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A Lonely Universe

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Re: A Lonely Universe

#181

Post by softjobs »

rewgs wrote: post #98
lubujackson wrote: post #24

Earlier quoted context omitted.

The third option is that everything is simply too far apart and any detectible transmissions are either too faint or buried behind all those massive fusion furnaces. For instance, if our best Earth tech was pointed at Earth from a distant star, how far away would we be able to detect our own traces of life? We know that life is "a little rare" at least, but there is a huge range of rarity where life is everywhere acr…

Yeah, I think that the Fermi Paradox can be pretty easily explained: the universe is fucking huge. Those who talk about the feasibility of alien life visiting us very simply haven't thought it through, or are ignorant of the reality of space. It's just too staggeringly big.

To drive home the enormous scale of the local solar system, and by extension the universe, I'm fond of this: https://joshworth.com/dev/pixelspace/pixelspace_solarsystem....

Re: A Lonely Universe

#182

Post by mrjangles »

me_me_me wrote: post #133
mrjangles wrote: post #45

Earlier quoted context omitted.

I always liked this description because it is so similar to the descriptions of untouched cultures in West New Guinea when they were first discovered in the middle of last century. These cultures were entirely untouched and it gave anthropologists a look into what life was like before before civilization. The island was divided into tiny tribes which lead an incredibly brutal way of life. One of the interesting featu…

I dunno, the dark forest trilogy definitely sparks interesting conversations. But a counter example to it is that only via cooperation a tribe can become technologically advanced. All those tribes are just tribes due to their constant squabbling and fighting, while the other that cooperated, traded and exchanged ideas ended up advancing. Wars were/are part of humans but in Europe it quickly became evident that techno…

Yes sure, but I feel like this stuff came later. Once we had the technology, knowledge about each other, institutions, rule of law, etc, then people could begin to trust each other and work together. This is what happened everywhere slowly.

But at the start where everything is unknown and everything is new, and we can't see beyond the next tree, when we don't know what is out there and what they want. In that world, it has always kill or be killed.

Re: A Lonely Universe

#183

Post by shagie »

GoblinSlayer wrote: post #151
shagie wrote: post #69

Earlier quoted context omitted.

An interesting problem is "how much energy would it take to launch from a super-earth?" https://www.space.com/40375-super-earth-exoplanets-hard-alie... > To launch the equivalent of an Apollo moon mission, a rocket on a super-Earth would need to have a mass of about 440,000 tons (400,000 metric tons), due to fuel requirements, the study said. That's on the order of the mass of the Great Pyramid of Giza in Egypt. We m…

We see only super earthes because they are easier to see. Small planets can be more numerous.

They can... but a challenge with a small planet in the habitable zone of a star is that it also has a weaker magnetic field and is more prone to having its atmosphere stripped away.

Consider that the moon had an atmosphere - https://en.wikipedia.org/wiki/Atmosphere_of_the_Moon#Ancient...

> In October 2017, NASA scientists at the Marshall Space Flight Center and the Lunar and Planetary Institute in Houston announced their finding, based on studies of Moon magma samples retrieved by the Apollo missions, that the Moon had once possessed a relatively thick atmosphere for a period of 70 million years between 3 and 4 billion years ago. This atmosphere, sourced from gases ejected from lunar volcanic eruptions, was twice the thickness of that of present-day Mars.

http://time.com/4974580/nasa-moon-had-atmosphere-volcanoes/

Which brings us to

https://worldbuilding.stackexchange.com/questions/13583/what...

While smaller planets are certainly more numerous - many of them likely lack the mass and active magnetic field to retain an atmosphere in the habitable zone.

Re: A Lonely Universe

#184

Post by hnzix »

hoseja wrote: post #77

Very good article. The Earth chauvinism in trying to theorize about extraterrestrial life is blinding. There could be magnetohydrodynamic life in star plasmas for all we know. We need to explore WAY more before we try to reach any conclusions.

"They're made out of... meat?"

https://mediachomp.com/theyre-made-out-of-meat-sci-fi-short-...

Re: A Lonely Universe

#185

Post by ncmncm »

nayuki wrote: post #153
foobarian wrote: post #141

Earlier quoted context omitted.

Thanks for the reply. Context: there are so few exponential processes in nature, especially around classical physics that it really stuck out here, so I made the comment. I should have searched and read up on it instead, but thought there is still some value in others seeing the conversation. And lastly: that is really depressing :-(

This phenomenon is called "The Tyranny of the Rocket Equation": https://www.nasa.gov/mission_pages/station/expeditions/exped...

Saturn, Uranus, and Neptune all have surface (well, cloud level) gravity nearly equal to Earth's. But try launching anything to orbit from any of them!

