Stephen Hawking is Afraid of Aliens.

[Surlethe]

Yes, because the results of later occupation can totally be ignored

But by all means, show that you are right - you know what a "source" is, rihgt?
Well, that's what normal people use to show that what they say is not just a figment of their disease-ridden imagination (brought by the conquistadors, obviously). I know you can barely believe that there is a world outside your fever-narrowed sight, but it's true!

So please, by all means, show me a credible source comparing the deaths resulting from diseases and the deaths resulting from violence during that period.

Here (Google Books) is a book that makes the case disease was the dominant source of death upon European conquest of the Americas. I'm seeing 80% kicked around the internet as a general proportion of American Indians who died in the centuries following Columbus' landing, and that magnitude of death is treated as common knowledge by academics (economics professors) I've talked to. One illustrative example is Tenochtitlan: when Cortez arrived, he found 50% of the city's population dying of smallpox. It seems unlikely that any results of later occupation are remotely comparable to the toll inflicted by even the initial wave of disease.

[Iosef Cross]

To kill millions without weapons of mass destruction you need millions of soldiers.

Really..how interesting.

I guess you deny the Holocaust, Stalins purges both Chinas and the USSRs famines as well, since they were all done without the aid of "millions of soldiers" - not that that would surprise me the least.

Only because you didn't call me moron the last time:

1- The Holocaust

Most of the holocaust victics came from 2 countries: Poland and the USSR. To begin the holocaust the Nazis had to invade Poland with 1.5 million men and the USSR with 3.5 million. Also, by invading Poland they started WW2, and had to mobilize 16 million soldiers to fight and lose it... So, if they wanted to do the holocaust, they had to start a war where they lost 4-5 million soldiers death while managing to kill 6 million Jews, gypsies and homosexuals, etc.

2- Stalin's purges

That case involves a country killing it's own population. So it is not analogous to the Alien case nor the Spanish case. Also, the USSR employed millions into their apparatus of coercion and compulsion to make these genocides.

3- Mao's hunger

That case was an non intentional outcome of Mao's industrialization plan of taking people out of agriculture, without caring about food production. It was a case of failure of socialism, not a intentional genocide.

But by all means, look at the number of people that died due to the occupation. I am feeling generous right now and therefore assume that you are capable of looking something like that up on your own.

Occupation? The Spanish didn't station a large army to occupy the Americas. They gradually colonized it with people, that mixed up with the local population, gradually extending their rule over the continent. The mortality rates after the native population adapted to the European diseases weren't higher than before.

Probably the bloodiest battle in the conquest of the Pre Columbian America civilizations was the battle of Cajamarca, were "in the space of just a few hours, the Spaniards had killed or wounded perhaps six or seven thousands native (some of these of course, had simply been trampled to death), while they themselves hadn't lost a single man" MacQuarrie K., The Last Day of the Incas, pg. 84." That battle resulted in the fall of the Inca empire. Also, those numbers of claimed casualties by the Spanish are probably exaggerated (claimed casualties are always higher than the real number).

[ArmorPierce]

Serafina, the Conquistadores increased the average life expectancy of Latin America by introducing new technologies, like the domesticated animals they brought.

The changes that they made to the continent, except by the bacteria, were positive or neutral, with the exception of the use of native labor force to do the mining work, with reduces the life expectancy since it is a dangerous. But the proportion of the native American population that worked on the mines was very small in proportion to the total population.

I agreed with you that the native death was primarily due to the diseases brought over by the Europeans rather than them slaughtering millions by the sword (written in many history books and it is considered offensive by some that the conquistadors would have been able to kill millions without the massive help of the combination of native recruits and natives themselves) but what you just posted is flat out wrong. The average life expectancy would have immediately plummeted due to all the deaths caused by disease and even after that tapered off I doubt that domesticated animal brought it up. If you actually have any information to show otherwise, please post it. Merely showing that domestication of animals increased life expectancy would be enough.

[Surlethe]

Wait, when did Bakustra make any claims that violated the theory of relativity? I just looked through the exchange -- and, granted, I might have missed something -- but I didn't see anything remotely close to ignoring fundamental physical principles.

[Big Phil]

He didn't... which is why I'm wondering what Patrick is ranting about

[Iosef Cross]

I agreed with you that the native death was primarily due to the diseases brought over by the Europeans rather than them slaughtering millions by the sword (written in many history books and it is considered offensive by some that the conquistadors would have been able to kill millions without the massive help of the combination of native recruits and natives themselves) but what you just posted is flat out wrong. The average life expectancy would have immediately plummeted due to all the deaths caused by disease and even after that tapered off I doubt that domesticated animal brought it up. If you actually have any information to show otherwise, please post it. Merely showing that domestication of animals increased life expectancy would be enough.

Of course, with the diseases, life expectancy would have decreased. But I said that after the diseases, them life expectancy would have recovered. And perhaps surpassed their Pre Columbian level due to the technologies introduced by the Europeans. However, since many slaves were used in the gold mines, and mortality in this job was high, it could have been still lower.

[GrandMasterTerwynn]

Of course not. We have far more insidious ways of destroying cultures now. Say these natives were sitting atop a proven 100 billion barrel oil field. There would be people hatching plans to get these people "educated" and introduced to the conveniences of the modern world. That way, they'll sell the rights to their land to the oil companies. Even if said natives weren't sitting on anything important, enough contact with our culture will have a profound impact on theirs.

You are watching too much Avatar.

1- If they found natives sitting over 100 billion barrels of oil, the natives will get a lot of money.

2- And what is bad about cultural influences?

I'm sure the assorted indigenous peoples on the recieving end of European imperialism and the White Man's Burden will be more than happy to tell you what happens when a far more advanced culture comes into contact with a less-advanced one. There used to be a dizzying variety of cultures, languages, and historical traditions in the Americas. Now . . . indigenous languages are dying out, indigenous culture has been almost completely obliterated by church and later McCulture, and indigenous people suffer staggering rates of alcoholism and diabetes.

Why wouldn't we be a valid target? After all, if an interstellar civilization is taking the extremely long view; we might be a direct competitor millions of years from now.

Competitors? Much better to integrate our civilization with theirs into a single civilization. The gains from integrating more sentients into their economic system are positive, while the gains of exterminating us are negative (the cost of exterminating, the small as it may be).

Once again, you fail to grasp the orders of magnitude of difference between us and an interstellar civilization. The difference between an interstellar civilization and us is of similar magnitude to the difference between us and elephants or chimpanzees. Are we integrating their civilization with ours? No. We're eating the chimpanzees and shooting the elephants because they object to their land being turned into farmland. Even in a relatively benign example, like our interaction with dolphins . . . we're poisoning their environment and slowly killing them off as a side-effect of our exploitation of the oceans.

