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Comment by PeterisP | Hacker News Reader

"Humans just might be the first intelligent life." is incompatible with the notion that life is common (which may or may not be true) - our planet is a bit older than the average (e.g. the examples in the article are suns/planets which have already gone through all the lifecycle that Earth will have eventually), so it's probable that we're the first intelligent life in the galaxy if and only if it's likely that we're the only intelligent life that the galaxy will ever spawn.

If there's no great filter before our current stage, then it's extremely unlikely that we're the first intelligent life in galaxy, and either there's a great filter after that or many civilizations have risen already (and have had more than enough time to colonize the whole galaxy a thousand times over at a relaxed, leisurely slow pace, if any of these civilizations wanted to) but we just don't see them for some reason.

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> our planet is a bit older than the average

But our galaxy and solar system is relatively young compared to the universe. Plus the universe is massive. There's approximately 10 billion galaxies in the observable universe with and average of 100 billion stars per galaxy. At that scale the processes that created life on Earth would have happened countless times before. The building blocks for life are common in the universe but weren't common on the early, inhospitable Earth. It was brought to our planet from comets which is where the Earth's water came from.

https://helios.gsfc.nasa.gov/qa_star.html#howmany

https://en.wikipedia.org/wiki/Panspermia

I'm not an expert, but didn't it take quite some time for stars to create heavier elements like iron, go nova, spread the star-stuff across the Universe, and then repeat until we have the current mix of light/heavy elements?

Combine that with:

* The fact that life on Earth was possibly dependent on life from other planets to form.

* Has had multiple near-total extinction events during it's time.

* We're outright dependant on fossil fuels left over from previous cycles in order to get to where we are now.

* Our own species have been close to extinction multiple times far before we reached our current technological level.

* Our own emissions most likely blends with the background noise and are probably not detectable that far out.

* It's taken us countless millennia just to get to the point where we're approaching a technology level that will allow a fraction of our population to scan parts of our closest galactic neighbourhood for disproportionately large signal sources that happens to be on the bands we find to be most convenient.

To me, it sounds like it's quite plausible that we could be amongst the first to spread on an interplanetary scale (assuming we actually manage to do that), or that something happens and we go back to pre-industrial levels, leaving the aliens on the next habitable planet wondering why the level of noise from group of stars a few hundred light-years away suddenly grew quieter.

Just because something is unlikely doesn't mean it can't happen. Furthermore, there could be something very special about Earth's position that makes it far more likely than we initially calculate. It doesn't make sense to dismiss theories as 'unlikely' when our degree of understanding of that probability is absurdly primitive.

"something very special about Earth's position that makes it far more likely than we initially calculate" - makes what far more likely ? Spawning life? If so, then that special factor, whatever it is, would simply be an example of a great filter behind us. I'm not saying that we can't be the first ones, I'm just noting that us being the first implies that we're alone in the galaxy.

To make that point perhaps more clearly, let's say that before and including us, our galaxy has had X planets like Earth. Whatever that X is (1 or 1000 or billions), the total number of such planets that our galaxy will ever have is less than 2X. That doesn't rely on any poorly understood theories, that doesn't rely on any aspects of how life or intelligence might form - the lifecycle of stars is well understood, the age of universe is well understood, and the future has less new stars and planets than the past; we're currently past the midpoint of star/planet forming and that's that, most of the planets that will ever exist in our galaxy either exist right now (most of them for longer than Earth) or are gone already.

So whatever the "dice" of a suitable planet existing and creating intelligent life are - if we're the first ones (and I'm not making a point whether we are or aren't, whether that's likely or not, that "if" is an assumption), if X rolls of dice resulted in just a single success - then the remaining less than X rolls simply won't suddenly roll a hundred more successes; if the total number of spawned civilizations until us is 1, then that means that the total number of spawned civilizations until end of the universe would be 1 or 2 - and if it's 2, then it would be a hit-by-a-lightning-while-typing-this level of coincidence is that second one happened to arise at the same insignificantly tiny moment in time that constitutes the existence of homo sapiens until now, just some tiny 100 000 years after us instead of some 10 000 000 or much more years after us.

OR, possibly, there are and will be much more civilizations than that - but then some of them have been long before us.

“if X rolls of dice resulted in just a single success - then the remaining less than X rolls simply won't suddenly roll a hundred more successes”

Mmhh.. not so sure you can conclude this. You assume all rolls of the dice are identical (same likeliness of all outcomes), but this ignores the fact that the universe is ever-changing from a particular state towards its inevitable fate.

Consider for instance the "pulse" of galaxies as they collide and 'ignite' their central quasars anew — this coincides with extremely harsh local conditions for said galaxy merger, which becomes likely very unhospitable to life. Conversely, when the jets calm down (mature) and winds recede, star formation kicks back up and a new galactic cycle begins until the next merger (if ever).

This mechanism alone could paint a very asymmetric past and future set of conditions (relatively to our rather 'calm' present, but it's actually a cycle). Some of these conditions would definitely affect life (for instance, during its active phase, we suspect that a galaxy's quasar might be strong enough to blow away planets atmospheres).

There's just too many unknowns at this point. Drake's famous equation was actually meant to expose this fact (he actually knew it was flawed/impossible to solve, but felt it was a meaningful thought experiment, iirc).

Exactly! You can only extrapolate statistical observations to identical scenarios but we know that every aspect of this universe has a great degree of variation and is anything but uniform. Statistics breaks down when you cannot ensure uniformity.

Most people's understanding of the complexity of a single-celled organism is absurdly primitive too.

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