Intelligent Life on Other Planets: Odds of Finding It

Intelligent life on other planets has fascinated our culture for centuries. Find out what two new studies tell us about our likelihood of discovering it.

I grew up in what the media called at the time “the space age.” Anything new and modern was called “space-age acrylic”, or “space-age transistors,” or whatever.

Science fiction was a huge part of the space age. Whether it was comic books or pulp novels or TV shows, space travel was all over the place.

Everyone took it for granted that we’d be travelling to other solar systems soon, and that we would find intelligent life on other planets. They’d look a lot like us if we spent a few hours in makeup, and, of course, they would speak English.

Space Exploration Isn’t the Force that it Was in the 60s

The space-age gradually dried up after the moon landings. Space exploration isn’t the dominant cultural force that it was in the 60s.

Still, I get the sense that this fascination with intelligent life on other planets still persists with many people. Popular culture continues to fuel the belief that there must be a plethora of aliens out there somewhere with whom we could interact.

So far, there hasn’t been much scientific evidence to verify or falsify this idea. However, this has been a good week for those who interested in the odds of meeting our galactic neighbours.

The Likelihood of Meeting Our Galactic Neighbours

The first study, published in The Astronomical Journal, comes from the University of British Columbia (UBC). Researchers there have estimated the number of Earth-like planets in our Milky Way Galaxy.

Even though we’ve all grown up with stories about intelligent alien life on other planets, we didn’t even know if there were planets beyond our planetary system until 1988. Now, we’ve detected more than 4,000 planets in about 3,000 solar systems.

However, before we go looking for ET’s home planet, we need to understand more about these exoplanets. We know that life on Earth is unique in our solar system, so how many worlds out there closely resemble the Earth?

How Many Planets Out There Closely Resemble the Earth?

The UBC astronomy and astrophysics team looked at data from NASA’s Kepler mission. The Kepler space telescope monitored stars in our region of the galaxy to detect when their planets passed in front of them, slightly dimming the light they emit.

First, we need to understand what counts as an Earth-like planet. To qualify, another world has to be:

·      Rocky

·      Between half and double the size of Earth

·      Orbiting a star similar to our sun (a G-type star)

·      Located within that star’s habitable zone

That narrows down the candidates considerably. Jaymie Matthews is a UBC astronomer. He explained it like this, “Our Milky Way has as many as 400 billion stars, with seven percent of them being G-type.”

93% of Stars Don’t Qualify as Hosts for Intelligent Life 

So, 93% of stars don’t qualify as hosts for intelligent life on other planets right off the bat. The study’s lead author, UBC researcher Michelle Kunimoto, applied statistical techniques to the Kepler data.

“My calculations place an upper limit of 0.18 Earth-like planets per G-type star,” she explained. That narrowed down the number of G-type solar systems with Earth-like planets to roughly one in five or a little over 1% of all the stars in the galaxy.

That leaves us with no more than about 6 billion stars with Earth-sized planets orbiting them in our galaxy. That’s still a vast number, but it also means that terrestrial planets are few and far between.

Terrestrial Planets are Few and Far Between

Besides, those Earth-like planets don’t guarantee life on other worlds, let alone intelligent life. That’s where this week’s other study comes into play.

The Astrophysical Journal also just released a study from the University of Nottingham. They worked from the reasonable assumption that if the same conditions exist on another planet, intelligent life will evolve there just as it did here.

Scientists call this the Copernican Principle. We now know that the Earth is not the centre of the universe, there’s nothing special about our planet, our solar system or our place in the galaxy.

Nothing Special About Our Planet or Our Solar System

Like the UBC team, the Nottingham researchers used the latest high-quality data and applied sophisticated statistical techniques to it. They call their new calculation the Astrobiological Copernican Limit.

Tom Westby is the first author of the study. He describes the approach this way.

“The classic method for estimating the number of intelligent civilizations relies on making guesses of values relating to life, whereby opinions about such matters vary quite substantially. Our new study simplifies these assumptions using new data, giving us a solid estimate of the number of civilizations in our galaxy.”

“A Few Dozen Active Civilizations in Our Galaxy”

Professor Christopher Conselice led the research. He shared the team’s conclusion that “There should be at least a few dozen active civilizations in our Galaxy under the assumption that it takes 5 billion years for intelligent life to form on other planets, as on Earth.”

The final number that the team landed on was 36. So, out of 400 billion stars in the galaxy, there might be three dozen cases of intelligent life on other planets. To quote Star Trek’s Captain Kirk, “finding a needle in a haystack would be child’s play.”

We also need to take distances into account. The team found that the average span between Earth and any of these planets would be 17,000 light-years.

Our Fastest Rockets Would Take 300,000 Years to Get There

My back-of-the-envelope guesstimate is that our fastest rockets would take about 300,000 years to get there. Except, we would never be able to find that much fuel on our entire planet.

Any signal we picked up from one of these planets would be approximately 17,000 years old. Our entire civilization on Earth is only about 10,000 years old. 

While the signal was travelling, they would likely have changed as much as we have since the stone age. If we tried to reply, our alien friends wouldn’t receive our message until 17,000 years from now.

We Don’t Know How Long an Advanced Civilization Lasts

We also don’t know how long a technologically advanced alien civilization lasts. Ours has only lasted for 100 years, and our future is less than promising in terms of energy sources, mass extinction and climate change.

Summing up, there’s a fair chance that intelligent life on other planets exists. On the other hand, the odds are slim to none that we will ever find it or be able to communicate with it.

We shouldn’t confuse science fiction with science. Civilizations on other worlds give authors a prolific setting for using their imagination and making comments about the societies in which they live.

We Shouldn’t Confuse Science Fiction with Science

Those are literary devices, and they make for good storytelling. However, what humanity really needs at this point in our development is a new, science-based story that explains our place in the universe. These recent studies, although discouraging in some ways, remind us that our Earth is a rare gem and that humanity is precious.

We always have more to learn if we dare to know.
Learn more:
As many as six billion Earth-like planets in our galaxy, according to new estimates
Searching the Entirety of Kepler Data. II. Occurrence Rate Estimates for FGK Stars
Research sheds new light on intelligent life existing across the Galaxy
The Astrobiological Copernican Weak and Strong Limits for Intelligent Life
Astrobiology: 3 Questions We Need to Answer
Exoplanet Water Common Yet Rare

Exoplanet Giant Orbiting Tiny White Dwarf


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