I don’t know what you mean. More likely than what? And why do you think my article says anything other than “[it’s] hard to deny that at least one other advanced alien civilization really is out there at the present time”? That’s literally my article’s entire thesis. So I fail to understand what your question is.

Perhaps you missed the sentence immediately after the one you quote: “So the probability of there being other civilizations like ours does start to approach 100% once you start counting regions of the cosmos beyond our visible horizon.” I then articulate my thesis in that paragraph: “even counting just the observable universe it’s close to that.” That’s called an argument a fortiori: even if the universe is much smaller than we are certain it is, the conclusion follows; therefore the conclusion follows with even more certainty when you adjust the premises to actuality.

If all you want to know is the relative order of probabilities for larger-than-observable universes, all physicists will tell you the lower assessment, as a minimum, is known with effectively 100% certainty (the laws of physics entail the actual universe is hundreds of times larger than the observable part of it), while the higher assessment is known with near 100% certainty. Most physicists are fairly certain Inflation Theory is true. I’ll bet most would put the odds of that at or above 95%; and if it’s true, then the universe is dozens of orders of magnitude larger still.

So the order of probability is:

• the radius of the universe is only just over ten billion lightyears: ~ 0%
• the radius of the universe is at least hundreds of billions of lightyears: ~ 100%
• the radius of the universe is dozens of orders of magnitude larger than even that: ~ 95%

And yet even on assumption one (“the radius of the universe is only just over ten billion lightyears”) the conclusion follows. It therefore follows with even more force when the most probable sizes of the universe are calculated in. I therefore don’t “need” to believe those larger estimates. They just happen to be quite likely true. Hence why I mention them.

Of course, the actual universe is vastly larger than the observable part of it. In fact the universe might be infinitely large; but observations fix its minimum size at 250 times larger than the observable part by volume (several times the observed radius). And that’s just the minimum. The currently most credible cosmological theory—the inflationary Big Bang model—entails the actual cosmos has a radius 10^23 times greater than observed. That’s a 10 followed by 23 zeroes. An absurdly vast size.

To get more specific, would you say that the latter one (“10 followed 23 zeroes”) is more likely, or that it is MUCH more likely? Perhaps it could be described like, “I’m leaning towards this being true” vs. “I’m extremely confident that this is true”.

Because a universe that big would offer a great deal of possibilities for extra terrestrial life, I’d think. Almost as if it would be hard to deny that at least one other advanced alien civilization really is out there at the present time.

[All updates here have been folded into the comment above.]

I only follow mainstream cosmological models. All of which are nearly or actually flat, and entail an actual universe orders of magnitude larger than is visible.

When cosmologists change their consensus on that, let me know and I’ll see if it affects anything I conclude.

The CMB is in much debate and would be interested in your view of flat versus otherwise – a Beach Ball with a surface of 3 mm x 1 meter expanded in XYZ until the surface appears flat and thickness of the surface exceeds by multiples of the visible universe – is that a model being considered?

Only someone who was science illiterate would think life arising by chemical accident on a planet somewhere in the universe and evolving by natural selection into a spacefaring race is “ridiculous.” And if it’s not ridiculous for us, it isn’t for anyone else either. It’s merely a question of how often it happens. By contrast, a wildly-convenient-yet-never-evident, disembodied superghost, is ridiculous by every definition of the term.

It’s actually a lot harder to kill a civilization than your arguments assume. Given millions of years, space colonization capability is statistically inevitable. No matter how many apocalypses and dark ages occur from such things as environmental mismanagement. And no matter what the lifespan difficulty may be. Not only because life extension is an inevitable tech and therefore “biological lifespan” not even relevant here (e.g. we are not talking about current tech, but tech a million years from now), but also because, even if some bizarre physical law existed that made life extension impossible, multigenerational arc ships are a tech we could build even now. Much more so when our tech is millions of years more advanced.

So, no. These are not relevant considerations to the math here.

If (assuming) space actually isn’t colonizable – that means we cannot expect “many” possible Em-signals, except from those very few who manage to reach this level of technology.

The outcome of a super-advanced civilization isn’t “unstoppable” – it’s actually unlikely. Our own civilization is facing environmental collapse (worsening daily), resource depletion, and even the possibility of pandemics, etc., that would prohibit our advancement.

For the one civilization that we actually do know about, our chances of future survival are lessening, even at this level of technological advancement. Using this as an example, what does that mean for other alien civilizations? Can we assume they face the same ecological and/or biological restrictions? Certainly so (resources are finite, biology isn’t immune to toxicity, pollution, depletion).

Our EROI advancement isn’t guaranteed either. Not even. All forms of energy (except photosynthesis) are products of fossil fuels (even nuclear, solar, wind, hydro, wave, etc., it takes fossil fuels to create, build, maintain, repair, transport these other energy sources) and when / if we run out of oil, we’re done building, maintaining or transporting what we still have in short order, we’ll have a very difficult time even surviving.

This Earthly example of energy isn’t a fair representation either – other planets may have far fewer or lesser energy sources then Earth once did. But we are using up our alottment very quickly. Civilization will not advance further without it.

Just using the above bottlenecks – if space travel really isn’t solvable for the vast distances, planetary / environmental / civil / asteroid / biology collapse is more likely then not, limited convertable energy sources are also more then likely then not – if even just one of these is true, we have a far less likelihood there being very many advanced civilizations that may or may not still be “detectable”.

Moreover, Jevons Paradox indicates that technological advances may improve efficiencies, but they also mean that any savings realized are swiftly used up, negating the alleged efficiency claims. Civilizations are not laboratories where any gains can be careful designed for and managed. They’re ugly biological garbage heaps where predatory practices rule (even among humans).

We also can’t save ourselves with technology. Technology is one of the root causes of environmental destruction – the more we embrace it, the worse things environmentally are. It could be that in our quest to leap to the stars (or wherever), we send our planet into a biological / environmental catastrophe. We’re well on our way there now. We cannot assume that this isn’t also true for alien civilizations.

There isn’t any evidence to support that we will survive a million years from now, or create a utopian world. We’re too predatory most likely for any of that to happen.

I can’t help but wonder how often does the assumed math (probabilities) actually deceive us? Have we consider all the variables? How did we reduce human nature down to a mathematical value? What about alien natures – how did we do that, lacking any observable or verifiable evidence?

Fortunately, science is often wrong – and is willing to correct itself. There’s no need to assume at this point that these conclusions are correct. It’s just as likely, they’re wrong and we’re all alone. And if we’re not, they either already died out or smartened up and stayed quiet.

The motivation was to be mildly humorous, and mildly provocative, just like Captain Kirk’s line. The idea that the enormous universe exists so that no one can know for a fact that the mere existence of life was a miracle, no matter how improbable, is a variation on the claim fossils were deceits. (In some version created by the Devil?) The interesting prior probability in either case was the idea God is a tricky devil.