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When Are the Intelligent Aliens?

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Re: When Are the Intelligent Aliens?

#51

Post by sampo »

abrichr wrote: post #42
sampo wrote: post #21

Earlier quoted context omitted.

The black space is at about 3 Kelvin temperature. A Dyson sphere would necessarily (the star inside would heat it) have a much higher temperature than mere 3 K above the absolute zero. Thus it would radiate heat according to whatever its temperature, and be quite distinct compared to the cold back space background.

This is assuming that the creators of the Dyson sphere haven't also figured out how to absorb the heat energy with extremely high efficiency.

You are assuming they'd have figured out how to break the laws of thermodynamics as we know it.

Re: When Are the Intelligent Aliens?

#52

Post by Udo »

jl6 wrote: post #47
Udo wrote: post #18

Earlier quoted context omitted.

Even a Dyson sphere can't just swallow the star's radiation. It makes use of a potential gradient, which means it would have to radiate away some energy on the outside. This would probably show up as, say, a brown dwarf. Still, if it's not in our direct neighborhood the chances of us discovering it are even lower.

Unless the engineers are concerned about detection and choose somehow to radiate in only one narrow direction, pointed away from any nearby stars.

That's true, and stealth is an interesting proposition. However, there are probably easier methods of preventing detection, such as not building a giant structure in the first place. Also, even if they manage to radiate away most of their waste heat, they'd have to assume eventual detection by an advanced civilization. Sure, with exponential effort you can always get infinitesimally closer to being virtually undetectable, but is that really feasible?

In the end, it's certainly not impossible that a civilization would go to extreme lengths in order to hide its enormous artificial structures. But the real issue is: why would all civilizations hide in this way? And if it turns out they do all have elaborate stealth tech in operation, that means there must be an incomprehensibly huge threat out there - which in itself might be the answer to why nobody is calling us up.

Re: When Are the Intelligent Aliens?

#53

Post by bane »

ChuckMcM wrote: post #31
exratione wrote: post #11

Obligatory talking points associated with the Fermi Paradox: - It takes a very short time in comparison to the age of the galaxy for a single self-replicating probe to result in a descendant probe visit to every star. A few million years. This means that you cannot really argue plausibly that all civilizations fail to do this - it would take trivial effort for just one faction within just one advanced civilization to…

This is a good summary. One of the missing pieces is we don't know what the minimum set of combinational factors are to create "advanced" civilization. The scare quotes for advanced here are that two incompatible definitions for civilization quality compete for the nominative "advanced." In the current context advanced means we've developed machines that carry us into space, we can create habitats to survive in even…

Right, we simply don't know the conditions to generate a advanced civilization. We're certainly not it (yet) -- at least in terms of the characteristics we're expecting space-faring extraterrestrials to have.

There might be billions of worlds full of dinosaur analogs running around happily eating and growling till their star burns out...and that might be all that you can expect out of life in the general case when it happens.

"Why didn't the Dinosaurs develop space flight?" Why don't we? Again, in absolute terms of the characteristics we're requiring of an alien civilization, we're not really any closer (in measurable absolute terms) to visiting Vega than a struggling ape is. The furthest distance a human has ever traveled off of the Earth is very slight navigational/rounding error when going to another Star.

Re: When Are the Intelligent Aliens?

#54

Post by [deleted] »

Udo wrote: post #18
chongli wrote: post #16

Earlier quoted context omitted.

>Where are the macrostructures? We don't see Dyson spheres or other evident macroscale engineering. Everything we can see so far looks natural. This is more troubling than an absence of detectable communications. Assuming a Dyson sphere was nearby, how would we detect it? What would it look like? If it's able to make use of most of a star's radiation output, wouldn't that make it very difficult to see? It wasn't unti…

Even a Dyson sphere can't just swallow the star's radiation. It makes use of a potential gradient, which means it would have to radiate away some energy on the outside. This would probably show up as, say, a brown dwarf. Still, if it's not in our direct neighborhood the chances of us discovering it are even lower.

[deleted]

Re: When Are the Intelligent Aliens?

#55

Post by sampo »

jl6 wrote: post #47
Udo wrote: post #18

Earlier quoted context omitted.

Even a Dyson sphere can't just swallow the star's radiation. It makes use of a potential gradient, which means it would have to radiate away some energy on the outside. This would probably show up as, say, a brown dwarf. Still, if it's not in our direct neighborhood the chances of us discovering it are even lower.

Unless the engineers are concerned about detection and choose somehow to radiate in only one narrow direction, pointed away from any nearby stars.

So, first you build a Dyson sphere, then you build a system to cool the outer surface of your Dyson sphere to near 3 Kelvin (except some narrow directions in space, where you radiate your excess heat).

Now the interesting question is, is the energy you capture from the star sufficient for running this cooling system of yours. I have no clue.

