A million planets could host intelligent life and we might never find out.
Are we alone in the universe? Probably not but, despite more than half a century of efforts, we still cannot connect with any other intelligent beings out there.
Maybe it is "because space travel is so difficult that we are not able to go to them to meet them or they are not able to come to see us here," speculated Jesuit Father Jose Funes, the Vatican's chief astronomer.
"The possibility is also that we are a rare case and this is the only case in our galaxy. We don't know that. Or another possibility is that they don't share the same desire to explore the universe.
"Or, if they are out there, we will be able to meet them some time; it could happen maybe tomorrow or maybe in 50 years, or 1,000 years; who knows?"
As part of the University of Alberta's Festival of Ideas 2010, Funes and astrophysicist and professor Neil Comins addressed the possibility of intelligent life beyond Earth in a panel discussion entitled Astrobiology: Are We Alone in the Universe? at the Telus World of Science Nov. 19.
A Jesuit priest with graduate degrees in philosophy and astronomy, Funes is currently director of the Vatican Observatory. He has stated in the past that the belief in the existence of intelligent extraterrestrial life does not contradict the teachings of the Church, and that dismissing the possible existence of aliens would be like "putting limits on God's creative freedom."
Comins, who is currently a professor with the faculty of physics and astronomy at the University of Maine, is well known for his research in several areas, including observational astronomy, general relativity, galactic dynamics and astronomy education.
He has also written several popular science books including two that explore alternative versions of Earth and one that debunks common scientific myths and life's curiosities.
Comins noted there are several projects that have been looking for extraterrestrial life for over 50 years and have not detected it yet.
"Have they been here?" Comins asked. "Some people would say 'yes' but until you can show me some thing that is alien and could not possibly have been made on earth, I'm doubtful. I can be persuaded but I'm doubtful."
Fr. Jose Funes
But he conceded the universe is big enough to contain intelligent life somewhere. "The numbers that we get for the other possible life - numbers of advanced civilizations in our galaxy - range from zero to something like 10 million," he said.
"That may sound like a big number but when you consider how big the Milky Way galaxy is, if there were, let's say, one million intelligent life forms on different planets, the separation between them still would be in the order of 1,500 light years, which would mean that it would take them 1,500 years to get to us and 1,500 years for us to get to them.
"And so if they are out there looking for us today and they are that far away then they are not going to know about us for another 1,400 years because it's only for about 100 years that we have been sending signals into space."
Added Comins: "The volume of space is so great that even though it is plausible that there are many other intelligent life forms on other planets in our Milky Way galaxy, the separation between us allows me to believe that they might exist but they have not been here and they probably don't know that we exist yet."
In answer to a question from a member of the audience, Funes said if aliens exist, they might not need redemption as human beings do.
"In the Christian belief we believe that we are redeemed by Jesus from our sins. But if these aliens are intelligent and they are free, it's not necessary that they have committed sins and therefore is not a given that they need redemption," he said.
"They still could share God's life, God's friendship without sin."
The difficult thing with astrobiology is one can never be sure if one is going to get results, Funes said. "Maybe we would never be able to answer that question (Are we alone in the universe?) because even if there is life out there we may never come to know that."