It is possible that radio is just a temporary thing and we will find something much better, perhaps faster than the SoL,which would be really handy if travel faster than the SoL is possible. Meaning that the time that an intelligent species uses radio is comparatively short.
In some ways we are running up against the limitations of EM spectrum and our solution is to reduce power, have more, smaller cells, re-using the same frequency. So our galactic radio signature is already fading in that respect. So even if a radio replacement is not found, there may be ways to efficiently use it in low power/repeater based ways.
Why do you think population pressure is the only reason for space exploration and even colonization?
The thrill of adventure. Seeking the unknown. Safety (if the home planet’s sun explodes, the race lives on.) Liberty (someplace where the Huguenots can live without being lit on fire.) Really large baseline interferometry. And just maybe, meeting other intelligent beings and selling them smart phones!
chappachula’s post also assumes that aliens would be just like humans (it also assumes that even humans would have no need, which doesn’t seem to hold together). The most important one on your list, however, is simply the continuation of the species. In the next 500 million years, probably less, complex life on this planet is going to be gone. In that time it’s almost a certainty that something else nasty is going to happen that will wipe out some or even most complex life. Could be another large impact, certainly climate change (we will eventually have yet another ice age period…they haven’t gone away, just been pushed back into the future). There are so many things that will or could happen that, assuming as a species we want to continue to exist we will have to move at least some of our eggs to other baskets. In our own solar system there are places we will almost certainly go at some point, but to REALLY be safe from eventual extinction we would need to figure out ways to expand outward. It’s not unreasonable that other technological species could figure that out as well (whether we ever do or not is yet to be seen).
Another big reason to spread out is simply resources. There is a finite amount of resources on any given planet. We haven’t come close to tapping ours, but then we are a type 0 (or maybe type .5) civilization. Eventually, we will tap out the potential here. We could either stagnate and decline or expand at that point.
Plus, I’m pretty sure there is an alien market for the iPhone 1000…
Trinopus has pointed out a misconception about the Drake Equation; it doesn’t make any assumptions- you (the person using the equation) make the assumptions, and everyone can make a different assumption if they wish. Think of it as a calculator.
There is a similar misconception about the Fermi Paradox; the question isn’t ‘why haven’t they made contact yet’ but ‘why aren’t they here already?’ If there were any number of expansive, billion-year-old civilisations in the galaxy (even if the number were one), they would be here already - they would be us. Or rather we would be them. We’d learn the billion year history of the civilisation in school.
For whatever reason, billion-year-old expansive civilisations don’t exist in our galaxy.
I think there are many unique attributes here that allowed life to overcome the bottlenecks of physics and chemistry:
Liquid water
Not too hot, not too cold
Relatively (perhaps) short days - some dark and some light
Relatively (perhaps) short seasons - not always cold and not always hot
Protective atmosphere all the time
A moon, causing the tides - part-time wet, and part-time dry
Happy mixture of elements in the right amounts
Enough time being stable - no planetary catastrophes for a while (OK, not counting a few extinction events).
We have a pretty good fix on how our planet generally operates, and we know with 100% certainty there is life here. Everywhere else outside our solar system we are guessing at what conditions may be like.
I find it interesting that discussions such as this often tap faith to explain why we are not alone, yet science has not found any evidence at all to suggest there could be life anywhere else. Do we accept science as fact or not?
? No one here has spoken of faith, and I don’t know of any scientifically literate people who have “faith” we’re not alone. (Leaving theology aside.) Instead, lots of people think that some of the Drake terms are likely to be favorable.
The recent spate of discovery of planets that probably have liquid water is heartening to those of us who want there to be life elsewhere.
(Even scientists are allowed to want certain things to be true!)
Yes on 1, 2, 7, and 8. The rest are of questionable importance. The day and season length, for example–provided that they aren’t extreme enough to allow oceans to freeze to the bottom (which would violate condition 1) I don’t think these are as important as one might think, since life very possibly originated around black smokers, and would have been chemosynthetic, not photosynthetic. The moon would also have been irrelevant because the black smokers would have had no need to be near the relatively narrow strip of near-continental land affected by tides. Plus, life on Earth is older than the bulk of continental crust anyway. As for the atmosphere, there would have to be something there to keep the water from boiling away into the vacuum (of course. boiling away water would form an atmosphere on it’s own) but the composition would also have little impact at the depth of black smokers (and the atmosphere present in the early history of life on Earth would be nearly instantly fatal for modern metazoans anyway.) The water would also be an effective protection from ionizing radiation.
An Earth without some of the things you mentioned may never have been suitable for complex, eukaryotic, muticellular life, but IMHO a little green slime coating a rock on an exoplanet is almost as profound as Little Green Men.
