How exactly can you evaluate whether there really might be life on other planets?

The answer is a paradox, says UVA astronomy professor Ed Murphy.

Murphy, who teaches a class designed to get students questioning whether intelligent extraterrestrial life exists, says the Fermi Paradox is perhaps the best way to consider the question.

The concept is plausible enough to follow: Our sun is a relatively young star out of hundreds of billions of stars in the galaxy. If Earth can support intelligent life in our infant of a solar system, it makes sense that there could be other planets in other solar systems with intelligent life as well.

“People love mysteries, but they don’t spend the time to reason it all out and wonder, ‘If aliens exist, then what should they be like?’” Murphy says.

But if there are aliens, why haven’t they made contact with us?

The hypotheses from that question run the gamut, but Murphy focuses on three major potential outcomes:

  1. aliens don’t exist;
  2. aliens exist, but they haven’t visited Earth or tried to contact us; or
  3. they do exist and they have contacted us.

Murphy says if they did exist, another reason we have not made contact with them may be because at some point in time, they destroyed themselves with biological or nuclear weapons.

“They may not have lasted long enough to communicate with us,” Murphy said.

Murphy himself doesn’t believe that aliens have recently reached Earth. If they had, he suspects they would be well photographed by lots of smartphones.

“Nothing these days goes unphotographed,” he said.

But he’s open to the idea that there are other intelligent life forms out in the galaxy somewhere that we just haven’t contacted yet.

That’s partly because searching for alien communication isn’t a priority for government researchers, especially since the process is expensive and no one is exactly sure what to look for, Murphy says. There is currently only one telescope—the SETI Institute’s Allen Telescope Array outside of San Francisco—dedicated to searching radio waves for communication from other galaxies.

“We have no clue how strong or weak their signal might be,” says Murphy, who runs the McCormick Observatory public night program. “We don’t know how they might have designed their transmission systems—what’s plausible to us may not be plausible to them.”

But for a culture whose fixation on alien life forms run deep, the conversation around intelligent life will persist, no matter how well reasoned the arguments are for or against alien existence.

“I hope I can change the students’ minds and make them take a more skeptical view,” Murphy said.