Sunday, January 18, 2009
Larger Milky Way has implications for the Drake Equation and the Great Silence -- or does it?
Apropos of Russell Blackford's recent posts about the Fermi Paradox, it should be mentioned that the Milky Way is 50% larger than previously thought. This will likely have implications to our appreciation of the Drake Equation and the Fermi Paradox.
What tipped cosmologists off was the discovery that our galaxy is spinning 15% faster than formerly assumed. The lead researcher on the project, Mark Reid of the Harvard-Smithsonian Center for Astrophysics in Cambridge, estimates that the Milky Way's spin is about 914,000 km/hour, significantly higher than the widely accepted value of 792,000 km/hour.
The only thing that could account for this increased spin rate was more mass -- a lot more mass. As a result of Reid's findings, our models now need to account for a galaxy that is 50% heavier, 15% wider and contains a mind-boggling 3 trillion stars! That is an astounding 750% increase from 400 billion.
You might want to pause for a moment and think about this.
This is remarkable news and the implications of these findings are going to take a while to sink in. My first reaction was to consider the implications to the Fermi Paradox. Does a significantly larger Milky Way accentuate or diminish the problem that is the Great Silence?
First off, it throws previous Drake Equation estimates out the window. Blogger Paul Hughes has already crunched some numbers and has come up with his own estimate: he believes there may be as many as 12 billion Earth-like planets in our galaxy capable of supporting liquid water and in turn carbon-based life as we know it (Hughes doesn't take the equation beyond that as he was inquiring into the number of potentially habitable planets).
But as many of my readers know, I'm not a great fan of the Drake Equation to begin with. It's in dire need of an upgrade and it completely fails to account for the cosmological development of the galaxy and other temporal aspects. That said, it's safe to assume that the probability of extraterrestrial life emerging in the Galaxy is now significantly higher than it was before -- both in the Galaxy's long history and now.
Second, the new and improved Milky Way throws off previous calculations as to how long it would take an advanced civilization to inhabit all four corners of the galaxy. An extraterrestrial migration wave would likely be comprised of self-replicating colonization probes that spread out across the galaxy at an exponentially increasing rate. Previous estimates placed complete Galaxy-wide colonization at a few million years. Given that we were wrong about the size of the Milky Way and the number of stars, we have to conclude that it would take longer to colonize the entire galaxy.
Just how much longer I'm not sure [sounds like a future project in the making], but given that we're talking about exponentially increasing migration rates I would have to think that we are not talking about an order of magnitude. And even if it does take significantly longer, we still have to take the extreme age of the Milky Way into consideration and the likelihood that intelligence may have emerged in the Galaxy as long as 4.5 billion years ago. The age of the Galaxy is still disproportionately longer than even the most pessimistic colonization rate estimates.
What does all this mean?
Well, nothing really. The Great Silence is obviously still in effect and something's still screwy with the Universe. A bigger Milky Way means that there's likely more intelligent life in the Galaxy than we had previously assumed, but that interstellar colonization and communication rates are slightly longer.
The Fermi Paradox lives on.