huge discovery—equal to the realization Earth isn’t the center of the universe. Fortunately, we’d be better prepared for the discovery, since we’ve had time to get use to the idea of alien life.

If we found non-intelligent life, we’d have a moral question: What do we do with it?

Some have proposed we should quarantine any world we discover to have life, only do minimal research, and leave the life to develop on its own. That’s a reasonable position, but it’s not the only one. It also seems reasonable to treat such life the way we do non-intelligent creatures here on Earth.

Either way, such a discovery would focus theological attention on the mandate we’re given to “fill the earth [literally, “land”] and subdue it” (Gen. 1:28). Does that limit us to planet Earth or give us broader scope?

If we meet intelligent life, there would be many new questions. Setting aside practical ones such as, “Do the aliens want to eat us, and, if so, how can we stop them?” there would be many religious issues, such as, “Do they have immortal souls?”

Christian theology commonly holds all living creatures have souls, since “the body apart from the spirit is dead” (James 2:26). But it’s often thought that only rational souls survive death.

Alien afterlife? Revelation? Redemption?

If we met aliens with human-level intelligence, the safe assumption would be they’ve got rational souls and thus an afterlife. This would be strongly reinforced if they have the concept of an afterlife.

Would their afterlife work the way ours does, with bodily resurrection? Since they’re embodied, spiritual creatures, that would be a good bet, but it’s ultimately God’s choice.

Learning God’s choices about aliens raises the question of what he’s revealed to them. He may have given their race revelation comparable to what he gave ours—or not.

This would be a tricky issue to sort out. The aliens might have many different religions, just as we do on Earth. Even if they only had one, the Magisterium would want theological experts to have extensive dialogue with them, and it would proceed slowly and cautiously in making any determinations.

Ultimately, anything contrary to Christian faith would be judged false, but we’d have to proceed in the knowledge God may deal with them differently than he deals with us, just as he deals with angels in a different fashion (2 Pet. 2:4).

Would we need to share the gospel with aliens? It certainly would be legitimate to tell them what God has done with our race, but there would be a big question about how they should respond to the gospel.

They might be unfallen—like the race in C. S. Lewis’s novel Perelandra—and thus not need redemption.

Or they might be irredeemable, like fallen angels (2 Pet. 2:4, Jude 6), though the Catechism indicates the reason angels aren’t forgiven isn’t because of a limitation of God’s mercy but because they’ve made an irrevocable choice (CCC 393). Intelligent aliens, as changeable, physical beings like us, likely would be able to repent in this life.

God may have made separate provisions for their forgiveness. Aquinas indicates that, in his omnipotence, God could’ve chosen to redeem us another way, without the Passion of Christ (ST III:46:2), and he might have done so for them.

He also might have even chosen to parallel the means he used here. Becoming incarnate doesn’t involve a logical contradiction, so he could choose to incarnate elsewhere.

This concept has been explored in science fiction. At the end of the Star Trek episode “Bread and Circuses,” the Enterprise crew realizes the “sun worshippers” they’ve learned about on an alien planet are actually “Son worshippers,” indicating a parallel incarnation of Jesus.

Alien Catholics?

Suppose the aliens want to be forgiven and ask to be baptized. What should we do?

The Magisterium would proceed with caution, but it’s really hard to say no to someone who wants to become a Christian. The likely presumption would be that if people want to be saved through Christ and his infinite sacrifice, then they can be. Even if they’re aliens.

The Church might initially use conditional formulas like, “If you are capable of receiving baptism, I baptize you in the name of the Father and of the Son and of the Holy Spirit,” but with time the initial scruples likely would fall away.

In a fashion, we’d be watching a replay of Peter’s question about the first Gentile converts: “Can anyone forbid water for baptizing these people?” (Acts 10:47). And we’d likely see the same answer: “Then to the [aliens] also God has granted repentance unto life” (Acts 11:18). Still, we might need a Church council to finally settle the matter (Acts 15).

If their race is very different from ours, there could be added complications. Suppose their method of reproduction works differently than ours, so they have no analog to matrimony and can’t participate in it as a sacrament. Orson Scott Card explored this idea for Catholic aliens in his novels Speaker for the Dead and Xenocide.

Time travel: what’s possible?

In one sense, time travel is unavoidable: All of us are moving into the future.

The only question is how fast we do so. Einsteinian physics has revealed it’s possible to do so at different rates, based on local gravity and velocity. If you travel faster, time passes at a slower rate for you, so when you decelerate, more time has passed for the rest of the world.

This even happens—and has been measured—for airplane travelers. We thus know it’s possible in principle to build a spaceship that travels so fast that when it comes back to Earth, hundreds of years will have passed, even though the crew experienced only a few years in flight.

What we don’t know is whether it’s possible to travel into the past. Some hold it’s impossible because only the present exists. If there’s no past, you can’t travel to it.

However, this view isn’t shared by most physicists, who regard time as another dimension, like the three dimensions of space. It’s possible to move forward or backward in space, and it might be possible to move forward or backward in time.

Einstein’s equations allow solutions where travel to the past is possible. One of the first was discovered by mathematician Kurt Gödel. For a simple discussion of ways travel to the past might be possible, see physicist Michio Kaku’s book The Physics of the Impossible.

Time travel and morality

If you traveled to another time, what would the religious implications be? The chief issue might concern what you are and aren’t allowed to do.

If you went to the future—by a spaceship traveling at relativistic speeds or through some other means—the ordinary rules of morality would apply to you. You wouldn’t need to do anything special, like trying not to affect the course of events.

After all, we’re constantly moving forward in time, and we always need to do good and make the world a better place. If you somehow went farther into the future than normal, that wouldn’t change: You’d still need to do whatever good you could in the new time period.