Or "uplifting" us, which would have the happy side-effect of doing horrible things to our culture. Unless there were some more powerful interstellar civilizations around to discourage others from doing Bad Things to the cavemen of the universe; there's no real penalty to dicking around with them.

You assume that contact with an alien civilization is bad for your human culture, just a contact with of an tribe with your civilization is bad for the tribe.

It almost universally is. You have a unique culture whose foundations are shaken or destroyed by contact with more "advanced" peoples. Their cultural distinctiveness is subsumed into ours. Even when governments are trying to avoid directly destroying the odd tribe of Stone Age hunter-gatherers living out in the savannah or the depths of the rainforest, their people's exploitation of the surrounding land and the odd accidental encounters are pressuring these cultural relics and driving them towards extinction.

Wow. No-limits fallacy much? For that matter, the astonishing idiocy of your statement only grows with each re-reading. Independent from natural resources? So, where do the hydrocarbons to make plastics and fertilizer come from? The Magical Free-Market Fairy?

You are so proud of your ignorance...

And you are one dumb dipshit.

The economic importance of the natural resources sectors of the economy (mining and agriculture) are growing smaller in each passing day. For an advanced alien civilization, their weight would tend to be zero.

Do you not understand that beings still need raw materials to make things with? To eat? Once again, where do you think the hydrocarbons come from to make polymers and fertilizers? Where do you think the steel comes from to build automobiles? The silicon to make computers? The Magical Free-Market Fairy? You are not going to support trillions of sapients on sunshine and happiness alone. If you can't grasp that, then you're even more retarded than I first thought.

For that matter, one can argue that planets occupied by industrialized cavemen offer huge supplies of conveniently pre-extracted and pre-refined metals, ceramics, and polymers. All you have to do is deal with a few pesky cavemen

An advanced civilization capable of reaching your star would be able to produce several orders of magnitude more value from the cost of the trip to earth than the value of everything that people produced.

To the enormous regret of the Humans who used to live on the scattered Zeta Reticuliian orbital habitats formerly known as Earth . . .

While the gains of integrating your 7 billion sentients into a interestelar economic system are positive.

Seven billion sentients barely more advanced than their chimpanzee cousins. Seven billion sentients with likely incompatible biochemistries (so less to trade) and with none of the industrial base required to produce any goods of value to an interstellar civilization at any rate sufficient to satisfy any theoretical demand.

For that matter, if the advance front of an interstellar civilization's galactic colonization effort was comprised of self-replicating VNs; they may not care that the planet they're converting into solar-powered antimatter or magnetic monopole generators is covered with organic matter that feels strongly that the mass of the planet in question ought to remain in one place.

1- That's a case of an irrational process. To us that would be like an natural process, i.e. like our sol going into a supernova.

What the fuck does this even mean?

2- An advanced alien civilization wouldn't be interested in destroying accidentally other civilizations.

Says who? You're counting on the fact that a human life will be more meaningful to an interstellar alien than the lives of chimpanzees, elephants, cetaceans and corvids are to us.

We have nothing of value to offer an interstellar civilization. Except maybe a few artistic curios. To a super-intelligent AGI capable of performing fine-grained ancestor simulations, or some other non-trivial computing task, we're little better than chimpanzees. If it wanted to amuse itself, or preserve humans for posterity while it converted Earth's mass into orbital habitats for the Empire of Zeta Reticuli; it could simply upload a selection of humans and simulate the development of human civilization on a virtual digitized Earth.

If they are beyond your level of sentience, why they would need natural resources from earth? Why they would even care about rocks if they don't care about a network of 7 billion human brains?

Because the 5.97x1024 kilograms of Earth's mass would build a lot of Dyson swarm-type stellar energy collectors, solar-powered antimatter farms, and habitable space for Zeta Reticuliians as expressed by O'Neill cylinders. Assuming our own civilization lives long enough, we'll probably end up doing the same thing to Earth ourselves.

What is the intrinsic value of some seven billion sapient beings barely sophisticated enough to work out that they're committing ecological suicide, even as they step up the pace of said suicide in pursuit of dangerously outmoded instinctive drives? What is the value of said sapients to a civilization with a population potentially numbering in the trillions or even quadrillions of sapients? Especially if said sapients could have millions or billions of variants created through natural selection, or outright bio and/or software engineering?

It is positive, although small. Just like the contributions of Chile to the global economy are small, although positive. Just as your individual contribution to the world is small and positive.

You completely fail to grasp the difference in orders of magnitude between seven billion humans and, say, a quadrillion Zeta Reticuliians. That's 7x109 humans versus 1x1015 Zeta Reticuliians. That's six orders of magnitude. The population of Chile is about 17 million, or 1.7x107 humans. That's two orders of magnitude.

Why don't other people kill you? If all world governments decide that you should die, you cannot do anything about it, you will die. But they don't do that, because you aren't a threat to other people.

Again, you are one dumb fuck. Or have you forgotten the various massacres perpetuated in the 20th century alone against people whose only crime was to be in the wrong place at the wrong time, speak the wrong language, and have the wrong skin color or political affiliation?

[ArmorPierce]

Agreed. Barring disease, domesticated animals by themselves being brought probably would have brought up life expectancy.

That would not be the only the only changes that they would be facing however. Encroachment and elimination of hunter/gatherer life styles and replaced with agricultural life styles actually leads to a lower health overall for a population. Agricultural societies are developed usually based on a need rather than it being superior(health-wise).

Need proof? Look at the average height of a skeleton of someone from agricultural times and then look at an earlier skeleton from the same region that is from hunter gatherer times. Which one is taller?

Wide scale farming is necessary to support a larger population. In Mezzo America, many tribes were already very agriculturally-based but else-where not so much (more hunter-gatherer life-styles further north where native populations were much less dense). Also, as you said, you have to factor in the slavery and forced labor.

[Iosef Cross]

Yes, ArmorPierce, that's true. It is very interesting that agriculture reduced average life expectancy. But as you said, you can sustain a much larger population with agriculture.

[Tritonic]

Anthropomorphizing aliens is a mistake to avoid, and that includes what timescales they may consider in their decision making. To a human, our civilization is no possible near-term threat to any extraterrestrial species, because near-term to us corresponds to our present lifetimes of a few decades. However, to entities with survival instincts and technology sufficiently advanced to live for eons, we could potentially well within their lifetimes lead to such as a unfriendly AGI replicator swarm.

Nobody should say interstellar conflict is absolutely impossible. Given enough capabilities resulting from self-replication taken to the extreme, even whole star systems can be moved over the eons, and there's also a non-trivial chance of destructive capabilities rising enormously with arbitrarily advanced technology (interstellar mini black hole missiles perhaps?).

Logically, we are a potential threat, and, if they value survival enough to not take even a 1% risk per thousand years unnecessarily, we will likely be of great interest to them as a threat to be neutralized. If FTL is impossible, they may need to send intervention as soon as they detect us, to minimize how many years (or centuries, or millennia) pass during the transit time, when our capabilities grow exponentially.

