THIS PAGE IS A WIP
Life on Other Planets
aka aliens, oops.
I feel the need to preface all of this with the fact that I'm not a conspiracy theorist, I just have a huge fascination with speculative science and planetary sciences. Emphasis on speculative there.
And if I'm being compeltly honest, 90% of my interest was kickstarted by smutty blue alien books with incredible worldbuilding. I don't care. Cringe isn't real.
There's genuinely so much to consider when we talk about the concept of life in space, or just lifeforms outside of earth in general. Because life exists off of earth, but I think oftentimes we only think of animals and humans (or human equivalent species like aliens) most of the time. Which isn't the case, there's actually proof of bacteria, DNA and RNA factors, insects, and more that we've gotten proof of on other planets and asteroids!
The Drake Equation
I feel like a great starting point is always the Drake Equation. Well maybe not the best starting point, it's confusing but I wanna talk about it anyways.
The Drake equation is essentially a mathematical formula used to estimate how many other planets in our Galaxy are capable of communicating with us based on a ton of factors. The equation was formulated in 1961 by Frank Drake.
N = the number of civilizations in the Milky Way galaxy with which communication might be possible (i.e. which are on the current past light cone);
R∗ = the average rate of star formation in our Galaxy.
fp = the fraction of those stars that have planets.
ne = the average number of planets that can potentially support life per star that has planets.
fl = the fraction of planets that could support life that actually develop life at some point.
fi = the fraction of planets with life that go on to develop intelligent life (civilizations).
fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space.
L = the length of time for which such civilizations release detectable signals into space.
On it's own, the equation doesn't look too special or exciting, and tbh I get it. But that said, the estimate for the probability of other planets like ours ended up being somewhere between 1,000 and 100,000,000! While it is a braod range, it's also just an estimate, as the equation is solely based on probabilities. If you look at the wikipedia page for it, it actually gives you more of the parameters they used to calculate this number, like explaining that one fifth to one half of all stars formed will have planets. Pretty cool right? Especially given that this particular estimate/equation isn't actually the 'total' number of all those civilizations, but is considered the 'freshman' rate for how many new socities appear roughly once a year in the milky way.
Well Kinda. Unfortunately, this is all speculative as we don't really have any way to properly test this or verify the validity of the equation just yet. But that doesn't mean that there are no planets out there with no life, we have proof of that. The Drake Equation SPECIFICALLY focuses on those planets that have enough technological advances to be able to communicate on the level we do. AKA, ones that we could potentially receive a signal from.
The wikipedia article also kinda touches on this and about how it's a very simple model that could ignore some relevant parameters, and a lot of people have actually suggested modifications to it. It was actually proposed to generalize the equation (Wikipedias words there oops) to include alien civilizations that could/have colonized other star systems. It adds in alot more variables and ends up being like a set of 3 seperate equations.
The Great Silence - the Controversy Concerning Extraterrestrial Intelligent Life by G. D. Brin actually touches on this and is mentioned in the article too. There's genuinely so many moving partsh ere and ways people contest this formula, but as a basis formula to give us at least an estimate, no matter how broad, is still pretty nifty. Everything has a starting point, right?
Another point of tension with this theory is that it could be multipled by how many times a civlization might occur on a planet, like after a mass exctinction event or something similar that wipes out larger numbers of life forms on the planet. Say a civlization deveop,s runs its course over like 10,000 years or so, life can still go on. It'd be like if humans were wiped out on earth, the nature and some animals and insects might still live on. Given how evolution worked in our favor, it's completely possible that this could happen time and time again, so it feels silly to not take that into account. For all we know, some planets in our solar system could be in between two heights of civilization, with centuries of history buried under the dirt the same as many ancient civilizations on earth. This factor is known as the reappearance factor!
Another great point mentioned on the main Wikipedia article is that while we, as humans, are in a communicative phase, we aren't {i}actually{/i} a communicative civilixation, as we don't really send regular interstellar transmissions. Because of this, it changes the equation even more because there could be other planets that also don't partake in regular transmissions like that. Alexander Zaitsev definie the factor as "The fraction of communcative civilizations with clear and non-paranoid planetary consciousness." AKA, the fraction of the planets in the original equation that actually engage in interstellar transmission. However, this factor (METI factor if you're curious!) is considered misleading, since purposeful transmission of messages isn't required for them to receive a message being sent by another. It's moreso just required that they have the technological systems/advancements in place!