But what about traveling into the past? The rules of morality would still apply, but there’d be a complication involving whether it’s possible to change history.

Changing history?

Aquinas argued it’s not possible to change the past. In fact, he argued not even God could change it because doing so would involve a logical contradiction (ST I:25:4). If Socrates was sitting at a certain moment in history, then that represents a truth. If God changed history so Socrates didn’t sit, the truth that he did sit would be false, which is a contradiction.

Modern physicists don’t argue this way, but some have made a “chronology protection conjecture” that would either prevent time travel or at least prevent history from being changed.

If you found yourself in the past and it turned out history can’t be changed, then any good you do in the past would have always been part of history. You just didn’t know about it before.

However, if you know history can’t be changed, you shouldn’t try to change it. For example, you shouldn’t try to stop the assassination of John F. Kennedy because something will prevent you, and you may as well not bother.

But if it turns out history can be changed, you’ll face a new problem.

New timelines

Physicists have generally argued that, if you did change an event in history, it would create a new timeline where events begin to diverge from what happened in our world. This is a possibility Aquinas didn’t envision. If Socrates sat down at a particular moment, then that moment is frozen and unalterable in that timeline. But it wouldn’t stop God from branching off a new timeline where Socrates didn’t sit.

This creates a new conundrum for the time traveler: If you change a historical event, you’re now journeying on a new timeline and you may not be able to get back.

If you’ve got a guaranteed “return to my own timeline” button, great. But if not, you’ve got a practical reason not to change things because of what you may find when you return to your “own” time. That possibility is explored in Ray Bradbury’s famous short story “A Sound of Thunder,” in which a man steps on a butterfly in the past and returns to a different world.

What’s more, your practical reason not to change things could be trumped by the moral obligation to do so. You could find yourself in a situation where you’re morally required to do something, yet it would guarantee that you never get back to your home.

If it is possible to “change” history by creating a new timeline, that would effectively create a parallel world, which brings us to our next subject.

Parallel worlds: what’s possible?

In a sense, we already know of parallel worlds. We found the first ones when we realized the planets or “wandering stars” (Greek, asteres planêtai) are other worlds, parallel to our own.

These worlds are part of the physical universe, but Christian faith recognizes non-physical realms as well, such as the heaven where the angels dwell. There may be multiple heavens. St. Paul mentions being caught up to “the third heaven” (2 Cor. 12:2), and early Jewish and Christian sources mention others.

Could there be worlds so similar to ours they contain parallel versions of Earth or even of us as individuals? This might seem unlikely, but there’s no logical contradiction in the idea, so God can create as many copies or near-copies of Earth as he chooses.

  • Particularly if the physical universe is big enough, it hypothetically could contain worlds like the Roman Earth the Star Trek starship Enterprise visited in “Bread and Circuses” or the plague-ridden Earth it visited in “Miri.”
  • If there are more dimensions than we’re presently aware of, parallel Earths might be located in them, perhaps a few inches above or below ours.
  • If it’s possible to change history, then every time someone makes a choice might create a new timeline and thus a parallel world.

Whatever we may personally think of these possibilities, they’re taken seriously by scientists. For a simple discussion of current thought, see Michio Kaku’s book Parallel Worlds.

Implications of parallel worlds

What implications would there be if we found a parallel Earth?

If it was very different—say, one where the dinosaurs never died and there are intelligent lizard people—it would be like meeting intelligent aliens, and many of the same issues would arise.

If it was closer to our Earth—say, the Roman world of “Bread and Circuses”—the ordinary principles of morality would apply. Morally speaking, you wouldn’t have any special non-interference obligation, though one might be imposed by civil law.

If we found an extremely similar Earth—with people who look like you and others you know—the important thing to remember would be that the alternate version of you is not you, just someone similar to you. The same is true of other alternates. For example, your alternate “spouse” is not your spouse, and you have to act accordingly. If you’re married back on our Earth, you have to be faithful to the person you’re actually married to.

A mind-blowing possibility

The situation is trickier if branching timelines exist. Suppose you go to a crucial moment in your past and talk yourself out of making a mistake, such as a mortal sin. This produces a new timeline and thus a new world.

Let’s suppose that, in the new timeline, the new version of you dies just after making the decision not to commit mortal sin. This version thus remained in a state of grace and went to heaven.

But you—the original you who did commit the mortal sin—are now a separate person with your own moral destiny. For you, going to hell is still a real possibility.

If this situation turned out to be possible, it would lead to a startling religious conclusion: it would seem our souls, like our bodies, could branch off in parallel timelines and have independent fates.

That would be a challenging idea! However, it—like the existence of aliens or time travel—would reveal a new aspect of the mystery of creation, and thus of the mystery of the Creator.

Sidebar: What Are the Odds?

The vast number of stars that exist might result in a huge number of civilizations.

In 1961, astronomer Frank Drake proposed the famous “Drake equation” as a way of guess-timating the number of technological civilizations in the Milky Way. He thought there might be between 1,000 and 100 million.

Others have plugged different numbers into the equation, with very different results. Some have suggested we may be alone in the galaxy.

Earlier, in 1950, physicist Enrico Fermi had challenged the idea there are many technological civilizations by asking a simple question: “Where are they?” If there are many, some should have had millions of years to colonize the galaxy, and we should have clear evidence of them.

The fact we don’t is known as the “Fermi Paradox,” and there are many solutions, including: (1) we’re alone, (2) the aliens are hiding and deliberately not making contact, and (3) UFOs are alien spaceships.

Until we find hard evidence of alien life—intelligent or otherwise—all this remains speculation. But suppose one day we find life.


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