Observable Universe contains 10x more galaxies than previously thought (2016)
spacetelescope.org
spacetelescope.org
That's entire galaxies. Not just stars, and that's just the observable universe.
We are still being surprised by the lifeforms we observe here on Earth, and the environments and conditions they can thrive in (including the outer hulls of our spacecraft), and we still have yet to discover and catalog all the life on our planet. Life may even come in the form of "artificial" constructs that build, learn, teach and reproduce on their own, created by "natural" life somewhere then set free into the cosmos.
How, when given the evidence of practically infinite planets out there (considering that almost every star may have at least one planet, and there are even rogue planets [0] that don't orbit any star, and that asteroids and comets or even dense nebulas could also harbor life), can we even consider the possibility that this is the only planet with life?
This game is Big, folks: Even if 90% of all planets had life there would still be billions if not trillions of them without any life, and the incomprehensibly vast distances (including voids, like the one our own galaxy is near or inside of [1]) between them may mean millions of years before life from one planet encounters life from another (which is good I suppose; every species would have some room to expand into at their own pace.)
And of course, not all intelligent civilizations will be "successful."
We will either die out on our home planet or expand.
We may not encounter other life for hundreds or even thousands of year after we develop interstellar travel, or the life that we encounter may turn out to be mundane and eventually unexciting (I mean, imagine being an spacefaring species discovering us; planetlocked and still collectively figuring many basic things out.)
For the "rogue" planets, it's easy -- we can be pretty sure they don't have any life.
For the others, we'll believe it when we see it.
Why?
Even if you assume all life requires heat and/or light, a rogue planet could produce heat/light from geothermal or other chemical activity.
A rogue planet drifting through certain nebulas might have more surrounding material for the processes of life to work with.
The life on a rogue planet may even be "artificial", say a colony of self-sufficient, self-replicating AI machines that originated elsewhere, but otherwise in-differentiable from "naturally-evolving" life.
Keep in mind that nebulae are in reality less dense than industrial-grade vacuum. From the point of view of a rouge planet passing through one, it's pretty much still empty space.
At the same time, it's extremely likely we never encounter them.
It reminds me of that (totally wrong) quote in The Hitchhikers Guide To The Galaxy that the population of the universe is mathematically zero.
The Universe is a very big thing that contains a great number of planets and a great number of beings. It is Everything. What we live in. All around us. The lot. Not nothing. It is quite difficult to actually define what the Universe means, but fortunately the Guide doesn't worry about that and just gives us some useful information to live in it.
Area: The area of the Universe is infinite.
Imports: None. This is a by product of infinity; it is impossible to import things into something that has infinite volume because by definition there is no outside to import things from.
Exports: None, for similar reasons as imports.
Population: None. Although you might see people from time to time, they are most likely products of your imagination. Simple mathematics tells us that the population of the Universe must be zero. Why? Well given that the volume of the universe is infinite there must be an infinite number of worlds. But not all of them are populated; therefore only a finite number are. Any finite number divided by infinity is zero, therefore the average population of the Universe is zero, and so the total population must be zero.
Art: None. Because the function of art is to hold a mirror up to nature there can be no art because the Universe is infinite which means there simply isn't a mirror big enough.
Sex: None. Although in fact there is quite a lot, given the zero population of the Universe there can in fact be no beings to have sex, and therefore no sex happens in the Universe.”
> But not all of them are populated; therefore only a finite number are.
There are infinities of different sizes
The same would apply for "divisible by 100" or "divisible by 1 million". This would apply to the fraction of worlds that are populated, whatever fraction of them are.
https://en.wikipedia.org/wiki/Aleph_number http://www.alephzero.co.uk/what.htm
> Area: The area of the Universe is infinite.
Right now there is more evidence for the universe to be finite rather than infinite.
But apart from that: Just because it has no borders doesn't mean it is infinite. This is a classic failure in understanding infinity. For example, the area of the surface of a torus is finite, yet when living on a torus surface you won't find any borders. Same for higher dimensions.
> Imports: None. This is a by product of infinity; it is impossible to import things into something that has infinite volume because by definition there is no outside to import things from.
This has nothing to do with infinity. This is solely due to the definition of a universe.
A finite universe doesn't import anything as well, and this is no contradiction whatsoever.
