SciWorks Radio is a production of 88.5 WFDD and SciWorks, the Science Center and Environmental Park of Forsyth County, located in Winston-Salem.
Are we alone in the universe? Last week I spoke with Dr. Rachel Smith, Director of the Astronomy & Astrophysics Research Lab at the North Carolina Museum of Natural Sciences in Raleigh and Assistant Professor in the Deptartment of Physics and Astronomy at Appalachian State University, about the formation of solar systems. This week we'll learn what it takes for life to evolve in one.
All life that we know of is water-based and that is why the scientific search for life is looking for water. And it has to be liquid water.
Earth is in the Goldilocks Zone. Where the temperature of the sun is just right for liquid water to exist. Chemicals move around in water and are more likely to react with one another. Here on Earth, they had 3 to 4 billion years to bounce around, eventually sparking life. Unlike other liquid chemicals, water ice floats. When the surface freezes, life can survive in the liquid water below.
The more complex the life is, the more restraints there are on surviving. That's why we think that if we're going to find any life in our solar system for example, it will be microbial. The reason is that we know these microbes can survive very extreme environments on Earth, and we know that environments in space are pretty unfriendly.
Single-celled microbes were the first life to evolve on Earth. The Goldilocks zone for microbes may be anywhere there is liquid water. But what about you and me?
Are we rare in terms of being able to support complex life? A cat or a dog, those are also very complex organisms, and so what leads to the evolution of these species is a complicated question.
The Punctuated Equilibrium hypothesis, which is kind of a companion to Darwinian evolution, basically says that species remain essentially as they are, until something happens forcing them to adapt. Often, it's simple chance.
Certain catastrophic events lead to our existence. There have been five major extinctions throughout the history of life that led to the evolution of several different types of species. The extinction of the dinosaurs; if that hadn't happened we would not, as mammals, have had a niche to evolve into.
Good luck for you and me, not so much for T-Rex. But there are other factors that can determine how or if life evolves. To name a few . . .
The existence of a moon, like our moon, which stabilizes the tides. This hypothesis of a snowball Earth where it literally was like a giant snowball could have been very important for the pattern of events that needed to happen to lead to us.
We hit the lottery and have the perfect conditions for life to have evolved and lead to us. But still, are we alone?
The definition of intelligence is civilizations that can send and receive signals out from their planet. We're about one hundred years into sending any signals out to space. A hundred years is nothing on a cosmic scale. The universe is 13.7 billion years old so statistics state that if there are intelligent civilizations out there they are most likely more advanced than we are. Even a million years is nothing on this cosmic time scale. And so there are planets and galaxies that could have been evolving for ten billion years.
Maybe civilizations on other planets have risen and fallen before our sun was formed, or are just so far away that their signals haven't reached us yet. For that matter, maybe we are alone.
We've gotten very good as scientists in constraining nearly all of the factors to try and put a number on star formation rate, the ability to form planets and sustain in a habitable zone, and that kind of thing. It's looking like the big constraining factor in the number of intelligent civilizations is lifetime of the civilization. And the scary thought is that given the pretty nice robust numbers of the other factors, longevity must be low, which means that intelligent civilizations just wipe themselves out before they really have a chance to get to the point of leaving their planet. This is the current hypothesis. Maybe that's the reason we don't have any signs of intelligent life beyond our planet, and if that's true, what does that mean for us? It brings in a lot of questions about our own species. And I think that's one of the most intriguing things to think about.