"The Killing Star" - R-bombs and interstellar genocide

[Simon_Jester]

It's not clear that we'd be able to hear the radio broadcasts, or other evidence, of other alien civilizations if they were out there. They could just be a thousand light years away, and we might have no idea of their existence.

[PeZook]

Another example is that, simply, we're first. I mean, somebody's have to be, right?

Ultimately, though all solutions are just speculation and determining which one is the most probable is probably impossible.

[Simon_Jester]

I'd be very surprised if we were first in this immediate region of space (say, out to a few hundred light years), let alone first in the galaxy. Unless intelligence is a monstrously improbable development, for reasons we don't know yet, then over the expected lifetime of a galaxy a LOT of intelligent species will emerge. In which case the odds of us being the first, when we aren't even orbiting one of the galaxy's first generation of G-class stars, are pretty low.

[Eternal_Freedom]

Well, maybe we weren't the first but maybe we're simply the first (or among the first but the others are very far away) to survive this long. We know that species can be wiped out easily enough by random events. There been, what, five mass extinctions in the last 500 million years or so? And that doesn't count the possibility that the species wiped themselves out.

Or, there are some advanced races out there who have quarantined our solar system from radio traffic because we're paranoid enough to come up with ideas like The Killing Star.

[Guardsman Bass]

SETI used to have an FAQ with what a telescope 100 times more sensitive than the Arecibo Radio Telescope could pick up at certain ranges, and it's not good. Detecting anything aside from powerful narrow-beam broadcasts was basically impossible from outside the solar system, and it's pretty unlikely that you'd pick up one of those unless you (or another civilization) were deliberately pinging other stars with them.

[CaptainChewbacca]

I seem to remember reading something to the effect of that at more than 30 light years radio and TV broadcasts are so weak that they're indistinguishable from background signals.

[Vehrec]

XKCD reported something to that effect here.

[cosmicalstorm]

I know they are not hard science, but I enjoy John Smarts attempts to answer the Fermi Paradox.
http://accelerating.org/articles/answer ... radox.html
http://accelerating.org/articles/transc ... hesis.html

[Simon_Jester]

I feel a personal dislike for anyone who sees "transcend" and thinks the appropriate noun for the state of transcending is "transcension" instead of "transcendence."

[SMJB]

Which is more important to his argument, out of the words in that phrase: "empire," or "million star?"

I assume you are talking to me? "Million star". That's what gives it the "strategic depth" he keeps talking about. I thought I already explained this, but this should be simple enough anyone can understand what I object to. I don't see how interstellar colonization can be taken so lightly in discussion for the purposes of realism, given the magnitude of the feat. Cavemen can't shoot for the moon.

Cave men did shoot for the moon, and it only took them ten thousand years to get it--the blink of an eye in astronomic terms. Imagine where they'll be a million years from now? Imagine where a sentient species that evolved a billion years ago would be today? Christ, man, civilization does not come with an expiration date!

I'd be very surprised if we were first in this immediate region of space (say, out to a few hundred light years), let alone first in the galaxy. Unless intelligence is a monstrously improbable development, for reasons we don't know yet, then over the expected lifetime of a galaxy a LOT of intelligent species will emerge. In which case the odds of us being the first, when we aren't even orbiting one of the galaxy's first generation of G-class stars, are pretty low.

Consider that the human brain uses about a quarter of our caloric intake--that is quite a strong selective pressure against a species becoming sentient. (Of course we don't know that whatever aliens use for neurons will be that greedy--but we don't know they won't either.) If we go by our own evolutionary history, it takes already being one of the cleverest creatures on the planet and already being more energy-efficient than rival species and then thrust into an environment that changes so rapidly that random mutation simply cannot be relied upon to allow the species to adapt quickly enough to survive to convince natural selection that bigger brains are worth it, and then you have to become more energy efficient still in order to feed said big brain. And even then, well, we're the only upright-walking ape left on the face of the Earth--what does that tell you about the odds of survival we faced?

[Formless]

You know why there is a rule against thread necromancy? I completely forgot that this thread existed and had to re-read it to know what you were responding to. Even though it was my own posts.

Cave men did shoot for the moon, and it only took them ten thousand years to get it--the blink of an eye in astronomic terms. Imagine where they'll be a million years from now? Imagine where a sentient species that evolved a billion years ago would be today? Christ, man, civilization does not come with an expiration date!

