A dying planet shotgunned trillions of life-bearing capsules far into the universe, consisting of basic organic molecules. One found its way to Earth, found purchase, and evolved. Others found their way to other planets. One day, two separate life forms will meet, and marvel at how their DNA is structured all the same. (Not so much a comment as a possibility. Thanks for the space.)
For example there is ~4 light years of empty space between us and our closest star.
And if you come upon a solar system but don’t hit a planet you’d probably get ejected into empty space.
And even if you did hit a planet, you could end up on water, land, lava, etc., so I guess you’d have to account for all possibilities, plus keeping your biological cargo alive during the extremely long journey.
So it would have to be a heavily calculated trajectory and heavily planned cargo to find much success.
Assuming the capsules followed planned trajectories, they could have used technology such as that which is being developed in the Breakthrough Starshot initiative, described here: https://breakthroughinitiatives.org/initiative/3
The trajectory is more of the issue rather than the speed. You’d probably need onboard AI navigation to course correct and make landing spot decisions.
And don't forget that there's a "when". Planets ready to be seeded with life are rare at a given point in the universe's timeline. So the AI also needs to make course timing decisions in the magnitudes of 1B years...
It's so much easier to build and train AI then migrate our "humanity" into machines and just go from there to the Tannhäuser Gate and beyond.
When I was a kid, my dad, a very spiritual guy, after tucking me in, revealed to me: "Son, humans can already travel faster than light". My young and inquisitive scientific self said "What?? How?!?!" And he goes: "Just close your eyes and imagine yourself on Mars. It's instantaneous."
If you have AI, it can make the decision to "deploy" or loiter. If the technology is sufficiently advanced, it can wait a while. A long while.
Plus - why only one source of these capsules? Does only one mold cell in a colony generate a spore? Drake suggests that perhaps many will have done this same thing.
Nah, just aim your capsules along the galaxy with a speed low enough to not leave the galaxy.
The capsules will go around the galaxy, travelling through or oscillating above and below the galactic plane just like other stars.
Bonus 1: Make your capsules charged so they're guided by galactic magnetic field lines into star-forming nebula where a high density of stars are created letting them mix into protoplanetary disks.
Bonus 2: Just keep spewing out more capsules to increase mixing rates.
To be honest, this seems likely to have happened _somewhere_ in the universe at least a few times. Maybe we are all secretly just an overgrown virus of self spreading amino acids that's been propagating through space and time slowly over billions of years.
"Interstellar plasma braking", as mentioned in another comment? The ship can slow down, but the passengers will all have died from the plasma radiation.
the habitable zone, defined as the distance from a star at which you could expect temperatures on a planetary surface consistent with the presence of liquid water
I know nothing about the search for extraterrestrial lifeforms, but isn't using this definition extremely limiting? Or are the various aspects of water really such that it's extremely unlikely any other lifeform not using water could exist? Like, based on another fluid? Or maybe just no fluid at all? Or is the issue that we wouldn't be able to detect another lifeform as being one if it's not water-based?
If you have a strong theory about how silicon based life might arise then of course you could look for signs of that. What are those signs? Well, ... that depends on your theory.
Versus carbon based water dependent life? We know it exists in at least one form and what its characteristics are. So we have plenty of candidates for "signs of life" in that form.
It doesn't mean it's the only or even best way to search, it just means it's the one we know how to begin!
(I am not a scientist) the assumotion is Earth is an average lifebearing plant until proven otherwise. If you find evidence of something, you are more likely to find it in the middle if the normal distribution.
The problem though is choosing which population we are "average" in.
Unfortunately we have a single sample for life. Its actually entirely possible we are literally the only intelligent life (or even Earth being the only planet with life) if you define the population as "life capable of wondering if they're alone in the universe".
This is the anthropic principle [1] which is an observer bias implies the universe supports observers. Coupled with the fact a spacefaring civilization at 1% the speed of light could colonize the galaxy in about a million years (0.007% age of the universe) this is decently strong statistical evidence intelligent life is exceedingly rare (Fermi paradox).
