Greta wrote:It's pretty clear that, to you, the Great Filter hypothesis is the only realistic one....
Not necessarily. Obviously this is highly speculative stuff - about as speculative as anything gets - so I don't really know. But, like you, I'm interested in playing with the ideas for the intellectual fun of it.
What I was saying in that last post wasn't really directly relevant to the Great Filter hypothesis. Even if there is no filter and the Universe is teeming with life, and even if, as you've said, some of that life, over billions of years, could develop to levels that we can't possibly imagine (any more than the "transient creatures that swarm and multiply in a drop of water" (HG Wells) can imagine us), even then, it seems to me that
if the fate of the Universe were to be the "heat death"
then, by definition, it would not contain any life, any structure, any gradients, any differences or any change.
And I would have thought that life, and/or whatever self-sustaining complex systems emerge from the technologies developed by that life, cannot exist without those things. Once the last brown dwarf has fallen into the last black hole, and that last black hole has "evaporated" and everything is in the same, uniform state such that there are no significant gradients to create changes and movements (and, therefore, arguably, no sense in which the idea of the passage of time itself is meaningful) then I don't see how living things exist. And, conversely, if that state doesn't obtain everywhere, and, as you've suggested, some unimaginable post-life entity has managed to carve out a little low entropy niche for itself, that just means that the fabled "heat death", by definition, hasn't yet been reached. But
if the 2nd law really is universal, then even that low entropy niche must eventually blend with the background.
Imagine a line of evolution, capable of spreading out to different star systems. It only has to happen once - in all of the universe over deep, deep time. What could destroy such entities? What challenge could they not meet? Galactic collision? They would simply calculate what would happen and where they need to be at a given time to avoid being exposed to too much of the Second Law, so to speak.
Yes, I see your point there. But, as I said, I think that, since the laws of physics are descriptive not prescriptive, if a super intelligent species can avoid the "heat death" in a way that demonstrates that the total entropy in a closed physical system (e.g. the Universe)
doesn't, after all, actually have to always stay the same or increase, that just means that the second law isn't, after all, universal. But if it is, then they can't do that. Eventually, if it really is universal, all gradients must even out. If it isn't, they don't have to.
Obviously the 2nd Law, and Eddington's famous words about it, aren't gospel. It's an inductively derived law of Nature like anything else, and his words are entertainingly colourful hyperbole in amusingly anachronistic language
1. Like all the laws of Nature, the laws of thermodynamics are descriptive, not prescriptive. So they survive for as long as they remain useful descriptions of the general character of what is actually observed. But some laws appear to be more solid than others. i.e. some of them form such a deep foundation for such a large variety of different observed behaviours of our Universe, that, though, by their nature, they're never certain, they seem to be as close as anything can be. I think that's the point about the 2nd law that Eddington was trying to convey, in suggesting that it, in some sense, trumps other laws, like Maxwell's Equations.
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1Speaking of amusingly anachronistic language, one of my favourite quotes is from Ernest Rutherford, to his assistant, called Frederick Soddy, when it was discovered that radioactivity could change the number of protons in a nucleus, and therefore change one chemical element to another (the dream of the alchemists of turning "base metals" into gold):
Rutherford wrote:By Zeus, Soddy, they'd have us out as alchemists!
One of my favourite exclamations of alarm.