Do you believe we are alone in the universe?

The universe is far, far, far too big and ancient a place to reasonably rule out life elsewhere. Even if the galaxy is currently lacking intelligent life other than our own (and I'm not convinced it is - our expectations of what intelligent life should be doing with itself is, obviously, prejudiced toward our own ideals), I don't think it was nor will be. I'm also much more optimistic about FTL.

 

[Maxperson]

The Great Wall was built in fits and starts over centuries, from local walls that were joined up later on down the line. But, even at 200 years, so what? You're talking about a million years. Again, it's an eyeblink. And the only reason the Great Wall was continuously built was because of the outside threats to China. AND, even after a relatively short span of time, they saw the effects of having the Wall. You really think that human society will continuously expend the resources necessary to terraform, say, Mars, for centuries? Not happening. There's just no way that any society is going to expend that level of resources for something that will have no benefit for centuries.

Perhaps no earth society is going to expend that level of resources. Are you assuming aliens will be and/or act like humans for some reason?

Even something like Von Neumann self replicating machines don't work. They run up against Newton. You cannot have perfect replication. There will always be breakdowns. And, once you go into deep time - such as a million years, the machines will simply not be able to replicate themselves fast enough to overcome failures. Heck, some species can't do it and they have a LOT easier time than trying to travel interstellar distances through all sorts of radiation, and whatnot.

At our current level of technology you cannot have perfect replication. I see no good reason why a sufficiently advanced civilization would be forced to use our level of replication, though.

Sorry, but, between Newton and Einstein, interstellar travel is pretty much off the board. You're talking FAR too many resources being allocated for virtually no gain.

Unless of course there are things we don't know about, which there are. Lots of them. I don't know why you take this position based off of our highly limited understanding of the universe. Heck, we even know our understanding is highly limited.

 

[Umbran]

I saw an interesting statistic that it would only take around 1 million years for a self replicating space ship with an average travel speed of 0.1 c to spread from one side of the Milky Way to the other.

That's not a "statisctic". It is an estimate. And it pretty much assumes no time is spent in the self-replicating. The Milky Way is about 105,000 light years across. So, it takes a million years to cross it at 0.1c, if traveling in a straight line, non-stop. If you have to zig and sage to reach stars with reasonable resources, and take time to build new probes, it would take longer.

Note that this assumes the existence of a *self-replicating* machine, that can fly across interstellar distances. And, that machine self-replicates with no notable change, *for a million years*.

With respect, that's not a great assumption. Over those timescales, any self-replicating system will be subject to selective forces - leading to evolution or extinction.

 

[Maxperson]

That's not a "statisctic". It is an estimate. And it pretty much assumes no time is spent in the self-replicating. The Milky Way is about 105,000 light years across. So, it takes a million years to cross it at 0.1c, if traveling in a straight line, non-stop. If you have to zig and sage to reach stars with reasonable resources, and take time to build new probes, it would take longer.

Note that this assumes the existence of a *self-replicating* machine, that can fly across interstellar distances. And, that machine self-replicates with no notable change, *for a million years*.

With respect, that's not a great assumption. Over those timescales, any self-replicating system will be subject to selective forces - leading to evolution or extinction.

The new estimates are that is is larger than that.

https://www.nbcnews.com/mach/science/milky-way-galaxy-may-be-much-bigger-we-thought-ncna876966

 

[Umbran]

We basically have a sample size of 1. It is indeed like taking a spoon full of water from the ocean, finding life, and then concluding that there for the rest of the ocean must not have any life in it.

Yes it is. Now, consider, if you took a spoonful of water from the ocean, and found life in it - what are the chances that you *just happened* to take the *only* spoonful with life in it? How many spoonfuls are there? And you got the *only one*? That's extremely unlikely, statistically.

Over the course of human discovery, one common thread has been that Earth isn't particularly special. We aren't the center of the Universe, or the Solar System. Ours isn't a particularly uncommon type of star. The galaxy has a bazillion of them. And the Universe looks pretty much the same in every direction, with a bazillion more galaxies each with its bazillion stars. We are also not particularly separate from other animals - with other species on the planet sharing 90% and more of our DNA. We have a couple of small differences that lead to stunning differences in behaviors, is all. We used to think we were special, even anointed, but it turns out... not.

So, when we pose the question of whether we are special in the Universe, which way should we lean?

 

[Caliburn101]

The Drake Equation shows increasing likelihood of life elsewhere due to the unpredicted number of planets popping up wherever they look now.

Even if you say the equation is out by 99.99%, that is still many civilisations in the Universe, never mind life.

If you believe we are alone based on the evidence, then you are relying on a 'representative sample' of the universe so small (i.e. that which humanity has seen so far) you probably couldn't express it as a sensible decimal fraction anyone could comprehend as it would be so small.

That doesn't even take into account the vanishingly small window of time in which we have been looking either...