But to answer more directly, Carl Sagan convinced Nasa to look for life on earth. [2] We assume we are typical therefore we try and replicate this with observations of other planets.
>This is the anthropic principle [1] which is an observer bias implies the universe supports observers. Coupled with the fact a spacefaring civilization at 1% the speed of light could colonize the galaxy in about a million years (0.007% age of the universe) this is decently strong statistical evidence intelligent life is exceedingly rare (Fermi paradox).
Wouldn't logically follow only that it is exceedingly rare that anyone colonises a galaxy? I mean there are a lot of assumptions in that statement:
It only makes intelligent life rare if you assume that intelligent life wants to colonise a galaxy and maintains the capacity to travel at 1% of the speed of light (which is still pretty fast) for 1 million years, while maintaining the desire to colonise a galaxy.
Maybe after 10000 years they go "Ahhh, enough Manifest Destiny... I'll go back home...." :)
Well, for life to emerge you likely need some kind of liquid medium/solvent to enable chemicals to move around and interact with each other. It's hard to imagine how that could happen in a solid/frozen environment.
So, assuming a liquid solvent as a basic requirement, the next question is, what sort? There are other options beyond water, but water actually some unique properties that make it a potentially ideal medium - not least it's less dense when frozen. This meant the seas in early earth never completely froze, with liquid water remaining under the surface. If ice was heavy than water, then ice would sink, the oceans would likely have completely frozen, and no life would have evolved.
Ice is a really interesting material in a number of ways--especially in conjunction with liquid water. I worked in a very different area that he was also researching at the time but my thesis advisor went on to create an ice lab and was probably one of the world experts on ice. (The US Army, especially in the 80s, was very interested in all sorts of things about cold regions--for obvious reasons.)
There are several aspects that make the search for non-water based life untenable. Multiple comments are pointing out the practical aspects.
A separate aspect that is very important to know is that inorganic chemistry (non-carbon chemistry) is actually quite limited overall: we have a pretty good grasp of the possible inorganic compounds and their properties, at least within certain ranges of temperatures and pressures. And a huge number of those compounds require water to be present in some way.
Now, organic chemistry is far richer and far harder to explore thoroughly. But, given all we know about inorganic chemistry, creating organic compounds in ways that don't involve the known inorganic ones, and doing so without water, seems extremely unlikely.
It's not limiting, it's in our current knowledge the only way for life to appears. Of course, our knowledge may be limited and other ways may be discovered one day, but it the meantime it is necessary to focus time, money and energy on things that have a provable chance to succeed
Once life gets intelligent enough we may be able to detect it by other means. For example, they would likely use electromagnetic waves to communicate, just like we do[1]. That's based on the physics on the constraints set by our physical universe, not on our biology.
If a civilization gets really advanced they might be able to do alterations to their own star that we would also be able to see. They might build megastructures around them, changing their brightness in unusual ways [2].
Non-microbial life might be plainly obvious visually. You expect it to move around, and it's probably not going to look like a landslide or the wind blowing.
Even if it's sessile at the bottom of some ammonia ocean trench, who will look at it and think that it's just a geological feature? When we talk about it being difficult to detect, we're talking about the microscopic stuff, aren't we? Or trying to notice it from interplanetary/interstellar distances, I suppose.
> trying to notice it from interplanetary/interstellar distances
That's the difficult part. "Visually" means different things when dealing with those distances. Often what we get from a whole star system is the equivalent of a few pixels worth of light. That's literally all we have to work with. If we are lucky we might be able to detect a planet orbiting the star if it happens to partially cover the star while we are looking at it. Still, it is surprising the amount of information that astrophysics can get from such a meager amount of data.
The point of the rule is to be extremely limiting. There are billions and billions of stars, and it's becoming clear that a lot of them are orbited by planets.
Given that there aren't obvious alien visitors or even communications reaching us regularly, it seems to be a needle in a haystack situation.
