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Aliens and the Fermi Paradox
First time accepted submitter sayhem (1842674) writes Various explanations for why we don't see aliens have been proposed—perhaps interstellar travel is impossible or maybe civilizations are always self-destructive. But with every new discovery of a potentially habitable planet, the Fermi Paradox becomes increasingly mysterious. There could be hundreds of millions of potentially habitable worlds in the Milky Way alone. This impression is only reinforced by the recent discovery of a "Mega-Earth," a rocky planet 17 times more massive than the Earth but with only a thin atmosphere. Previously, it was thought that worlds this large would hold onto an atmosphere so thick that their surfaces would experience uninhabitable temperatures and pressures. But if this isn't true, there is a whole new category of potentially habitable real estate in the cosmos.
Well, it is always possible we are simply the first. We do have an unusually old population I star and it still took billions of years for humans to come on the scene, so it is possible that the typical case simply takes longer and many suns are younger then our's.
It's meaningless.
Space is REALLY BIG. In fact, space s bigger than time is long.
You could have started sending out robots 12 billion years ago and they wouldn't have even made a scratch in colonizing the universe.
The Kruger Dunning explains most post on
It is not certain that we would recognize it if it was right under our noses.
Maybe travel at the speeds necessary to reach other star systems is impossible, and there ARE a TON of civilizations out there. But, they're all talking on some type of communication form - like Quantum CB or something - that we haven't discovered quite yet.
One day we will, and we won't make first contact with ONE species that day. We'll meet millions.
:::The Spear in the heart of the Other is the Spear in the heart of You; You are He - Surak of Vulcan:::
Or maybe we're just the only ones here.
Or maybe aliens have their own shit to worry about.
Or maybe they're already among us.
Or maybe nerds should stop wasting their time wanking off about shit for which their is zero evidence - for, or against - and trying to derive concrete meaning from it.
I fully expect and eagerly anticipate the day we make first contact (hopefully without subsequently getting blown to shit, enslaved, whatever). But I'm also sensible enough to realize that no amount of masturbatory theory, such as this shitty link to an absolutely retarded article about climate change and aliens, means anything.
At a certain point that starts looking like an attractive option. If NASA announced that they've managed to create a warp bubble, no matter how small, then I'd say the low hanging fruit is that aliens are in contact with certain elements of humanity and that this isn't widely known because a huge percentage of the world would freak the fuck out.
At Los Alamos, right around the time of the Fermi Paradox, everyone was agog at the green fireball phenomenon. One of the greatest collections of scientists ever assembled were pretty evenly split on the subject. Some though the the green balls of fire flying through the sky and changing direction as if being intelligently guided were some kind of secret earthly craft, while many other were certain they were extraterrestrial in origin. No one doubted they were real, however, and no one thought they were natural.
You don't really hear about this, but it's part of what started Fermi along the way towards his paradox.
As for the usual "OMG, nobody could keep that secret!" meme. Even if someone had 100% proof of alien encounters, the signal to noise ratio is assumed to be no signal and all noise. Someone could have been shouting the truth from the rooftops for forty years and nobody would care because they'd be lost in the din of people seeing little green men and anal probes.
Between "every civilization eventually kills itself" and a high level conspiracy to keep the world from shitting their pants at alien life, I'll pick the conspiracy. The fact that half of humanity isn't really ready to stop killing one another over five thousand year old superhero stories is kind of telling. Hell, half of humanity is confused by shoes.
I think expecting intelligent life to have visited earth is a bit arrogant. The fermi paradox is mysterious because we haven't been visited by intelligent life yet? It is highly likely that intelligent life either wouldn't want to visit us, or maybe they have something like the prime directive where they aren't allowed to interfere in our lives until we can match them technologically.
YOU might not see aliens, I might not see aliens, but hundreds of thousands have had very unusual experiences and there's more than enough evidence -- including high level military witnesses -- that the US Government makes a big deal about this topic and goes out of the way to ridicule anyone who gets close to making a big deal about it.
Regards, Lex
If, as seems possible, the first civilizations in the galaxy arose billions of years ago, they presumably know about us, or at least our planet (as the galaxy can be inventoried in a billion years). If they cannot exceed the speed of light, they are also used to very long scale conversations and travel delays. My guess, and it is just a guess, is that they wait 5000 or 10,000 years before getting back to any new civilization, because that's how long galactic conversations take, and also to weed out the flash-in-the-pans; either way, we may have a while to wait.
As for where they are, "any sufficiently advanced technology is indistinguishable from astrophysics," so look around. As just one example, the spiral arms of the galaxy are more recent than the possible age of the first civilizations, so they might be engineering constructs.
and for everything but the most recent part of human history even if we had been visited we would likely have reacted in one of 3 ways:
1. What is that kill it and burn it
2. What is that run away and tell the story only to be ridiculed
3. Grunt grumble scratch hide in cave *MAY BE* draw a crappy picture on the wall with another rock
hell #2 is still true to this day.
Actually it isn't. And also what balance?
The problem with being unintelligent and a virus is that you die when the host dies, and so you can only ever kill everyone in a small geographically specific area. Global pandemic only became possible with the rise of trading civilizations, but any organism which kills a large % of the population will burn itself out before it can kill all of them.
We worry about disease today because we are trying to do a lot better then middle % survival rates through adulthood.
The others have a pretty good idea what is going on on our planet from decades of radio and tv broadcasts. Nobody in their right mind would visit our dirt-ball with vicious and stupid people in abundance.
Most ACs are not even worth the keystrokes to insult them. Be generically insulted by this and ignored otherwise.
this makes a lot of sense to me. Given that EM radiation only travels at the speed of light, and falls of with the square of the distance, it is the cosmic equivalent of writing a letter, stuffing it in a bottle, throwing it in the ocean and hoping that your friend in Japan gets it. We think we are clever monkeys, but we are in effect beating on a log with a stick, when the rest of the universe is likely sending data packets via the cosmic version of fiber optic.
It speaks to our hubris that we assume that we are smart and we use this technology, and that other people will use the same technology. They probably don't even look for 'young civilizations' that use EM for communication, because they blow themselves up half the time before achieving a useful form of communication technology. Would you try to talk to an amoebae on the off chance that it might evolve into something interesting in a few million years?
If there is any way to communicate in a faster than light fashion with others, it will be the standard by which advanced civilizations talk.
HA! I just wasted some of your bandwidth with a frivolous sig!
We haven't even dug into our planet passed 12 kilometers! We've barely explored the bottom of the ocean! Who cares about cubic parsecs of sucking void?