Also, an inifinitely large "part" can still import and export, despite being infinite. For example, take an infinite universe and split it into two halfs. Those "parts" import and export, despite being infinite.
There is the observable universe and there are good reasons to believe that there is "some universe" beyond the observable universe. The observable universe is finite, the reason for that is the geometry of spacetime and the consequences of it (cosmological horizon/particle horizon). But I would not make absolute statements about what lies beyond the horizon(s), since there is (and can be) no data that would justify a statement about the infinity of space or the falsification of it.
IIUC everything in the observable universe is sufficiently far away from anything else that any causal relationship with anything is either from before inflation or within the universe we can observe.
And given how the existence of matter seems to be rather connected to time, it self a by product of interaction, it seems to follow that there is, relatively speaking, nothing beyond the horizon.
>> IIUC everything in the observable universe is sufficiently far away from anything else that any causal relationship with anything
I don't think that is correct. Suppose you have a particle that is very very near the horizon. This particle has its own observable universe and we are at the edge of its horizon. Now, this particle can have casual contact with the other parts of the universe (the parts beyond). But by the time the interaction takes place, it has already slipped out of our horizon. So from the perspective of the particle casual contact is possible. But from our perspective: Not even a chance to detect this interaction.
To be honest, that question never made any sense to me, because this whole discussion is merely about refining a semantic detail of the common word "existing". It says nothing about the particle itself, but just about our language.
For me, a far more interesting question is: Is it relevant? (for science?)
And the answer is: As long as it doesn't interact in any way with us, it is certainly not relevant whatsoever.
> A finite universe doesn't import anything as well, and this is no contradiction whatsoever.
It's not far-fetched that a satirical sci-fi series could have multiple universes with travel between them.
The Hitchiker's Guide actually both does and doesn't if you look at the "Whole Sort of General Mish Mash" joke. Though the WSOGMM joke is pretty explicit that it's one infinite mish-mash with infinite perspectives and universes are just an illusion.
> Also, an inifinitely large "part" can still import and export, despite being infinite. For example, take an infinite universe and split it into two halfs. Those "parts" import and export, despite being infinite.
He actually covers this in the quote on WSOGMM.
> The reason they are not universes is that any given universe is not actually a thing as such, but is just a way of looking at what is generally known as the WSOGMM, or Whole Sort of General Mish Mash. The Whole Sort of General Mish Mash doesn't actually exist either, but it is just the sum total of all the different ways there would be of looking at it if it did.
> The reason they are not parallel is the same reason that the sea is not parallel. It doesn't mean anything. You can slice the Whole Sort of General Mish Mash any way you like and you will generally come up with something that someone will call home. Please feel free to blither now.
You can split the universe anyway you like, it doesn't make 2 universes, just a divide in the universe. Your 2 divides are exporting/importing but the universe as a sum is not.
Of course, we're just arguing over a joke in a fictional universe now. But if you're going to do that you should get the fictional physics right :P
This part of the Hitchhikers' Guide might not have aged well, but because it contributed to that effect.
> it is impossible to import things into something that has infinite volume because by definition there is no outside to import things from.
If you cut a 2d plane with a line, then both halves are infinite, yet both have "outside". You can repeat this and get infinite (aleph 0) number of divisions, each still as infinite as the initial plane.
Same way you can cut infinite 4d universe into countably many infinite 4d universes.
> not all of them are populated; therefore only a finite number are
By same logic: not all integer numbers are even, therefore only a finite number of numbers are even.
Certainly, cutting is the arch example of proportional rationing, so the word alone implies rational numbers. Then, cutting is the act of removing a set of points from one set. So, the same construction over the real line but circled only a quarter around a midpoint is effectively removing two quandrants, half of the circle. So then you could say you have two infinite sets, but exactly because they don't touch (interact with) each other.
> How, when given the evidence of practically infinite planets out there (considering that almost every star may have at least one planet, and there are even rogue planets [0] that don't orbit any star, and that asteroids and comets or even dense nebulas could also harbor life), can we even consider the possibility that this is the only planet with life?
Who gives a shit?
If our spaceships landed on a distant planet populated by a vast hyper-intelligent civilization of decidedly not-alive robots, would we shrug, say "no life here," and head home bored?
Maybe life isn't what we're looking for?
