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A Lonely Universe

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Re: A Lonely Universe

#151

Post by GoblinSlayer »

shagie wrote: post #69
pfdietz wrote: post #57

Earlier quoted context omitted.

It actually doesn't require THAT much energy to get into orbit. The energy of a kilogram of mass in low earth orbit is about 9 kWh, although rockets will use a bit more than that (not enormously more, though). Fuel cost remains a minor fraction of launch cost, even with Falcon 9. In comparison, the best aluminum plants in the world use 13 kWh to make a kilogram of aluminum. Yet no one says aluminum is out of reach be…

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.

Re: A Lonely Universe

#152

Post by WillPostForFood »

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…

is absurdly premature.

Only relative to our own existence. If the universe is ~14 billion years old, and life was plentiful, you might expect life to have emerged elsewhere hundreds of millions or a few billion years before us. That allows for enough time for signals to have reached earth, even at slow light speeds.

Re: A Lonely Universe

#153

Post by nayuki »

foobarian wrote: post #141
pfdietz wrote: post #123

Earlier quoted context omitted.

No, exponentially. I used that word precisely, because the mass ratio in the rocket equation is exponential in (delta V)/(exhaust velocity).

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...

Re: A Lonely Universe

#154

Post by pharke »

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 one foolproof probe that can bootstrap a manufacturing facility in the next system. More likely you would send a few backup probes but you wouldn't send billions of them.

I think multiple Von Neumann probes could have come and gone from our system using little more than a few asteroids and a sip of the Jovian atmosphere.

It's also worth repeating that Von Neumann probes are only useful for information gathering. It would be highly impractical to pre-build all of the colonization infrastructure ahead of time and then mothball it for millions more years while the biologicals caught up, assuming they ever did. So these devices would be limited to scientific exploration or monitoring.

The only thing that I think Star Trek got right about the future is that many people will live in space full time aboard starships. All the planet hopping they do is just to further the plot and provide a familiar backdrop to the audience. Once a species transitions to living in space they will most likely stay there and have little use for planets. Depending on their mastery of fusion or other energy sources they may not even bother hanging around stars anymore. If we want to talk about anthropocentric perspectives the whole concept of visiting other worlds is probably as progressive as vacationing in natural caves, an entertaining novelty done once but never repeated by people who enjoy a roof over their heads, modern conveniences and climate control.

Re: A Lonely Universe

#155

Post by mmh0000 »

7thaccount wrote: post #48
kingcharles wrote: post #30

Earlier quoted context omitted.

How about the possibility that perfect VR is invented, every person can live inside their own perfect universe, and the whole species just doesn't give a fuck about exploring the (real) universe? That would stop a civilisation from exporting any spacecraft or signals outside its homeworld.

This is my main theory. Humans will eventually abandon their own bodies and live in a VR world. I think you'd still have massive energy requirements in the real world to deal with of course.

There was a great documentary[0] on this a few years ago. They specifically talked about the energy requirements and how they solved them.

[0] https://m.imdb.com/title/tt0133093

Re: A Lonely Universe

#156

Post by GoblinSlayer »

brabel wrote: post #85
ncmncm wrote: post #19

Earlier quoted context omitted.

A galaxy is really a pretty dangerous place for organic life. One supermassive black hole merger in the same or nearby galaxy, a biggish black hole merger within 10,000 light years, a magnetar hiccup within 500 ly, or a workaday supernova 5 ly off might be enough to sterilize a whole solar system. There is no guessing how many times life has been wiped clean that way. The sooner our descendants can get the hell out o…

I think we are in a relatively safe corner of the galaxy though... IIRC there's no cosmical existential threat we know of within the next billion years or so, and the kind of cataclism you're talking about would be the kind of thing we should already be able to predict millions of years in advance.

We are in the galactic habitable zone.

Re: A Lonely Universe

#157

Post by pharke »

andrei_says_ wrote: post #62
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…

Whales for example are intelligent, but I don’t see them ever getting excited about space travel. Is it not possible for intelligent life to exist but not be interested in more ?

It is but they get cleared out of the equation by f sub c, the fraction of intelligent life that invents high technology capable of interstellar radio transmission.

Re: A Lonely Universe

#158

Post by lhorie »

wruza wrote: post #101
lhorie wrote: post #56

Earlier quoted context omitted.

Why are we assuming that we would be able to see intelligent alien life by just looking at the right spot in space? If we take it at face value the figure that the universe is 13 billion years old, and that the observable universe is 90 billion light years wide, presumably that means that there's a whole lot of universe that could have evolved intelligent life at a pace similar to our own, but that we just can't see…

Our evolution was not a straight line. We could stay in bacterial form for a couple of billion years if not the great oxygenation event, or have a couple of billions of years of advantage if it happened that earlier. The evolution from simple marine life to us happened in an instant compared to pre-O2 era. https://www.shutterstock.com/ru/image-vector/evolution-life-...

Sure, but that doesn't really address the point. Suppose aliens got really lucky and managed to achieve interstellar travel in just 1 billion years since the big bang. That still leaves the entire area outside of a 12 billion light years radius from us invisible, i.e. they would have to be somewhere within that radius within the next 12 billion years, for us to be physically able to see them. But that radius is like less than 1% of the known universe.

And in actuality, they would need to sit there detectably within the narrow period of a few hundred years or so that humanity is actually looking at that spot in the sky. So, for example, if they were galaxy hopping every few million years rather than cancerously leaving dyson spheres everywhere, and just happened to temporarily brush into our radius of visibility during their nomadic travels, we wouldn't necessarily see them if they got within view too early or too late.

Re: A Lonely Universe

#159

Post by GoblinSlayer »

jason-phillips wrote: post #122
wruza wrote: post #94

Earlier quoted context omitted.

Expansion is a property of k>1 reproduction. We could make a sustainable happy civilization even on this dirty planet, if not our biological drive to multiply and eat all gifted to us resources with time. My bets are not on climate ops or hunting-gathering for mature civilizations, but simply on k~=1, the simplest form of existence that brings more value with time instead of more size.

In my opinion this comment brings the discussion full circle, from reasoning the difficulties of intergalactic travel back to the quandary of our home.

Sustainable reproduction is what enables space travel, expansive species spend their time on infighting, they have no resources to fly anywhere, example: humankind. But even in case of humankind, our exponential reproduction is winding down over time. Irrespective of reproduction, a barbaric species won't be able to fly beyond moon.

Re: A Lonely Universe

#160

Post by PicassoCTs »

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…

That fate is the technology acceleration with the scientific method versus the glacial development of species.

Meaning its comparable easy to unlock exponential technologys (energy density/ information density) and its very hard to actually self + "tame" a species fresh out of the woods. Just look at our world of 9 billion, longing for ever more surplus, handing dangerous technology to the individual without providing any self-control beyond basic self-surveillance to society members.

Anyone with a basic understanding of biology and a garage full of hamsters, can create a new covid based bioweapon right now. Ever more centralizing systems allow for one hacker to do incredible damage to a society. And while this plays out, there are still people demanding flying cars, so whoever hacks them, can fly them into buildings in case of civil unrest.

The denial about this species being unfit for the stars, unfit even for nuclear energy and the idea that ever more powerful toys will magically fix this "retardation" is whats at the core of the fermi paradox. Most species just murder one another off with exp-tech once the environment and the surplus machinery runs out.

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