We have several threads in World Building to discuss sci-fi ideas.
Edited by Fighteer on Nov 16th 2022 at 10:30:49 AM
"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"Signal coverage approach to the detection probability of hypothetical extraterrestrial emitters in the Milky Way
apparently even if there are a lot of civilizations in the Milky Way, detecting their electromagnetic emissions would be a fool's chance.
This paper
that references the one above touches onto a major issue: We don't know what extraterrestrial societies would look like from Earth's sensors. And without knowing that, we can't say whether the number of currently known such societies (0) means anything at all.
Yeah, like my laser communication example from before.
There's also pretty likely planets with overly active magnetospheres that would really fuck with radio transmissions and so wired communication networks would be the norm with very little sent over the air.
Alien civilizations using either of those approaches would look totally silent to us.
Or, hell, any activity around a major gas giant. If there was something on, say, Ganymede, broadcasting radio signals, we'd have a really hard time picking it out from the enormous amount of output from Jupiter if we didn't already know it was there.
Edited by Zendervai on Nov 16th 2022 at 10:07:11 AM
On the other hand, while "civilization" may be difficult to detect, life itself should have certain chemical signatures that we could detect from an analysis of a planet's atmosphere, even at interstellar distances.
If life itself is rare, then civilizations even more so, but if it is common...
I'm done trying to sound smart. "Clear" is the new smart.@Galadriel:
But why assume any culture wants to do that? Or that it wants to do that for any longer than it might take the reach one other star system? That’s a staggering amount of time that demands a culture place and EXTREMELY high value on space expansion at the expense of anything else, and that a species’ culture will remain similar enough, across millennia, for them to want to KEEP continuing to do it.
But why assume any culture would stop expanding... or more to the point, why assume every culture would? You have no evidence for this assumption. Even if 99 percent of civilizations decide not to go further or kill themselves trying to do so, the one percent that's left over could colonize the entire galaxy.
It doesn't have to be in thousand-year doublings. It could be ten thousand, and then it takes a whopping 350,000 years to inhabit every possible planet. This is an eyeblink on cosmological scales and could have happened dozens of times in the history of the Milky Way galaxy.
"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"I don't think that's quite right. It's like pointing out that it takes a person about 10 minutes to paint a 10' x 10' section of pavement green, and since we have had green paint and pavement for hundreds of years, naturally we have painted all our roads green. Except we haven't, so "paradox?"
What the usual formulation of the Fermi paradox doesn't account for are the actual probablilites of each step, because we can't because we don't know them.
I'm done trying to sound smart. "Clear" is the new smart.This is exactly what I'm saying and why it is considered a paradox. The formulation of those probabilities is the Drake equation.
Edited by Fighteer on Nov 16th 2022 at 10:37:34 AM
"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"But then it just runs into why anyone would want to do that. That's a ridiculously high level of resource expenditure over an absurdly long period of time for unclear gains. If there's a strong central authority (assuming no FTL) behind the expansion, it would inevitably collapse from the difficulty of maintaining control and then the resources required to colonize a planet would cease to be as accessible. If it's just random colony ships with minimal support, we'd have to assume a really high failure rate.
It would also require a lot of colonization with the deliberate intent to seed more colonies and even if a culture tried doing that, it'd likely be super patchy and increasingly spread out the further you get from the home system. If a planet intended to be the next colonization hub just decides "eh, we aren't gonna bother", and they're far away enough from the home system, you'll get a huge slice of the galaxy that won't have any presence because the chain was broken. And that'd likely happen an increasing number of times.
And that's assuming the planning was otherwise perfect. If an intended hub world is just really shitty or had a horrible disaster before the colony ship arrived...how do you fix that?
The only way for that to work is chains of worlds and if you break a chain, the process stops dead in that particular area unless someone down the road deliberately decides to pick it back up. Not to mention the question of what's actually desirable or not. If an alien species really disliked red dwarf stars, for example, they'd leave our corner of the galaxy mostly alone because we're fucking swimming in them and they'd hang more around the inner parts of the galaxy.
Edited by Zendervai on Nov 16th 2022 at 10:47:25 AM
The things you're talking about are all factors in the equation. They are not absolute stops, but they are probabilities. If the probabilities stack up enough, it explains why there are no galactic civilizations (that we can see). The problem is that we cannot know the values for them.
Any assumptions we make about the psychology or political organization of aliens are literally just guesses.
Edited by Fighteer on Nov 16th 2022 at 10:52:50 AM
"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"Something Eartherly: Bone histological correlates for air sacs and their implications for understanding the origin of the dinosaurian respiratory system
. I think it's fair to ask if the evolution of large sizes/flight in dinosaurs (and consequently, in birds) was only possible thanks to the evolution of air sacs.