Nothing prevents us from exploring them all...
First off, forget Hitler's Munich Olympics broadcast, that's way to new. The most interesting thing about Earth is roughly half a billion years old, and that's its "unnatural" atmosphere. Our atmosphere shouts, "Life!" like nothing else. The stuff in our air just doesn't cohabit from ordinary chemical processes - it has to be maintained. Not as old, but still older than Hitler's broadcast is the sustained presence of pollutants in the atmosphere. This might suggest, "intelligent, if immature/foolhardy life."
We can almost see this kind of stuff with Kepler, though to get to this level of detail we use several instruments in parallel - Kepler is the first-weeder. We're nowhere near having interstellar technology, so any race that does will likely have commensurate technologies in other areas as well. Most notably, if you're going to travel far, you want to know which direction to go, and as much about your destination as you can. They would have tools that make Kepler look like a child's toy. They would know how interesting Earth is. Where that ranks us with respect to other planets in another question, but I'll bet it's not as bleak a prospect as some say.
Personally I think the presence of us on Earth has to do with it's "sufficiently interesting history", including the collision that formed the moon, several asteroid/comet strikes like the dinosaur killer, etc. Not to mention plate tectonics, the magnetic field that keeps the solar wind from blowing our atmosphere away, etc. Like I said, I think Earth would be on the short-list.
By the same token, I also think they would observe. Our society and existence are fragile enough, one big kick could easily topple the whole mess. Imagine a preemptive strike by one power to prevent another power from getting "the advantages of alien technology," etc. We're also pretty darned "memetically susceptible," and even allowing an alien idea to reach us might upset the apple cart.
Or as an alternative, perhaps the Catholic Church was right, and Galileo (and Copernicus) were wrong. If not the physical center of the universe, if we're all there is, perhaps the Earth is the philosophical center of the universe.
So:
1 - We're all there is, perhaps to become the Progenitors, perhaps not.
2 - There is other life, hasn't gotten here yet, may not bother, may not be able.
3 - There is other life, observing us, careful to remain unknown - the Prime Directive.
4 - There is other life, getting ready to invade/destroy us.
5 - There is other life, in contact only with the Illuminati and Club of Rome.
Personally I'd prefer option 3. Option 2 is equally likely. Option 1 is rather sad. Options 4 and 5 are IMHO silly.
The living have better things to do than to continue hating the dead.
Zefram Cochrane has another 49 years to 'invent' warp technology.
A primitive society as found on Earth is of little interest.
What if there ARE 100's of millions of civilizations advanced as us?
Wouldn't that sound an awful lot like background noise?
Perhaps no one else has cable TV and all 200 channels in each country are OTA and there are 200 billion signals floating around ;O
Perhaps think SETI is simply overmatched unless someone targets us and that signal would still be inroute most likely.
Here's your explanation:
1) We don't know shit about the universe, physics, or exobiology
2) We have not been listening very long
Give it time - lot's of time.
I am very small, utmostly microscopic.
We are just on the edge of being able to upload humans into the machine, and give everyone virtual reality. Once we achieve that, everyone can have anything they want, without needing to colonize or mine anything. Turn the moon into our Matrix supercomputer, upload everyone, and turn the Earth into a nature preserve. Once you have that set up and everyone starts cranking out game modules, why would you want to give that up to visit another star? You think the colony ship will support the latest VR's?
Space is big, but not intractably big.
A civilization in a galaxy the size and structure of our own, expanding at an average of 0.1% of lightspeed, could still colonize every habitable planet in that galaxy in 100 million years. 0.1% of lightspeed is only about 20 times faster than Voyager 1 is currently moving, and well under the theoretical limit for a nuclear pulse drive. And 100 million years is not that long compared to cosmological and evolutionary timescales.
The Rare Earth Hypothesis is still the strongest contender for the solution to the Fermi Paradox. Suppose that there are a hundred different conditions necessary for intelligent life to evolve. These could include basic requirements (like liquid water and protection from ionization radiation), up to more subtle components (like a moon that massive enough to cause tides or an axial tilt to create seasons). Until we have another data point for reference, any condition on Earth might be considered a necessary condition. If each of these conditions has an independent probability of 1 out 10 or less, then it very well could be that Earth is unique in the galaxy, possibly the the universe. The universe is big, but it is not 10^100 planets big.
So if we wanted to signal a civilization on the other side of the Milky Way (assuming we could muster the power), We would have to aim the focused radio beam on where that world would be in somewhere 50,000-100,000 years from now and they in turn would have to know the signal is coming and instantly reply to where we would be in another 50,000-100,000 years.
The whole communication thing is a total joke.
Any smart civilization would just want to make their world a nice place to live for as long as they could.
Not only is interstellar travel possible, we've already done it (at least, we've sent 2 space probes outside our solar system which will eventually reach other stars). Interstellar travel within the lifespan of a single human being might be impossible, but enough other solutions exist (robotic probes, generational ships, suspended animation, long-lived alien species) that this limitation is not an adequate explanation for why alien ships have not reached Earth.
Support Right To Repair Legislation.
Pasteur was right all along, and spontaneous generation isn't a thing
I currently subscribe to a variant of this climate change theory. (Natural, not anthropogenic.)
My variant is that all, or almost all the civilizations the aliens know about formed around red dwarf stars. It's nice and stable there for very long periods of time. We're only stable here by luck - and our big moon helps some.
Another fun thing to think about: If you look at our system as a whole, from a very long distance, we look like we're still a pre-multicellular world. Sure, there's free oxygen and water (Earth), but there's lots of iron still to be oxidized (Mars), and lots of free CO2 (Mars and Venus). I imagine there are a lot of pre-multicellular worlds (like Mars IMHO) orbiting yellow stars, so we don't stand out. (But for our radio transmissions.)
(T>t && O(n)--) == sqrt(666)
Before diplomats from one country meet with diplomats from another country on Earth, they study everything they can about the situation and their counterparts. What if aliens are monitoring our communications to learn more about us -- what we do, why we do it, what we believe, how we're likely to respond to different scenarios, etc.? No one says that even if aliens came to Earth the first thing they'd do is find some schlub and say "Take me to your leader." Nor is it unlikely that a race capable of crossing the void between stars could hide from us, say by looking like a comet or asteroid.
Everyone is looking at this all wrong. When a species is sufficiently evolved, it loses its motivation to either live or reproduce. A 2nd option is personal power of any individual increases with technology until one person can annihilate an entire planet purposely or on accident. The level of power it would take to travel faster than light be bending space would destroy a planet. A 3rd option is that technology or pharmaceuticals can basically make a safe version of meth where it triggers the brain's happiness receptors and then all motivation to do anything else fails and the species dies off. Considering that all of those 3 are incredibly likely, that explains why all the alien races are dead.
