Observational Signatures of Self-Destructive Civilisations

by gnocchi • 11 years ago

53 17 11 years ago

ChuckMcM• 11 years ago

I believe it was Vernor Vinge who made the comment that perhaps unexplained gamma ray burst were the last gasp of a planet or star that had been obliterated in anger by an adversary.

That said, if, for example, humans kill themselves off with a climate change it would have very little external signature.

stcredzero• 11 years ago

Vernor Vinge also made the observation, that if most civilizations undergo an exponential increase in technological and societal progress, they're likely to disappear within a dozen generations after inventing radio. I'm not so sure we can reasonably imagine the signature of a civilization "subliming" to put it in Iain M. Bank's "Culture" terms.

So if the likeliest outcomes of industrial civilization are environmental self-destruct, self immolation in war, or "subliming" to something we can't imagine, then this would handily explain the Fermi paradox.

trhway• 11 years ago

we know that we can't "see" most of the Universe - the dark matter/energy. That pretty much can happen to be the real Universe, and we're just living in the part set aside for the non-intelligent species. It is like being an ant on Earth - there is a planetary tech civilization being developed while you have no idea what is going around. The only interaction you my have with the civilization - if you're lucky, and you are some kind of special ants, then your colony may get moved before dam valley to be flooded, otherwise - not even that...

kordless• 11 years ago

I'm not so sure we can reasonably imagine the signature of a civilization "subliming"

Based on the number of people lost in their phones on BART, the streets and meetings, I'd say we're already well on our way to subliming ourselves.

matt_morgan• 11 years ago

This was not obvious to me from the title, but what they're talking about is ways that with tomorrow's telescopes, we could infer via observation how a technological civilization had destroyed itself, and therefore that an advanced extra-terrestrial civilization had been on that planet.

They seem to say that given Fermi's paradox and the possibility that most civilizations self-annihilate, this is actually a good way to do SETI. Makes sense.

jleahy• 11 years ago

> As a star’s gravitational well will likely be the deepest in the system, it is also energetically efficient to launch material on a stellar intercept trajectory.

Quite the opposite, that's one of the most delta-v expensive trajectories to embark upon. In fact from earth it's about twice as expensive as leaving the solar system.

3pt141592• 11 years ago

Really? Why? Isn't the sun moving along some path in the milky way and can't we use that to accelerate the launch of a spacecraft? It looks like Voyager 2 used the effect, at least according to this image:

http://abyss.uoregon.edu/~js/images/voy_traj.jpg

xenophonf• 11 years ago

Are you confusing gravity assists (unpowered) with the Oberth maneuver (powered)? You can't use a gravity assist with the Sun because it's at rest relative to the rest of the Solar system. The Sun is only ever dragging you down, whereas a gravity assist maneuver drags you around the target body. (Imagine me waving my hands a lot while you read this.) You can kind of think of it like coming up from behind a planet relative to it's motion around a star, which will will accelerate you, or going in front of it, which will slow you down.

For interstellar trajectories you can use stars for gravity assists, but I'm not sure that would work for escaping the Sun. There, you would want to use the Oberth maneuver, where you get into an elliptical orbit around the sun and then fire your engines at perihelion to raise your orbit to a parabolic or hyperbolic trajectory.

In any case the Voyagers both used gravity assists around the gas giants (Voyager 2 used all four, while Voyager 1 just used Jupiter and Saturn because NASA decided to swing past Titan and didn't have enough propellant left to resume the Grand Tour course).

demallien• 11 years ago

Orbits are not intuitive. To head "downwards", you have to slow down your orbital velocity, which reduces the radius of the orbit. In other words you have to decelerate. When you do the maths, you actually have to decelerate more from Earth orbit to get to the sun than you do to accelerate up to solar escape velocity.

em3rgent0rdr• 11 years ago

obviously they haven't played Kerbal space program!

nickhalfasleep• 11 years ago

I don't think these can differentiate between Self-Destruction and Murder by other parties?

jerf2• 11 years ago

Under their assumptions, murder doesn't come up very often, because civizilations rarely-to-never cross paths in the first place.

Observational Signatures of Self-Destructive Civilisations

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