The form of neutralization is up to them. It may or may not even be violent at all, depending on whether they have human-like ethics concerns towards other species or not. Peaceful benevolent cooperation (or domination) may be just as much a solution as slagging earth. If they could reach us near our present limited level of technology, I'd wager a postbiological civilization with intelligence and capabilities approaching the limits of physics wouldn't need to send an armada, maybe just an initially tiny nanorobot probe which replicated and built what it needed at its destination star system.

[Samuel]

I'm sure the assorted indigenous peoples on the recieving end of European imperialism and the White Man's Burden will be more than happy to tell you what happens when a far more advanced culture comes into contact with a less-advanced one. There used to be a dizzying variety of cultures, languages, and historical traditions in the Americas. Now . . . indigenous languages are dying out, indigenous culture has been almost completely obliterated by church and later McCulture, and indigenous people suffer staggering rates of alcoholism and diabetes.

Do you have a representative example that doesn't involve intential genocide or disease culling the natives? Of the top of my head Europe is benefited from being exposed to more advanced cultures (when they weren't trying to conquer them), China managed to spread its cultures to the "barbarians" without murdering them all, etc.

It almost universally is. You have a unique culture whose foundations are shaken or destroyed by contact with more "advanced" peoples. Their cultural distinctiveness is subsumed into ours. Even when governments are trying to avoid directly destroying the odd tribe of Stone Age hunter-gatherers living out in the savannah or the depths of the rainforest, their people's exploitation of the surrounding land and the odd accidental encounters are pressuring these cultural relics and driving them towards extinction.

So what? As long as the individuals who made up the culture are better off afterwards, it really doesn't matter if the old culture dies out.

Do you not understand that beings still need raw materials to make things with? To eat? Once again, where do you think the hydrocarbons come from to make polymers and fertilizers? Where do you think the steel comes from to build automobiles? The silicon to make computers? The Magical Free-Market Fairy? You are not going to support trillions of sapients on sunshine and happiness alone. If you can't grasp that, then you're even more retarded than I first thought.

Presumably he is refering to the idea that when you have enough energy material costs become trivial because you can simply make what you want from the constituent elements. Hydrocarbons may be rare, but hydrogen, oxygena and carbon aren't.

Seven billion sentients barely more advanced than their chimpanzee cousins. Seven billion sentients with likely incompatible biochemistries (so less to trade) and with none of the industrial base required to produce any goods of value to an interstellar civilization at any rate sufficient to satisfy any theoretical demand.

Damn, I don't remember the name of the story. Anyway, an alien group called the Festival comes to a world and rains down phones and in return for a story grants a wish to the teller.

Yes, if you are that rich, you can give out copurnica machines for free in return for anything you want. Aliens will not come for material goods- Earth has no elements that aren't freely available in the rest of the universe. They will come for ideas, stories and art because they can.

At least that is one possibility.

Because the 5.97x1024 kilograms of Earth's mass would build a lot of Dyson swarm-type stellar energy collectors, solar-powered antimatter farms, and habitable space for Zeta Reticuliians as expressed by O'Neill cylinders. Assuming our own civilization lives long enough, we'll probably end up doing the same thing to Earth ourselves.

Yeah, but the opportunity costs for cannibalizing Mars is lower. If they went to ate Earth, you'd have to have a race that was extremely callous towards all other life... of course, that would be the kind of lifeform that would destroy its own homeworld for raw materials.

Iosef seems to think that aliens will act extremely rich people (after all, they should have that much stuff) and care alot about culture to compete with status with their friends and take care of the environment because it looks nice and to upscale its neighbors. I don't know if this would hold true, but you have to admit it is hilariously disturbing. I hope we don't get fined for screwing up the park.

[Patrick Degan]

He is the one claiming that my proposition violates the theory of relativity. He has not actually shown that it does so, and this is not a negative claim. We do not automatically assume that something violates a physical law until proven otherwise, do we not? A proposal cannot be said to violate reality until it is shown that it does so. I would not have to prove that a solar panel is not a perpetual motion machine of the second order, the person claiming it is would have to do so. While in this case there is a burden of proof on me to show that my proposal is feasible, there is also a burden of proof upon Mr. Degan to show that it violates the theory of relativity and principle of inertia, as he is claiming.

And that, child, is yet another strawman of my arguments, and an evasion. You claimed the existence of principles which, as you said, "while they violate your pathetic understanding of inertia and relativity, do not violate the actual principles". You have not done so. In fact, you REFUSE to do so and bluster your way around the challenge. I will put this to you on rather basic terms: demonstrate the backup for your claims or just kindly concede them.

Burden of proof, child, is your own. Get cracking. I grow tired of your bullshit.

I'll do it when you present the evidence for your claim that my proposal violates the theory of relativity and the principle of inertia, as you have claimed oh-so-many times:

No no, child, you first: do demonstrate your superior grasp of physics and outline for the class those "principles" which will allow anybody to one day circumvent relativity limitations and the laws of inertia. I'm waiting for this one. Another claim you put forth, and now your burden of proof on that one as well. YOU put up or shut up. And I do hope you're going to be a bit more original than invoking Alcubierre.

and

Then I presume you can demonstrate for us technological principles which allow anybody to circumvent the laws of relativity and inertia to support your argument.

So you will first have to prove that my proposal violates the laws of relativity and inertia, I am afraid.

You yourself opened the door to the charge when you said this:

There are principles that, while they violate your pathetic understanding of inertia and relativity, do not violate the actual principles.

—and then refused to explain yourself any further than that.

But if you insist, my evidence is simple:

Simple-minded, you mean. But do go on...

There is no provision of relativity that says "reserve fuel is an impossibility; one shall only carry enough fuel to get there and back, without a margin of error." Perhaps you have confused Tom Godwin's The Cold Equations with the Theory of Relativity?

Furthermore, there is no provision of inertia that says this either. Inertia does say that at relativistic velocities, changes in direction (or angular momentum) are far more difficult, because the mass of the object is greater. However: difficult is not a synonym of impossible, and neither relativity nor inertia says that starships must travel at more than nine-tenths of the speed of light, which is where relativistic inertia becomes a major problem.

Frankly, when I stated that your understanding of inertia and relativity was pathetic, I was being too kind. I now see that apparently you have confused relativity with a short story and inertia with... something. I can't really figure out what the hell you've confused inertia with, but all I know is that in the Encyclopedia Degannica, "difficult" means "impossible".

Sigh...

Shall we wind back to where you departed the rails, child?

I said:

The fuel they can't spare to simply decelerate and check out any old star system they happening to be wandering past. Interstellar travel isn't going to be like going down Route 66, child, where you can pull off the next exit to gawpe at the Wigwam Motel. Nevermind that it would take them a very long time to reverse course from a relativistic frame to begin with or even to alter course by a degree or two. Given the light-year radius before any artificial signal would fade into static, they'd already would have to be practically entering the star system to even pick it up in the first place. If they're on their way somewhere else, the chances of them hearing anything are about zero.