I have never seen a convincing basis for life that isn't carbon. The next best candidate is silicon, but it seems like the problems are unlikely to be overcome.
However, strongly showing that an alternative is possible is a super, super uphill battle. If we weren't made of carbon and water, I'm not sure we could conclusively show that life could be built on it. But we probably couldn't disprove it. Ammonia is probably at least in the "not disproved" category. But I think most everything else is. If you seriously think about it, beyond the "my mind is so open it's falling right out", it's a pretty tall bar to find an alternative. (If you don't think so, spend some more time with organic chemistry, and consider why we call it that. There is a reason life is based on it, and there's a reason we cleave the entire chemistry world into two pieces along that division.)
It is also in my opinion not that interesting a question ultimately. The big jump is the one from zero possible life substrates to one. Having a second one doesn't really change much, e.g., I don't see any compelling reason to believe there would be an "ammonia solvent" view of the universe versus a "water solvent" view of the universe or something.
That's not what I said. My last question covers this exactly: are there metrics other than 'conditions like we know them' which can be used? Maybe the answer is just 'none that we know of', again: no idea, and yes then one cannot look for it. But here on earth we can distinguish between a rock and a cell based on various metrics. They way they reflect light is perhaps different enough to tell that one is a relatively simple solid consisting of chemical bonds which are all alike, whereas the other one isn't. Or processes in the cell make the atmosphere slightly different. Now suppose some other lifeform also consists of cells but instead of water-based they use something else which happens to be liquid at 200 degrees Celcius. A rock can still look like a rock at that temperature and maybe won't alter atmosphere. Maybe something living would?
Also I don’t non-carbon/water lifeforms are at all compatible with our understanding of biology and chemistry?
It's not because we cannot understand it that we cannot observe it. In fact that's usually how it goes: first observ, then understand. Isn't that basically what we're doing already with a lot of telescopes/wide band radiometry/... ? Looking for things without understanding how they can exist or where they came from (the OMG particle etc)
Yes, it's limiting, but that's because anything outside of that definition of life would be purely speculative. On the other hand, we not only have an example model of how life can work, but reason to believe that other forms of life may be similar. Both carbon and oxygen have relatively unique traits that make advanced life possible without extreme inefficiency or spontaneous combustion.
Why isn't there life that relies on other gases like fluorine chlorine to perform oxidization? Besides the fact that oxygen is presently far more abundant than those other gases, oxygen (specifically dioxygen or O2) has very interesting and important characteristics; it has a highly energetic double-bond that's easier to break apart than other similar molecules, and it has both a stable state (triplet ground) and a highly reactive state (singlet). Without getting into the weeds, this has to do with the quantum property of the "spin" of its electrons. Life, including the human body, uses some neat tricks to be able to transport oxygen and switch it to be highly reactive where it's needed, particularly in the Krebs/TCA cycle. If oxygen didn't have both a stable and a reactive state (while being the same molecule!), it would either be a less effective oxidizer or be too reactive to be safely transported biologically, let alone to be exposed to. So there's reason to search for life in parts of the universe we know to have oxygen – it's really an amazing molecule.
Carbon might be more replaceable than oxygen (IMO), but even it so far seems to have the most advantages to life in contrast to other molecules, from what I understand. I'm sure someone will correct me on this (which I absolutely welcome!), but carbon is advantageous for life because it is almost an opposite of oxygen; it will accept multiple bonds with other molecules but doesn't need those bonds so badly that it needs to steal electrons from other molecules (oxidization) or go out of its way to lend its electrons, causing a redox reaction. It's a chill ass molecule that's really good for being a building block for far more complicated molecules.
