NASA estimates 1B ‘Earths’ in our galaxy alone

Whoa there. First off, don't use the Shuttle or ISS as the yard stick for "manned spaceflight", they are some of the most expensive programs for the least results in history and are not representative of what can be done with manned spaceflight.

Additionally, spaceflight is not just about scientific research. Manned spaceflight is not just about exploration, it's also about colonization. At the end of the day space is just a place, a place where we live, though we have been restricted to a tiny corner of it for most of human history. We can do manned spaceflight cost effectively (orders of magnitude better than the Shuttle, ISS, or Apollo), and as our technology improves our capabilities will only increase while costs fall.

"It will be difficult enough to avoid disaster on planet earth in the next 100 years, let alone the next 1000 or million. The human race shouldn't have all its eggs in one basket or on one planet. Getting a portion of the human race permanently off the planet is imperative for our future as a species." - Stephen Hawking

Human spaceflight isn't just about scientific breakthrough, or even planetary life insurance.

It's also about inspiring people and radically changing people's worldviews. After all, once we're on two planets, it becomes "best in the worlds".

The implications this has on people's imaginations is non-trivial: https://www.youtube.com/watch?v=CbIZU8cQWXc

Indeed, Kepler covers only 0.25% of the sky, and is only capable of detecting systems that are edge-on (around 0.47% probability for Earth-like planets)[1]. The mind boggles at what we might discover with a more complete picture...

[1] https://en.wikipedia.org/wiki/Kepler_%28spacecraft%29

$100 billion is still a drop in the bucket when compared to iur own federal budget, let alone the budgets of all the participating countries in the ISS. It is also a showcase as to how we can survive the depths of space if we ever need to migrate off this planet.

Let's assume the Great Filter is in front of us. Perhaps biological life eventually creates machine life and then either withers away while machines take over, or fizzles out along the machines it made. Let's also assume that all these other lifeforms, like us, realize that the galaxy is full of livable worlds. There's no FTL, and nobody wants to take over a planet where life has a chance of making it past the filter.

This would mean that the only contact would be machine probes who left their civilizations tens of thousands of years into the past. Such probes would be programmed not to initiate contact with worlds with life on them. Instead, collect some data and leave, moving on to other planets and systems.

If this is the case, heck, we might have been visited by millions of other intelligent civilizations. The only thing we'd have to show for it would be perhaps the appearance of truly mysterious lights in the sky every decade or so. If you want to stretch your imagination a bit, perhaps a Rendlesham Forest-type incident.

I seriously doubt biological life is very interesting to any other civilizations. I doubt they communicate in any way similar to the ways we communicate, and I feel that any direct contact would be so removed and non-reproducible to be useless.

There are a lot of hidden assumptions you have to make for Fermi's Paradox to truly be a paradox. (Same goes for my argument, of course.)

"They're made out of meat" http://www.terrybisson.com/page6/page6.html

Ok. I'll be the crazy person.

At what point do we consider that at least some percentage of the more credible and interesting UFO sightings might be evidence of visitation?

We now know with a high level of certainty that earth like worlds are common, and we also know that a high percentage are older than Earth. That means more time for the evolution of intelligence and the growth of knowledge in any civilization. Interstellar flight is hard, but is technically possible with technology contemporary with The Beatles: look up Project Orion and read about Dyson's thermonuclear performance estimates... And if that is possible with 60s tech, there are surely better ways. Of course we are also assuming no undiscovered physics, which is an arrogant and naive assumption given that we haven't been doing this for very long.

The UFO topic is verboten largely because of all the bizarre and often silly folklore and quasi-religion that surrounds it, but it isn't hard to strip that off. For the longest time I was a climate change skeptic because of a distaste for green ideology, but then I realized that the physics of atmospheric CO2 is utterly unrelated to how humans process issues culturally.

One potential answer to the Fermi paradox is that there isn't one. Life is common, intelligent life is common, and occasionally something stops by. Of course "then why do they not land in the middle of a city?" But turn that around: why would they? It would place both them and us at risk. I can think of many rational reasons not to.