Only in Bakustra-world did that conceivably translate into: "no provision of relativity that says "reserve fuel is an impossibility; one shall only carry enough fuel to get there and back, without a margin of error. Furthermore, there is no provision of inertia that says this either. Inertia does say that at relativistic velocities, changes in direction (or angular momentum) are far more difficult, because the mass of the object is greater. However: difficult is not a synonym of impossible, and neither relativity nor inertia says that starships must travel at more than nine-tenths of the speed of light, which is where relativistic inertia becomes a major problem." I especially said nothing about inertia like you're yammering on about here.

To illustrate the problem: A ship is coasting at .11c when it comes within detection range of a planet in another star system. The ship's crew (or onboard computer) had not originally decided to alter course to its target star system and thus the vessel continues along on a flyby. It passes close, comes within a light year of the primary, when the sensors pick up a very faint radio pulse, at a trillionth of a trillionth of a trillionth of a watt (let's say for purposes of argument it's artificial and came from one of the inner planets). At the velocity the ship is coasting at, it will already have passed through and be on its way back outward along its original course in an hour. Which means that reversing course involves: one month decelerating down to a reasonable velocity at 1g continual breaking thrust, by which point the operation begins the ship is a further 9.3 billion kilometres distant from the point the sensors went "blip" and now will have to claw its way back that distance plus the additional distance covered during deceleration —which means it will have burned up a considerable percentage of its onboard storage in this operation and is in open space— and is facing an inward journey of a light-year to reach the inner core of the star system with a now much-reduced fuel reserve. We'll grant the ship has the capacity to refuel itself by tapping the atmosphere of a gas giant for the hydrogen it needs. The problem is that such operations are predicated upon a mission plan to visit a given star system, not to suddenly divert to a system which wasn't part of that mission plan and after the ship has already passed through the outer periphery of that system's sector in the galaxy. Burning up your onboard fuel reserve is fine if you're already headed in to your destination (the object of the mission plan) or have made the decision in advance (by at least a month or longer) to alter course to another star system in the same general direction but a degree or two off-vector. Making an extreme course change in open space, however, is going to take months and burn a lot of fuel, which reduces the ship's margin of error for decelerating to a relative stop within the system it's now headed for. There is no getting around that physical fact. Thus the reasoning behind:

And as for a hypothetical species altering course to check out some odd radio signals, barring the fact that the inverse square law pretty much guarantees that anything we've transmitted since the invention of wireless would fade into the cosmic background noise past a light year or so, no migration fleet is going to risk burning up fuel it can't spare to alter their course simply on a whim: they're going to need every ton they've got in reserve to decelerate at their target system.

So explain to the class, child, where your stupid strawman version of my arguments in any way addresses the basic problems of inertial change and deceleration time from a relativistic velocity and allows a completely unplanned course-change for our hypothetical alien migration fleet simply on a whim. Do you think you can actually manage that?

[Ziggy Stardust]

If someone says the bombardier beetle violates evolution, it's up to them to prove it. Do YOU not understand the concept of the burden of proof?

Nice red herring. Did you even read the whole thread?

[Bakustra]

Only in Bakustra-world did that conceivably translate into: "no provision of relativity that says "reserve fuel is an impossibility; one shall only carry enough fuel to get there and back, without a margin of error. Furthermore, there is no provision of inertia that says this either. Inertia does say that at relativistic velocities, changes in direction (or angular momentum) are far more difficult, because the mass of the object is greater. However: difficult is not a synonym of impossible, and neither relativity nor inertia says that starships must travel at more than nine-tenths of the speed of light, which is where relativistic inertia becomes a major problem." I especially said nothing about inertia like you're yammering on about here.

To illustrate the problem: A ship is coasting at .11c when it comes within detection range of a planet in another star system. The ship's crew (or onboard computer) had not originally decided to alter course to its target star system and thus the vessel continues along on a flyby. It passes close, comes within a light year of the primary, when the sensors pick up a very faint radio pulse, at a trillionth of a trillionth of a trillionth of a watt (let's say for purposes of argument it's artificial and came from one of the inner planets). At the velocity the ship is coasting at, it will already have passed through and be on its way back outward along its original course in an hour. Which means that reversing course involves: one month decelerating down to a reasonable velocity at 1g continual breaking thrust, by which point the operation begins the ship is a further 9.3 billion kilometres distant from the point the sensors went "blip" and now will have to claw its way back that distance plus the additional distance covered during deceleration —which means it will have burned up a considerable percentage of its onboard storage in this operation and is in open space— and is facing an inward journey of a light-year to reach the inner core of the star system with a now much-reduced fuel reserve. We'll grant the ship has the capacity to refuel itself by tapping the atmosphere of a gas giant for the hydrogen it needs. The problem is that such operations are predicated upon a mission plan to visit a given star system, not to suddenly divert to a system which wasn't part of that mission plan and after the ship has already passed through the outer periphery of that system's sector in the galaxy. Burning up your onboard fuel reserve is fine if you're already headed in to your destination (the object of the mission plan) or have made the decision in advance (by at least a month or longer) to alter course to another star system in the same general direction but a degree or two off-vector. Making an extreme course change in open space, however, is going to take months and burn a lot of fuel, which reduces the ship's margin of error for decelerating to a relative stop within the system it's now headed for. There is no getting around that physical fact. Thus the reasoning behind:

Well, Mr. Degan, I can see that you have quietly abandoned your assertion that my proposals violate the Theory of Relativity. Well, that wasn't defensible in any way, so I will grant you that freely. However, I see that integrity is not on the menu at the Degan Diner today.

I see that you have been gracious enough to include one or two numbers in your qualitative analysis. While I will continue to ask that you provide actual evidence, I grow weary of the continuous back-and-forth, so I will take your example, assign actual numbers, and then point out how little is necessary to make this far more possible as a chain of events. I will show my entire methodology, so this will be a long post, but this will ensure that the people following along will be able to follow my reasoning, and these equations can also be used for aspiring sci-fi writers or plain ol' sci-fi fans.

Let us begin with the distance. You have assigned a distance of one light-year for the Earth's radio transmissions to be heard. I decided to start with your number of "a trillionth of a trillionth of a trillionth of a watt" for the received radio transmission. One light-year is 9.4608e15 meters. By the inverse square law, we can square this value, multiply it by the power intensity at this range (1e-36 W/m^2), and therefore obtain the initial power at the source.

(9.4608e15 m)^2 * (1e-36 W/m^2) = 8.951e-5 W, or 89.51 microwatts.

Yes, that is less than one-thousandth of a watt initially. Let us see how far a one watt source would go to be intelligible:

sqrt((1 W)/(1e-36 W/m^2)) = (1e18 m)/(9.4608e15 m/ly) = 105.7 ly.