Now let's talk about water. It's actually a really good solvent and can dissolve a wide range of substances, thus making it effective as a carrier of many things. Water is a polar molecule due to the way it has an oxygen end and a hydrogen end (think of the way an H20 molecule is normally represented as being triangular), which allows it to interact with other polar molecules (including other water molecules) and reject nonpolar molecules. At the same time, it's capable of interacting with some nonpolar molecules. By being polar, it forms hydrogen bonds with other molecules. These properties are important for things like the creation of proteins, for example. Water is also a side effect of organic chemistry; both respiration and the actual burning of organic material results in CO2 (and other carbon molecules) and water. Water stores heat very well, and temperature may be an inherently limiting factor to where organic life of any kind can thrive. Oh yeah, and it also has a neutral pH. Though it doesn't conduct electricity on its own, a solution of a water and an electrolyte allows it to conduct electricity. The ability to create balances of electrolytes is another critical use of water in organic life.
I'm missing a bunch of things, but the picture I'm trying to paint for you is that molecules such as water, carbon, and oxygen, aren't simply replaceable in the only example of life that we know of. Their role isn't by mere happenstance, but because they have inherent advantages over their alternatives.
Searching for life elsewhere in the universe is an expensive endeavor. While we shouldn't be close-minded to other models of life, searching for life similar to our own is simply more efficient from a logical perspective. It would be one thing if Earth was the only object circling a star that has these important molecules, but we know that it's not.
Something to consider is just how similar life is on our own planet. We like to think of some animals like octopuses as "alien", and while they are indeed strange in many ways, they still share properties with other animals. Take for instance the fact that octopuses have two eyes, just like other animals; in fact, the vast majority of animals have two eyes. Even spiders, which have more than two eyes, usually have eyes arranged in two rows, and many spiders have two eyes that are more dominant than the others. Eyes have evolved multiple times independently in the tree of life. While it's an interesting idea that extraterrestrials might have multiple eyes, there's reason to believe that, if we were to meet extraterrestrials that evolved on a similar planet to Earth, they would feature two eyes. Although we might not completely understand why evolutionary pressure hasn't widely promoted more than two eyes, it still appears to have an inherent advantage. This same line of thinking is why scientists have focused on searching for life similar to our own; there are properties to our form of life that are based on environments and traits that have inherent advantages. The evidence suggests that the way our life has arranged itself isn't merely a jumbling of various things that happen to function together.
We better hope we don't find sentient life around Alpha Centauri because that's very bad news for us. Let me explain.
Imagine if there were exactly 2 sentient lifeforms in our galaxy, us and 1 other. What is the probability that the other evolved around our closest star in a galaxy with 100-400 billion stars? Extremely low. So, just based on that one data point the far more likely explanation is that the galaxy is teeming with sentient life. Instead of 2 lifeforms, it's more likely in teh thousands.
So why is this bad news for us? Because we don't really see any evidence of spacefaring life anywhere. In Fermi Paradox terms, we think of certain events as "filters". To get to where we are we have survived a number of filters. Some are minor. Some are what we call "Great Filters", meaning life is highly unlikely to get passed eg the presence of phosphorus and other elements necessary for life as we know it.
So a galaxy teeming with sentient life is highly suggestive that a Great filter is ahead of us.
Consider this: many (including myself) believe that the most likely path forward for our species is in a Dyson Swarm. The ultimate problem for any civilization is energy (even resources are simply a question of energy) and living space. A Dyson Swarm solves both of these problems without requiring any theoretical or essentially magic materials. It can be built incrementally. It may also be the only viable method of producing the energy required for interstellar travel.
These stick out like a sore thumb because orbitals need to dump heat. The only way to do that in space is to radiate it away. At any likely temperature for doing this, this means outputting a lot of infrared. So a star with a massive IR signature (compared to its visible light) would be an indicator of a Dyson Swarm that you cannot hide and can be seen from massive distances, particularly if you start spreading to nearby stars. A galaxy of such constructs could be seen from millions of light years away by us.
Even at 1% of the speed of light, it would take no more than about 10 million years to fully colonize the galaxy. In terms of the 4.5 billion years it took us to get where we are this is a rounding error. We are likely to be able to build such orbitals within 1000 years, possibly within 100 years.
