Organic compounds recently discovered, and water abounds everywhere. Zones of life are found around most stars at a certain distance from each star. Life (slime) was kicking around on earth very early in Earth's history. What kicked off life in early Earth's history? Something did, and if it was just pure chance, then that means that by pure chance, it can and probably will happen again.

Too many stories of UFOs (most explained away as experimental craft, but key word here is most, NOT ALL).

Universe simply is too big and our technology has still quite a ways to go, in order to detect anything, if anything is being sent by non Earth entities.

Radio and/or electromagnetic waves were discovered only 150-+ years ago.

What are the mathematical odds for intelligent life existing in a certain volume of space-time?

The universe is 13.6 billion years old.
Our sun and planet are a few billion years old.
Life on Earth is 500 million years old.
Intelligent Life on Earth is 100,000 years old.
Civilization is 20,000 years old.
Civilization capable of reaching beyond its own planet is less than 100 years old.



What are the odds for that?

What are the odds for a planet being capable of supporting life?

What are the odds of life springing into existence from random chemical processes?

What are the odds of a situation occuring where intelligence gets favored by evolution?
(In all of the history of Earth it happened just once: In the african Savannah, when weak primates faced perfect predators.)

What are the odds of these intelligent beings thriving long enough to build a civilization?

What are the odds of these intelligent beings discovering science?
(The scientific method is a result of multiple theological, philosophical, social and political coincidences. Without the scientific method, we would still be on a medieval level, technologically and culturally.)

It is not possible to determine any meaningful odds...

The frequentist way to determine the probability of life in the universe is to take the number of inhabited planets and to divide by the number of all planets.

The bayesian way to determine the probability of life in the universe is to multiply the probabilities of all the coincidences that need to be in place for life to happen.

even with Bayesian probabilities.

And our knowledge base is SO utterly limited that I don't see how even Bayesian probability can be remotely accurate.
What we don't know far exceeds what we do know.
Our ability to observe is akin to looking into a very very very large, dark room with a matchstick.
What constitutes life isn't even nailed down.
How that life might communicate across interstellar space could very well include means we can't detect yet.

I think you can only really say the following:

1. The odds that life only exists on Earth are infinitesimal even if we consider just the finite observable universe we can see.
2. If the universe is suitably big enough (especially if it is infinitely large) then statistically there are an infinite number of Earths just like ours, in fact, exactly like ours. The tiniest coincidences multiplied by infinity lead to infinite occurrences. Of course, we don't know that the universe is infinite...we only know out to the observable universe. We don't know if there are multiverses.

That's about it. Whether intelligent, space-faring life is rare, common, or ubiquitous is something we simply do not have enough information to determine yet IMO.

It's mathematically impossible to get a result with 100% statistical confidence from an experimental measurement. For 100% statistical confidence we would need an infinite amount of data. But we can calculate estimates and the more data we have, the more accurate the estimate is.

We have nearly zero data relatively speaking.

What if alien life forms are not perceptible to our senses? Why do we include "civilizations" in the quest for life on other planets?

As a non-science-type person, I don't understand why we assume that our abilities to experience the world are the only abilities to experience the world to exist. If alien life exists, and we are unable to experience it because of the shortcomings of our sensory apparatus, does it count? Does it matter? And how will we know?

we have many, many tools to examine a multitude of properties... from the furthest reaches of the universe to the point so small no meaningful measurement can be made. We have a pretty good handle on what is.

That said, we have a heck of a lot to learn, but we have the means, the motive and hopefully the opportunity to learn more.

there seems to be reason to believe that it takes long enough for intelligent technological civilizations to develop, that we may possibly be the very first one in this galaxy.

It could also be that intelligent life develops but for various reasons never creates the kind of technology that would be obvious or findable by outside observers. Not to mention, all species eventually go extinct, and the possibility of actually overlapping in time and being close enough to discover each other, let alone get in touch, is probably unlikely at best. The getting in touch part is especially problematical. It is probably not ever going to be possible to travel faster than light, which means that even if we develop a means of travelling at 99.9% of light speed, it will still take years to get to nearby stars. Our galaxy, Milky Way, is 100,000 light years across. So to travel from one edge to the other (although we are not ourselves all the way on the edge) is 100,000 years at light speed. Interstellar distances, let alone inter-galactic distances, are far vaster than most people appreciate.

although statistically unlikely. It does take a long time for metal rich stars to form...at least a second or even third iteration so you are talking possibly double digit billion years to get to that point.

And I would guess you'd need that to form the materials you'd need for a spacefaring civilization or possibly even life itself.

When in reality it's not. Earth had highly advanced, multicellular species, none of which evolved to the point of intelligence, on it for 500 MILLION years before humans evolved. Dinosaurs had a 150 million year run, yet we have no fossil record of intelligent dinosaurs using tools or building cities.

Modern-day chimps, elephants, dolphins, octopi and whales all have levels of intelligence approaching sentience, yet none of them are anywhere near the ability to build technology to explore the galaxy or even communicate with other worlds. The smartest ones, the dolphins and whales, may never be able to advance further due to their aquatic environment restricting things like tool use, the inability to use fire, etc.

Native Americans inhabited the Americas for 15,000 years and never even developed the ability to forge metals like their counterparts in Europe and Asia did. Yet they had very advanced, culturally rich civilizations. If the Black Death had hypothetically mutated and wiped out all human life in Europe, Asia and Africa, would the American survivors have EVER developed modern tech and space travel? Would they have even developed wooden sailing ships to explore the now-depopulated continents of their own planet? Maybe, maybe not. Perhaps they would have just contently lived their lives for another million years before going extinct for some reason.

The development of an advanced, space-faring species depends on so many factors, many of them random and rare, that it wouldn't surprise me if we were relatively lonely in this galaxy.

Lamarckian hangover. Species evolve and adapt to their environment and their environment evolves and adapts to the species. Occasionally something else comes along and upends that environment and all bets are off.

There is no guarantee of survival, let alone "Advancement" whatever that means to those expecting it.

between extra terrestrial life, even intelligent life, and life that creates a technological civilization. The former could be very prevalent, given how many Earth like planets there are. the latter seems rare at the very least.

of Extra terrestrial life, even intelligent life. However, until evidence is provided, it's big-foot city.

Science-fiction is my fave genre, but I don't BELIEVE in it as truth.

As the Australian advertising slogan went, "Where the bloody hell are ya?"

We know that the per-cursors to life are prevalent throughout the Universe.

We know that life arose on Earth relatively early after it's formation.

The probability is there is life of some kind elsewhere in the Universe.

Bigfoot has a high probability of not existing.

But for now:

0) We are alone
1) In the future we may not be alone

Sorry to go all binary on the chat!

not intelligent-sentient life. Life could evolve into a highly intelligent civilization with developing technology.
Think of super-intelligent whales.

Technological civilization is obviously rare. But intelligent life may not be.

Technological civilizations have a v high probability of destroying themselves and, in time spans that are essentially infinitesimal compared to geological or cosmological times. Our example of one i.e. earthlings, have been a "technological" civilization only for a couple hundred years or so but even in that short time span, we have come close on more than one occasion to nuclear annihilation and are in serious danger of future extinction by additional means such as mass starvation or disease and/or environmental collapse.

So, over the eons of time there may well have been many technological civilizations briefly come and go within our galaxy but almost never more than one at the same time. That's the situation we are probably in now.