One hundred and five point seven light years, for a one-watt source. Mr. Degan, your numbers stink. Might I suggest not mixing hyperbole with semi-quantitative analysis next time?

Let's find our own value for the minimum intensity, since the one Mr. Degan provided was worse than useless. I will take an initial source of 2 MW (this is a conservative assumption, as this is in the upper range of radio transmitters here on Earth, giving us a larger minimum intensity and therefore smaller total distances) and use the common figure of 1 ly as the point where the fade-out becomes too great to be discernible. So then:

(2e6 W)/(9.4608e15 m)^2 = 2.235e-26 W/m^2

Let us call this the threshold intensity.

Now let us presume that we ignore Hawking's suggestion of not trying to draw attention to ourselves, and then build transmitters just for the purpose of attracting aliens. I will use a total figure of 1 GW for all the combined transmitters (or 500 radio towers like above) doing this, and then use the inverse square law:

sqrt(1e9 W)/(2.235e-26 W/m^2) = 2.115e17 m

(2.115e17 m)/(9.4608e15 m/ly) = 22.36 ly.

Yes, that means that a 1 GW source would be discernible 22.36 light-years away. There are over 130 stars within 20 light-years of us, including Sirius, Procyon, Altair, Delta Pavonis, Tau Ceti, Epsilon Eridani, all of which should be familiar to the well-versed in science fiction or astronomy. Now, let us presume that this starship moving at 0.11c picks up the signal at the threshold intensity again. Now, they have 200.86 years, subjectively (at 0.11c, the relativity factor is 1.0122, and so the 203.27 objective years they have contracts to 200.86) to decide what to do. They have time to decide, and time to plan a course change and execute it. However, the greatest benefit the 21.36 extra light-years gives them is how it affects their ability to make course changes.

Let us presume, for simplicity's sake, that the starship would pass by the exact edge of the solar system, tangentially in other words. This is literally the middle-of-the-road, and simplifies calculations besides. Now, in the initial scenario, I will presume that they have the ability to enter the solar system and reach rest with earth, and that to do so, they would need to alter course by pi/4 radians (45 degrees). This has the advantage of also being the most middle-of-the-road possible, and gives us a total fuel capacity of twice the delta-v necessary to decelerate to a rest with their target. This is not actually necessary for my calculations, and indeed we could adopt any value of theta we want, but I want a baseline to show how much fuel the aliens would have left after reaching Sol.

So, then, we extend the hypotenuse of our right triangle by 22.38 times, while keeping the opposite the same. I will express the following algebraically, but you can use any values for x and y, since we are looking for the angles here, and it is the proportions that are necessary.

x^2 + y^2 = z^2
(22.36z)^2 - y^2 = (34.91x)^2
cos(θ) = (34.91x)/(22.36z) = 0.99953
θ = arccos(0.99953) = 0.0307 radians (= 1.76 degrees)

So we have an angle between the destination vector and the Sol vector of 0.0307 radians at 22.36 light-years of distance. Now, when I said that the spaceship would need enough delta-v to fully decelerate as it would to make a pi/4 rad (45-degree) turn, we may treat course changes as though they were on the unit circle, and the velocity were 1. I I will presume that the starship captain will perform his course changes so as to have the same final speed. So we can represent the fraction of velocity necessary by this equation:

1v - vcosθ + vsinθ = Δv
Δv/v = x
x*100 = % of v

At pi/4, this yields a value of 1, or 100% of v. Let us see what Δv would be needed at 22.36 light-years distance:

1 - cos(0.0307) + sin(0.0307) = 0.0312

This is equal to 3.12% of the total velocity, and seeing as we have 0.22c of Δv in fuel, that means that our alien starship will have 0.1066c of Δv available on arrival at Earth, plenty to to refuel and take in the sights of the solar system. (If you want to use a different value for Δv in fuel, then this is a generally applicable equation.)

At 1 g of deceleration, the starship would then take 4375270.14 seconds, or 50.64 days to complete its course change, and 3363914.4 seconds, or 38.93 days, to fully decelerate. This leads to a total of 89.57 days spent in deceleration, or 0.12% of their total trip time.

So then, Mr. Degan?

[Guardsman Bass]

Why wouldn't we be a valid target? After all, if an interstellar civilization is taking the extremely long view; we might be a direct competitor millions of years from now. We're also apt to kill ourselves before we achieve interstellar civilization status, so an alien species may figure it's doing us a favor by dropping a rock on us now. Or "uplifting" us, which would have the happy side-effect of doing horrible things to our culture. Unless there were some more powerful interstellar civilizations around to discourage others from doing Bad Things to the cavemen of the universe; there's no real penalty to dicking around with them.

The "Killing Star" hypothesis? The problem with that is that you never know who might be watching (a third, more powerful civilization might catch a glimpse of the second civilization wiping out competitors and think, "These guys might be a problem in the future", and hopefully the second civilization realizes that possibility), and there's always the risk that you'll misguage how wide-spread another civilization is. Better to avoid them whenever possible, and just generally keep to yourself as a civilization.

What is the intrinsic value of some seven billion sapient beings barely sophisticated enough to work out that they're committing ecological suicide, even as they step up the pace of said suicide in pursuit of dangerously outmoded instinctive drives? What is the value of said sapients to a civilization with a population potentially numbering in the trillions or even quadrillions of sapients? Especially if said sapients could have millions or billions of variants created through natural selection, or outright bio and/or software engineering?

You know, this raises a question I've had ever since I've read of Von Neumans and fully uploaded civilizations - why would they necessarily be gung-ho expanders? It's not like with biological beings such as humans, where you have a built-in drive pushing us to fuck and reproduce, and after a certain amount of expansion a civilization is essentially immortal against anything except the Heat Death of the universe and possibly other civilizations.

Massive expansion has its own issues, too - assuming there aren't any "cheats" around the light-speed limit in terms of communication or propulsion, the civilization is likely going to fragment into a bunch of mini-civilizations just due to distance alone (unless they set themselves up as a gigantic network and are willing to tolerate some insane processing time).

[Oni Koneko Damien]

The "Killing Star" hypothesis? The problem with that is that you never know who might be watching (a third, more powerful civilization might catch a glimpse of the second civilization wiping out competitors and think, "These guys might be a problem in the future", and hopefully the second civilization realizes that possibility), and there's always the risk that you'll misguage how wide-spread another civilization is. Better to avoid them whenever possible, and just generally keep to yourself as a civilization.