Maybe chemistry is not so poor that it has to repeat itself by re-creating something that we would consider to be alive. Maybe the non-living things are vastly more interesting.
Maybe finding distant life is like visiting a distant country and finding a McDonalds.
Maybe "let's find life" is just a failure of imagination. It's SETI, not SETL.
The thing about searching for "life" over "intelligence" is that life doesn't necessarily need to be intelligent for it to be interesting.
I also think the SETI example you've made is a tad unfair because their process dictates that their search be for intelligence (crudely put, radio transmissions). Whereas when you're visiting a planet, you can observe a wider scope of life as it need not be intelligent (as we can perceive anyway) for markers to be identified.
That's right! So how would you define life? Or the meta-question, why bother? We gain nothing from figuring out what's "alive" and what has "merely" a rich complexity.
"Search for life" is a category error.
> The thing about searching for "life" over "intelligence" is that life doesn't necessarily need to be intelligent for it to be interesting.
If something is interesting, why do we care if it's "life?"
Anything we find is likely to operate on some scale vastly different than what we're familiar with. We won't even agree on whether it's alive.
> Whereas when you're visiting a planet, you can observe a wider scope of life as it need not be intelligent (as we can perceive anyway) for markers to be identified.
My hope is we'll find markers that are clearly weird and that aren't evidence of life but maybe something more and weirder that we don't understand.
Isn't that even more interesting? Why hope to find life, when we know life is already possible?
We know it's possible, but we've also seen it happen only once. The observational data we have suggests the universe is mostly dead - that is, not complex. Or, in other words, boring. Discovery of any complex process on a comparable level to even simplest of what we call life would be a civilization-changing breakthrough. It would prove the universe is not boring.
(It would also ultimately kill off most of our existing religions.)
I think you may be underestimating the tenacity of religions
Unconditional belief in the unknowable gives you an awful lot of wiggle room when it comes to evidence.
Religion tends to be very careful to stay in the area of not providing a testable hypothesis which means that new alien knowledge won't prove it wrong.
> Religion tends to be very careful to stay in the area of not providing a testable hypothesis which means that new alien knowledge won't prove it wrong.
That's true, but until very recently, the idea of life elsewhere wasn't really considered seriously.
Source: I'm not religious but I've been dragged to plenty of sermons by the extended family.
> "Search for life" is a category error.
To be honest I think you're over thinking the whole "life" thing. It's just a label. You could replace that term and still have the same arguments. eg "What would someone define as 'interesting'? What does that category even mean?". Or "complex", or "intelligent" or any other label.
> Why hope to find life, when we know life is already possible?
Possible, yeah. But it's unique in that we are constantly finding a multitude of other phenomena in the universe yet we've only ever observed life on our own planet. That alone makes this topic interesting in my opinion.
I don't see why it has to be an either / or though. Nobody is suggesting we search for life at the sacrifice of learning more about black holes...or whatever.
This is not to subtract from geology which is an interesting and useful study, just to say it is unlikely we would discover anything very new if we could somehow examine every planet in the universe. However if we add in life we would expect a lot of interesting variety to study.
As a different take on that: Suppose we develop "robots" that can sustain themselves, mine resources, produce [ever improving] copies of themselves, and learn on their own and teach each other. Then we send them to colonize a distant planet.
Fast forward a hundred years. Those robots now have a "civilization" of their own.
By what criteria would that civilization fail to be counted as "life" by an species looking for such?
- Jupiter & Saturn pick out most of the comets, so we encounter massive reset only very rarely
- thanx to hitting other planet long time ago, we have a spinning molten metal core inside planet generating magnetic shield for all nasty radiation
- moon gives us tides & stability
- our sun is just the right size and age to be stable
- we're located at quiet part of the galaxy, which itself is pretty stable
I think some primitive life (ie stromatolytes equivalent) can exist on many places, simply because it happened on our planet very early when it was very violent place to be - so random arrangement of matter into self-reproduction is feasible.
But to evolve into specialized multi-cellular organisms took more than billion of years, a step that might not happen at all.
And to create an intelligent life is another massive step up (or accident). There is Drake equation to manifest it, but basically all variables in it can be anything including 0, so it's kind of useless.