Really? You don't understand how the immune system can go off the deep end on either side?
Immune system too weak -> infection, cancer.
Immune system too strong -> self-attack (rheumatoid arthritis, lupus, multiple sclerosis, a LOT more).
Sufficiently advanced races who develop the technology to travel to other planets find that same technology eventually allows them to exit the universe entirely. This leads to custom universes that are far more suitable for stable permanent civilizations outside of the chaos of the original birth universe. Colonizing other planets just seems like a chaotic inefficient messy task with little reward.
First of all, all the astronomers know about the Mega-Earth is that its total mass is about that of Neptune, and total volume is such that its density is unlike our gas giants (Jupiter, Saturn, Youranus, Neptune), but more like our rocky planets (Mercury, Venus, Earth, Mars.) Boo hoo, that's not much. And how the heck they know it has a thin atmosphere. I beg to differ - it's simply a gas giant with an Iridium (22)-Osmium(22)-Platinum(21)-Gold(19)-Mercury(13)-Lead(11)-Iron-Nickel(8) core and not much silicate(2.2-3.0 sp.gr.).
Earth-like life supporting planets with liquid water and hydrogen free oxygen atmosphere have to meet certain conditions of temperature and gravity, and a planet 17x the mass of Earth does not meet conditions of gravity, or requirement for liquid water (all you can get at high pressures and temperatures is supercritical non-phase separating water/steam mix), or if the temperature is lower, then at that gravity hydrogen is retained in the atmosphere too, with continuous buildup of planet size from vacuum absorbed hydrogen til you get a double star, like Jupiter is on the way to become, if it can grow faster than probably something like 2 mm/year and grow to adequate size before the Sun runs out of fuel.
Also a 17x Earth mass planet might have a huge internal temperature and lava from the stray radioactive isotopes in silicates or what not, and this one thing might be different about it than what we have here, i.e. the stray radioactive isotopes have been consumed, and then it does not glow at that size. Or they might be so high in abundance, that they heat the planet surface to high enough temperature where most of the stuff boils off, and all you get is a thin atmosphere, but no hydrogen. Venus is kind of on the hot side of the balance, with even smaller gravity than Earth, and only CO2, O2 and N2 with moleculare weights of 44, 36 and 34 are retained in the atmosphere, but H2O with a molecular weight of 18 distills off. Had the gravity been higher than Earth, (possibly 17x higher), then besides the CO2, O2 and N2, you may be able to retain the H2O too, but possibly in a supercitical, nonphaseseparating state, and then standard solvent properties disappear, as in it's unable to ionize sodium chloride into its components, and the whole biochemistry of Earth is probably impossible without the solvent effects of water, which becomes more like gasoline or alcohol in solvent power when supercritical. Possibly someone calculated a 17x Earth mass as an upper limit just under supercritical temperatures, and as we have extremophile bacteria living in very hot waters, life might be possible really hot, in really high gravity environments, as long as not too hot(no superciritical water) and not too high gravity (not retaining hydrogen gas).
http://en.wikipedia.org/wiki/K...
I have always thought that civilisations must accelerate there way from 0 on the Kardashev Scale (us 200 years ago, and we are not even close to type 1 yet) to 2 in a very sort period of time, perhaps 10,000 to 100,000 years. It certainly seems to be the scale we are on.
When they reach type 2 they are capturing & using all of the available energy from their star and would be totally invisible to us. No light, radio signals, zip, nana, nothing would be escaping from the civilisation or their solar system because they are capturing it and using it. As far as we are concerned they are undetectable.
We have had the ability to send out communications to the cosmos roughly the same amount of time we have had weapons capable of killing us all if used improperly. What are the odds that we will have sent something to someone listening before we either kill ourselves or are thrown back into the stone ages by some natural event? Basically I do not find it hard to believe that intelligent life, over time, may not be so great at propagating itself for the time needed to communicate with other civilizations.
JPL's DSN was in the business of tracking spacecraft in interplanetary space emitting very low levels of power in crystal-controlled "pilot tones" that could be detected at great distances, doing this front ends with noise temperatures at liquid helium values. The idea is that a terrestrial TV station carrier would be emitting enough narrow-band power to be detected at interstellar distances, even with wide aperture low-gain antennas. If a tone is crystal controlled, it is sufficiently narrow band to be picked out of the background with a FFT filter bank of millions and then later billions of channels.
Does a digital TV station even emit a carrier or a pilot tone signal anymore? 30 years ago when a Caltech seminar speaker was a JPL engineer who had received a Senator Proxmire "Golden Fleece" award for doing SETI, which the Senator from Wisconsin thought was a misuse of public money, his colleague joked about "the aliens switching everything to fiber optic cable", but digital TV was a distant dream then.
Since then, haven't we pretty much ruled out aliens announcing their presence with narrow-band radio emissions at the level of our technology out to a few hundred light years?
The rest of the galaxy has unfriended us.
Oliver's law of assumed responsibility: If you're seen fixing it, you will be blamed for breaking it.
I find it fascinating that everyone here feels that what they've come up with in 5 minutes is somehow new and unique, and going to add to the 65 years of professional interest in the Fermi Paradox. Many of whom confuse the question, because they don't even know Fermi's Paradox.
So here I present the full list of possible answers to Fermi's Paradox, that everyone here thinks they just came up with:
https://en.wikipedia.org/wiki/...
Slashdot gets worse every day... Pipedot: News for nerds, without the corporate slant
and after earth he got bored and went off to play some intergalactic CoD.
THey see all the dup articles on Slashdot and decide there is no intelligent life on Earth.
Of course there's intelligent life in the universe. They don't make contact with us because we are not intelligent life.
The people on our planet seem to only be interested in killing and dominating each other, all in the name of their tribal god-image, or green pieces of paper. Why would a spacefaring civilization consider such a people worthy of contact? It'd be as dumb as taking the family for a vacation in Supermax.
There are plenty of stories about human contact with alien life, and of course none of them ever seem to be verifiable, but strangely, nearly all follow the same pattern — forcible abduction and horrifying medical-like experiments. The aliens are here...and think of us only as guinea pigs...and are superior enough to avoid our pathetic attempts at evidence-gathering.
I would like to hear a defensible reason why any spacefaring civilization would be interested in making contact with us as equals. Because, in my opinion, there is no defensible reason.