There is also no evidence at all to suggest that there couldn’t be life anywhere else. In the lack of empirical proof, the principle of mediocrity is as good a rule of thumb as any.
The other problem is that, out of billions of humans on Earth, there are still people who love having kids and if it were an easy thing to do, would have ten each. It’s way too soon to assume our instinctive, evolutionary impulse to reproduce has actually changed. Similarly, out of all the thousands or millions or even billions of potential star faring species out there, not a single one bucked the trend and did decide to continue reproducing and expanding.
While other posters have addressed the issues with a lack of evidence not meaning much in science I think that there are a few assumptions above that may be in error.
While water is an effective solvent the fact that we use it does not mean that it necessarily is required for life.
There’s been growing evidence that Pluto is hiding a liquid water ocean beneath its frozen surface so even the seasons and daylight assumptions may not be correct.
If you look at the a periodic table showing the cosmogenic origin of each element it would be highly unlikely that a correct mixture of elements is rare. The most critical to life (carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur) These are all fairly common and all below the exothermic fusion limit of Iron.
The speed at which life arose on the earth tends to indicate that it may very well be the default given the correct conditions.
Despite the poor explanation of entropy, it is not a tendency to disorder. To offer another equally invalid summary, entropy change tends to increase information. But really the essence is that Entropy change is an energy-dependent property. It may be driven because DNS lower energy state constituent particles and thus wouldn’t require any form of faith.
The math, observations and other data makes it highly unlikely that we alone and almost all scientists expect extraterrestrial life to exist. The lack of unambiguous evidence on the existence of extraterrestrial life does not require scientists to ignore the large amount of data that suggests that it does. It is just not scientific to claim that it is established fact, a tested hypothesis etc…
That personally believe that the difficulties and cost of interstellar travel are greatly diminished. As an example high energy particles/radiation are a serious barrier to our ability to manned interplanetary spaceflight and most people ignore the implications of redshift in relation to travel approaching the speed of light. It doesn’t take much to shift even visible light towards gamma rays if you want to shorten travel times.
If we are lucky enough to detect another civilization I would consider it equivalent to every person on the earth winning powerball at the same time.
That said we have two major fields of Physics, Quantum and General Relativity that are in conflict with each other, yet both seem to meet every test we throw at them. At a minimum both are incomplete but if something replaces them maybe it becomes more practical.
That said without the dreamers we wouldn’t have hypotheses to test, and so while people like to criticize theoretical fields I hope they keep it up.
Science has found plenty of evidence to suggest there could be life out there, but so far none to establish that there actually is life out there. Science helped us get a handle on what chemical elements are, how certain chemical elements could form life (at least on this planet), where chemical elements come from, and how to detect chemical elements from far away. If we detect spectral lines for hydrogen, oxygen, carbon, phosphorus etc. on some distant exoplanet, I take that as excellent evidence that life (as we know it) could exist there (though I don’t accept as given that life does - or did - exist there), because it would demonstrate that the life-supporting elements that make up what we call “organic chemistry” are not exclusive to Earth.
That’s not entirely true. The equation might leave out important (mathematical) factors that may need to be quantified. OK, to be fair, these factors may be subsumed (assumed) into the existing ones, but, just as a counterpoint, examine the “Rare Earth” equation here.
The reason “science” hasn’t found evidence of life elsewhere in the Universe is because we haven’t been anywhere else. To make a critical assessment of the probabiliy of extraterrestrial life from what we’ve currently explored is like going to New York and evaluating he culinary options of Manhattan by ordering exclusively from hotel room service. We’ve landed exploratory craft on four extraterrestrial major bodies (Luna, Venus, Mars, and Titan), the first two of which are almost certainly devoid of any kind of life as we could recognize is, and have only explored very tiny swaths of Mars and only the landing area around the Huygens on Titan.
The chemical compounds of terrestrial life are composed of the most commonly availalble chemical elements (H, C, N, O, P, S) save for the chemically inert helium, and the conditions of Earth are almost certainly not in any way unique or peculiar. On that basis alone we can assert a high probability that the conditions under which life on Earth formed over four billion years ago have likely been repeated frequently across the Universe, and unless there is some kind of élan vital that biology has yet to identify, there is no reason to think that life is in any way special to Earth, or that the specific environments of Earth is necessary to cultivate life. Whether complex (multicellular-like) life, much less something akin to terrestrial Animalia exists elsewhere is unanswerable, but given how it has come to spread so widely and survive so many catacalysms on Earth it seems reasonable that other worlds could produce a self-replicating form of analogue to animals.