So from my perspective there are couple of options:
- universe is too young (if you consider average star age compared to estimated universe age), so we're one of the first sentient arrivals, others are behind in evolution
- we're just not interesting enough to be contacted by superior races - just look at the news, I wouldn't blame them. We're 'meh' category at best, although most like to think of themselves in very different perspective
- we're fucking alone, weird random anomaly (by far the most scary option of them all)
There is a wonderful TV series from BBC called Earth: Power of the Planet, which explores this topic to great details, highly recommended!
Mars lost its magnetic field long ago, but it had one once.
Venus, well, it's an acid rain oven but it could have been different.
Both could have had conditions for life (as we know it) once.
• Hive-mind species where there are no individuals.
• Species without any gender or sexual reproduction, whose individuals are spontaneously "born" in specific locations and conditions on their planet.
• "Species" consisting of a single, massive/long-lived individual.
• Parasitic intelligences that "infect" various other, unrelated species and direct them towards the goals of the parasites.
• Lifeforms floating around in gas giants or even in nebulas.
• Life-bearing planets themselves being a lifeform; that "reproduces" when the civilizations it supported upon itself go on to terraform other planets to become like their home planet.
It could be on the surface on active star, neutron star (someone already tackled that in sci-fi), all kinds of dwarfs, nebulas, maybe even something living off dark energy? Or black hole.
Energy means movement, and if matter/energy will eventually arrange into something 'alive', it might be enough.
The fundamental thing about life as we know it is not just that it's made of the few particular elements it uses. It's about those elements being a sweet spot for molecular nanomachinery. It's not clear that any other combination of elements might be able to form a stable replicator and bootstrap itself into large-scale complex system. In fact, it might be that life can only arise by itself using materials our life is made of, directly because of laws of physics in our universe.
Or put in another way - if abiogenesis of our life is improbable, a spontaneous creation of robots - large scale machines with digital brains - is orders of magnitude less likely still.
Carbon is the only atom [I know of] that can form long chains of double bonds (even triple though they tend to be unstable enough to not matter). Nothing else allows the chemical complexity needed for self reproduction.
Water is a weird molecule. Many chemical reactions happen in water that would be uncontrolled or not happen at all without water. The polar properties, the fact that is expands when it freezes (that is frozen water floats on liquid), and acid/bases are all interesting properties that are very useful for life. I suppose that something else could fill this role, but since water is common in the universe I doubt it.
Yes life elsewhere is unknown and so we cannot say for sure it will not look like our, but chemistry is a known.
Given we didn't arrive until 14.5bn years into the universe's existence, I'd find that extremely hard to fathom.
Let's ignore the 'bn' part - this place is 14-old. Our system is 4-old. Life is 3-old. Multi-cellular is 2-old. Sentient is 0.00001 old. With usual star life has +- 10 to escape, or it will be destroyed. It doesn't sound so far-fetched to me.
But maybe it's all different - plenty of life all around the place, even super smart & evolved, but maybe speed of light simply can't be broken no matter what. That would dampen any rise of galactic civilization. Or some other unbreakable constraint.
That assumes they're consecutive, not overlapping. Assume it takes 4-old, space them out by 0.1-old, and you could have 100+ generations between the first and us.
While it's true that life "out there" may look vastly different, I feel like sometimes ET-optimists use that as a hand-wavy defense that overlooks two curious details: First, we haven't found any different-looking-life-out-there on, say, Venus, or Mars... so clearly even in a solar system with some "lucky" aspects for life there are plenty of environments where life just doesn't "find a way." Second, the relative quickness with which our kind of life appeared in Earth's history suggests an oddity that we haven't even found other examples of our-general-kind-of-life out there.
A good book that explores some of the proposed solutions to the Fermi Paradox is Where is Everybody? by Stephen Webb. (It does a good job using math to explain why it's a little surprising that we haven't found ET life even within our own galaxy, and it does a good job knocking down most of the sociological explanations by noting that it would require every other civilization in the galaxy to behave that way with no exceptions.)
Until we actually observe it, no, we can't be sure; the probability of it existing is high simply due to the sheer amount of dice rolls there are in the universe, but the likelihood of us observing it is low. We already know there is and was no intelligent life in our solar system besides what's on Earth; there's still hopes of finding traces of microbial life on Mars and maybe that ice moon. But unless we get a signal from far away (what the SETI project has been scanning for for decades now), we'll not find evidence of alien life in this generation.