All in all there's a LOT of variations on the original equation, and to be quite honest with you i do NOT want to try to explain all of them. This is more or less just context for my yapping session.
Another reason for some of the issues with the drake equation is the Fermi Paradox! But I'll go into that later on this page, but the line of reasoning is what lead to the Great Filter Theory, which is also talked about down below.
Some closing points on this one, mostly because these didn't quite fit in anywhere else. Drake himself suggests the number is closer to 10,000 societies producedannually, based around his estimate that it's yearly and they have an average lifespan (of the society itself, not the individual species members) of 10,000 years. I highly suggest reading the wikipedia article and checking out the SETI Institutes website if you're curious about more on this!
Rare Earth hypothesis
The Rare Earth hypothesis suggests that the very unique and specific set of conditions on Earth allowed for life to form, and that because they're extremely uncommon, they're not likely to happen widely in the known universe. I don't really like this one, even though it only applies to complex life. While it's totally possible that this is the case, it doesn't seem extremely likely to me, given what information we've been able to find through samples taken by space robots (help me, i can't remember what the hell they're called T-T). They mention that if there is life out there, it's more than likely to be microbial, which I agree with to some extent, but I don't think that's all thats out there. We already have proof of microbial life just from things like asteroid chunks. Their point with this though is that simple life forms have less needs, and therefore could live far longer and in more varied conditions than complex life forms.
Okay, in truth I'm not totally being fair to this theory. They do have some genuinely good reasons to back up why this theory exists, which I respect, even if I think it's unlikely. They do also go a bit into the period of time in which we have oxygen in our atmosphere, which is roughly like 10-20% of Earth's lifespan at most, which still seems like a lot given that they estimate that Earth will have a lfietime of about 12 billions years and the Earth's current estiamted age is 4.5 Billion years, putting us at around 1/3rd of it's lifespan already. Which, that part is horrifying enough on it's own tbh.
All that said, the duo that's primarily responsible for the theory do in fact encourage new data that suggests otherwise. Just because they don't think it's common/possible, doesn't mean that they don't want it to be found. This part of the article on Astronomy.com also talk about the need for Oxygen, but I feel like that's also discrediting the possibilty that these life forms have evolved on their own planets to breathe a different chemical composition in the air. It's not a totally far off thought or concept to have.
The more I read about this particular theory, the more it kinda irked me the wrong way. A lot of their thoughts are based around the assumption that life on other planets would have the same requirements for forming and developing. Some I can totally get behind, like temperature and water, but even those I feel like aren't as strict as they claim them to be. We have species on our own planet that have adapted to living in conditions that would normally be unliveable, so again I don't think it's that far off to assume that some planet out there contains other complex life forms like our own that have different planetery conditions they live in. Although it is science fiction based romance, Ruby Dixon's Ice Planet barbarians comes to mind in terms of a different environment. Again, I know it's fiction, but it's the thought train thats important here, not the source material. That planet in particular has an air composition that is deemed unliveable, and actually toxic, to humans, alongside the aggressively cold weather. That said, there's still complex life forms on that planet, albeit in this case they have a symbiote in them. Even the species native to the planet in this series, are born with this symbiote inside of them to help them sustain life. That part isn't important, but it'd be foolish of us to throw out the notion that another planet in a different solar system or neighboring galaxy could be capable of life. For all we know, there are elements we haven't discovered that are similar to our own on these planets.
The Great Filter Theory
The Fermi Paradox
Planetary Habitability
Roughly one-fifth of stars have planets in the habitable zones, where temperatures could support life as {i}we{/i} know it according to NASA.
Other cool planetary science finds!
Sources/Extra links:
Drake Equation
WikipediaSETI Instititute NASA
Rare Earth Theory
Astronomy.com Rare Earth hypothesis Exploring Science articleThe Great Filter Theory
The Fermi Paradox
Other
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