Maybe We Are Not Alone.
Maybe We Just Missed Each Other.
For thousands of years, humans have looked into the night sky and wondered the same thing.
Are we alone?
It is one of the oldest questions we ask, and recently it has returned to public discussion.
Government hearings, released reports, military observations, and discussions about Unidentified Anomalous Phenomena (UAPs) have renewed interest in the possibility that something unusual may be happening in our skies.
Some observations remain unexplained.
That is interesting.
But unexplained does not automatically mean extraterrestrial.
A statement that “we do not know what something is” is very different from saying “it came from another civilization.”
The bigger question may not be whether there are things we cannot explain.
The bigger question may be whether another civilization could realistically find us—or whether we could find them.
A recent article by astrophysicist Ethan Siegel caused me to look at the issue from a different perspective. Most discussions focus on distance. Siegel suggested we may be overlooking another obstacle entirely.
Time.
The Aliens We Imagined
For many of us, our expectations about alien contact were shaped more by science fiction than science.
Steven Spielberg gave us two of the most memorable examples.
In Close Encounters of the Third Kind, mysterious visitors arrive on Earth and humanity struggles to understand them.
In E.T., an alien visitor is stranded here and simply wants to return home.
Both are wonderful stories.
Both begin after the hardest problems have already been solved.
The aliens are already here.
They crossed the enormous distances between stars.
They found Earth.
They arrived during the brief period when humans were technologically advanced enough to recognize them.
Science fiction allows us to begin at the interesting part of the story.
Reality requires us to start much earlier.
How did they get here?
Why now?
And why us?
Star Trek Solved the Distance Problem
I have written previously about how many Star Trek technologies turned out to be closer than we once imagined.
Communicators became smartphones.
Voice-controlled computers became AI assistants.
Automatic translators are rapidly improving.
Many ideas once considered fantasy became ordinary within a single lifetime.
But Star Trek depended on one invention that has stubbornly resisted reality.
Warp drive.
Without faster-than-light travel there is no Enterprise visiting a new star system every week.
Other science fiction stories solve the problem differently.
They use:
- wormholes
- hyperspace
- jump drives
- exotic propulsion systems
The details change, but the purpose remains the same.
The story needs a way around distance.
Physics has not yet provided one.
Distance Is Only the First Problem
The nearest star system, Alpha Centauri, is more than four light years away.
That sounds manageable until we remember what a light year means.
Light travels at approximately 186,000 miles per second.
Even light requires more than four years to make the trip.
The fastest human-made object ever launched travels at less than seven miles per second.
At that speed, reaching Alpha Centauri would take tens of thousands of years.
Even if future technology increased our speed by a factor of ten or twenty, the journey would still be measured in centuries or millennia.
That is not transportation.
That is civilization-scale planning.
And propulsion is only the beginning.
Humans Were Not Designed for Interstellar Travel
Suppose we somehow solved the propulsion problem.
The next challenge is keeping people alive.
A journey lasting decades, centuries, or longer creates problems unlike anything humans have ever attempted.
Outside Earth’s protective magnetic field, travelers would face continuous radiation exposure.
Extended weightlessness causes muscle loss, bone deterioration, and other physiological changes.
Food, water, air, and medical care must be provided without outside assistance.
Equipment failures cannot be solved by calling for help.
A spacecraft traveling between stars is not really a vehicle.
It is a tiny self-contained world.
The crew must survive.
The systems must survive.
Perhaps even multiple generations must survive.
Exploration across oceans was difficult.
Exploration between stars is something else entirely.
Maybe Robots Make More Sense
At this point, some readers may be thinking that robots are a better solution.
They may be right.
Robots do not require food.
They do not need oxygen.
They do not suffer from boredom or isolation.
A robotic probe could potentially travel much longer than a human crew.
But even that raises interesting questions.
If a robotic explorer requires 10,000 or 20,000 years to reach its destination, what happens if the civilization that launched it no longer exists?
What happens if the destination civilization no longer exists?
Even robots cannot escape the problem of time.
But There Is Good News
None of this means we are alone.
In fact, modern astronomy is steadily making that possibility less likely.
Only a few decades ago, we did not know whether planets around other stars were common.
Today we know they are everywhere.
Thousands of exoplanets have been confirmed.
Scientists estimate there may be billions of planets in our galaxy alone.
The James Webb Space Telescope and future observatories are beginning to analyze planetary atmospheres, looking for possible signs of life.
Researchers continue to search for both biosignatures and technosignatures—evidence that life or technology may exist elsewhere.
The search is already underway.
Importantly, finding evidence of life and meeting another civilization are very different goals.
We may discover life elsewhere long before we ever communicate with it.
The Drake Equation
Scientists have been thinking seriously about these questions for decades.
In 1961, astronomer Frank Drake developed what became known as the Drake Equation.
The equation was never intended to provide a final answer.
Instead, it organized the uncertainties.
- How many stars exist?
- How many have planets?
- How many planets can support life?
- How often does life become intelligent?
- How often does intelligence develop technology?
Most discussions focus on these questions.
But there is one final factor.
How long does a technological civilization survive?
That may be the most important question of all.
The Problem of Time
This is where Ethan Siegel’s argument becomes fascinating.
We spend enormous amounts of time discussing distance.
Perhaps we should spend more time discussing timing.
The universe is approximately 13.8 billion years old.
Earth is about 4.5 billion years old.
Modern humans have existed for perhaps 300,000 years.
Agriculture appeared roughly 10,000 years ago.
Radio communication has existed for a little over a century.
Spaceflight has existed for less than one human lifetime.
On a cosmic timescale, our technological civilization appeared moments ago.
Now imagine another civilization.
Perhaps it reached our level of development one million years ago.
Perhaps it reached that level ten million years ago.
Perhaps another civilization will not emerge until ten million years from now.
All three civilizations could be real.
All three could be intelligent.
All three could look into the night sky and wonder if they are alone.
Yet none would ever meet.
They simply missed one another.
The Cosmic Appointment Problem
Finding another civilization requires a remarkable alignment of circumstances.
- They must exist.
- They must become intelligent.
- They must develop technology.
- They must survive.
- They must be close enough.
- They must communicate in ways we can recognize.
- And they must do all of this while we are looking.
Imagine trying to schedule a meeting when nobody knows the location, nobody knows the date, and nobody even knows whether the other party is still alive.
That is the challenge facing interstellar civilizations.
The universe may contain many intelligent species.
The overlap window may be surprisingly small.
Maybe We Are Asking the Wrong Question
For decades we have asked:
“Where are they?”
It is a reasonable question.
But perhaps there is another one.
“When were they?”
The silence of the universe may mean many things.
Perhaps intelligent life is rare.
Perhaps civilizations destroy themselves.
Perhaps advanced societies communicate in ways we cannot detect.
Or perhaps the universe is full of civilizations separated by oceans of both space and time.
They may have risen.
They may have explored.
They may have wondered exactly what we wonder.
But they arrived too early.
Or too late.
Maybe the greatest challenge is not crossing the stars.
Maybe the greatest challenge is sharing the same moment.
And if Ethan Siegel is right, that may be the most overlooked obstacle in our search for company in the universe.