Even if you cannot give the slightest credence to the Drake Equation, you cannot deny the vastness of the universe, or that human experience can in any way reliably estimate what is out there, so applying the precautionary principle it would be illogical to assume there is no life anywhere else.

You can guess there isn't, but you cannot on balance support a 'there isn't any' conclusion with the application of logic.

 

[Umbran]

At the same time. The evidence of only ONE intelligent species on planet earth − when there are roughly 8 million species. Suggests the odds of an intelligent species on a planet is apparently, 1 in 8 million. Yes we would like other planets for comparison, but evidently intelligent species are extremely unlikely.
...
On the other hand, I agree with the ‘first in’ effect here. Where humans entering the intelligent species ‘niche’ might prevent other species from entering it.

This is an important element - the presence of one such species likely suppresses others from developing. Historically, when tool-using humans enter an area, extinctions of larger fauna follows. So, the probability of producing one intelligent species could be high, but the probability of producing a second while the first is around may be very low. This makes the 1-in-8-million to be a bit simplistic.

(Heh, of course, the capacity of language itself is a biological instinct, albeit an especially potent one that can override other instincts.)

You are misusing the term "instinct". An instinct is a fixed behavior that does not need to be learned. Humans are born with the capacity to use language, but actual language use is a learned behavior. Some of our language capacity is developmental - exposure to language impacts how our brains grow and develop early in life, and a human who is not so exposed to language until after the brain is mostly developed seems to have a hard time picking up the trick. We have blessedly few examples of this, but a few children growing up in isolation have displayed the problem.

Otherwise, an other extraterrestrial species before us may have already arrived and edged us apes out before we even evolved into humans.

If FTL is denied us by physics, this is unlikely, as moving viable colony-sized groups across interstellar distances may not be tractable for any species.

 

[Doctor Futurity]

This poll is missing the scientific answer #3 which is that "We're still looking, and I'd hate to say yes without direct and compelling evidence, and I'd hate to say no when it's hard to prove a negative like this."

But by the mere fact that we are on a world teeming with life, and the poll does not ask "are we the only sentient life in the universe," I'd have to vote for aliens being out there. They just may not be sentient, technological aliens.

 

[Umbran]

The new estimates are that is is larger than that.

Yes and no. Stars with chemical composition similar to those in the rest of the galactic plane are found at great distances, but there's some question as to their density. It may be that there are some outliers, but the main disk could still be 100 - 150 thousand light years.

But, either way, that only makes the job of getting across the galaxy harder. Folks often talk as if self-replicating machines are somehow static, never-changing entities, as if they can last 10,000 years without alteration, and would replicate perfectly, and that's a naive position to take. It would be more reasonable to consider such a probe to be a living thing, with an electro-mechanical (or whatever) basis rather than a biological one.

 

[Doctor Futurity]

So, when we pose the question of whether we are special in the Universe, which way should we lean?

Well, it's worth noting that Earth had meaningful life on it for 500 million years before it had sentient life that could ask this sort of question (and I believe it took 3 billion years to get to that point in total!) So any consideration of life on other planets has from the one model at hand the following points to consider:

1. Life on a world like ours can easily take 500 million years to go from early bacteria to sentient civilization.
2. We had the potential for sentience only within the last 2.5 million years, basic sapient behavior with language within the last 200,000 years or so, and the ability to conduct civilization within the last 10-15 thousand years; and that only reached fruition in a manner allowing us to study the sky meaningfully for other signs of life within the last century.
3. We can't know whether we are special in the universe, but we can state that we are the only representative sample we have to study. As such, it's not unreasonable to assume that the length of time it took life on Earth and eventual sentient civilization to develop wouldn't take at least as long on other planets of the same composition/placement in the Goldilocks zone of other star systems.
4. We can say with certainty that assuming the circumstances are right, and the potential for life is realized, it will happen at different times in different systems. The question then becomes: how many of these circumstances happened long before us, and how many long after us, or around the same time? How many are happening right now, but are millions or billions of light years away, impossible for us to detect or interact with?

I think the answer to whether we are special or not boils down, at least for now, to the notion that we can consider ourselves special in the sense that we are a "sample of one," and the only sample we have unless something interesting rears its head in the frozen oceans of Enceladus or elsewhere. But we are by all probabilities not "special" in the sense that there is a vanishinghly small likelihood that our circumstances have not repeated to some degree elsewhere in the universe, probably many times.....but unfortunately not nearby, or necessarily in the same timeframe we have developed.

 

[Umbran]

OTOH, barring something weird like a precursor species seeding worlds with early human ancestors...the idea that any of these two species could mate and produce hybrids just flies in the face of reason and biology. (Sorry Behlanna, Spock, Jothi, and heaven knows who else.)

Yes. Which is why Trek introduced the Progenitors into its canon. B'elanna and Spock are covered.