I also doubt humanity will find a way to travel fast enough to get to another solar system within a human lifespan. If we do, it'll probably involve bending the fabric of space-time and the Great Old Ones will return from Beyond the Observable Universe and will start eating us.
We do not know all that was on Earth. We wouldn't have known about dinosaurs if we didn't chance upon their remains, and we only recently learned that they had feathers.
There is probably no way to know everything that has happened on this planet.
–
And that brings another facet of the point in the GP:
It's not just the distances between different planets that hinders life from meeting other life; even life on the very same planet is prevented by vast periods of time from ever encountering each other.
The next solar system is only four lightyears away. Given the will to break nuclear test ban treaties we think we could develop nuclear pulse propulsion drives that achieve about 10% the speed of light. Even after accounting for acceleration and deceleration that gets us there in a human lifespan.
Granted, even at that speed generational ships make a lot of sense, and the selection of targets is still somewhat limited. But we can get to our neighbouring solar systems in "reasonable" time if we want to, with very doable development effort
Also plenty of water out there and sunshine, burning hydrogen as fuel should be possible.
Now you will have enough machinery in space to mine building stuff and enough fuel. Gradually build permanent colonies in space.
It won't get all humans out of earth soon or ever. But it will put some humans permanently out of earth. Then keep building colonies as population in space grows.
Once you have done this you have done two things:
1. Eliminate a existential threat to humanity more or less permanently.
2. A slow but steadily growing population of humans in space.
Several decades/centuries after that you could have humans permanently living and working in space. From there its a matter of population growth, resources are a plenty and you have a universe for the taking.
Once you have a massive presence in space interstellar travel by definition is a question of acquiring real estate to keep up with population growth.
But if you told them they could get unlimited clean fuel. There could be plenty of funding to extract water/ice from asteroids and send it back to earth.
It gets _something_ there in a human lifespan. The only really well though out models for that are Daedalus and Icarus, and they would involve flybys only of probes the size of a hockey puck, or a washing machine at most. The cost of which would be civilisation impoverishing.
I think it's a very reasonable chance that humanity will never, as a functioning human populated civilization, ever spread beyond this solar system. Now 'never' is a pretty long term statement, but no matter how advanced our technology becomes, it's still likely to be constrained by the physics we know. It looks like spreading beyond this system would cost a very large fraction of all the resources we have in the system to start with, if it ever becomes practical at all.
The basic idea is to combine two kinds of ship, neither of which we know how to make work individually, to form one that we can make work.
The first is the generation ship. The problems with those are that (1) we don't know for sure how to make a completely self-sustaining ecosystem that can keep a large enough population for viable colonization alive for the hundreds of generations it would take to reach their destination, and (2) such a population would require a freaking large ship, raising all kinds of challenges.
The second is the cryogenic suspension ship. The problem there is that we don't know how to unfreeze them without killing them.
Can we address the generation ship problems? Both problems stem from the need to have a large population. If we didn't need a large population, we could use some of the space that would have otherwise been consumed by colonist families to bring food to supplement the food produced by the ship's ecosystem, and eliminate the rest of the space they would have occupied.
Assume we can develop a food that can be stored indefinitely and that has the caloric density of rice (200 calories/cup). There are ~4 200 cups in a cubic meter, which gives 840 000 calories in a cubic meter. At 2000 calories per day, that's 420 days of food. A storage unit 10 meters on a side gives 1150 years worth of food for one person. And this is assuming that the person is getting all their calories out of storage, not depending on the ship's ecosystem.
If the storage food only needs to be a supplement designed to make up for things that we can't figure out how to get from the ship's ecosystem, then the numbers get even better.
This is where the cryogenic suspension comes in. We can't suspend and revive people--but we can do eggs and sperm indefinitely and revive them. Our cryonic generation ship will carry the colonists as frozen eggs and sperm. The only warm people on board would be the crew to operate the ship, and to raise the next generation crew.
Note that the next generation crew could come from the frozen eggs and sperm rather than from mating among the current generation crew, so we don't have to worry about a small crew becoming severely inbred during the trip.
If we can ever develop robots to the point that a robot can raise and educate a human baby without any human supervision, then we can leave out the crew and the food and the ecosystem, and just send robots plus frozen eggs and sperm.
The Orion project was designed for sending a city-sized space ship to Alpha Centaury in ~100 years.