Edit: not arguing it is so, just thst it is possible. The more extrasolar planets in habitable zones we find, the less I think we should laugh.

Just for the record, the "flat Earth" stuff is mostly a myth pushed by latter generations to make earlier generations look and sound dumb.

This is such a bad analogy (I think you got it from Neil Tyson or something). What you've done is that you've taken examples of things that we got wrong. However, there's a lot more things we got right back then, that are still right nowadays!

So your point that whenever we make predictions, we get them wrong, is totally unfounded.

And as for the "Earth is a special unique snowflake -> no, there are 1B "Earths", while actual confirmation of the existence and number of exoplanets is a recent development, the shift for general population was made long ago, thanks to science fiction literature and later cinema.

> Life is an incredibly rare event

Precisely why I am so exited about exploration of Europa and Titan and others in our solar system. Imagine if we find life beneath the surface just in our system, then the probability of finding life outside our system would be much higher.

Life is probably pretty common, Intelligence... well we may just be alone in our neck of the woods until we create more.

Exactly, electromagnetism is too primitive. Quantum entanglement modulation is more plausible. Or some other phenomenon that could factor out space and time like some hypotetical tech that can interface with Consciousness.

- FTL is not possible.

- Technological life exists for a few thousand years. They are a small blip so basically nothing in terms of cosmic timelines.

- Even if it sends out probes, those probes generally fall into the gravity wells of the planets they are sent to over the millions of years.

- Hence why intelligent life is common, but not often seen.

One thing to do, and we should do it fast... is to make self replicating robotic probes that spread throughout the galaxy. I guess it should collect samples of life once it finds it and find ways to seed the universe with it. Or create some sort of Ark of Life to carry DNA from intelligent life forms to other places where they could perhaps be cloned.

We should not focus on our own survival, but increasing the chances of intelligent life in general to survive in the universe and find each other. We are probably doomed as a species, but we can do that for the universe.

Isn't it technically twice... the Neanderthals? whom possibly would have gone onto further technological advancements had we not out competed them for resources?

These observations don't discount the possibility that life is incredibly pervasive throughout the universe, yet on each planet that harbours life it is natural that just one species reaches dominances to make observation about Life, The Universe, and Everything, such as we are making... but are still ultimately prevented from becoming Type III civilisations by physical constraints (i.e. interstellar flight is impossible) and therefore the Great Filter lies before us.

We are so special, the only intelligent species in the galaxy etc reminds me of the sun revolves around earth statement a few hundred years ago, the fact is we don't have the technology to explore even the closest stars, even our own solar system is unexplored, think europa, so making statements about life in the universe based only on one planet is science fiction.

A good start in answering these question is to look for life in our own solar system. Maybe it is not as rare as we think.

I tend to believe that molecular technology and AI are the great filter. Just picture the situation we find ourselves in: We are stuff made from the rules of the pattern generating system that we call our universe. We are figuring out the rules and we are continuously improving our tools to manipulate stuff at an ever lower level. Once we can easily manipulate the building blocks our existence is based on, it opens the door to such a tremendously large number of ways how things can go wrong that the probability of self-destruction comes very close to 1. It would require an extremely high intelligence to deal with all these failure modes, something that an biochemistry-based evolutionary process is highly unlikely to bring forth. The problem is basically that figuring the rules out is much easier than using them safely. The invention of AI makes our tools to manipulate matter vastly more dangerous, for example, intelligent gray goo would be smart enough to not immediately eat away its basis for existence and to plan ahead instead of just executing a simple rule set.

That DNA gains dominance proves very little. It stands to reason that in the primordial soup, once one self-replicating molecular biology came into existence it pretty quickly consumed all the elements any others would need.

Moreover, life on Earth proves little about the nature of life anywhere else - for example what type of self-replicating biology might exist in the high pressure environment of a gas giant? We don't know, but all the components are there and there's plenty of energy so why not?

The reason Earth-like's are interesting is because we know what we're looking for when we go looking for life on them. They're a sure thing to expend limited resources on.

