Comment by jrapdx3 | Hacker News Reader

Comment by jrapdx3 | Hacker News Reader

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.

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.

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.

"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.

> 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.

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.

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.

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