That was a metaphor, you buffoon. Obviously when I use the word "cavemen" I mean people living tens of thousands of years ago. Not modern man. Its also an irrelevant attempt to shift the goalposts, because once again you have ignored two facts:

A) Interstellar travel in any realistic scenario is a massive undertaking no matter how "advanced" your civilization. It may not even be feasible. It has nothing to do with expiration dates or whatever buzzwords you came across in the last two months.

B) Getting back to the original point of the thread, an interstellar civilization will not follow the same lines of reasoning as terrestrial ones from ANY era due to the immensity of their "territory", for the same reason. They may not even qualify as a unified civilization as we currently understand it. Each star system is so far away from the next that the only thing you can easily transport between them is information thanks to the speed of light. That includes any weapon that doesn't carry energy as photons. The only way around this is if faster (as in lightspeed or faster) or more energy efficient interstellar travel can be achieved, which would mean making discoveries that may not exist. Outside of fiction, anyway.

I get the feeling this is going to be tedious and repetitive.



By the way, though I'm treading on someone else's argument here, but your argument against S_J about evolution is kinda contradictory and makes some common mistakes as well. First of all in thinking that human brains are somehow that different from other mammalian species. Really, the main difference between you and a dog is that the dog is specialized to be a predator, so its brain is organized for those tasks. Its not much less powerful than ours. And yet, mammals are a dominant animal group on this planet.

Also, the evolutionary history of our species doesn't restrict how other species might evolve. Birds for instance have a more efficient brain architecture than mammals. Mammal brains only use the outer surface of the organ to do complex processing, hence why our brains need all those folds. Birds use the full 3d volume for connections. This means theirs have more processing power for the size than a similarly sized mammal brain-- after all, flight is a pretty intense activity mentally, but also requires the whole body to be as light and efficient as possible. Including the brain. So its possible, likely even, that an alien "brain" might not have the same selective pressures against it that shaped the human brain. What about a distributed intelligence, for example, like a plant, fungus, or insect colony? It would be a completely different beast.

[SMJB]

You know why there is a rule against thread necromancy? I completely forgot that this thread existed and had to re-read it to know what you were responding to. Even though it was my own posts.

It was on the top page. I assumed that meant it was active sometime more recently than two months ago.

That was a metaphor, you buffoon. Obviously when I use the word "cavemen" I mean people living tens of thousands of years ago. Not modern man. Its also an irrelevant attempt to shift the goalposts, because once again you have ignored two facts:

I was extending the metaphor, dumbass. Because, once again, civilization does not have an expiration date! If we can colonize one other star system, we can colonize them all.

A) Interstellar travel in any realistic scenario is a massive undertaking no matter how "advanced" your civilization. It may not even be feasible. It has nothing to do with expiration dates or whatever buzzwords you came across in the last two months.

Considering that we've had about three hundred different ideas about how to do it coming from NASA-grade scientists over the last six decades, I somehow doubt they'll all be prohibitively expensive forever. Even if all we ever manage is to send out a handful of sentient AI in Van Neumann probes going one tenth of a percent of the speed of light at some date only slightly prior to the sun exploding, that still counts.

B) Getting back to the original point of the thread, an interstellar civilization will not follow the same lines of reasoning as terrestrial ones from ANY era due to the immensity of their "territory", for the same reason.

Which has what to do with anything I ever said, ever?

They may not even qualify as a unified civilization as we currently understand it.

Would you get this through your thick skull: AT NO POINT IN TIME DID I IMPLY ANYTHING ABOUT THIS BEING A UNIFIED POLITICAL ENTITY!!!!! It doesn't matter if the civilization falls and rises a million times on a million worlds or if the people on one side of the sphere of expansion have anything in common with the people on the other side, including planet of species' origin--if the expansion can be traced back to a single planet, it is a civilization for the purposes of this conversation. Fucking Christ, exactly how many ways do I have to explain that to you before you start taking a hint???

I get the feeling this is going to be tedious and repetitive.

Yeah--for me.

First of all in thinking that human brains are somehow that different from other mammalian species.

Um, I didn't say that. Except for being larger than average for our bodymass and specialized for sentience, of course.