So, life on Alpha Centauri would mean that rare life evolved on our closest neighbor, it became sentient and hasn't gone this route but it still in the narrow window of emergence of sentience and not becoming spacefaring, all of which is incredibly unlikely when put together, or there's a Great Filter ahead of us.
It would actually be great news. Your argumentation is sound, but in reality there either is a big filter ahead of us or there is not, this will not change at all when we find alien life. Instead, this would actually give us a solid hint as to which reality we are living in, increasing our chances to pass the filter.
I think OC's point is that if the universe is teeming with non-interstellar life, then the great filter will be life's ability to spread beyond its host star, or something before that. But we already can assume that based on the lack of interstellar visitors.
We'd need to discover evidence of extinct life and surmise their end to narrow down what the great filter might be and therefor have a better chance of surviving it.
IMO the dyson sphere model assumes energy demands go up exponentially as if we are some cancer growing unchecked with no constraints. How we "should" be is rooted in bias. E.g. modern life is certainly not that healthy for a lot of people, mentally and physically. Maybe living a more primitive life, closer to how we evolved as a species before our rapid cultural evolution phase and desire to make short term profit with all the low hanging resources on earth, might make you more likely to die from various disease without modern medicine. During that lifespan, however, you might have overall better physical health or even mental health being a forager who has to worry about little beyond what you can see in front of you. No existential worries, plenty of physical activity.
We are the only species on earth who lives like this, reorienting how lifestyles should work with every generation, iterating towards not biological efficiency but to further individual resource accumulation supported by society. I think its far more likely most intelligent life in the galaxy looks more like a pod of whales or a herd of gazelle than human society, which is inefficient and selfish in most respects.
> Maybe living a more primitive life, closer to how we evolved as a species before our rapid cultural evolution phase and desire to make short term profit with all the low hanging resources on earth ...
I find this nostalgia for a time when a broken bone was a death sentence to be the misdirection of valid frustration and legitimate grievances. Modern technology in many ways has been great. What hasn't been great is the capitalist organization of the economy that constnatly demands extracting every ounce of value from us so a handful of people can get even more ludicrously wealthy.
Subsistence living has a really low population density. To get to that point would mean a massive decrease in our current population. That's going to be traumatic no matter how it goes down.
If there were more equitable distribution of wealth today, we'd be incredibly well off.
As for continually expanding, that's... every species on Earth. It's necessary for survival. A species might have a bad year and the population needs to recover. Individuals may not successfuly produce the next geneation. Every species on Earth expands to fill available resources.
A complete Dyson Swarm around our Sun would (IIRC) take 1% of Mercury's mass to build, give enough living area per person about the size of Africa and have enough energy per person about what the world as a whole world currently consumes. This represents unimaginable possibilities for freedom.
But again, the Fermi Paradox is not viewed as what the likely outcome is for a given species but whether all species will follow that path. How likely really do you think it would be that no civilization would continue expanding to gain access to more energy and resources?
Fermi's Great Filters don't need to wipe out a species to work. All a filter needs to do is to prevent them from becoming an obviously detectable spacefaring colonial species.
When we develop the means to live in space away from a planet, there isn't much reason to keep the habitat close to a stellar gravity well. Provided a fleet of habitats is self-sufficient, it could just orbit the galactic center and swing by star systems on its own trajectory, replenishing materials or seeding planets for building further habitats, as needed. It wouldn't be easy to detect relatively small habitats crossing interstellar space, but they could have surfaces and usable volumes, and populations, much greater than Earth has.
So this doesn't actually help. In fact, it creates a major problem from the outset: what is your energy source? The candidates are nuclear fusion, antimatter or black holes. The last two are extremely theoretical and it's not yet certain if nuclear fusion will ever be commercially viable.
But let's say you solve the energy problem. Well, you still have to radiate heat away into space so you're creating the same IR signature. In some ways it's more obvious because it's a huge IR signature with no apparent source or star overshadowing it.
