Going with the most conservative side of that (5%), and the lower end for the number of total stars (10), gives us 500 quintillion, or 500 billion billion sun-like stars.There’s also a debate over what percentage of those sun-like stars might be orbited by an Earth-like planet (one with similar temperature conditions that could have liquid water and potentially support life similar to that on Earth).There are a number of other possibilities—some even think the most recent leap we’ve made to our current intelligence is a Great Filter candidate.
Any possible Great Filter must be one-in-a-billion type thing where one or more total freak occurrences need to happen to provide a crazy exception—for that reason, something like the jump from single-cell to multi-cellular life is ruled out, because it has occurred as many as 46 times, in isolated incidents, just on this planet alone.
For the same reason, if we were to find a fossilized eukaryote cell on Mars, it would rule the above “simple-to-complex cell” leap out as a possible Great Filter (as well as anything before that point on the evolutionary chain)—because if it happened on If we are indeed rare, it could be because of a fluky biological event, but it also could be attributed to what is called the Rare Earth Hypothesis, which suggests that though there may be many Earth- conditions on Earth—whether related to the specifics of this solar system, its relationship with the moon (a moon that large is unusual for such a small planet and contributes to our particular weather and ocean conditions), or something about the planet itself—are exceptionally friendly to life.
This scenario would explain why there are no Type III Civilizations…but it would also mean that could be one of the few exceptions now that we’ve made it this far. On the surface, this sounds a bit like people 500 years ago suggesting that the Earth is the center of the universe—it implies that we’re .
However, something scientists call “observation selection effect” suggests that anyone who is pondering their own rarity is inherently part of an intelligent life “success story”—and whether they’re actually rare or quite common, the thoughts they ponder and conclusions they draw will be identical.
Moving back to just our galaxy, and doing the same math on the lowest estimate for stars in the Milky Way (100 billion), we’d estimate that there are 1 billion Earth-like planets and 100,000 intelligent civilizations in our galaxy.1 SETI (Search for Extraterrestrial Intelligence) is an organization dedicated to listening for signals from other intelligent life. As an example, let’s compare our 4.54-billion-year-old Earth to a hypothetical 8-billion-year-old Planet X.
If we’re right that there are 100,000 or more intelligent civilizations in our galaxy, and even a fraction of them are sending out radio waves or laser beams or other modes of attempting to contact others, shouldn’t SETI’s satellite dish array pick up all kinds of signals? If Planet X has a similar story to Earth, let’s look at where their civilization would be today (using the orange timespan as a reference to show how huge the green timespan is): The technology and knowledge of a civilization only 1,000 years ahead of us could be as shocking to us as our world would be to a medieval person.This forces us to admit that being special is at least a possibility.And if we are special, when exactly did we become special—i.e.If this is indeed The Great Filter, it would mean that not only is there no intelligent life out there, there may be years before making the evolutionary jump to being complex and having a nucleus.If this is The Great Filter, it would mean the universe is teeming with simple prokaryote cells and almost nothing beyond that.___________ Everyone feels something when they’re in a really good starry place on a really good starry night and they look up and see this: Some people stick with the traditional, feeling struck by the epic beauty or blown away by the insane scale of the universe.