So? To follow that logic to its conclusion, no civilization would ever expand on an interstellar scale, as there's always the possibility that the next star over might be under the watch of another, much more powerful civilization, and it's better not to risk pissing them off. There's reasonable risk analysis and there's outright paranoia. If a civilization has been exploring the galaxies for centuries, possibly millennia, and never has encountered a single shred of evidence of anything more powerful than them, but maybe a small handful of other civilizations less powerful, would it be reasonable for them to assume that humanity is under the protection of some much more powerful race that, at the same time, has left no evidence of its presence or intentions? This was already covered earlier in the thread, this is far from the only reason why what you assert wouldn't be an issue to a hypothetical interstellar civilization.

You know, this raises a question I've had ever since I've read of Von Neumans and fully uploaded civilizations - why would they necessarily be gung-ho expanders? It's not like with biological beings such as humans, where you have a built-in drive pushing us to fuck and reproduce, and after a certain amount of expansion a civilization is essentially immortal against anything except the Heat Death of the universe and possibly other civilizations.

There's very little you can claim to be necessary or required for an alien race, or civilization. But a few things will be represented in every civilization, regardless of species or origin, simply because by the very definition of 'civilization', they have to present. One of the defining factors of civilization is the urge to increase the population and expand ever outward in some fashion, either with territory, resources, etc. This urge has to be powerful enough on a species-wide scale that individuals of that species are willing to give up certain liberties for the greater good, be it giving up a nomadic lifestyle and being tied down with agriculture, following religious dictates one doesn't necessarily agree with, following laws imposed by others, or paying taxes one doesn't necessarily agree with. Thus if there are aliens, and they are in a 'civilization', by necessity they got to that point by expansion, are either still attempting to expand, or are in a decline.

Massive expansion has its own issues, too - assuming there aren't any "cheats" around the light-speed limit in terms of communication or propulsion, the civilization is likely going to fragment into a bunch of mini-civilizations just due to distance alone (unless they set themselves up as a gigantic network and are willing to tolerate some insane processing time).

Highly likely given those conditions, but if we're on the hostile end of a something that is several magnitudes more powerful than we are, it probably isn't going to be much comfort or use to us to find out that it's just one disparate faction of a formerly unified whole, the closest other faction of which is several hundred light-years away.

[GrandMasterTerwynn]

Why wouldn't we be a valid target? After all, if an interstellar civilization is taking the extremely long view; we might be a direct competitor millions of years from now. We're also apt to kill ourselves before we achieve interstellar civilization status, so an alien species may figure it's doing us a favor by dropping a rock on us now. Or "uplifting" us, which would have the happy side-effect of doing horrible things to our culture. Unless there were some more powerful interstellar civilizations around to discourage others from doing Bad Things to the cavemen of the universe; there's no real penalty to dicking around with them.

The "Killing Star" hypothesis? The problem with that is that you never know who might be watching (a third, more powerful civilization might catch a glimpse of the second civilization wiping out competitors and think, "These guys might be a problem in the future", and hopefully the second civilization realizes that possibility), and there's always the risk that you'll misguage how wide-spread another civilization is. Better to avoid them whenever possible, and just generally keep to yourself as a civilization.

Yes. The first rule of interstellar diplomacy. Always assume there's somebody out there more powerful than you are. Though you can quickly determine how widespread a civilization is. A civilization like ours has zero detectable presence in the solar system at large, outside of Earth. A self-sustaining planetary civilization will have more detectable presence (thrusting ships, some number of orbital constructs, etc.) A near-interstellar/interstellar civilization will have huge numbers of orbital constructs. Meaning the quantity of far-infrared light being radiated from the region around a given star increases more and more with time. Interstellar civilizations will also tend to expand outward from their home stars. At first, they'll likely skip and jump to choice properties . . . i.e. stars with planetary bodies at the right orbital distances; and then they'll backfill as the time cost of getting to the next choice property becomes too high to be immediately desirable.

Though the first argument against the first rule is that there's no feasible way to administer an interstellar empire in Einstein's universe. The communications and travel delay imposed by the speed of light tends to ensure that that the most unified an interstellar state can be is a very loosely unified confederation of independent one-star states. Each daughter colony owes precisely jack to its mother system, since the time spent in transit dictates that any interstellar colony be entirely self-sufficient the moment it arrives and sets up shop.

What is the intrinsic value of some seven billion sapient beings barely sophisticated enough to work out that they're committing ecological suicide, even as they step up the pace of said suicide in pursuit of dangerously outmoded instinctive drives? What is the value of said sapients to a civilization with a population potentially numbering in the trillions or even quadrillions of sapients? Especially if said sapients could have millions or billions of variants created through natural selection, or outright bio and/or software engineering?

You know, this raises a question I've had ever since I've read of Von Neumans and fully uploaded civilizations - why would they necessarily be gung-ho expanders? It's not like with biological beings such as humans, where you have a built-in drive pushing us to fuck and reproduce, and after a certain amount of expansion a civilization is essentially immortal against anything except the Heat Death of the universe and possibly other civilizations.

The drive that would push a fully-uploaded civilization towards further expansion is other civilizations and further insurance against entropy. Turtles are effectively immortal, after all, but they still have reproductive drives; since turtles perish from accidents, sickness, and being eaten. An effectively immortal uploaded being could have its personality destroyed by the crash of a server farm, or the post-Singularity version of a computer virus or a jealous lover, etc, etc, etc.

Massive expansion has its own issues, too - assuming there aren't any "cheats" around the light-speed limit in terms of communication or propulsion, the civilization is likely going to fragment into a bunch of mini-civilizations just due to distance alone (unless they set themselves up as a gigantic network and are willing to tolerate some insane processing time).

I once postulated such a civilization. A sort of Matryoshka doll of post-Singularity AGIs; with person-scale intelligences, networked into planet-scale intelligences, networked into starsystem-scale intelligences, all of which tied into a massive and ponderously-slow interstellar-scale intelligence. The chief problem this civilization would encounter is that a single member starsystem going rogue would likely bring the whole thing crashing down. Even though the multi-stellar intelligence is significantly more powerful than a single star intelligence, the one star is much faster.

[Guardsman Bass]

The "Killing Star" hypothesis? The problem with that is that you never know who might be watching (a third, more powerful civilization might catch a glimpse of the second civilization wiping out competitors and think, "These guys might be a problem in the future", and hopefully the second civilization realizes that possibility), and there's always the risk that you'll misguage how wide-spread another civilization is. Better to avoid them whenever possible, and just generally keep to yourself as a civilization.

So? To follow that logic to its conclusion, no civilization would ever expand on an interstellar scale, as there's always the possibility that the next star over might be under the watch of another, much more powerful civilization, and it's better not to risk pissing them off. There's reasonable risk analysis and there's outright paranoia. If a civilization has been exploring the galaxies for centuries, possibly millennia, and never has encountered a single shred of evidence of anything more powerful than them, but maybe a small handful of other civilizations less powerful, would it be reasonable for them to assume that humanity is under the protection of some much more powerful race that, at the same time, has left no evidence of its presence or intentions? This was already covered earlier in the thread, this is far from the only reason why what you assert wouldn't be an issue to a hypothetical interstellar civilization.