"Once we've identified and embraced our sickness, we'll have strength...and that's when we get dangerous." - John Waters
A given intelligent being is most likely to be alive during the most populous times of the species. My existence here and now thus suggests were are near the maximum and it's down-hill from here, I'm afraid to say.
Table-ized A.I.
Intelligence sufficient to survive -- what evolution really pushed for -- is very low performance for us. Assuming another species will exceed the required baseline for survival may be an entirely unwarranted assumption. We don't know yet.
But in our case... we regularly produce *really* smart individuals. Almost incomprehensibly so as compared to that required for survival. We also figured out the scientific method and left hand-waving philosophy in its own backwater, staring at its navel, while science actually focuses on objective reality. That got us into space fairly quickly. Whereupon we also learned that space travel is (a) expensive and (b) really, really hard. If, in fact, we can manage interstellar travel, it will be because we either become so very rich (total economy of plenty) and can afford anything we like, or because someone *really* smart makes something like the Alcubierre drive actually work.
In order for us to see another non-spacefaring civilization at this point, they have to be doing some unintentional things that are detectable from here (not much in that category quite yet, and even so they have to be very close), or they have to be spacefaring enough to either signal us (expensive, also requires motivation) or actually come see us. I just don't think it's a given that evolution commonly pops up with massive intelligence sufficient to solve problems at the level humans can. My evidence? Of all the myriad species on this planet, we're the only one with even remotely this level of intelligence. So here, at least, the mutation for high intelligence is *extremely* rare.
I think we're mutated well beyond any possible need, evolutionarily speaking, but that the mutation was useful and desirable in context of our own likes and dislikes, and so it sticks. IE, people preferentially mate with really smart, successful people who can even be simply average in other areas (and let me say, I am profoundly grateful for this bias. :)
I could certainly be wrong. But then again, something should explain what we're seeing, and I think this is one of the possible explanations. If this is the case, then the "intelligence" factor in the Drake equation is so small as to be nearly equivalent to multiplying the rest of the terms by zero. No matter how large they are, multiplying them by significantly near zero is fatal to the outcome.
Earth:
5000+ mammal species
8000+ reptile species
10000+ avian species
23000 species altogether
ONE really intelligent species
1:23000 odds on a planet that is absolutely teeming with life and resources. or .00004348
Slap that in the Drake equation and see what you get.
I've fallen off your lawn, and I can't get up.
Mars doesn't have internal dynamo because it it tiny, it cooled off already. Earth sized rocky planets with similar composition take billions of years to cool, and so will have magnetic field.
I say your intuition is off, from Kepler's observations (and realizing it can only see transits of about 2 percent of stars because most orbit orientation don't allow it), there should be hundreds of millions of planets with life but spaced 100 light years apart. However, life usually is single celled, as we know from most of earth's history. Intelligent life, existing at the same time as intelligent life? spacing gets greater, 1000 light years maybe?
I think that's the answer to the Fermi paradox
nonsense, those "smarter" people had no hard data, kepler is finally the beginnings of some data to even gauge the first couple terms of the Fermi Paradox problem
Or if it is coming, it is coming in the form of a simple single cell size, frozen in space, riding a simple rock. Perhaps that is how we got here. (plus the 3 billion years of evolution.)
People with auto-immune diseases aren't less susceptible to being killed by regular infections. That's usually what kills them.
Autoimmune diseases are an interesting problem where for some reason the chemical self/not-self signalling gets messed up, and the immune system starts attacking a host of identified "not self" cells. Other ones - like asthma - are a hypersensitivity of the primary (non-specific) immune response.
Cancer is the exact opposite problem: cancer is when you get a specific series of mutations which do not result in the normal cellular apoptosis mechanism destroying a body cell. The immune system doesn't target cancer because it doesn't target "self" cells. Cancer is immune-invisible, and the holy grail of cancer therapy has always been to find something unique about cancer cells that the immune system can be sensitized to to attack.
None of this is caused by some weird idea of "balance" of the immune system, and the way you used the phrase to start with was a weird thing to do with antibiotics and nature or something.
I suggest thinking hard about your positions before you start advocating withholding treatment from patients and letting people die, which is what you were trying to circumspectively say without sounding like a monster (also looking up the actual causes of antibiotic resistance and how drug-resistance evolves - it's really not what you seem to think).
1) 2011 "Out of the Blue" - Best researched UFO documentary: https://www.youtube.com/watch?...
2) 2001 Disclosure Project - Dozens of high ranking goverment+military officials testify publicly of aliens+UFOs: https://www.youtube.com/watch?...
3) 2013 Citizen's Hearing - 40 researchers and military/agency/political witnesses testify for 30 hours before 6 former congress members: https://www.youtube.com/watch?... (part 1)
4) Bob Lazar Area51/S4 whistleblower - 10.5 hours of testimony : https://www.youtube.com/watch?...
5) Ex CIA death bed confession on reality of aliens/ufos - https://www.youtube.com/watch?...
6) List of countries that have disclosed UFO files: (loooong list) - http://www.disclosureproject.o...
I could go on, but there's already week's worth of material here alone.
No trees were killed in the making of this post; however, many trillions of electrons were horribly inconvenienced.
Or maybe drug abuse. Or space Nazis. Or pedophiles. Or terrorism. Or digital piracy. Or inequality. Or male chauvinism. Or sex slavery. Or whatever other insignificant problem people fabricate a crisis out of these days.
> No one's going anywhere. Not me, not you, not now, not ever. And no one else is coming here either.
The power of positive thinking
The question is: How do we detect said aliens? We can probably not use radio, because as some of you have touched, modern spread-spectrum communication is indistinguishable from noise. Add to this that we have this HUGE wide-band noise-generator right next to us called the sun. The radiation from alien suns is hard enough to block out at stellar distances in the visible regime, even harder at radio frequencies.
So how do we detect aliens? By the bulk. E.g. by looking at the atmospheric composition and saying "here are compounds that can not be produced by any natural method ".
So we will be checking against our models and trying to find deviations. Which leads me to my point:
Here we have a planet with the mass 17 times of earth, but with an atmosphere way of the chart of any predictions!