Re: When Are the Intelligent Aliens?

#56

Post by hga »

Cookingboy wrote: post #46
VladRussian2 wrote: post #26

Earlier quoted context omitted.

>The way I view it, by definition someone has to be first. no :). That is the beauty of this Universe - global full order of things on timeline isn't possible. Specifically space-like separated events don't have a preferred order, i.e. given 2 space-like separated events A and B, both statement - A precedes B and B precedes A - have the same validity, basically it is meaningless to talk about their timeline order.

Just because they are space separated events does not mean you cannot give assign them chronological order. Can't you just simply refer to a literal universal chronological reference point (i,e Big Bang) and then achieve successful ordering of events? For example: Civilization A achieved space flight x time units (whatever time units, such as Planck time unit) after Big Bang, and civilization B achieved space flight…

Without getting too deep into this issue of relativity, let me point that that the Milky Way is per Wikipedia "100,000–120,000 light-years in diameter".

Rather than go down to Planck level granularity, if reaching space flight, or better, serious engineering works in space that are visible from afar is a low probability thing, with time scales say in the millions of years, then "first" will I think do for our purposes.

Re: When Are the Intelligent Aliens?

#57

Post by DavidPlumpton »

exratione wrote: post #11

Obligatory talking points associated with the Fermi Paradox: - It takes a very short time in comparison to the age of the galaxy for a single self-replicating probe to result in a descendant probe visit to every star. A few million years. This means that you cannot really argue plausibly that all civilizations fail to do this - it would take trivial effort for just one faction within just one advanced civilization to…

Maybe interstellar travel is just really hard even with technology far beyond our own.

Re: When Are the Intelligent Aliens?

#58

Post by ChuckMcM »

bane wrote: post #53
ChuckMcM wrote: post #31

Earlier quoted context omitted.

This is a good summary. One of the missing pieces is we don't know what the minimum set of combinational factors are to create "advanced" civilization. The scare quotes for advanced here are that two incompatible definitions for civilization quality compete for the nominative "advanced." In the current context advanced means we've developed machines that carry us into space, we can create habitats to survive in even…

Right, we simply don't know the conditions to generate a advanced civilization. We're certainly not it (yet) -- at least in terms of the characteristics we're expecting space-faring extraterrestrials to have. There might be billions of worlds full of dinosaur analogs running around happily eating and growling till their star burns out...and that might be all that you can expect out of life in the general case when it…

I think you don't give us enough credit :-) We have developed enough technology to leave the planet and walk around on our Moon. We are, perhaps within a decade, going to have that capability again but with a much higher level of base technology. While it would be unlikely for Dinosaurian satellites to have remained in orbit for millions of years, anything they left on the moon would still be there.

"There might be billions of worlds full of dinosaur analogs running around happily eating and growling till their star burns out...and that might be all that you can expect out of life in the general case when it happens."

This is the essence of the Fermi paradox I believe. (And I've ordered a copy of the book mentioned below, it looks intriguing) So what hypothesis could support billions of iterations of 'life' evolving into the multicellular form we see today and in our past, and so few evolving technology?

I totally agree it is a somewhat useless question to ponder but I can't help it.

Re: When Are the Intelligent Aliens?

#59

Post by sampo »

sampo wrote: post #55
jl6 wrote: post #47

Earlier quoted context omitted.

Unless the engineers are concerned about detection and choose somehow to radiate in only one narrow direction, pointed away from any nearby stars.

So, first you build a Dyson sphere, then you build a system to cool the outer surface of your Dyson sphere to near 3 Kelvin (except some narrow directions in space, where you radiate your excess heat). Now the interesting question is, is the energy you capture from the star sufficient for running this cooling system of yours. I have no clue.

Let's see if someone in Physics StackExchange could answer this:

http://physics.stackexchange.com/questions/69649/thermodynam...

Re: When Are the Intelligent Aliens?

#60

Post by lovemenot »

The Fermi paradox is useful in that it shows us that something must be wrong with Drake. It is more likely to be something wrong in one or more of the assumptions, than with the empirical facts. I think the problem is with notions of "advanced" and "intelligent". When it comes down to it, that really just means like present humans. There is nothing inevitable nor qualitatively special about technology. It is just one particular evolutionary advantage which has helped one particular species on one particular planet. Dwelling on why there seems to be nobody else out there exactly like us is just narcisistic; a super-sensitive kid pining for their one-true-and-never-met soul-mate, when they are surrounded by potential lovers. These hypothetical advanced aliens seem like the scholastic pinhead angels of this age of reason. Having said that, life in general is utterly amazing. I have no evidence for this, but I imagine that if and when we humans discover extra-terrestrial life, we will find that some living organisms on this earth have already "known" about it for eons.
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