Science and pop culture look to the skies to answer the ultimate question: Are we alone?

If you're ever studied astronomy, you've probably been exposed to something called the Drake equation.

One side of the equation posits the number of civilizations in our galaxy with which it might be possible to communicate. The other side gives all the variables that add up to that number, including the average rate of star formation, the number of planets around those stars that have developed intelligent life and the ability to send radio signals.

"Depending on how you calculate it, the answer can be none, or it can be a billion," said theoretical cosmologist Katie Mack, author of the recent book "The End of Everything (Astrophysically Speaking)."

Astrophysicist Frank Drake, who formulated the equation way back in 1961, said it's really a way of showing "all the things you needed to know to predict how hard it's going to be to detect extraterrestrial life."

Mack put it more directly: "The point of the equation is really to show how little we know."

If it's hard for professional scientists to run the numbers, it's harder still for us mere-mortal Earthlings to do the work.

That's where the imagination comes in. So for generations we've been putting our creative minds to work in guessing if extraterrestrials exist, what they might look like and how we've going to greet them and they us, whether with a sign of peace or a ray gun.

UFOs: Have we been visited?

"It's a curious thing that for as long as we've imagined extraterrestrials, they look pretty much just like us," observed Chris Impey, a professor of astronomy at the University of Arizona.

"A couple of centuries ago, they came in galleons in the sky. When zeppelins were invented, the aliens flew in dirigibles. After World War II, they came in flying saucers, the latest and greatest technology we could imagine."

The anthropomorphism — putting things that are not human in human form — is a constant. So, too, is the belief in alien life forms to begin with.

Strong beliefs in alien visitations

According to a 2018 Chapman University study, 41.4 per cent of Americans believe that extraterrestrials have visited Earth at some time or another, and 35.1 per cent believe that they have done so in recent times.

There are understandable reasons for such beliefs, Impey noted.

For decades, some people have been convinced that the US government has been harboring secrets about visitors from afar ever since 1947, when they believe an alien spacecraft supposedly crashed near Roswell, New Mexico.

"When you know that people aren't telling you everything they know, you start filling in the blanks yourself," said Impey. "The videos, the stories of Air Force and Navy pilots seeing mystery spacecraft, all of these things add up. It's just that people connect the dots way too quickly."

Both scientists and many civilians hold to the maxim that extraordinary claims require extraordinary evidence.

As a recent CNN story revealed, for years government and military officials alike ignored sightings of UFOs reported by both military and civilian pilots — just the sort of extraordinary evidence that might substantiate the reality of ETs. The Pentagon, which refers to UFOs as unidentified aerial phenomena, has confirmed the authenticity of videos and photographs accompanying those reports.

Before that recent and still-unfolding news appeared, though, a hard-to-penetrate cone of silence has surrounded the whole question of UFOs, at least as far as the US government and military have been concerned.

Fiction fills in the gaps

Popular culture filled in the blanks, giving expression to UFOs and their otherworldly passengers in vehicles such as ComicCon, movies such as "Independence Day" and "E.T. the Extra-Terrestrial" and the classic television series "Star Trek" with its bold search for new life and new civilizations.

Beyond that, there's a host of conspiracy theories — some benign, some full of foreboding — with dark warnings of abductions and unwanted experiments.

Impey called the question of UFOs "a cultural phenomenon, not a scientific one."

For all that, he cited the late astronomer Carl Sagan's call for all sides in the discussion to keep an open mind — "but not so open," as Sagan said, that "your brains fall out."

 

Searching the skies

 

"From time immemorial, humans have wondered about whether we're alone," said Stephen Strom, former associate director of the National Optical Astronomy Observatory.

Just because the popular imagination diverges from the scientific one doesn't invalidate our hope to encounter lifeforms from other worlds.

After all, the question isn't just whether we're alone, but also whether other civilizations have done a better job of taking care of their planets than we have of taking care of Earth.

It's a matter, then, of "whether it is possible for putative complex civilizations to avoid self-destruction," as Strom put it, and whether we can learn from them before it's too late. Those are among the most pressing questions we can ask these days.

Granted, most space scientists don't share the view that extraterrestrial life is going to arrive on Earth via spacecraft in humanoid form. One who did, the late cosmologist Stephen Hawking, worried that if ETs did arrive that way, they'd likely be on a mission to destroy us.

That doesn't mean that space scientists aren't serious in their search for extraterrestrial life.

"Do we think aliens are out there?" asked Mack. "We don't know where, but there almost certainly are.

"It's very unlikely that life has evolved in only one place in the entirety of the cosmos — the sorts of physical processes that had to occur on the early Earth are probably things that have happened countless other times on distant worlds."

We're likely to learn about other life forms from rovers, spectrometers and chemical analyses of distant atmospheres, she added. When we do, the news will spread fast.

As Mack said, "People really do want to know."