It is far out, even for me :-) but this is actually the "kind" of signs for life we are looking for. Alright in this case, I have a hard time imagine what could suck the air out of the alien atmosphere - but then again, that would make it really alien! - probably not carbon based :-)
Bacteria and other unicellular lifeforms are the most evolutionarily successful on Earth by any measure -- numbers, biomass, adaptability to changing environmental conditions. The expectation that complex multicellular life is an inevitable product of evolution is unwarranted, even when looking at our own example -- look how late complex life came on the scene in the history of this planet's biome. Even less justified is the expectation that, when complex life evolves by chance on some place where simple life is present, it is unlikely to become extinct before it begins spreading through the galaxy. That assumption is without basis and comes from the same bias that makes people presume humanity being extant at some indefinite time in the future, in one form or another. A further assumption is that spacefaring ability leads to, well, spacefaring. Given our own experience, there seems to be a lot more focus on inner space -- the virtual world of information technology -- than outer space, primarily because the former is very cheap to explore in comparison (cheap in terms of difficulty and expenditure of energy and other resources). As the virtual allows us to bypass ever better the biological mechanisms which drive us towards taking real life risk and putting real effort into exploration and expansion, the impetus to move into space will remain weak and likely even weaken. (I'll acknowledge here transhumanists' wet dream of a nanomachine-based grey goo substrate for our minds eventually expanding to feed itself with more matter, once it eats up the planet, but that is extremely unlikely, and I'll point out that Richard Smalley's basic science criticisms of the futurists' views of nanotech possibilities have yet to be properly addressed.) Let me end this by noting that it is a good thing there almost certainly is no other spacefaring civilization in the galaxy, for reasons another poster brought up last time slashdot discussed extraterrestrial life: http://science.slashdot.org/co...
"Politicians and diapers must be changed often, and for the same reason."
I see Bob Lazar. I see Steven Greer. Anyone actually curious about the UFO phenomenon should not look at those.
For more serious stuff:
- Belgium 1990 UFO flap
- Tehran 1974 UFO
- Rendelsham Forest
- The age old Betty and Barney Hill case is still good
and if you are patient, read something written by people like John Mack or even Bruce Maccabee.
But the OP has a point. Aliens might be around, even when they have not landed on the White house lawn.
Science doesn't seek to prove god doesn't exist but the learnings of science is that any god would be irrelevant, so might as well not exist
> With no real facts, intuition only,
Which sums up how religion works and fails when thinking about science.
There may not be intelligent life out there but looking for it does not cost much and exploring is not that expensive. So we might as well do it.
Do not forget that there were several extinction level events here on earth, spanning millions of years.
So it is not the case that it took so long for us to "evolve". It was just a case of luck that nature wiped out the last owners for us. Who is to say how the original higher life forms on earth would have evolved had they not been wiped out so many millions of years ago.
Of course, we do not know if it is true or not, but "they" think that life started very quickly after the conditions of the planet were conducive. I expect the same is true on any planet.
The problem is that the power of the signal very rapidly went down (in 1/R^2) so even when we were broadcasting in the 50ies-60ies, our best signal did not even go beyond 1 light year before being indistinguishable from noise , in the best case scenario (actually probably much less depending on the signal). There are only 2 signals which went beyond the 1 or 2 LY, and those were intentional "we are here" signal, sent toward M10 i think (or was it M52?) and those signals were maybe a few dozen minutes all combined together.
We would not be able to detect ourselves if we were located on our direct neighbor, 4 LY away, alpha centauri. By that point even our most powerful unintentional signal is beyond the noise floor (again except those few dozen minutes TOTAl over all our whole civilization time).
C. Sagan : A demon haunted world:
http://www.amazon.com/gp/product/0345409469/
visit randi.org
Beyond our solar system.
If it did take until around about now (in terms of numbers of stars in universe with heavy atom planets) for complex life to form, it's not really surprising others haven' visited us. It's paradoxical why Fermi expected them to have visited us when we haven't visited them.
Space is big. Really really big. You just won't believe how vastly, hugely, mind- bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space.
Where are we going and why are we in a handbasket?
There are no old, space faring civilizations, for one inescapable reason. Technology is incompatible with species. No ifs or buts.
Brief explanation: Life of any kind, in any environment must always evolve as species - defined as multiple beings sharing a common 'genetic code base' - regardless of how the information is encoded. In our case it's DNA. In all species the individuals serve as reproductive vectors for the code they carry, and individual survival of the fittest is required for any species to evolve and adapt to its environment. This implies that individuals also die - this is necessary, otherwise natural selection cannot operate, hence no evolution.
Life is likely quite common in the Universe. Even if intelligence is statistically a rare development, there still should be countless instances, including plenty long ago, where 'long' means more than one star lifetime. So if intelligence results in technological cultures, including any kind of major engineering or space travel, where are they all? Even if such civilizations choose not to say hello to us, we should still see evidence of their works.
But we don't. There's apparently nothing. Just elusive local UFO sightings, of unknown reliability. Certainly no daylight landings in city park, so to speak. That was just to restate the Fermi Paradox. Where is everyone? We exist, so there should be other civilizations like us, but much older and more technologically advanced.
The logical error here, is to assume that technology is a continuum; that a society develops technology and then just continues to progress as a society - a cooperating population of individuals with a common genetic heritage, hence species.
But this NEVER happens. Can never, will never, never does. Here's the inescapable reason.
As a species develops technology, they inevitably discover the nature of the physical encoding scheme of their own biology. They develop the means to manipulate that coding scheme. Our fledgling genetic engineering is an example of how that starts. Quite rapidly the science of engineering their own coding will advance, since after all it's just a messy 'wet' version of computing science, and you can't have high tech without already being well advanced in computing technology.
Somewhere in the process of unraveling their genetic coding, an intelligent species will also develop a science of consciousness - what we presently think of as AI, but which is ultimately about minds in general and how they work, including our own.
As these two science threads advance, genetics and mind-science, it is 100% totally inevitable, that at some point individuals will gain the technological capability to begin modifying their own nature. We already do this - for instance using altered viruses to perform corrective edits of faulty DNA, eg the Cystic Fibrosis cure.
But that is primitive stuff. Ultimately, gene engineering and AI technology provide individuals with the means to 'transcend' - to embark on total self re-engineering.
At this point in the analysis, most people become incapable of logically carrying through. It seems there's another strong cognitive bias or two, not listed in the Wiki. One is that most people seem incapable of thinking impartially about the probability of termination of their own species. Another is a mental block against thinking logically about the likely motivations of entities that do not share the species-centric world-view of us genetic humans.
Here's an idea: try thinking about an intelligent entity, that does NOT share any of our reproduction-motivated species-protective instincts. Nor any of the many cognitive biases in the Wiki list.
Because that's what you get eventually, after any species-based individual achieves self-engineering capability, then immortality, an ability to deliberately optimize and enhance it's own mental capabilities, weed out instincts no longer appropriate to it's new existence as an immortal space-traveling entity.
