Seth Shostak, Senior Astronomer and Director at the Center for SETI Research said in 1914: “”One in five stars has at least one planet where life might spring up. That’s a fantastically large percentage. That means in our galaxy there’s an order of tens of billions of Earth-like worlds.” He predicts that extraterrestrial life will have been discovered by 2040.
I think that if we haven’t discovered extraterrestrial life by 2040, chances are we never will.
About half a century ago physicist Enrico Fermi was surprised by the apparent contradiction between the lack of evidence and high probability estimates for the existence of extraterrestrial civilizations. Given the billions of stars in our galaxy and the billions of years since life could have thrived in so many places, the Milky Way should be bustling with alien activity. “Where is everybody?” Fermi asked.
“We still have plenty of time to discover alien civilizations,” optimists say.
Maybe. The problem is most of the action in the universe has already happened. The first generation of galaxies appeared when the universe was about 400 million years old. Early galaxies were only several thousand solar masses but they increased in size through successive merges until they were reached the size of up to billions of solar masses. Certain scientists (such as David Sobral) think that fifty percent of the stars ever created were already born nine billion years ago. For nine billion years the universe has been producing the other half. At the moment the rate of star formation has diminished dramatically – only a number equal to a twentieth of the total number of today’s existing stars could still be generated until the end of time.
Plus, the dark energy that makes up over 2/3 of the universe’s energy causes the universe to expand at an accelerating rate. It’s been quite a while since dark energy has superseded other forms of energy and galaxies themselves – matter started to become quite dilute billions of years ago. Since the effect of dark energy increases as the space expands, one of its consequences is that new structures are less and less likely to form from now on. That is, gradually dark energy will become so strong that it will rip apart galaxies, stars and even atoms.
I think the heyday of extraterrestrial civilizations is now or has already passed. If we still want to discover them, we’d better hurry.