Intelligence is really the one big unknown, particularly given that most species, including some of the most evolutionarily successful on Earth, do not have what we would regard as any kind of conceptual intellect. However, given the number of species in different classes and even clades that have essentially independently developed a high degree of problem solving and social intelligence, it is not beyond expectation that something comparable to some terrestrial intellect could developed, although it may likely be more different than the intelligence of a human from an octopus, or a dolphin from a parrot. How long advanced intelligence is stable and useful, however, is another question; although it has worked for primates for a few tens of millions of years, we are hardly the most enduring species on the planet, and as smart as we’d like to think we are, we haven’t even figured out how to effectively regulate our use of terrestrial resources to prevent depletion and pollution, much less gain access to the wealth of material just a few million miles away in space. It may well be that extraterrestrials are watching us with as much amusement as a human child might watch an ant farm, and wondering at our obliviousness in seeing the real world around us for our nearsightedness.
We’re not nearly smart enough to make any definitive arguments about the existance of extraterrestrial intelligence. Hell, we’re barely smart enough to even make qualified speculations on our own intellectual capabilities.
I believe it’s safe to assume that contact with the vast majority of potential civilizations in the universe is impossible. Most of the universe is expanding away from us faster than the speed of light (everything beyond ~13.7 light years from us). That’s a speed limit that’s no doubt impossible to exceed no matter how technologically advanced any civilization has evolved.
So, at best, we have only galaxies within our Local Supercluster with which we could possibly make contact. This certainly includes a plethora of star systems that could (and I believe do) sustain life, but life that can contact us? I doubt it. It’s a matter of odds.
If no civilization within the Milky Way has developed interstellar travel/communication, we won’t make contact with them. I think the odds are good that no civilization within our galaxy can travel between stars.
If a civilization in a galaxy beyond the Milky Way has developed interstellar, but not intergalactic travel/communication, we won’t make contact with them either. I think the odds are good that no civilization within our Local Group can travel between galaxies.
Are there civilizations beyond our Local Group, but within our Local Supercluster that have developed intergalactic travel/communication? Maybe. But, why would they expend the resources to travel beyond their own local galactic group? What could they possibly seek to gain that they could not get from galaxies closer to home (with much less expenditure of resources)?
Civilizations beyond our Local Supercluster would need faster than light travel/communication to reach us. I’m not holding my breath on that happening.
I think you are being incredibly over-ambitious in your idea of communication range. I’d put the practical outer limits at a few hundred light years at best.
They already came over thousands of years ago; built the pyramids; instituted the ancient mysteries and started what is now known as freemasonry and the Occult.
But we’re only talking about a finite time in the future, so a finite amount of material is fine. And if a finite amount of material isn’t enough, then you’re screwed anyway, because there’s only a finite amount of material that we can possibly reach.
Non-mutating replicators that are built cheaply, never run into problems they can’t solve, never get out of control in your own system, and keep working forever are pure fantasy. Once you start invoking magical technologies, the answer to ‘why haven’t we been contacted…’ becomes ‘because things work according to what we understand of physics and your magic doesn’t happen’.
How are you going to gather the immense resources needed to create an interstellar colony ship and go through the long and highly technical process of creating the ship when other people are lighting you on fire? If you’ve got the resources and time to build interstellar craft, you’re not in that bad of shape. And if you’re a minority so persecuted that you’re willing to spend immense resources colonizing another star to get away from it, why don’t your persecutors just take your resources for themselves and leave you poor or dead? Especially since most ways of propelling and interstellar craft are also suited to being weapons of mass destruction.
Technically, the universe only has a finite amount of time left. The sun only has some billions of years.
We are not talking about infinite time, but thousands, maybe tens of thousands of years. And that’s not when history ends, that’s just when it begins.
That seems like alot, but it really isn’t. Not on the timescales of stars and galaxies.
How long term are you willing to think? Do you think that we will be content to sit here on earth for a few billion years till the sun burns up, and that’s that?
Now, if your contention is that civilization won’t last that long, and we will never get to that stage, then I don’t know that I disagree that that is a likely scenario. But, assuming that we manage to survive these upcoming bottlenecks, what limits do are you putting on our engineering capabilities?
I am not talking about nanobot replicators. I am talking about automated factories and mining equipment.
We already have our resource extraction and preparation into consumer materials fully automated. Humans are barely involved in actually touching the product from the time the materials are mined, to the time the product is in the consumer’s hand. That will only increase in time. In a few decades, it is likely that there will not be a single human touch on 90% of consumer goods. By the end of the century, I seriously doubt that any human will physically handle any material for production, unless it’s a hobby or niche for “handmade” products.
So, if we have fully automated systems in place here on earth, that require no human intervention to chug along happily creating materials and goods, is there a particular reason you don’t think we would be able to do that in space as well?
As you claim that such technology is pure fantasy, can you quote to me the laws of physics that forbid such? It seems you are unfamiliar with Clarke’s third law.