Now you can argue that a given civilization will remain small (and thus quiet). The reasoning with the Fermi Paradox doesn't really care about that though. If there are 3 civilizations in a galaxy then being quiet may be a factor. If there are 10,000 then what are the odds that all of them will be small and quiet? Not great, logically, given the abundance of energy that is sitting there waiting to be used with tech we already have (ie solar).
Also, where is your matter coming from out in the void?
As for the idea of relatively sparse orbitals (orbiting the galactic center in your example), this doesn't seem that likely for a number of reasons, primarily that solar energy is so abundant and easy to get and also the time lag in communications. Civilizations over light years may as well be different species. And again, will everyone do that?
> Well, you still have to radiate heat away into space
How much you'll need to radiate varies with the design of the habitat. A thick-walled one will have to radiate less and, at the same time, need less energy to be kept habitable.
It'd still be a very hard to detect infrared source - unless it radiates like crazy.
> doesn't seem that likely for a number of reasons, primarily that solar energy is so abundant and easy to get
No individual prediction here is likely. The most likely explanation is still that everyone else is either dead or uninterested in interstellar space travel.
> And again, will everyone do that?
Given enough spacefaring civilizations, it's certain someone, somewhere, will.
Spoiler alert. In /The Three-Body Problem/, by Cixin Liu, a planet in the Alpha Centauri system is inhabited by an advanced alien civilization that evolved to survive the hardships related to the unpredictable effects of the three stars on the planet. Though able to survive, it comes at a great cost to their civilization (requiring them to “dehydrate” and hibernate for, sometimes, hundreds if not thousands of years) and eventually they hatch a plan to move to another habitable planet. Fortuitously they receive a message from Earth, from an astrophysicist who detests humanity and invites aliens to invade.
I found the rest of the book (and the two volumes that follow it in the series) to be very entertaining!
> "Pellet-Beam Propulsion for Breakthrough Space Exploration"
More than 250,000AU separate us from Alpha Centauri and at a speed of 500AU in 15 years, that doesn't look very realistic... More realistic is however a faster exploration of the solar system.
Pellet beam propulsion can allow fairing efficient travel at 10% c, fast enough to reach Alpha Centauri in a human healthspan, when combined with interstellar plasma braking.
I can only find very high-level descriptions of the pellet-beam approach. What's the advantage of accelerating the pellets after launch via laser ablation versus using a more powerful mass driver to launch the pellets and omitting the laser?
It’s more cost effective, assuming the mass driver is taking most of your budget. Both driver length and force required scale with the square of launch velocity.
Got me thinking whether capturing asteroids, mining them and shoting pellets with a solar powered automated facility will drive future space exploration. Seems easier than other challenges like terraforming.
This sounds like a great sci-fi premise. We think we’re being attacked by intergalactic missiles but they’re really just probes sent by a more advanced, albeit clumsy civilization in an attempt to move fast and break things in the name of discovery.
Humanity vehemently debates the meaning of the “attacks” but ultimately decides we must go to war with these aliens. Eventually the aliens do arrive, interested only in peaceful communication. They disarm our arsenal trivially, but understand why we wanted to fight them and apologize for the misunderstanding.
The interstellar void is not a pure void but is filled with diffuse plasma, the Interstellar Medium. Which, because plasma is electrically conductive at large length scales, you can brake against using gargantuan superconducting coils producing a magnetic field (which induces eddy currents in the plasma, producing a force opposing the direction of motion), slowing down like a magnet dropped into a vertical copper pipe: https://youtu.be/uh0bbW6S3BY?si=kE-1jYagQxGHIVMA
With current technology NASA get 3100s of specific impulse for ion drive, 2.3kw, 92mN. For a larger ship, not just small satellite, it should be doable to increase the voltage and get 10x specific impulse at 10x power with the same thrust. A nuclear reactor without much protection - on a long stick with small screen protecting only direction of the payload - can be something like 5-10kw/kg. That allows to have 90% of the mass to be propellant, and thus reach the speed, in about 30 years of acceleration, of more than 600km/s. With 2 stages, in 60 years with some optimization/etc. we can get 1500km/s, or 800 years to Alpha Centauri.
