
The Irreplaceable Carl Sagan (2014) - prismatic
http://www.smithsonianmag.com/science-nature/why-carl-sagan-truly-irreplaceable-180949818/?all
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jrapdx3
The article is a nice tribute to Sagan, certainly one of the more interesting
characters in 20th century science. Of course I remember "Cosmos", Sagan being
as much poet as astronomer in that series the show was truly powerful and
influential.

In the mid-80's I heard Sagan give a talk. He spoke about his usual themes, of
future possibilities, the man was remarkably optimistic regarding human
potential despite the evidence of missed opportunity all around. I think that
contributed greatly to his popularity, he understood the difficulties of human
frailty but refused to be overwhelmed by it.

I imagine Sagan would be disappointed that we still have no evidence for
intelligent life anywhere in the universe other than our own "pale blue dot".
It seems odd that Earth would be the only location life evolved to a human-
equivalent stage, if not beyond. Maybe it's simply technological limitation,
or attributable to distance that we have not detected signs of life out there.
I have to agree with Sagan, it sure would be thrilling if it were so.

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jacquesm
It's a problem of scale, not a problem of technology per-se. Life could be
abundant on an absolute scale but tiny on a relative one. We could easily miss
it for centuries before accidentally running into some evidence. Imagine the
opposite, the aliens looking for us. They'd have to be within ~100 lightyears
to be able to detect our radio transmissions. Otherwise they'd have to have a
biochemistry enough like ours (or a very vivid imagination) to be able to even
recognize that earth can support life.

Just like we are always looking for 'earth-like' planets.

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rbanffy
That. Plus our discernible high power radio emissions can be a short lived
phenomenon: we may end up switching to very directional emissions for long-
distance communication and to low-power for local communication. The spectrum
allocated to radio and TV already seems a waste. While it will be somewhat
evident something strange is happening in terms of energy being radiated to
space, any civilization will have to work very hard to separate the multitude
of signals they get. The combined murmur of billions of radio voices will be
indistinguishable from white noise.

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keeringplastik
"A candle against the sun" or something like that.

I wonder if the gamma bursts from nuclear testing are discernible from the
solar noise? It would reduce the distance to about about 60 light years.

If some ET were looking in our direction, I imagine the radiation signature
would look like camera flashes on the far side of a dark stadium where a
pyrotechnic performance was occurring on stage.

So long as your eyes are not blinded by the main event, a burst of sparks off
to one side might catch your attention - if you are watching during those
precious few years when such events happen, and the orientation of all
relevant celestial bodies are favorably aligned.

Now, having put it to words, it becomes a hopelessly unlikely signal.

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rbanffy
> I wonder if the gamma bursts from nuclear testing are discernible from the
> solar noise? It would reduce the distance to about about 60 light years.

Maybe. It's a given a civilization more advanced than ours would be able to
observe the Solar System with better resolution than we currently can observe
our neighbors, but that's a very narrow time window to watch. We no longer do
test blasts. Any alien species would have to be incredibly lucky to be
watching us at the precise decades we would be visible. While any seriously
alien-life seeking advanced civilization would have tons of telescopes all
over the spectrum looking at everything interesting they have the resources
watch, as well as a couple probes on their way to promising targets, there are
literally billions of places to examine.

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jacquesm
It would also serve as a warning that we're only 'mostly harmless' so if a
house-call is in order (or a preventive visit) then better come packing heat.

Of course that assumes a whole raft of things such as the ability of ET to
show up in person but since we don't know anything about the technological
state of the rest of the universe mostly because we don't know anything about
them at all that's not too far out.

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rbanffy
To any civilization capable of showing up face to face, we are completely
harmless. They don't even need to bring the guns: just pointing the engine our
way while braking would do the trick.

