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Comment by xenophanes | Hacker News Reader

> He suggests that aliens might simply raid Earth for its resources and then move on

Umm, if they can travel to earth and gather resources (at a cost less than the fuel, time, etc), why wouldn't they just raid an uninhabited planet? there are plenty, and they have resources too. this makes no sense.

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Why would you go through the effort and uncertainty of hunting wildlife when you can just saunter down to the local grocery store and pick up prepared meat?

Why go to the store to buy bottled water when you can get clean fresh water from your tap at home?

We have enough of a challenge explaining human motivations, we can't know any potential alien motives. We don't have any context. So far science has taught us that reality consistently overturns our preconceive notions and it indeed far stranger than what we've anticipated. Just one example: We knew that light was propagated by the luminiferous aether until the Michelson Morley experiment blew that assumption out of the water.

Given the highly logical minds required to develop technology that could let them traverse the stars, assuming them to make a decent cost-benefit analysis is not unreasonable. If they raided Earth for resources, it would either be because we had something rare, or because they're malicious sons of bitches.

You make it sound as if there'd be no reason at all. There's always a reason, and it's generally comprehensible even to us. We can understand the motivations or behaviors of non-human life just fine so far, and we have examples of our continued understanding all around, ranging from simple single-celled life forms to complex plants, animals, etc. . Why should life be incomprehensibly different "out there"? It can be modeled, motivations examined. Basic evolution will most likely still apply. They want to survive, and this is a basic logical tenet that weaves the fabric of the psychology of any lifeform.

We can argue back and forth as to how aliens could think. You are assuming that logic follows the way humans think. I'm not saying there is no reason, I'm saying that we have a single data point for intelligent life, here, on Earth. Why should life be the same as on Earth? Because that is what makes sense to us given our current knowledge of the universe, our biases? I would like to think that aliens, whether or not they inhabit the same rough space and time as we do, would follow the same logic, the same science of right, which we humans have, but I would still be making the assumption based on life on one single planet, where only one tool making species someday maybe capable of interstellar travel. For that matter, practical interstellar travel may not even be possible except for generation ships.

There is no "human logic". Logic is logic. It encompasses thoughts both natural and foreign. Who, for example, really finds the Banach-Tarski paradox intuitive? And yet it's logical. In fact, it follows from somewhat intuitive logical rules. But, hell, we can throw those out, too. We can accept a logic that, for example, rejects the entire concept of implication and the principle of explosion. A logic which can have two contradictory things both be true, without causing the system itself to fail. The limits of logic have nothing to do with what is natural to humans.

Axioms are not things that exist just floating in space, but neither are they things that only exist to a human mind. Logical implications can be defined, and inferred, in a useful way that applies to systems that don't understand logic at all! Even if aliens thought in a way entirely, well, "alien" to us, they could still be described by logic, even if they themselves found the idea patently ridiculous, because even their formation followed physical laws, and their development followed biological laws.

Perhaps not laws that we are familiar with. Perhaps the life we hypothetically encounter is just one monolithic life-form that developed in solitude on a planet, and self-developed. Normal rules of evolution do not apply when there is only one creature. But, that's not to say that there were no rules. For to survive, it still must have done something right. And in a universe with some known laws, what is right to survive can be surmised quickly: it obviously didn't jump into its sun right away and perish. Suicide cannot coexist with life. So already we can figure out one thing: this singular life-form that "evolved" in such a strange manner does not commit suicide. Other aspects might be harder to find. Is it peaceful? There's no way of knowing. Whether it's peaceful or not has nothing to do with whether it survived and developed to get here, because it developed entirely in solitude. But, is it very sociable? Almost certainly not. A thing that has never before seen other life won't even comprehend what it is to be social. It's just like us examining quantum physics. What on earth is going on? We can't understand things totally outside of our experience except by analogy and coincidence, and here there is almost definitely no analogy, only a freak coincidence of mental structure.

So you see, we can reason about things logically, even if they are alien. We've reasoned about quantum mechanics, despite never seeing it, and despite never even understanding it. We've reasoned about single-celled organisms, things that are incapable of even thinking. We have reasoned about automata and machines, about chemical and nuclear reactions on a scale so far beyond the realm of our comprehension that we can never hope to appreciate it on anything more than a dumb, primitive level. We do it even if we don't understand, because the tools of logic are universal. Not by virtue of some belief or god, but simply because things have patterns. Even alien things.

http://en.wikipedia.org/wiki/Banach-Tarski_paradox http://en.wikipedia.org/wiki/Paraconsistent_logic

> Why would you go through the effort and uncertainty of unting wildlife when you can just saunter down to the local grocery store and pick up prepared meat?

Because, to use your analogy, that would be like the aliens living in New York, but doing all their shopping at a local grocery store located in London.

The distances to these far of galaxies are measured in the hundreds of millions of light years, if not further.

I think your scale is off a bit. I'm not sure what "these far off galaxies" refers to, but according to this Wikipedia page:

  http://en.wikipedia.org/wiki/List_of_nearest_galaxies

all the local group galaxies are within 10 million light years of Earth.

For that matter, some of the "life is everywhere" theories assume many space-faring civilizations within our own Milky Way galaxy, which is only(!) about 100,000 light years across.

With a univers estimated at some 4 billion light years in size, I choose 100 million light years as a ball park figure.

But lets assume these aliens are in fact our neighbours and live just a million light years away.

If they are planning to pop over for a visit, it's going to take them a very long time to get here.

Unless of course Einstein is wrong and in reality it is possible to travel faster than the speed of light.

For the same reason we consider a piece of land full of plants, animals, and insects uninhabited.

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