If there are actual super advanced civilizations, i just wish they give us a searchable DB of all planets and systems such as highest population planet, largest rocky planet, or habitable planet closest to a blackhole etc.
I know it's very difficult to explore, but I think one possibility would be to look for life on gas giant moons in habitable zones. Even if they are tidal locked, they would have a day-night cycle.
Has me thinking about the Drake (RIP) equation, thinking about life in terms of probabilities.
Seems like the chances of finding intelligent life on a planet vs. plain ol' plants and sponges life must be markedly smaller. Humans have existed on this planet for what fraction of the whole of life on this planet?
Of course, that's from one data set — and one in fact where the jury's still out as to our longevity as a species.
Sci-fi haș me thinking that pretty much any planet with life also has intelligent life but that doesn't ring true when you look at the numbers.
Hell, we'd be "lucky" to find anything that's multicellular, or even similar to our eukaryotes. "Life" on this planet has been (and still is) primarily simple prokaryotes, with horizontal gene transfer, no sex, very small size, very small genome, low energy production, etc.
First couple billion years was all that, and they still are the vast majority of organisms. And eukaryotes seem to have evolved (only once!) pretty much by chance and not by necessity.
Chances are the galaxy is teaming with that kind of thing, but what we get excited about as "life" (stuff like us) is exceedingly rare, and there's no reason to assume that next-level "complex" life will exist in a form we even recognize, if it exists at all.
I think we can know this counterfactual. On bad science fiction shows like Sliders, they visit "parallel universes" where just one or two things are changed from our world.
In one episode, they finally believe themselves to be "home". Until, late in the episode, one of them notices that the Golden Gate Bridge is blue. Supposedly, nothing else is even slightly different than the one they are from.
Well, if we examine that premise, it's pretty dumb. At some point in the 1930s when it was built, someone had to source the paint for the damned thing. The plant that made the paint, even if it was the same one, used different pigments. Mined somewhere other than where they found the raw materials for whatever color of orange the bridge really is. Each of these slight changes, 70 years before the protagonists showed up, would have caused even bigger changes. Trucks taking different routes, causing different traffic patterns, different delays. Suddenly, people are being conceived 5 minutes earlier, or 5 minutes later (or not at all). It's doubtful that anyone born after whenever the divergence occurred (whenever that was) is genetically identical. Doubtful that anyone born even half a generation later has the same birth name.
Pretty safe to say if the dinosaurs weren't godbombed, there wouldn't be humans. The number of magical convergences is too high, even for a shorter period of time.
An alternate idea is that mammals, due to some survivability superiority, were the inevitable outcome and that god-bombing only accelerated us to that. The butterfly effect is sci-fi.
If you want wild speculation, imagine there was no accelerant and lizard-people eventually ruled the planet — perhaps in the way we're headed, they would end up god-bombing themselves ... and then finally the mammals get their (long over) due.
Popular opinion seems to be that the cockroaches are waiting their turn.
What allowed mammals to take over from the reptiles / birds in the first place wasn't some inherent superiority, it was the dying out of all the ginormous hunter-killers, both animal and plant, that allowed for 'gentler' animals (mammals) and plants (grasses) to emerge. Mammals were there, grasses were there, with all the advantages that their unique physiology gave them. They were just too slow and killable in the dinosaur era to do anything more than just stick to tiny enclaves where the big dinos couldn't get them.
After the KT event that killed the dinosaurs, mammals sought to fill the niches left by dinosaurs. They grew big and huge. The few dinos that did survive, sat at the top of the food chain, enormous flightless birds. Sharks took over in the water because all the reptiles that were there were gone. It took mammals 40 million years after the bomb dropped to slowly spread over and gently outcompete the big bads. Collectively.