The hard part seems to be how to build a city-sized ship, not how to move it.
https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls...
Basically nothing of it was actually built (nuclear propulsion wasn't an well accepted idea - for good reasons that won't matter as soon as we start building in space). There was just some very small scale prototypes.
In comparison, project Daedalus moved much faster.
So life can apparently adapt to extra-Earth locations. The leap of faith is then, that it hasn't left Earth, or that life on Earth didn't come from somewhere else to begin with? Because either scenario becomes plausible. It'd be strange to believe it didn't happen.
> Looking at all of those galaxies forces you to come to terms with how little any of us really know for sure.
Only if you are forced to look at all that - in detail - and since that's not essential to a mundane life, there is no obligation to believe anything much.
I mean, I'm trying to make a point about believe in distinction to knowledge. There is yet a weaker modus operandi, which I'd call awareness for now, but that's a loaded term, too. If you hold two thoughts about contradicting possibilities in mind at the same time, that's not believe. Believe happens when externalities force a decision, also called leap of faith. Then you choose to believe in one possibility. Knowledge on the other hand means the possibility of round about 1.
"Are we alone in the universe?" she asked.
"Yes," said the Oracle.
"So there's no other life out there?"
"There is. They're alone too."
The evidence becomes more and more every day that life is not a one in a trillion miracle but a natural product of certain environments. To assume we will never have contact with other lifeforms seems like a huge jump.
I'd say there certainly is life out in the Universse and it's quite possible there is intelligent life.
But the distances are so large that we will never meet any other intelligent life before our own civilization vanishes.
Can we even detect any of the probes that we ourselves have sent out, without knowing exactly where they are and how to communicate with them?
Human minds aren't good with very large numbers. What seems "practically infinite" to us - isn't, really.
The number of all planets in the universe is said to be in the ballpark of 10^24.
Meaning (obviously) if you keep on dividing it by 10, in just 24 steps you get down to 1.
Meaning if there are 24 factors crucial for life to evolve, and each has a 10% chance of occurring - it's actually quite likely only one planet would win on this lottery. (At a given point in time, that is - that's another aspect of course).
Or 12 factors, but each with a 1% chance. And suddenly it doesn't seem like a number big enough to warrant certainty claims...
Basically it is the "wheat and chessboard" problem in reverse.
You start with a huge pile of planets, but once you start splitting the pile, it shrinks very very fast.
Personally I'm not sure either way, and I think being sure (either way) is just naive.
I believe there is microbial life out there, and I accept a slim chance we may actually discover it - say, over the course of the next few centuries - but I'm sceptical about the existence of intelligent life, and even if it did exist, I see the chances of any contact to ever occur as zero.
We even have evidence of life we have never seen, will never encounter, and may never even have conceived as being possible to exist without that evidence: the enormous dinosaurs.
Life on Earth evolved and spread under specific conditions - our gravity, sun brightness, geology, magnetic field, large moon, etc etc. It then spread to all possible environments on the planet and evolved to live there.
Unfortunately, it could be that the 'growth conditions' for life are quite specific even if - once it gets going - life can evolve to more general environments.
Look, humans already adapted to being in space for prolonged periods of time. We adapted to every climate. But drop a naked human in a random spot on our planet, and he will die with high degree of probability. And that's after billions of years of evolution.
Who knows if this jump alone should be taken for granted - plus, not many planets could provide 3 billion years of "good weather" (or staying habitable) to start with.
Lewis Wolpert : https://link.springer.com/chapter/10.1007/978-3-0348-8026-8_...
We might be a slow developer and poor representative sample in that respect, but without more data it's hard to tell.
> plus, not many planets could provide 3 billion years of "good weather" (or staying habitable) to start with.
I suspect the opposite will be true, red dwarfs are the most common type of star and are stable for trillions of years. Even if the average time it took multi cellular life was 30 or 300 billions years then it might not matter for life evolving there. They do come with some other caveats though: https://en.wikipedia.org/wiki/Red_dwarf#Habitability
But all lifeforms we know evolved from one common ancestor, it's one tree of life. As far as we know life evolved here only once.
So we know that once life happens it can become completely ubiquitous, but it doesn't say anything about that crucial first step.
That's not nessisarily true. Single celled organisms have a rather fluid exchange of genetic information even our 'single cells' are really several different organisms. It's possible life evolved many times on earth and current single celled organisms and thus all life has a mismatch of ancestors.
