Astronomers Detect a Possible Signature of Life on a Distant Planet

This is unsettling. If we are not the only intelligent beings in the universe, it adds credence to the idea of a "great filter."

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

I think it would be cool if the conversation on this post could go more into detail about hycean planets instead of the pretty standard and played out one about the Fermi Paradox and Great Filters.

That stuff is interesting but I'd rather hear experts talk about less talked about stuff like hycean planets and detection methods of them and other bodies that are that size.

My greatest desire is to know why we don’t see any galaxy-sized colonies. A great filter would certainly be a fascinating response!

Well, it’s better than what I came here to do, which was to leave a snarky joke along the lines of, “Sounds like we just found another place we need to tariff.”

But in the interest of keeping the discussion productive, I’ll refrain from doing that.

The Great Filter hypothesis is based on an analogy with the European conquest of the globe in the 19th century. Little by little all the white spots on the map were first explored, then annexed. The (unspoken) parallel is that an advanced civilization would explore and conquer the entire galaxy. But even if a civilization could achieve interstellar travel capabilities, it is entirely possible that they colonize, let's say, only 80% of the galaxy, not 100%. Or maybe only 50% or 10%. If our solar system is in the complement of their zone, how would we know they are out there. How would we know there are aliens around Alpha Centauri, let's say. They could be busy living their lives, broadcasting in all the regions of the radio spectrum with abandon, maybe even nuking each other from time to time. And we would just hear absolute silence. The distances between stars are just so mind-bogglingly huge.

i don't see the connection. being the only intelligent beings in the universe (at the moment) lends credence to the great filter, and finding large numbers of other inhabited planets eliminates it, and in between why wouldn't it monotonically decrease?

My guess is any civilisation advanced enough to populate their galaxy knows that it's inherently pointless. Unchecked growth is the impetus of lesser lifeforms

Life is probably extinguished by machine intelligence before it gets the chance to.

Infinite expansionism is just one of a whole tower of assumptions that underlie the Fermi paradox. It’s a good thought experiment and does rule out certain scenarios with ET life but beyond that it’s a speculation.

The main scenario it rules out is one where intelligent ET life is common and we are late to the party. I feel like both those things can’t be true or we would see evidence.

I do find it fun to think about because it unfolds under scrutiny into such a vast tree of possibilities. But that same huge tree of possibilities makes it hard to say much.

One of my favorite wild speculations is that there is somewhere more interesting to go than space, and more accessible, and eventually whatever that is gets found before starships get built. What could that be? A traversable multiverse maybe?

That belongs to a subset of scenarios I call “positive great filters.” That’s where the great filter is a big success that renders space flight unimportant or uninteresting but does not result in extinction.

What about hyper-miniaturization. Maybe you can have something the size and scope of a galactic civilization without leaving home by folding your minds and everything else up into quantum states or hidden extra dimensions. Think a civilization of “sophons” (three body problem reference) with trillions upon trillions of minds occupying a few square meters of space and consuming a few hundred watts.

Yet another is some kind of remote sensing that lets you explore without physically moving, like a real equivalent to remote viewing. There’s a sci-fi novel called Blind Lake about this. Combine with miniaturized super efficient information processing and you could have superintelligences that explore everywhere and learn everything without going anywhere.

Lots of speculations and possibilities if you allow for the fact that we’ve only been doing science seriously for about 150 years and surely do not know everything.

the idea is: if we do find life elsewhere, especially basic life, it suggests that getting to that stage isn't super rare. which means the great filter probably isn't behind us (like abiogenesis or single-cell to multi-cell jump), but possibly ahead of us - maybe in surviving long-term, avoiding self-destruction, spreading beyond one planet, etc.

finding life doesn't eliminate the great filter - it raises the unsettling possibility that we haven't hit it yet.

Greg Egan's Permutation City is a great sci-fi novel partly about 'positive filters,' as you nicely put it.

The argument you're referencing is usually about finding life on a nearby planet, e.g. on Mars. Nick Bostrom has articulated [0] this argument. But finding life on a distant planet lacks the same statistical power for instilling this existential fear.

[0] https://nickbostrom.com/papers/where-are-they/

Of course. It'd be much worse if we found life on Mars than on a distant planet. In either case, the chances of humanity being ahead of the "great filter" are greatly reduced.

> The main scenario it rules out is one where intelligent ET life is common and we are late to the party. I feel like both those things can’t be true or we would see evidence.

There are a thousand scenarios where those things are true, e.g. the Zoo/Planetarium Hypothesis, but they tend to result in the conclusion that we're being somehow manipulated and can't trust our observations, so they're strongly disfavored on scientific grounds... Which does not rule them out.

what happens if you have lightning on a hycean planet?

ALL of it? EVERY time? There should be some signs somewhere.

Or everyone quickly discovers a better way of communicating, and the era of blasting out radio is a short one.

I mean, communication is insanely hard. If there's no way around the speed of light, life would still likely (slowly) expand across the stars, but it would be functionally impossible to continue to act as a unified civilization or colony across even a couple solar systems much less a whole galaxy

That's not taking into account that each solar system has its own set of circumstances, it could just be panspermia between earth and mars.

I find myself believing less in the great filter. My comment here: https://news.ycombinator.com/item?id=43712645 explains why.

One thing that I haven’t seen discussed much in terms of galactic colonization is genetic drift, speciation and communication.

I believe there are simulations theorizing that galaxies can be thoroughly explored in 10M - 100M years.

But how would those species even communicate their discoveries across a 100k LY galaxy? The delay would render data inaccurate by the time it arrives. It seems challenging to persist in a common purpose for millions of years across vast distances.

And would they even be the same species on those timescales and distances? On Earth isolation leads to some unique physical and cultural evolutions.

Maybe life already colonized everything within possible reach, made most of it inhospitable, and the remaining three survivor galactic empires sent an ark and some supplies to a small planet called Earth.

Unless there’s enough oxygen, it shouldn’t be a problem