But it couldn't have happened in the first place without Giant Meteor making the choice for us. The Cretaceous was just that gnarly, and it would have only gotten gnarlier. The world found a local maximum, and then that maximum got flattened. The only thing that could have ended it, did.
But just because some mammal or another evolves into a sapient doesn't make that sapient "human" in the way we're using the word in this context.
The path from the little critters that existed at the time of the dinosaurs to H. sapiens today is very specific, and we know of at least 2 or 3 bottleneck events in our recent evolutionary history. The idea that our species could have arisen anyway is beyond absurd. The universe does not work in this fashion.
Ok, so it's your theory that mammals could continue to evolve in a completely different direction, with different evolutionary pressures for say 45 or 55 million years, but then all of the sudden veer off in a wild direction where they follow pretty much the same exact path that early human ancestors followed...
Such that, at the end of it all, we have something that either or both looks like an anatomically modern human and would (hypothetically) be able to have fertile offspring with a H. sapiens human?
Because, I have to tell you, that's pretty batshit.
just read an article yesterday that its not an asteroid its a super volacano that killed the dinos. of course, I don't care. I wish academics would allow us to study 40K years in the past without it being contraversial or feeling the need to injure peoples reputations
We're talking abut any life here though, right? Not just intelligent life. There was life on earth along time before humans arrived and surely will be for a while after we're gone.
Totally get that post industrial life is theoretically easier to detect via radio signals etc but the article didn't seem to specify anything so particular.
It's also extremely interesting to think about how much the statistics or thought process will change if we just find _one single additional planet with life_ - then what kind of life, etc.
Somehow finding a second planet with life seems statistically infinitely more significant - the whole thing right now is a data experiment, and for now earth (as far as we know) is an anomoly - a single "positive" data point across thousands and thousands of "negative" data points.
People keep thinking in terms of Drake's equation, and I for one am puzzled. Don't people realize that under any imaginable and non-imaginable scenarios, life outside our galaxy is irrelevant for us? There's no way we can exchange a single "Hello" with a neighbor in Andromeda, and that's the closest galaxy out there.
I don't personally deny that there could be life in other galaxies, but equally, there could be angels dancing on the tip of a hairpin. Maybe there are, but neither can affect my life in any way.
I’m getting annoyed at the disingenuous researchers and reporters who keep repeating it. A cursory look into any red dwarf based system will immediately show how unlikely it is you will find complex life in them for two reasons:
1. The planets will be tidally locked so any habitable region would at best be in a small ring like region around the planet.
2. These stars are prone to massive storms which will likely eradicate if not the full atmosphere at least any life form that would need time to multiply before it gets mutated by radiation.
We should spend time looking for the nearest sun like stars and finding technology that can study their planets instead of saying “yeah this is the closest star so obviously we should expect life there” when all evidence indicates otherwise.
Alpha Centauri is the closest, easiest star to study by far.
The technology to find Earth-like planets is pretty much an entirely separate field of astronomy to the technology required to characterize those planets (i.e. JWST doing atmospheric-transient spectroscopy).
Whatever technique you apply to some "better" candidate would be the same as a technique which works well on Alpha Centauri, so that's the place you use it (absent something more convenient - like a space probe hanging out looking back at Earth with the same methods).
Your analysis rests on a big silent assumption: that life elsewhere in the universe would be like life on Earth. A different strain of thought holds that life is actually the norm, and the way it developed on Earth was just how it thrived with our conditions. Thus looking for life in the nearest star system would be most logical. We don't know enough to rule out either and I welcome dissidence and widespread investigation, even through avenues some think would be illogical.
Like everything else ever studied. We use theory to make predictions and try to find measurements inconsistent with the theory to find out what we need to change about it. Ontology is entirely immaterial to this effort.
Moons around gas giants solves both problems. Being tidal locked to its planet and not the star, and could be protected by the gas giants magnetic field.
You better search for life instead of hunting for life, please. Hunt (as a noun) sounds especially appalling. I suspect that you _really wanna find life_, hence hunting, but still...