Anyway, the point is that 'technological speci
If a species was capable of interstellar travel:
1. Why would they stop and visit us? We can barely get into low earth orbit reliably.
2. Why would they even bother to colonize other planets? I'll bet with unlimited energy, their spaceships are pretty comfortable.
Sure, but words don't move mass, you have to build it. And you're sending people? We have no example of a man made 100% self-sustaining, self-repairing and self-powered technology.
It's not just some theoretical rocket drive, it's all the engineering realities around it. What engineered system is 100% reliable?
You know any Home Depots in space on the way?
No one's going anywhere. Not me, not you, not now, not ever. And no one else is coming here either.
Deal with it.
If it were up to folks like you, we'd still be living in caves and scavenging (raw) what the big predators couldn't eat.
-- George Bernard Shaw
So why don't you stop being so fucking reasonable! Jerk.
No, no, you're not thinking; you're just being logical. --Niels Bohr
Every once in a while, a universe is born. The random quarks align and PUFF, big bang, expansion, all the shebang.
Stars appear, planets appear, then life and, eventually, intelligent life.
And in every universe, invariably, the first intelligent species thinks "The odds of us being the first ones are ridiculously microscopic!".
But someone has to be the first. Someone has to be the one who visits the others to tell them "Hey! You aren't alone. There's at least two of us!".
We are the precursors.
Taxes, that's it. The taxes are killing the whole civilizations.
We are kinda in the middle of the sticks in our galaxy. We are a good bit out in one of the arms. So even presuming there is other intelligent life in the galaxy (which of course we have no way of calculating the probability of) it could very well be quite far away. If they haven't figured out a method of FTL travel, or if indeed FTL travel is simply impossible, then it is the kind of thing where contact might ever happen.
Never mind the silly idea that there MUST be other intelligent life out there and that it MUST be way more advanced than us (neither of which have any evidence for or against) but it could easily just be way too far away for the laws of physics to make any kind of contact a reality.
You can actually make realistic predictions, see the results, etc, etc. Doesn't mean it accomplishes much, but it is more grounded in fact and reality than this kind of crap.
We know -nothing- that we need to know to determine if there is other intelligent life in our galaxy, if so where, how advanced, etc, etc. We have no idea and there's no way at this time for us to have any idea.
So it is nothing but babble when people start speculating as to what might be going on. It is in every way as vapid any any talk about celebrity gossip and even less relevant and founded in reality.
If we ever start to have some of the information we need, then it might be useful, however right now we just have no damn idea.
perhaps interstellar travel is impossible or maybe civilizations are always self-destructive. But with every new discovery of a potentially habitable planet, the Fermi Paradox becomes increasingly mysterious.
No, it doesn't. It just suggests that interstellar travel and communication are very, very difficult. They don't have to be impossible, just hard enough to put a spoke in the Ponzi-scheme galactic colonization plan that the Fermi prediction relies on, and why SETI hasn't found any needles in the haystack yet.
We know that space travel is hard. We got from powered flight to landing on the Moon in a single human lifetime, then hit the wall. We have hugely successful, experimentally proven theories of physics that say that FTL travel is impossible, and well-reasoned scientific speculation showing that the possible loopholes (Alcubiere warps, wormholes etc.) require access to exotic matter, consume ridiculous amounts of energy, and (fortunately, for causality's sake) have deal-breaking complications... and even if they work may only provide near/at/slightly over lightspeed travel. We know enough about energy and matter to start doing the sums for slower-than-light interstellar travel and work out how difficult it is* (even SF writers fall back on Unobtanium power rather than 'old fangled' fusion drives for their generation ships, now).
As for communication/detecting signals, our only data point is us: A century or so after inventing radio, we're already switching to highly compressed, encrypted digital signals indistinguishable from noise without the 'key', transmitted at the lowest power and tightest beam possible.
So, despite all the plausible resolutions of the 'Fermi paradox' which, while not proven, are built on reasoned extrapolation of what we do know, why do people focus on the least plausible resolution: 'there are no aliens' which, while impossible to conclusively disprove without actually finding an alien, relies on us existing on the tail end of a probability curve?
That is anthropocentric thinking bordering on religion.
* Plus, if you can build generation ships that can survive in interstellar space, and manage their populations, it would be far, far easier to build space habitats and park them somewhere with solar energy and big chunks of raw materials floating around. Kinda reduces your incentive for Ponzi colonization which, as Greg Egan put it, "is what bacteria with spaceships would do".
In a survey of 100 programmers, 111111 thought that duck-typing was a good idea.
The problem is not so much technology as simple physics.
It's just THAT HUGE a distance between even stars, let alone cavorting around the galaxy looking for places that might - with a few years of resource collection - provide you with a usable amount of energy to get to the next place.
And on the way, stop-offs are few, far-between, hard to make profitable and stopping, landing and then taking off again costs an awful lot of time, effort and energy that you have to take with you.
The chances are that if anything comes near, it'll only be interested in using us as a slingshot onto somewhere more interesting and what's to say our solar system is particular interesting to someone who's coursing their way across the galaxy by doing that - or even that our sun is worth riding past for those purposes at all.
It's not a question of technology really - if you have the technology, we hold no interest to you, if you don't, we won't see you any more than you'll see us. And the distances and forces involved and to be overcome are just so stupendous.
And then you work out that even if there are a billion stars in a galaxy, and a billion galaxies, the chances of someone bothering to wander past us, even if they are looking for us, is so infinitesimally small that it pales into insignificance.
And the biggest problem is really time. What if we're late developers, and everyone else has already been and gone? And quite how long would you need to explore a galaxy once you got the technology to hop around it, and are you still going to be strolling around in a billion years from now? Probably not. The chances of two such civilisations coinciding are small, the chances of them meeting are small, so it's not at all surprising.
More likely, our view of quite how unlikely it is is so underestimated because of our limited view of the universe that we just don't understand how optimistic we're being to even suggest the possibility.
Galaxy-hoppers would laugh at us from our one-planet, night-sky observations from which we're trying to extrapolate the entirety of existence for a universe.
That said, I firmly believe that there's other life out there somewhere. I just believe, even more strongly, that the maths says that the chances of us meeting it are so tiny that it's not worth worrying our "haha, just ONE planet? That's all you managed?" heads about it.
If there is intelligent life close by to notice us they probably have monitored us pretty well and could detect use of atomic weapons in the 1940s, 50s and 60s(nuke tests).
IIf I were a more advanced peaceful civilization id probably quarantine earth for a while and keep it under observation remotely.
if intel is a function of predatory intelligence... who needs them?
there is NO paradox here.