Really, the main difference between you and a dog is that the dog is specialized to be a predator, so its brain is organized for those tasks. Its not much less powerful than ours. And yet, mammals are a dominant animal group on this planet.

Yeah, I have no idea what you're even objecting to here.

Also, the evolutionary history of our species doesn't restrict how other species might evolve.

No, but it's still the best roadmap we have.

Birds for instance have a more efficient brain architecture than mammals. Mammal brains only use the outer surface of the organ to do complex processing, hence why our brains need all those folds. Birds use the full 3d volume for connections. This means theirs have more processing power for the size than a similarly sized mammal brain-- after all, flight is a pretty intense activity mentally, but also requires the whole body to be as light and efficient as possible. Including the brain.

Firstly, that whole thing about us only using the surface of our brain for thinking is a folk tale. Secondly, I once again have no idea what it is you're even objecting to.

[Borgholio]

I was wondering just how much lead time a civilization would have to detect a RKV heading in their direction. If you assume the RKV is one giant rocket that was self-propelled using some extremely high energy fuel such as antimatter, then it should put out a very large flare that could be detected by the potential target. But how much time would there be between detecting the engine flare and impact? So I figured the following:

Vehicle accelerated to 92% lightspeed.
Launch point 10 lightyears away.

Assuming they used a source of fuel such as antimatter that put out emissions bright enough to be detected from Earth, the light from the engine plume would travel away from the rocket at a speed of no less than 14,880 miles per second (vehicle traveling at 92% lightspeed once fully accelerated, light traveling at 100% lightspeed, 8% difference = 14,880 miles per second).

At a relative speed of 14,880 miles per second over roughly 10 years, the light from the engine exhaust would arrive about 9 months prior to impact. That seems to me plenty of time to throw up a cloud of "brilliant pebbles" (similar to what they considered using to destroy incoming nukes). If the attacker was farther away (20ly, 30ly, or more...) then the lead time grows to the point where you can have years to prepare.

Now if an RKV is somehow launched using a non-luminous method, such as an impossibly large coilgun, then we'd just be screwed. But if it required a sustained thrust over time (far more likely), then it's something we could detect and protect against.

This sound about right, or am I missing something?

[SMJB]

Man, we are finding all sorts of logical holes in this idea, aren't we?

[Simon_Jester]

Have you read the rest of the thread? It got picked apart pretty thoroughly in June.

[Jerry the Vampire]

I was wondering just how much lead time a civilization would have to detect a RKV heading in their direction. If you assume the RKV is one giant rocket that was self-propelled using some extremely high energy fuel such as antimatter, then it should put out a very large flare that could be detected by the potential target. But how much time would there be between detecting the engine flare and impact? So I figured the following:

Vehicle accelerated to 92% lightspeed.
Launch point 10 lightyears away.

Assuming they used a source of fuel such as antimatter that put out emissions bright enough to be detected from Earth, the light from the engine plume would travel away from the rocket at a speed of no less than 14,880 miles per second (vehicle traveling at 92% lightspeed once fully accelerated, light traveling at 100% lightspeed, 8% difference = 14,880 miles per second).

At a relative speed of 14,880 miles per second over roughly 10 years, the light from the engine
exhaust would arrive about 9 months prior to impact. That seems to me plenty of time to throw up a cloud of "brilliant pebbles" (similar to what they considered using to destroy incoming nukes). If the attacker was farther away (20ly, 30ly, or more...) then the lead time grows to the point where you can have years to prepare.

Now if an RKV is somehow launched using a non-luminous method, such as an impossibly large coilgun, then we'd just be screwed. But if it required a sustained thrust over time (far more likely), then it's something we could detect and protect against.

This sound about right, or am I missing something?

A coil gun would be detected just the same as antimatter rockets would. Not to mention we would notice something was up with gravity due to the increase in it's apparent mass at those speeds.

[Simon_Jester]

I highly doubt that, Jerry. A high-relativistic impactor traveling at, say, 0.9c would not have nearly enough mass-energy density to create noticeable gravity.

[Jerry the Vampire]

Hmm well I'd have to have a ballpark figure for the rest mass before concluding anything but I will concede.

However, I don't see any reason we wouldn't detect its launch from a coil gun because of the amount of energy it would have to pump in a short time span.