(Strangely, with hydrogen and helium the majority of all three atmospheres, they have water and ammonia clouds. What holds them up?)

Re: A Lonely Universe

#186

Post by ncmncm »

pfdietz wrote: post #125
brabel wrote: post #84

Earlier quoted context omitted.

Not to mention that when we talk about other galaxies, then distances are on a whole different scale again. While travelling to other stars takes "only" a few thousand years, to go to another galaxy you might need several hundred million years with any technology we can currently even imagine. Even if intelligent life is rare enough that it only appears once on a single galaxy every several billion years, we're still…

We can achieve relativistic speeds with technologies we can imagine (specifically, laser light sails). This would require just millions of years to get to M-31, for example (which is 2 million light years away).

Arriving not in atomically finely tattered shreds is left as an exercise for the descendants. And, stopping.

Re: A Lonely Universe

#187

Post by ncmncm »

omnicognate wrote: post #146
rewgs wrote: post #98

Earlier quoted context omitted.

Yeah, I think that the Fermi Paradox can be pretty easily explained: the universe is fucking huge. Those who talk about the feasibility of alien life visiting us very simply haven't thought it through, or are ignorant of the reality of space. It's just too staggeringly big.

Yep, the Fermi "paradox" is no paradox at all. We have basically no evidence that life (including intelligent life) isn't common yet. There are so many ways to think of how big our galaxy is but two are particularly relevant to how difficult it would be to detect other life, or be detected: 1. The first radio signals the human race produced have so far travelled something like a thousandth of the distance to the othe…

I wonder whether any organic life in a galaxy could survive merger of a pair of 1e9-solar-mass black holes. Would 25,000 light years be far enough out? 5,000? 500 light years is supposed to be the sterilization range of a minor magnetar hiccup, 5 light years for a workaday supernova, IIRC. We will soon find out how much energy is released in such a merger; one is about to happen in a year or three, about a billion light years out. Sadly, we will not have deployed a gravity-wave detector big enough to measure it with, by then, and will have to wait for the next one.

If life sorts more or less neatly into expansionist and sedentary cultures, the sedentary species will generally be much older and, typically, much more technologically advanced than the expansionists that try to encompass them. Aggressive expansionists will tend to be destroyed by the first, second, or anyway tenth sedentary culture they try to strong-arm. So, the galaxy is full of very old, sedentary cultures not interested in visiting us, and young expansionists popping up all the time and being obliterated before they reach us.

Re: A Lonely Universe

#188

Post by ncmncm »

pharke wrote: post #154
Causality1 wrote: post #2

Either intelligent life is rare in the universe or there's something that happens to it that prevents it from what we envision as the future of our own species, i.e., colonizing and spreading among planets. Maybe 99.99% of species ruin their own climate before getting off-world. Maybe they all decide it's happier living as hunter-gatherers. Unless we're alone, there is some fate that's common to all intelligences and…

I've never understood the Von Neumann probe conjecture. Why would anyone design a probe that uses all of the available resources within a system to produce new probes that are sent to the N nearest systems? Surely it's more efficient to use a smaller number of more capable probes than to use a larger number of less capable ones when you consider the fuel mass necessary to get them to the next star. Ideally, you need…

Stars, anyway, have Kuiper belts full of useful materials, with lots of room to spread out, and far enough out not to be inconveniently warm. Any civilization working with very large energies will have large cooling needs: if there is anything we can say confidently about future technologies, it is that they will remain bound by thermodynamics.

Re: A Lonely Universe

#189

Post by ncmncm »

viovanov wrote: post #134
Causality1 wrote: post #2

Either intelligent life is rare in the universe or there's something that happens to it that prevents it from what we envision as the future of our own species, i.e., colonizing and spreading among planets. Maybe 99.99% of species ruin their own climate before getting off-world. Maybe they all decide it's happier living as hunter-gatherers. Unless we're alone, there is some fate that's common to all intelligences and…

I think you need multiple generations (subsequent) of stars in order to get heavier elements - which are probably needed by life. So maybe the universe is not _that_ old. https://www.quora.com/How-many-generations-of-stars-have-the...

The stars that make the elements we need form and blow up in only a few million years. A billion years is plenty of time, once you get the hydrogen gathered together enough to get things started.

Re: A Lonely Universe

#190

Post by ncmncm »

GoblinSlayer wrote: post #161
rel2thr wrote: post #124

Earlier quoted context omitted.

It’s pretty rare on earth too, 10 million species but only 1 has space flight and the others aren’t anywhere close to developing it!

We had neanderthals.

And Denisovans, and still have raccoons. The raccoons shouldn't need more than another 10My.
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