I'm somewhat curious, what's the reason that more birds, I dunno, just become as huge as their ancestral cousins? They've dropped flight sometimes, certainly got big from it, but nothing really as big as the "average" big dino. Not enough time for such traits? Lack of certain anatomy traits due to flight? Is it the beaks?
There is no evidence that the air being different plays a role. For one thing, Mesozoic and Cenozoic air is largely the same.
I think the actual problem is that for dinosaur-sized or dragon-likenote birds to evolve, birds would have first to grow to the size of large mammals. Where, you know, existing mammals are in competition. This is the concept of a "fitness landscape
"; it doesn't matter whether a given organism can exist if there is no evolutionary pathway leading to it.
Another factor to consider is the icehouse climate; compared to the Mesozoic Earth might just not have enough life to feed really large land animals.
(Mammals themselves cannot evolve to dragons or dinosaurs b/c they don't have air sacs and would become too heavy and anoxic)
"For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled." - Richard Feynman@alekos23
So, once the non-Avian dinosaurs went extinct, you can think of there being a sort of dash to refill the lost niches. Mammals ultimately came out on top over birds because birds are highly specialized, whereas mammals are more versatile and their form can be more easily adapted.
The fact that birds are specialized towards being small, flying things essentially makes it difficult for them to evolve towards too many other niches. Their bodies have various features that exist specifically to support flight, some of which come with drawbacks, and these also aren't necessarily easily evolved off. Also consider that birds are very successful in their own set of niches.
They'd also have to compete with mammals, whose body design, again, is more easily adapted towards various ground creatures.
So, basically, it's just not feasible at this point in time for birds to reclaim the throne that dinosaurs had.
@Zendervai To my understanding that's actually not that big a deal. It's mostly only arthropods who have to care too much about fluctuations in the amount of O2 in the atmosphere. A sauropod brought to the modern day would be able to breathe mostly fine.
Leviticus 19:34How fast relative to what? All of those velocities are in different directions at any given moment.
The Milky Way travels about 630 km/s
with respect to the Hubble Flow (i.e. the motion of local galaxies based on the expansion of the universe), and the solar system circles the Milky Way at about 200 km/s
. Earth orbits the sun at about 30 km/s, and a point at the equator travels about 0.5 km/s.
Edited by Noaqiyeum on Nov 18th 2022 at 5:22:50 PM
ERROR: The current state of the world is unacceptable. Save anyway? YES/NORelative to the speed of light, the one constant in this godforsaken hellhole of a universe.
Edited with more information. :P
While checking my numbers I found out that Earth set a new personal best for fastest rotation just this last 29 June
!
Edited by Noaqiyeum on Nov 18th 2022 at 5:27:21 PM
ERROR: The current state of the world is unacceptable. Save anyway? YES/NOApparently the cosmic background can work as a frame of reference for this.
To answer your question:
- The Earth spins at ~1670 KPH
- The Earth orbits the sun at ~107,000 KPH
- The Solar System moves at ~720,000 KPH
- The Galaxy moves at ~2 million KPH, if my math is right.
So what you're saying is, depending on where the positions of everything are and if everything lines up, I could be moving at a maximum of 2,828,670 KPH, or a minimum of 1,171,330 KPH? The speed of light is 1,080,000,000 KPH, that means I am hurtling through the universe between 0.1% and 0.26% the speed of light.
Edited by PushoverMediaCritic on Nov 18th 2022 at 11:01:02 AM
The speed of light is the same in all reference frames; this is a core tenet of relativity. It doesn't matter which way you're moving or how fast; any test you can perform will show light to be moving at exactly c in every direction. note This has been proven so thoroughly that it is indisputable, although there are some ideas suggesting that there are limits to our ability to observe its one-way trip speed. (Short version: our measurements actually observe the average round-trip speed of light.)
From the perspective of a hypothetical observer who is still with respect to the cosmic microwave background (the only thing we can reasonably use as a universal reference point), Earth (along with the rest of the Milky Way galaxy) is moving at somewhere between 400 and 800 km/s, although my attempt to Google search the answer came up with a range of results. This is enough to Doppler-shift the CMB; indeed, that shift is how we are able to make the observation.
If you could accelerate to 0.9 c (and somehow avoid getting instantly vaporized by particle collisions), you would still see the speed of light to be equally fast in all directions. However, since you'd be moving very fast with respect to most other things in the universe, the light they emit would be blue-shifted ahead of you and red-shifted behind. You would also observe distances to be contracted and your field of view to be compressed in of your direction of travel.
What we think of as time, distance, and velocity are flexible concepts. They mean different things from different points of view. Only the speed of light is constant, and everything else warps as needed to fit.
Edited by Fighteer on Nov 19th 2022 at 9:44:45 AM
"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"

Okay I think this thread has gotten too deep into sci-fi territory. Aliens, mermaids, and now freaking grill organs?
Disgusted, but not surprised