Further, life may regularly evolve even today, but simply get eaten due to the stiff competition.
PS: We know life evolved at least once, but the high end could be multiple times a second on earth.
It's also possible it evolved elsewhere and rode here on a meteor - or was brought here by some other lifeform several orders of magnitude more advanced than us, using earth as their own cosmic terrarium.
It's good practice to assume the simplest possible solution. However, the full range of the full range of what might have happened is ridiculously large.
Meaning if there are 24 factors crucial for life to
evolve, and each has a 10% chance of occurring - it's
actually quite likely only one planet would win on
this lottery.
a very large number of planets * a very small chance of life forming = ???
We don't really know how small the chances of life are. It may be that the chances of life forming are so small it dwarfs the number of planets in magnitude. It may be an incredible miracle that we live.
It seems that whenever an article says "there are more planets than we expected", someone concludes "this makes it more likely that there is life somewhere out there", but it's also fair to conclude that "this means the odds of life forming are lower than we previously thought" since we haven't actually found any other life. As Fermi asked, where is everybody?
However I do think that you vastly underestimate the probability of life. Take a look at https://en.wikipedia.org/wiki/Earliest_known_life_forms . See how quickly life appeared once the earth had cooled down? It's almost immediately!
I'm pretty convinced that almost all star systems have some complex energy conversion cycles that could be classified as life. Let's not make the mistake of assuming all life has to be carbon based.
[1]: https://en.wikipedia.org/wiki/Hypothetical_types_of_biochemi...
What if life can only appear as a planet is finishing to cool down?
https://en.wikipedia.org/wiki/Panspermia
I find this a compelling possibility.
DNA's 'half-life' is about 500 years. Meaning that each nucleotide-bond has a 50% chance of breaking every 500 years.[0] At the time scales of interstellar travel, DNA based life is very unlikely to survive.
EDIT: This then means that DNA based life was likely a local phenomenon. This also means that other planets may have done the same and that a 'interstellar seed' is not required.
[0] https://www.the-scientist.com/?articles.view/articleNo/32799...
I think it's worth pointing out that there's lot of space between "absolutely sure there is" and "absolutely sure there isn't", and I doubt any fairly intelligent person actually holds either of those absolute positions. Which is to say that really, the arguments are over the degrees to which we think it's likely there is life, or intelligent life, elsewhere.
Yes, especially if you take into account the speed that entire galaxies travel in space. It's mind boggling high. So the effort for any civilization to build technology that allows them to travel through intergalactic space until they get "hooked" by Milkyway's black hole magnetic field is infinitely complex. That's where the whole idea around worm holes makes sense.
Street-Math time!:
Lets assume that means you need to resolve a meter sized elephant on another planet. Lets choose Vega, as that is ~25ly away, really the furthest star we can go to (and return from) and still have someone alive here to have a beer with afterwards (50 year round trip). 25ly is about 2.3E19 meters away.
A 1 meter sized elephant at 2.3E19 meters is about 4.3E-20 radians.
Lets use wavelengths in the visible spectrum. Hydrogen's Balmer peak at 656nm is a nice red color to look at (though stellar issues abound here).
The resolution of a telescope is approximately : R = L/D. R is resolution, L is the wavelength, D is the diameter. Rearranging we get the diameter to be : D = L/R. Plugging in a L of 656nm (~6.6E-7m) and a R of 4.3E-20radians and you get D.
D is about 1.5E13 meters.
For reference the earth is about 1.2E7 meters, about 6 orders of magnitude smaller. 1.5E13 meters is about 14 light-hours, much larger than the Earth-Sun distance.
Soooooo, I think it's going to be a while ...
;)
Ehm... sorry to be a bit pedantic, but the distinction between the two has no effect on your argument here. Either way there are ten times as many environments in which stuff happens.
Also, as b3lvedere's comment points out elsewhere, you really shouldn't trust gut instincts when it comes to reasoning about infinities. Unless you're a mathematician specialized in the subject, you're pretty much guaranteed to be wrong about them.