Would YOU want to go to darkest africa, where the meds werew bull, the natives might eat you and they'd cheerfully KILL for your socks? (NA Indians got the death for that)
urbanized: a clean water supply. (how's the home village doing, bucko?)
civilized. No psychotic (cannibal) neighbors
enlightened. (lemme see, there was this monk in med-evil Italy that could fly...)
packrat ; writer-informer. http://packrat.comicgenesis.com http://www.youtube.com/area163 https://www.smashwords.com/
I don't really find Fermi's paradox to be at odds with the finding of exoplanets and the increasing intrigue around panspermia. We're pointing dishes at the heavens with SETI based on the idea that intelligent life necessarily acts the way our 20-21st century civilization would, and use radio to communicate.
Already, we're looking at quantum teleportation and entanglement and non-broadcast communications. We're already moving past the means of communication we expect other advanced civilizations to be communicating with. That wasn't the first assumption.
Other prior assumptions have included that we are the one intelligent species on this planet. Why, because we use tools? So do caledonian crows. Because we have organized warfare? Chimpanzees have been observed in the wild sharpening sticks and moving in formation. Because we have language? Humpback whales have callsigns at the beginning and end of their songs that will actually cause consternation amongst other humpbacks if spliced and played back around another's song. There's even evidence to suggest that dolphin's sonar is a form of visual language: they're literally sending ultrasound holograms to each other, which would explain why their brainstem has roughly twice the "bandwidth" ours does.
Slime mold solves mazes. Plants hooked up to electromagnetic sensors hooked up to MIDI synthesizer units can figure out how to play ordered music instead of send random signals, and even play in styles "by ear" - one anecdote I've heard has it that a group of them at Damanhur played ragas for two weeks after a classical Indian musician visited. Bees tell each other where to find the flowers. Ravens have a theory of mind.
There are many forms of intelligence, and we've been hung up on the fact that we have symbolic language and tell stories about the past, future, and fictional as a litmus for one form of it. We are just beginning to recognize the many degrees of intelligence living on Earth with us. The Inuit have a proverb: "Every animal knows something more than you do." There's some truth to that.
When we expect to find life out there that is necessarily a magnified form of 20th century Westerners, we're starting with what we know, but let's prepare for a huge level of diversity on the theme of life, and what kind of technology (if any) other life would actually use. I'm pretty sure it's out there, and IMHO, it's almost certainly going to surprise us in many ways when (if?) we finally run into it.
The universe is indeed full of life. And life becomes intelligent and thrives. And every ten million years or so...
Gets hit by a meteor.
Another meteor.
Comet this time.
Solar flare.
Nearby nova, supernova or far-away hypernova fries them.
Ice age.
Heat age.
Bacteria this time.
Here comes some volcanoes.
Food poisoning.
Drought.
Floods come.
War.
Mutations.
And finally, time happens, if nothing else. The universe is full of life - BUT NOT ALL AT THE SAME TIME, and not all at a time that happens, in each case, to emit radiation that arrives at our sensors at this tiny opportunity of ours to detect it. The universe is full of little flashes of life in the dark that wink on and off like fireflies, and we can't possibly see them - in time. We are alone, and we had better damned well take care of ourselves.
PS: what makes people think that successful life stays on a planet? That's a surefire way to die, by the list of events above. Successful life gets off the planet, builds terraria in orbit, and sends some off into the darkness to spread and survive the death of the home planet. At the very least. At the most, they spread into adjacent universes or dimensions. Or even travel in time, whatever that is. Life, successful life that lives a long time, grows up and gets out of the petri dish. Or dies with all the other failed flashes of life.
Could humans survive on a planet with 17x the gravity of Earth's? Not very effectively, I would guess.
There may be millions of intelligent species out there, but they may be perfectly happy swimming in the ocean all day. Think about it for a minute. There's a potentially second intelligent species here on earth, but we don't give them a moment's thought because they didn't develop an opposable thumb and create tools.
And in hundreds of years, we've never learned to communicate with them on any level that counts. Which makes our chances of every making contact with "aliens" almost impossible.
If they landed in Central Park tomorrow, it might be decades before we could communicate with them because their brains may work in an entirely different way, and we have no frame of reference for communication. They, of course, may have a solution for that, but we sure don't. We're a very, very dumb species when you get right on it.
If telephones are outlawed, then only outlaws will have telephones.
The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore, all progress depends on the unreasonable man.
-- George Bernard Shaw
The quote above is interesting, but he left out an important bit when he wrote it. Let me add it in...
The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore, all progress depends on the unreasonable man, while survival depends on the reasonable man.
Think on that for a bit.
Given the size of the Universe (that we understand so far), and the over 400,000 galaxies strung, web-like, across it, perhaps there is plenty o' Life out there, but each sentient species is isolated on it's own remote galactic island, unable to travel to any other galaxy, let alone cross it's own...
New 3-D Map of Massive Galaxies
http://www.sdss3.org/press/dr9...
Or maybe it's simply that all other sentient life is approximately the same age as us -- given the age of the Universe and how long it took *us* to show up and start questioning everything. If so, then they likely have similar technological capabilities as we do. Ergo, if we can't visit --let alone find-- them, they can't visit or find us either.
Strangers, passing like blind ships in an infinitely vast, inky night...
Well, so you can convert those pagan heathens to the proper admiration and worshiping of His Noodliness, the Flying Spaghetti Monster, of course.
"There is no god but allah" - well, they got it half right.
A lot is made about how hard it is to detect radio signals and how SETI is pseudoscience because all of the terms in the Drake Equation are wild guesses.
The meat of this proposal was answering the question whether anything like a terrestrial (analog) UHF TV station was "out there" anywhere up to about 400 light years. The search was "all sky" and didn't even involve highly directional (and hence high gain) antennas -- the plan was to use the feed horns, only, from the Big Dish at Goldstone, California.
The detection probability is a concrete formula in terms of factors such as the transmitting antenna gain (omni-directional), receiving antenna gain (low as they were going to use the feed horn), receiver noise figure (low -- at liquid helium temperature), data rate (one bit per observations -- you were trying to detect a beacon in the form of a pilot tone), and source entropy (very, very favorably low -- a crystal controlled carrier wave is a very stable, predictable signat that the JPL people had experience "picking out" from the background, even when needing to correct for Doppler, in "recovering" spacecraft that had lost their high-gain dish antenna).