That the current thinking and evidence on abiogenesis says that this all happened very very early in the earths history would lead me to believe that abiogenesis is probably quite common. The existence of only DNA based life forms, given we now have good evidence that other chemical elements could have become the bases of dna (as opted to g c t and a) would also tend to indicate that it was probably just the 'winner' of that early evolutionary arms race, i.e. What chemical formula can reproduce the fastest under those early conditions

I think it's likely that higher intelligence could evolve more often were it not a "first past the post" race where whichever species gets there first prevents the others from doing so by squeezing them out with regard to the necessary natural resources.

Thus, I'm inclined to think that if there are many planets with the required ingredients for life, there could likewise be many examples where intelligent life has arisen, but like on Earth, limited to one advanced species per planet.

Well, for (i), we wouldn't necessarily see any of the other life systems if DNA life outcompeted it. Bear in mind that we've only really explored a handful of Earth's ecosystems --- it's known that the microbial biosphere extends way into the lithosphere, for example. I'd be totally unsurprised (although thrilled) to learn of a discovery of an alternate life system there.

For (ii), remember that we can't observe any other Earth-like planets in enough detail to know whether there's human-like technological life there or not; all we really know is that we haven't observed any here, and there are plenty of simple explanations why not, one of the most plausible being that transporting human-like creatures from one star system to another in a reasonable time is almost inconceivably hard.

In fact, life like ours is so unsuited for living in space that it's probably reasonable to assume that any successful space-based civilisation isn't going to be using life like ours.

That assumption leads to some interesting corrolaries: for example, once you're adapted to living way out in the dark, the inner solar system is going to be horribly inhospitable. And you're likely to be quite slow, because everything's going to take a long time.

So if such a civilisation existed on the outskirts of Sol system, it would be entirely plausible that they wouldn't come and visit --- coming here is too dangerous, and besides, if we're going to be interesting to talk to we'll be rebuilding ourselves to be like them and be out there soon...

The problem is we don't know a lot about the probabilities of abiogenesis. We do know the basic components for life, such as complex hydrocarbons and amino acids, do occur in non-biological nature. The question is how likely they are to combine into something self-replicating.

> Essentially it was about how all species branch from DNA

That is not correct. Most models consider RNA as a precursor to DNA. Over time, RNA has come to fulfill more narrow intra-cellular roles, but at some point in time it was probably the dominant gene format. By the same token, it's likely that RNA as an information carrier was preceded by other molecules, and very early proto-organisms might not even have had a unified gene carrier system - they might have been just "running systems" that split in two every once in a while.

> (ii) we evolved into advanced technological species.

This is also doubtful. Humans do combine several fortunate intellectual capabilities, but the components making up our neuronal structure are not unique to us. What's more, we do find advanced capabilities in organisms that developed after we split from a common ancestor, suggesting that the building blocks of general intelligence might arise readily under different circumstances and using different biological implementations (albeit with the caveat that we share a common biochemical machinery, the details of which may or may not make general intelligence more likely).

Intelligent life is rare on Earth. Out of tens of millions of species on our planet that exist or have existed, only one is intelligent enough to make a civilization.

Beautiful read on the Fermi Paradox http://waitbutwhy.com/2014/05/fermi-paradox.html

The idea, however unlikely, that there could exist documentary footage of prehistoric Earth is truly mind-blowing when you stop to think about it.

Try https://en.wikipedia.org/wiki/Alien_Planet

I used to work at SpaceX. I firmly believe that Elon Musk will establish a colony on Mars within my lifetime, and I hope to be there. Everything SpaceX does is working towards that conclusion, and the plan is solid.

Imagine what they must have said 300 years ago about landing on the moon!

I agree - we won't make it. We are rapidly improving our means to kill each other and become extinct while space colonization is neglected. It's obvious where this will lead.

Actually with time dilation the people on the spacecraft could reach several close stars in decades - if we construct fast enough spacecrafts (just needs to be a small fraction of light of speed).