By Andrew Anderson (@AndersonEvolve)
One of my favorite shows is Firefly−if you haven’t heard of it, check it out. An aspect of the show I found enjoyable was, despite being science fiction, it explicitly stated there were no known aliens across the regions humans had expanded to. The thought of seeing the results of evolution on another planet would be amazing, and the mental games trying guess at what that life might look like are enjoyable. In reality though, I don’t think we will ever encounter alien life*, much less intelligent life, for a long while (>1000s of years) if at all. I am hardly the first to make such a claim, but I would like to bring up some of the reasons I don’t think we’ll encounter extraterrestrials within anyone’s lifetime.
Therefore, the chance of each successive event is multiplied by the previous then multiplied by the time that all chance events have occurred. As you can see the Drake Equation includes 6 conditions that have to be met, making the odds of an outcome lower with each condition (e.g. rolling a 1-5 on a die occurs ⅚ of the time, but doing it 6 successive times happens ~⅓ of the time). What’s more, we have no idea what the probabilities are for the later parts of the equation. The rate of star formation and the fraction of stars with planets are able to be reasonably estimated. Everything else is challenging to define. The big issue is we have a sample size of 1. We only know of one planet that formed life, evolved intelligent life, and sent signals−Earth. This is a two-fold problem. If I drew a number at random, what was the probability of drawing that number? Without knowing either how many draws it took or what range of numbers I had to choose from, you cannot know. Additionally, we now have what is known as a sample bias. While we are piecing together how life got started here, is that the ONLY way? Once life begins developing on a planet, what is the likelihood intelligent life appears? We might conclude it’s 100% given what happened on Earth, but remember the majority of Earth’s history is dominated by non-intelligent life*. Humans are a relative blip on the history of life and there’s no evidence that other groups evolved intelligent life. Were it not for a well-timed meteor, there still might not be intelligent life. All of this is to say, we’re not sure how to define all the portions of Drake’s Equation, so anyone claiming it supports their idea (even one saying it’s not possible) is on unstable ground.
Now we can get into some fun probabilistic concepts. Drake’s Equation doesn’t offer much help, but it comes down to a fairly simple question: is Earth, and the process of life on it, rare or common? Some would invoke the mediocrity principle, that is if you only have one observation, it is more likely you observed a common event than a rare one. Imagine it’s your first time snorkeling on a reef; the fish you see are probably the more common fish on the reef. The problem with this is, since we are alive, we had to come from a planet that met the criterion for life, so there is no way our limited observations would NOT include a planet with life on it. I actually think life on Earth could be more along the lines of the Wyatt Earp Effect; given the amount of attempts (planets in this case) it is an almost certainty that 1 will hit on the rare event. Wyatt Earp was notorious for winning gun fights without getting hurt, but given the number of gunfighters and gunfights, someone had to survive multiple gun fights through sheer luck. So life forming could be rare, but it happened at some point and, since we’re here, we see that outcome.
My point so far is we have no idea what the odds of life are, and I acknowledge that my suspicion it’s rare is just that, a suspicion. I think life likely does exist somewhere else out there, but we won’t see it anytime soon because: physics. Let’s assume there is a planet we want to check out for life. There’s a candidate at our nearest star ~4 light years away. Let’s assume that we have a spacecraft right now capable of traveling ~2% the speed of light, the current record is ~1.5%. That means it would take 200 years to reach the planet, plus 4 more just to hear if they found anything. Even if we hit on our first pass, it still wouldn’t happen in our lifetime. Our ability to detect non-sentient life is severely limited and there are no ways to be certain other than direct exploration.
Instead we would have to hope that lifeforms on another planet are sending some signal we can detect, which means they are likely intelligent, or they are likewise looking for life*. Radio waves are electromagnetic waves and travel at the speed of light but there is a delay. Try to imagine a conversation on Messenger where you only see what was written 4 years ago, that’s what it would be like to converse with our nearest star (Alpha Centari could only now tell us how they felt about Lost). This also makes Sci-Fi movies amusing with how communication and observation of events unfold (think about every intense radio conversation in space and how far apart they were–likely they were getting that message minutes or hours after it was sent). Humans have only been sending out signals for ~100 years which means only things 50 light years away could be responding at this point (travel to and from) which is 1/2000 of the distance of the Milky Way. We’ve only been listening for 50 years which means some civilization has to be sending signals at the right time to have them reach Earth in this exact range of listening time*. Consider a planet looking at Earth but is on the other side of the Milky Way, they would not find anything and have to wait 100,000 years just to hear it. All of this assumes we know what to look for or what to broadcast.
In order for us to find life it would have to be close, sentient, and signaling. While the universe is incredibly large, we’ve now severely narrowed our search window, which means life has to form easily and evolve intelligence frequently if we are to see it while you and I are here. I just don’t think that probable. Got something to add or something I missed?* Give me tweet!
Scott Mattison (@FoolsPizza) added some thoughts (* in text, his thoughts in italics) that should be shared and responded to (my thoughts in bold).
- I imagine we will find microbial life on colonized planets. I mean, we think we might have bacterial life on other planets in our local system −This seems most likely, although we don’t have every step down for the formation. What we do know doesn’t seem like something any other planet would have gone through in its formation.
- Non-intelligent or non-sentient or just not up to our levels. It could be reasonably argued multiple forms of sentient life developed on Earth. Humans just won the competition. (Neanderthals vs. Homo sapiens). Also there is the question of intelligence level of apes and dolphins which clearly can learn communicative behaviors −In this context I equate intelligence with the ability to send and detect signals to space. This is not at all the correct definition, but for a short piece it’s the easiest term I can think of. Yes, this means humans didn’t become intelligent until quite recently.
- Fermi paradox –It starts with supposition that life is common and we should see them. I don’t agree with the premise.
- This gets even worse. EM waves decrease intensity as they spread out through space through the inverse square law (not that inverse square law, the other one).Essentially intensity decreases on the order of distance squared. So even if someone is screaming out into space. They have to scream really loud to appear over the background noise and be screaming in our direction (although we can get pretty sensitive detection especially if they are sending out patterned signals). −Neat.
- We could also see visible signs from ancient, more advanced races. Concepts of super structures that utilize the energy of their local star would be observable. (we have had some pretty well publicized incorrect interpretations of these things). −It’s still a matter of timing, the ancient civilizations had to have formed at just the right time for us to see, or the structures are durable enough to keep going. I guess the fun question is does intelligent life persist once it is formed?