Spectral signal in halo stars, ETI suspected.

Yeah, third time i had written it, and lost it trying to post, so just blurted this out.

But,

As the paper points out, this is about 1 in 10k stars, a realistic number to punch into the drake equation, and they are all full spectrum types.

i have convinced myself that the only truly "universal language" in the universe won't be binary, decimal, or duodecimal, but spectral. You have to be studying stars to really understand what they are telling in red/blue shift. Chemistry of elements is only to teach you the letters of the alphabet. I don't know what that language would look like, but, as a contact language, it would be a universal base, at least.

These are mostly halo stars, and it would make sense if you were coming in just sub-c, that you wouldn't aim at the densest part of the disk, but take the "high ground", and take instrument readings, "below", as you did a local survey of likely targets in the area you are in now. You could also "see" which areas have recently been cleaned out by supernova and other extreme events, and know where to focus the search to other areas.

The galactic invaders, and the machine culture are spec, but that is where reason takes you, if you follow the lead.

from Atomic Rockets:

The great silence (i.e. absence of SETI signals from alien civilizations) is perhaps the strongest indicator of all that high relativistic velocities are attainable and that everybody out there knows it.

The sobering truth is that relativistic civilizations are a potential nightmare to anyone living within range of them. The problem is that objects traveling at an appreciable fraction of light speed are never where you see them when you see them (i.e., light-speed lag). Relativistic rockets, if their owners turn out to be less than benevolent, are both totally unstoppable and totally destructive. A starship weighing in at 1,500 tons (approximately the weight of a fully fueled space shuttle sitting on the launchpad) impacting an earthlike planet at "only" 30 percent of lightspeed will release 1.5 million megatons of energy -- an explosive force equivalent to 150 times today's global nuclear arsenal... (ed note: this means the freaking thing has about nine hundred mega-Ricks of damage!)

I'm not going to talk about ideas. I'm going to talk about reality. It will probably not be good for us ever to build and fire up an antimatter engine. According to Powell, given the proper detecting devices, a Valkyrie engine burn could be seen out to a radius of several light-years and may draw us into a game we'd rather not play, a game in which, if we appear to be even the vaguest threat to another civilization and if the resources are available to eliminate us, then it is logical to do so.

The game plan is, in its simplest terms, the relativistic inverse to the golden rule: "Do unto the other fellow as he would do unto you and do it first."...

When we put our heads together and tried to list everything we could say with certainty about other civilizations, without having actually met them, all that we knew boiled down to three simple laws of alien behavior:

THEIR SURVIVAL WILL BE MORE IMPORTANT THAN OUR SURVIVAL.

If an alien species has to choose between them and us, they won't choose us. It is difficult to imagine a contrary case; species don't survive by being self-sacrificing.
WIMPS DON'T BECOME TOP DOGS.

No species makes it to the top by being passive. The species in charge of any given planet will be highly intelligent, alert, aggressive, and ruthless when necessary.
THEY WILL ASSUME THAT THE FIRST TWO LAWS APPLY TO US.

...

Your thinking still seems a bit narrow. Consider several broadening ideas:

Sure, relativistic bombs are powerful because the antagonist has already invested huge energies in them that can be released quickly, and they're hard to hit. But they are costly investments and necessarily reduce other activities the species could explore. For example:
Dispersal of the species into many small, hard-to-see targets, such as asteroids, buried civilizations, cometary nuclei, various space habitats. These are hard to wipe out.
But wait -- while relativistic bombs are readily visible to us in foresight, they hardly represent the end point in foreseeable technology. What will humans of, say, two centuries hence think of as the "obvious" lethal effect? Five centuries? A hundred? Personally I'd pick some rampaging self-reproducing thingy (mechanical or organic), then sneak it into all the biospheres I wanted to destroy. My point here is that no particular physical effect -- with its pluses, minuses, and trade-offs -- is likely to dominate the thinking of the galaxy.
So what might really aged civilizations do? Disperse, of course, and also not attack new arrivals in the galaxy, for fear that they might not get them all.    Why? Because revenge is probably selected for in surviving species, and anybody truly looking out for long-term interests will not want to leave a youthful species with a grudge, sneaking around behind its back...

I agree with most parts of points 2, 3, and 4. As for point 1, it is cheaper than you think. You mention self-replicating machines in point 3, and while it is true that relativistic rockets require planetary power supplies, it is also true that we can power the whole Earth with a field of solar cells adding up to barely more than 200-by-200 kilometers, drawn out into a narrow band around the Moon's equator. Self-replicating robots could accomplish this task with only the cost of developing the first twenty or thirty machines. And once we're powering the Earth practically free of charge, why not let the robots keep building panels on the Lunar far side? Add a few self-replicating linear accelerator-building factories, and plug the accelerators into the panels, and you could produce enough anti-hydrogen to launch a starship every year. But why stop at the Moon? Have you looked at Mercury lately? ..."

End Transmission.

The problem with ID in biology is not that it is assigning a cause which is not "a naturally occurring phenomenon." ID advocates will no doubt say that their cause does, in fact, occur in nature, whether or not that you believe that it does. The problem with ID in biology is that 1) we know vast amounts of biological organizations that came to be without being caused by intelligence, and 2) we know that there lots of other biological organizations that might have come to be without intelligence, and 3) we have not yet seen any case which clearly was caused by intelligence. Given those three facts, if you come upon some organization and do not know how to explain it, it is more likely than not that the true explanation does not involve intelligence.

All of these factors apply to the case the supposed extra terrestrials.

It is true, of course, both in this case and in the case of ID advocates, that they might be right. It is just very unlikely.