Not exactly. Terwynn points out a couple of ways you could pick up activity around a star. Moreover, accidentally wandering into another civilization's turf is not the same as actively trying to wipe them out "Killing Star" style.

As for "exploring the galaxies for millenia and never come across anything more powerful", then yes, maybe they could make the conclusion that they could stomp on weaker civilizations with no ramifications. Of course, it's a big universe, and that type of behavior might be trouble if they end up running into something like themselves.

There's very little you can claim to be necessary or required for an alien race, or civilization. But a few things will be represented in every civilization, regardless of species or origin, simply because by the very definition of 'civilization', they have to present. One of the defining factors of civilization is the urge to increase the population and expand ever outward in some fashion, either with territory, resources, etc. This urge has to be powerful enough on a species-wide scale that individuals of that species are willing to give up certain liberties for the greater good, be it giving up a nomadic lifestyle and being tied down with agriculture, following religious dictates one doesn't necessarily agree with, following laws imposed by others, or paying taxes one doesn't necessarily agree with. Thus if there are aliens, and they are in a 'civilization', by necessity they got to that point by expansion, are either still attempting to expand, or are in a decline.

Yes, but once they reach a certain point, technology to modify themselves and their biological nature is a major possibility and option for them. This is particularly a possibility if they upload themselves into machine form - they could, for example, edit out the unthinking biological drive towards sex and reproduction, so that duplication and reproduction was just another choice to achieve whatever objectives they have. And if your key objective is long-term species survival, you don't need to be gung-ho expansionistic - in fact, if that causes your civilization to fragment into competing factions that try to destroy one another, it could actually be a disadvantage (and that's a major potential problem in a universe where you're limited by light speed).

Massive expansion has its own issues, too - assuming there aren't any "cheats" around the light-speed limit in terms of communication or propulsion, the civilization is likely going to fragment into a bunch of mini-civilizations just due to distance alone (unless they set themselves up as a gigantic network and are willing to tolerate some insane processing time).

Highly likely given those conditions, but if we're on the hostile end of a something that is several magnitudes more powerful than we are, it probably isn't going to be much comfort or use to us to find out that it's just one disparate faction of a formerly unified whole, the closest other faction of which is several hundred light-years away.

That's true, but I was pointing out that it might be seen as a major negative by other civilizations. Particularly if your civilization places immense importance on relatively rapid, continuous communication between its members.

The drive that would push a fully-uploaded civilization towards further expansion is other civilizations and further insurance against entropy. Turtles are effectively immortal, after all, but they still have reproductive drives; since turtles perish from accidents, sickness, and being eaten. An effectively immortal uploaded being could have its personality destroyed by the crash of a server farm, or the post-Singularity version of a computer virus or a jealous lover, etc, etc, etc.

Yes, but entropy doesn't necessarily mean continuous, rapid expansion. Your hypothetical civilization could plunk itself down around a couple of stars with good resources spread out far enough that no single cosmic catastrophe could kill them (and even a hostile civilization would be hard-pressed to find and kill them all), and sit there for potentially billions of years at a time if they keep their overall population large but steady. There's plenty of room for back-ups with that.

I once postulated such a civilization. A sort of Matryoshka doll of post-Singularity AGIs; with person-scale intelligences, networked into planet-scale intelligences, networked into starsystem-scale intelligences, all of which tied into a massive and ponderously-slow interstellar-scale intelligence. The chief problem this civilization would encounter is that a single member starsystem going rogue would likely bring the whole thing crashing down. Even though the multi-stellar intelligence is significantly more powerful than a single star intelligence, the one star is much faster.

I could definitely see that fragmenting down to the star-system level over time. The relative communication lag would just be so immense - decades, centuries, thousands of years versus a couple of hours - that you would need some really compelling reason to keep it going.

[Patrick Degan]

Time permits me to address only two points in this exchange:

Well, Mr. Degan, I can see that you have quietly abandoned your assertion that my proposals violate the Theory of Relativity. Well, that wasn't defensible in any way, so I will grant you that freely. However, I see that integrity is not on the menu at the Degan Diner today.

Oh, I'll quite readily withdraw that challenge, since it's apparent that you weren't proposing a physics-breaking "principle" so much as setting up yet another of your stupid strawmen to knock down. Which rather disqualifies you to comment on the subject of integrity, child.

I see that you have been gracious enough to include one or two numbers in your qualitative analysis. While I will continue to ask that you provide actual evidence, I grow weary of the continuous back-and-forth, so I will take your example, assign actual numbers, and then point out how little is necessary to make this far more possible as a chain of events. I will show my entire methodology, so this will be a long post, but this will ensure that the people following along will be able to follow my reasoning, and these equations can also be used for aspiring sci-fi writers or plain ol' sci-fi fans.

Let us begin with the distance. You have assigned a distance of one light-year for the Earth's radio transmissions to be heard. I decided to start with your number of "a trillionth of a trillionth of a trillionth of a watt" for the received radio transmission. One light-year is 9.4608e15 meters. By the inverse square law, we can square this value, multiply it by the power intensity at this range (1e-36 W/m^2), and therefore obtain the initial power at the source.

(9.4608e15 m)^2 * (1e-36 W/m^2) = 8.951e-5 W, or 89.51 microwatts.

Yes, that is less than one-thousandth of a watt initially. Let us see how far a one watt source would go to be intelligible:

sqrt((1 W)/(1e-36 W/m^2)) = (1e18 m)/(9.4608e15 m/ly) = 105.7 ly.

One hundred and five point seven light years, for a one-watt source. Mr. Degan, your numbers stink. Might I suggest not mixing hyperbole with semi-quantitative analysis next time?

Obviously, child, you forgot about this little thing called the "area of a sphere". For omindirectional radio waves, such as the type we've been transmitting for more than a century now, the signal strength at distance is calculated by:

F=Pw/4πr^2

That gives, for a one megawatt signal:

1e6W/4π(9.4608E15m)^2

an intensity at one lightyear distance of 8.84564352E-28W

I suppose that would be a ten-thousandth of a trillionth of a trillionth of a watt. Which is still nonetheless indistinguishable from the cosmic background noise and quite unintelligible at one lightyear.

The remainder of my address to your points to follow. Meanwhile, recheck your sums.

[Surlethe]

What is the power density of the CMBR? My crude, crude approximation (universe is a 46 billion light year-radius cavity surrounded by and in thermal equilibrium with a 2.7 K blackbody) gives about 2E-32 W/m^3.

[Bakustra]

Time permits me to address only two points in this exchange:

Well, Mr. Degan, I can see that you have quietly abandoned your assertion that my proposals violate the Theory of Relativity. Well, that wasn't defensible in any way, so I will grant you that freely. However, I see that integrity is not on the menu at the Degan Diner today.