If this project was ever conducted, they would have been able to rule out the presence of a UHF TV station out to 400 light years. Yeah, yeah, over what portion of life on another planet is there a civilization with UHF analog TV stations, and that question was asked during that seminar with a lot of wisecrack comments that the ET's have switched to fiber optic cable. But Fermi Paradox wise, were there an advanced Asimov-style intergalactic civilization, and were the civilization trying to get our attention, if they had a beacon anywhere near us, we would have found it by now.
That is, if this plan ever got funded. A quick look at Wikipedia suggests that owing to the spotty funding of SETI on account of anti-ET skepticism, maybe this simple search, which just needed some antenna time on the DSN and a digital FFT analyser, never took place.
The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore, all progress depends on the unreasonable man.
-- George Bernard Shaw
The quote above is interesting, but he left out an important bit when he wrote it. Let me add it in...
The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore, all progress depends on the unreasonable man, while survival depends on the reasonable man.
Think on that for a bit.
You've made my point for me. Without unreasonable men, we'd still be cowering in caves. Without reasonable men, we couldn't have made it this far. The OP suggested that it was foolish to even try to explore space. Unreasonable men extend our reach. Reasonable men put that reach within our grasp. We need both.
No, no, you're not thinking; you're just being logical. --Niels Bohr
Obviously, we are in quarantine until we learn to act civilized !
They have been here before, where do you think all of the religions came from?
If you saw an alien or a starship, do you think you would even recognize it? Dream on!
Anyone who acts too certain of all this is obviously wrong. (No matter which side they are on.) 8-)
Intelligent life with thumbs is probably rarer. If you're a happy dolphin in a worldwide ocean that the damn land dwellers haven't irrevocably poisoned yet you probably aren't busy building a starship with your bottle nose.
I think the problem here is that infrared doesn't penetrate our atmosphere that well, there's too much 'noise', and how do you tell the difference between a dyson sphere and a brown dwarf?
Unless we caught them in the act of constructing it we'd need to both spot the signature and recognize that it's unusual(we barely know what's usual as is), and figure out WHY it's unusual.
For that matter, even the lightest of dyson spheres, which would consist mostly of panels that are little more than foil, elicit comments of 'You need HOW many planets worth of mass?"
I don't read AC A human right
Life may not be so common as we dream about, and then, there may be no technical solution to the brutal distances. The recently discovered "mega-earth" (17 x Earth's mass) is 500 light years away. A spaceship would need at least 20 generations' time, time dilation notwithstanding. Even if we could reduce the number of generations by slowing down life processes, it would not be a mass migration opportunity.
If the ship weights a mere 100 tons, accelerating that to 80% of the speed of light, and then decelerating it, requires a huge amount of energy, many times the current world's yearly output.
Back home we will have to wait for another 500 years to learn what happened. Spaceships will be sent out only in desperate situations, and only to planets near the source, and only to planets that have been ascertained to have the desirable properties.
Intelligent life may be rare, because even if there are numerous planets in the habitable zone, few of them will have a benign climate for sufficiently long time as stars increase their output. The case of the Earth gradually reducing its greenhouse effect, tracking the increase in the sun's output sufficiently closely, may be extremely rare, and the nearest such case may be several tens of thousands light years away.
There is no substitute for common sense. Especially, no body of rules will do.
We went from horses and wagons to steam powered trains to space flight in a matter of a few generations. On the human timescale, we just figured out the basics of physics and chemistry. On the geological or astronomical timescale, the human timescale barely exists at all.
It's not crazy to assume that we'll be around for at least a few times as long as we've currently been doing serious physics. It's definitely not crazy to assume that if there's more than one intelligent civilization out there, a few of them would have been doing science and engineering for thousands or tens of thousands of years. It's not outside the realm of possibility that some of them may have operated for hundreds of thousands or millions of years.
It seems a little be pessmistic to put the cosmic "upper limit" on technology at our current level of development.
An interesting anagram of "BANACH TARSKI" is "BANACH TARSKI BANACH TARSKI"
1. Most of the worlds evolved more to fantasy-like societies, like special-ability oriented, earthbound. For what we may know, special biological abilities akin to magic are norm, and tech is a deviation. (Total speculation).
2. Societies have space travel, but are very introverted in general and live inside mental macrocosm, rather than (space) macrocosm. (Read: "The Pod and the Barrier", by Theodore Sturgeon for what I'm referencing here)
3. There exists force that is extremerly dominant and prevents any free interstellar travel. May be active, may be passive relics, may be programmed bots/nanobots. (I think this one is highly likely, because it is extremely probable that some societies have say, at least ~10 million year technological headstart over others, and that is, paradigm-changing (pardon the word). We may not even understand such technology, and it unavoidably has, perfect cloaking, because at this point it would be trivial. We may already have invisible aliens among us, and we'd be none the wiser. In this case advertising our presence by use of nuclear weapons / other stupid activities (EM footprint, may be easily identifiable / detectable) may be a very, very bad idea, in case they are hostile / exploiter type.
4. Luck, which I think is totally unlikely.
5. They may already have left footprint (may be likely ?), if you think it's not the case, then explain the artifacts on Earth (pyramids all over the world aligned in certain directions (would require 1 world civilization which organizes building of them all to certain precise measurements, for all we know, they may not have been built by savage natives (pharaohs), but rather claimed by them by scribbling their writ on them), Moon being very peculiar distance from Earth and having very peculiar measurements, various reported phenomena found in coal mines reportedly hundreds of millions of years old (hard to prove, but interesting nonetheless)). DO NOT DISCOUNT WHAT IM SAYING HERE, IT IS NOT ALL CLEAR CUT AND IS NOT ALL"WOO CONSPIRACY". There are too many outliers found for them all to be natural deviations of a single civ (ours).
After all the considerations, same things apply even if light speed barrier is unbroken, because with high automation, you need only max 70K-100K years at lightspeed to totally map the galaxy, so if any civ existed in our galaxy, it is a certainty in statistical sense that it visited Earth either as bots, or living creatures.
All of the above is wild speculation taken with large doses of salt or soy sauce, your preference.
I have nothing to lose but my bindings.
Mars doesn't have internal dynamo because it it tiny, it cooled off already. Earth sized rocky planets with similar composition take billions of years to cool, and so will have magnetic field.
Why does Venus then, which is about the size of Earth and fairly similar in composition so lack a magnetic field?
Current cosmology theories suggest that only 5% of the energy content of the Universe is matter. We assume that dark matter which accounts for 84% of matter is boring stuff that only interacts with gravity. What if we are missing out on most of the Universe because dark matter has its own dark forces meaning that dark matter is as varied as our matter?
In this case most aliens are made of dark matter, we can't see them and they can't see us.
The most dangerous drug