(having said that, I'm also more inclined to believe that there's plenty of life out there. I'm not as hopeful about complex life-forms escaping planets though)
Either way, I actually think that the Dark Forest principle applies heavily in the universe (https://en.wikipedia.org/wiki/The_Dark_Forest) - no halfway intelligent civilization should assume the intentions of any other civilization are benign until proven to be so, and will always take steps to either hide themselves or shoot first and investigate later.
There’s 250 billion stars in our Milky Way galaxy. Our local supercluster has 100,000 galaxies in it. Previous estimates were that there are 100-200 Billion galaxies in the observable universe and this article suggests the figure is 10x as much as that.
The Kepler telescope has been discovering planets around nearby stars for a while now, and the impression we get are that at least half of the stars seem to have planets around them.
With 250 Billion stars in our galaxy and 200 Billion galaxies or more just in the observable universe (also cosmologists believe the actual universe is larger than the observable universe by an unknown amount), that leaves us with somewhere in the neighborhood of 25 Billion trillion (that is, 25 Billion * 1 trillion) planets in the observable universe. 100 Billion + worlds just in our galaxy.
We also believe that the laws of physics are the same across the universe and that water and other basic elements are abundant throughout the universe.
So to me it seems like even with extremely remote probabilities of life existing, to me it seems most likely that there would be lots of planets where life started.
There's an extremely remote probability that the atoms in your body might teleport to the Great Wall of China. How much are you willing to bet that it happens?
Yes, we can. I don't personally think life is all that rare in the universe- we agree there. But I think it's perfectly fair that it's possible we're alone.
It's really a question of how many unlikely events lead to us existing and how improbable those events are. People always start with "Let's imagine only 0.1% of planets have conditions for life! How rare that must be!". But is 0.1% a fair estimate? What if the true number is 1E-20? Or 1E-40? 0.1% is easy for humans to understand and think about so we always start there. Then apply the same reasoning to the jump from single-cell life to multi-cell life, to the odds of become larger animals, the odds of becoming intelligent.
We don't know what the odds are, so we always use odds that sound low but are actually quite large.
Just like humans are biased towards not seeing how big the universe is, you (like everyone else) are biased towards using probabilities in the realm of human understanding. That is just as wrong.
The question isn't how big the universe is, it's the comparison of how-big to how-unlikely.
https://www.haystack.mit.edu/hay/staff/jball/etiy.pdf
Dark Forest
The tyranny of ‘c’
But, as impressive as that all sounds, that's describing scale with exponential growth, but exponential growth pales in comparison to combinatoric growth.
The number of ways you can arrange 100 people is far greater than the number of estimated atoms in the universe. And not _just_ greater, greater in a way that is difficult to explain. A drop in a bucket? No. A drop in the ocean? No. All our metaphors are physical, and so they're inadequate, but let's just it's beyond all that.
Of course, that doesn't mean the probability of other intelligent life is best assumed to be of a combinatoric nature, but let's get ahead of ourselves and let our awe of the universe's size cloud our judgement. It's far from infinite, and silly to assume intelligent life is certain.
The article is about work, using models of galaxy formation, that tries to better estimate the number of galaxies we can't detect due to limits on telescope sensitivity, but which are nevertheless theoretically observable.
It might be useful to describe the detectable part of the observable universe as the "visible universe", but astronomers have a different meaning for that. See https://en.wikipedia.org/wiki/Observable_universe.
"It makes me so impatient for a more powerful telescope with the ability to see far into the infrared, because I can’t help but wonder what’s still invisible to even the XDF. Twice as many galaxies? Four times? Fainter ones, redder ones, more distant ones, or all of them? There’s at least 176 billion of them in our Universe, but I can’t help wonder, “how many more?”"
http://blogs.discovermagazine.com/crux/2012/10/10/how-many-g...
"It boggles the mind that over 90% of the galaxies in the Universe have yet to be studied."
Maybe this one's different, but when discussing astronomical terms, a factor of 10 doesn't ever surprise me. What does surprise me, continuously, is how many unimaginably large numbers of factors of 10 are involved in anything related to the size of the universe. There are so many estimated stars in the universe, it would make little difference to my already boggling mind if our estimates were off by a factor of a million.
A demo:
...
To be clear, per the article, the new discovery isn't about the early universe being a significantly different density (i.e. anything other than 'approximately flat', total omega ≈ 1) than the current one. Like, it's not that there was more mass-energy in it that's somehow vanished, rather that it's just distributed between more & smaller galaxies