[PoachedSausage]

Maybe there has been some sort of accident of scale, like the intergalactic fleet in Hitch Hiker Guide to the Galaxy that arrives to destroy Earth but is eaten by a dog.

There could be a banging ET party going at the Planck scale and we would never know, they might as well be on the other side of the universe.

[godelski]

The problem with this is that mechanics is not scale invariant. This puts bounds on creatures. Unless there's some crazy different way to compute I wouldn't expect a being to be able to have strong cognitive functions and be the size of a fly. They would also have a difficult time building advanced machinery to get to galactic travel scales. Similarly I wouldn't expect a creature the size of a Brontosaurus to become space faring. Because of their sizes they would have to consume significantly more resources to build simple things. A two story house probably couldn't be created out of wood or other basic biological materials making it difficult to transition into even the stone age. They also require higher food because energy requirements aren't linear. But think how much it costs to send a pound to space. Their first to space would be significantly more expensive.

This doesn't mean these things are impossible because maybe there are ways around them, but it certainty shifts the probabilities by quite a bit. Given our current understanding of biology and mechanics it makes it much more probable for creatures to be within the ballpark of our size (let's say crow to elephant?).

[PaulDavisThe1st]

I think this is a mistaken way of thinking in general, because you're omitting time. Your assuming that intelligent/thinking/conscious creatures would necessarily function on timelines that make sense to us. If that were true, then what you're saying makes sense - there are real bounds on how fast you can move chemical energy from A to B, for example.

But I see nothing preventing intelligent life from operating on massively longer timescales. This requires, of course, that you believe that intelligence (and maybe consciousness too) is substrate and timescale independent, which may or may not be a big ask depending on where you stand on these issues.

[godelski]

I think this is strange thinking because it breaks our laws of physics. The clock ticks at the same rate in internal reference frames, it is only different when looking at two different frames. But if you're talking about them acting at slower speeds or faster, then that brings along other problems similar to the mechanics ones we discussed (assuming we're not counting that they are in a slower reference frame). It really shifts the probabilities around. Even trees act relatively quickly because forces act fast. You'd have to be in a pretty extreme environment for other things to happen.

As to chemistry, if they are moving faster then that means that they have more thermal energy. That comes with radiative problems (why humans stand) and this is much more difficult the smaller you are because you have less surface area. Which then puts large energy requirements on intake. And then the inverse is true.

The thing is that aliens would still have to follow the laws of physics. There is no reason to expect that wouldn't be true and reasoning otherwise would take some pretty extraordinary evidence and probably win you several Nobel prizes.

[PaulDavisThe1st]

Good points, but ...

consider the range of timescales that humans can have effective control over. We manage to organize subatomic collisions that occur in femto-seconds, and we manage to build things that last thousands of years. All this despite the fact that our own lives are measured in units that are several orders of magnitude smaller or larger.

So I can imagine (just about) an intelligent system that can also effectively build systems operating in time domains orders of magnitude from their own experience/lifetimes. If they were very "slow" then certainly launching objects into orbit may appear almost impossibly fast to them. But it wouldn't be notably different than what we do with particle physics (or even firing a gun), where the timescale of the event is essentially impercetible to us, and far beyond our ability to control with our own bodies.

The other way around is harder, because creating things that last much longer than an individual's lifetime has to fall back on culture, and that seems to evolve (change) much more rapidly. There are very few buildings still in use that are more than a thousand years old, even though the physical construction of such a thing is relatively trivial.

[godelski]

> So I can imagine (just about) an intelligent system that can also effectively build systems operating in time domains orders of magnitude from their own experience/lifetimes.

This isn't the problem I'm getting at. The problem I'm getting at is that it'd be highly unlikely for an intelligent lifeform (or really any) to develop under those extreme conditions. Advancing under other conditions and then developing towards extreme conditions after they have reached a sufficiently advanced state is a different issue.

For extreme conditions like operating at a speed much faster to us (imperceptible) would mean that they would be under high amounts of acceleration than compared to us. Gravity already puts major constraints on humans and for a lifeform to be operating at a rate imperceptible to us we're not talking about 10x or 100x the gravity but more like 10^10^10^10 (or more). Mind you that their internal reference frames (their internal clocks) would operate at a different speed than what we see their clock moving at. Subatomic particles have a difficult time operating at a fraction of that gravitational force. That means you have no building blocks.

What you're not considering is that I've accounted for things like chemical processes and electrical processes not being needed. The problem is that I don't know how you get two particles to change state (at least in non-extreme or destructive ways) under the conditions you're talking about. This isn't about "oh we just don't know" it is that there are some things we do know. We know that lifeforms have to be able to change their state (e.g. you can move your fingers or you can have a thought. These are state changes). We know the basic building blocks of the universe, quarks (or at best strings). There's certain rules these things have to abide by. You can let your imagination run wild but there are still limits of what you can do within this universe. And any being even visiting this universe would still be subject to these rules even if they were from a different universe that had a different set of rules. You can't just trash these rules in the spirit of imagination (which btw testing and updating these rules is what the job of a physicist or really any scientist is. But it is still a convergent process).

Creating things that last longer than an individual's lifetime isn't hard at all. We've done it by accident, they are called artifacts. Nature does it all the time, they are called fossils or just dirt. Trees last longer than human lifetimes. I know you think you're keeping an open mind but instead what you've done is limited it. Operating within the bounds of the rules doesn't have to be a limiting process. There may still be an infinite number of configurations under these rules. But abandoning them makes your search space so open (and open in a way where you wouldn't expect to find solutions) that you can never find what you're looking for. It is like if you're looking for needles in a haystack and arguing that the way to find the needle is to add more hay because the needle is inside the hay.

[ChainOfFools]

https://archive.org/details/OnBeingTheRightSize-J.B.S.Haldan...

[godelski]

I'm sorry, you dropped a 130 page book with no other comment. Is there anything specific you want to say?

[ChainOfFools]

sorry, the relevant part of the book is in the first few pages of the first chapter, where JBS Haldane discusses the physical limits of mammalian anatomy due to load bearing constraints on bone cross sections and hydraulic implications for a heart that must circulate blood/lymph through a gigantic body, and how all of these and other separate systemic envelopes merge to form what we understand as the "right" sizes for living things etc.

Some portion of this chapter is occasionally excerpted to deflate claims about extraordinarily large or small purported alien creatures, though Haldane was setting up an argument for dynamically limited systems in general.

I thought it might be an interesting skim given the similarities to your comment above.

[LargoLasskhyfv]

Have you heard of https://en.wikipedia.org/wiki/Portia_(spider)? Or that birds brains are "wired" more dense, like our cerebellum?

[godelski]

I haven't, that's pretty cool. You can update my terrible range guesstimate accordingly. Though that doesn't change the main thesis of there being more likely sizes than others.