[Borgholio]

Given how big a coilgun would need to be to launch something like that, would the gun itself generate measurable gravity?

[cosmicalstorm]

I highly doubt that, Jerry. A high-relativistic impactor traveling at, say, 0.9c would not have nearly enough mass-energy density to create noticeable gravity.

Noticeable gravity to what? A single Earthbased gravitational observatory? That would certainly miss it. But would not a more capable, future controller of Sol decide to build a very large amount of detectors looking in every direction? Is it ridiculous to believe that the entire Oort cloud would not be filled with 100.000's to 1000.000.000's of sensor platforms monitoring the surrounding universe? It would seem to be possible to get a very good look at the surrounding galaxy.

[Eternal_Freedom]

Given how big a coilgun would need to be to launch something like that, would the gun itself generate measurable gravity?

To hurl something heavier and faster the coilgun is (I'm pretty sure) bigger and longer. So while it will have plenty of mass and will have a gravitational effect on other stuff (a measureable one, with the right instruments) it wouldn't be noticeable to humans. Even if the hypothetical coil gun had the same mas as Mercury, it would be stretched out over a huge length, not concentrated around a point.

[Simon_Jester]

Hmm well I'd have to have a ballpark figure for the rest mass before concluding anything but I will concede.

Check the gravitational perturbations caused by, oh, say, a ten-kilometer rock that has enough kinetic energy to vaporize a small planet. Just to see if that might somehow be noticeable... although honestly in that case you'd have to be very curiously blind if you could see the gravitational effect of its mass on other things but NOT the projectile itself; if nothing else it'd generate a bow shock of low-energy X-rays and stuff just from all the interstellar hydrogen smacking into its nose.

However, I don't see any reason we wouldn't detect its launch from a coil gun because of the amount of energy it would have to pump in a short time span.

That's one problem with a coil gun (huge associated bursts of radio-frequency and/or higher-frequency noise in a "muzzle flash.") The other is the length of the flight path. Seriously, just sitting down and doing the math for a 'gun' designed to accelerate a projectile at, say, 1000g until it reaches speeds around 0.5c... we're talking about a barrel roughly a billion kilometers long, and that's for an acceleration that is really very, VERY ridiculous from an engineering perspective, there's no feasible way to do it. Scale down the acceleration to something vaguely sane within the context of hard SF and the barrel length goes up ridiculously, to the point where it runs out into the Oort cloud or something.

How would you even build something like this without other people noticing, come to think of it? I don't know. So yeah, not going to work well.

I highly doubt that, Jerry. A high-relativistic impactor traveling at, say, 0.9c would not have nearly enough mass-energy density to create noticeable gravity.

Noticeable gravity to what? A single Earthbased gravitational observatory? That would certainly miss it. But would not a more capable, future controller of Sol decide to build a very large amount of detectors looking in every direction? Is it ridiculous to believe that the entire Oort cloud would not be filled with 100.000's to 1000.000.000's of sensor platforms monitoring the surrounding universe? It would seem to be possible to get a very good look at the surrounding galaxy.

At some point, the detector sensitivity required to spot the gravitational perturbations it causes is comically high compared to the sensitivity required to spot the thing itself. A big, fast-moving rock in interstellar space just isn't going to cause noticeable perturbations from trillions of kilometers away.

[PeZook]

Just FYI, we can now take pictures of pretty faraway star systems with resolutions measured in AU per pixel. If you built a gigantic coilgun sticking out the oort cloud it would be visible even by just looking through a telescope, and not for very long, either - months of light collecting with our relatively primitive and limited equipment. With hundreds of thousands of dedicated early warning telescopes working in concert, detecting a launch or even the launch platform itself would be relatively trivial.

...for anybody in vicinity, too, and they'd know well before you finished the project, AND the early warning network would be extremely stealthy in comparison.

[PeZook]

In short, this is the age-old problem of the defender's advantage, except turned up to 10E24. Imagine a situation where an attacker has to haul the ammunition for his gun one round per ship from the other side of the solar system, while you had a gigantic arsenal of every weapon in existence twenty metres behind the position you have to defend.

[Jerry the Vampire]

This is why if your going to fire a weapon across lightyears it should be a laser or related weapon. Obviousely to make a laser powerful enough has it's own challenges but at least there would be no early warning.