Oh, I'll quite readily withdraw that challenge, since it's apparent that you weren't proposing a physics-breaking "principle" so much as setting up yet another of your stupid strawmen to knock down. Which rather disqualifies you to comment on the subject of integrity, child.

You mean, except for the part where you decided to ignore Hawking's actual scenario, right? Because you presumed no actual effort to contact aliens, which is what Hawking is warning against. You also provided a mix of qualitative and quantitative analysis that led to deeply amusing conclusions. But now you have been gracious enough to provide corrections where my analysis was flawed.

I see that you have been gracious enough to include one or two numbers in your qualitative analysis. While I will continue to ask that you provide actual evidence, I grow weary of the continuous back-and-forth, so I will take your example, assign actual numbers, and then point out how little is necessary to make this far more possible as a chain of events. I will show my entire methodology, so this will be a long post, but this will ensure that the people following along will be able to follow my reasoning, and these equations can also be used for aspiring sci-fi writers or plain ol' sci-fi fans.

Let us begin with the distance. You have assigned a distance of one light-year for the Earth's radio transmissions to be heard. I decided to start with your number of "a trillionth of a trillionth of a trillionth of a watt" for the received radio transmission. One light-year is 9.4608e15 meters. By the inverse square law, we can square this value, multiply it by the power intensity at this range (1e-36 W/m^2), and therefore obtain the initial power at the source.

(9.4608e15 m)^2 * (1e-36 W/m^2) = 8.951e-5 W, or 89.51 microwatts.

Yes, that is less than one-thousandth of a watt initially. Let us see how far a one watt source would go to be intelligible:

sqrt((1 W)/(1e-36 W/m^2)) = (1e18 m)/(9.4608e15 m/ly) = 105.7 ly.

One hundred and five point seven light years, for a one-watt source. Mr. Degan, your numbers stink. Might I suggest not mixing hyperbole with semi-quantitative analysis next time?

Obviously, child, you forgot about this little thing called the "area of a sphere". For omindirectional radio waves, such as the type we've been transmitting for more than a century now, the signal strength at distance is calculated by:

F=Pw/4πr^2

That gives, for a one megawatt signal:

1e6W/4π(9.4608E15m)^2

an intensity at one lightyear distance of 8.84564352E-28W

I suppose that would be a ten-thousandth of a trillionth of a trillionth of a watt. Which is still nonetheless indistinguishable from the cosmic background noise and quite unintelligible at one lightyear.

The remainder of my address to your points to follow. Meanwhile, recheck your sums.

Well, I must thank you for your correction, but caution you that this does does not improve the situation for you greatly. I must ask that you provide your source for the intensity of the CBMR, then. Using Surlethe's suggests that your "indistinguishable" is actually some forty thousand times greater than the CBMR. Until then, I cannot actually redo my figures.

[Bakustra]

What is the power density of the CMBR? My crude, crude approximation (universe is a 46 billion light year-radius cavity surrounded by and in thermal equilibrium with a 2.7 K blackbody) gives about 2E-32 W/m^3.

I have no idea. This chart I found combined with Planck's law suggests an intensity of 4.57e-36 W/m^3, but that was using the 156 billion ly diameter universe.

[Bakustra]

What is the power density of the CMBR? My crude, crude approximation (universe is a 46 billion light year-radius cavity surrounded by and in thermal equilibrium with a 2.7 K blackbody) gives about 2E-32 W/m^3.

I have no idea. This chart I found combined with Planck's law suggests an intensity of 4.57e-36 W/m^3, but that was using the 156 billion ly diameter universe.

And that is totally wrong, because I somehow read 1.5 mm as 0.15 mm. I really shouldn't try to do physics just after waking up.

[Iosef Cross]

The form of neutralization is up to them. It may or may not even be violent at all, depending on whether they have human-like ethics concerns towards other species or not.

The problem is that civilizations with much violence always fail to become much advanced.

The only question is if they would become violent to other civilizations that they may discover. But to themselves, they wouldn't be violent if they managed to reach us.

Our "human like ethics" evolved from the evolutionary pressures of a society made up by a large number of independent rational decision makers, where each rational decision maker learns to trust the others thought the institutions of society. I would think that any civilization based on multiple minds would tend to develop the same type of humanistic ethics.

The only type of civilization that wouldn't care for others, would be a civilization made up of a single mind (like the borg). However, I do think that such civilizations are improbable.

[Tritonic]

The form of neutralization is up to them. It may or may not even be violent at all, depending on whether they have human-like ethics concerns towards other species or not.

The problem is that civilizations with much violence always fail to become much advanced.

The only question is if they would become violent to other civilizations that they may discover. But to themselves, they wouldn't be violent if they managed to reach us.

Our "human like ethics" evolved from the evolutionary pressures of a society made up by a large number of independent rational decision makers, where each rational decision maker learns to trust the others thought the institutions of society. I would think that any civilization based on multiple minds would tend to develop the same type of humanistic ethics.

The only type of civilization that wouldn't care for others, would be a civilization made up of a single mind (like the borg). However, I do think that such civilizations are improbable.

There's some truth in such. We must not underestimate the variety of ways a civilization could avoid self-destruction, though, and, while some of them involve humanistic ethics, those are still only a subset of the total. Your Borg-like example is one illustration of an exception, although it wouldn't even necessarily have to be a single mind civilization. For instance, perhaps Zekanio'k The Great long ago conquered their whole planet, unified it under one government, and became an immortal emperor through life extension 10000 years ago before their expansion into space, preventing unrestricted internal infighting or self-destruction but not guaranteeing benevolence if his empire encountered a new species. Or maybe one side in a partial equivalent of earth's Cold War won by AGI development but in the rushed process made an unfriendly AGI, leading to a swarm of replicators who survive by hard limits on not harming other replicators but charmingly regard new species and their worlds as raw materials.

With that said, certainly there is a significant chance of us being handled non-violently. Superior technology gives them countless options, including the carrot as much as the stick. If we're lucky, they'd help us.

Just, without more data, the situation is like a 50 / 50 chance in terms of us not knowing whether an encounter would be beneficial or harmful, so, ideally, I'd rather not take the risk, like not going out of our way to send powerful transmissions intentionally towards other star clusters. But, of course, mostly the matter isn't in our hands anyway.

Though unfortunately I forget the name of it, I once saw a proposal for a hypothetical future space telescope array which could image planets from many light-years away, and, in general, the orders-of-magnitude greater capabilities of a sufficiently advanced civilization probably would allow them to detect earth at vast distances (thousands of light-years??), even without any dependence on later detecting radio wave transmissions. The chemical composition of the atmosphere suggests life, which probably isn't too common. This leads to the Fermi Paradox of why hasn't anybody apparently checked us out already, hurt or helped us, or done anything noticeable over prior millions of years as far as our telescopes can see, suggesting possibilities like a rarity of aliens.