Alien Supercivilizations Absent from 100,000 Nearby Galaxies

[C C]

http://www.scientificamerican.com/articl...-galaxies/

EXCERPT: [...] more evidence mounts that the warm, wet conditions for life as we know it prevail throughout the cosmos. Surely simple, single-celled life should be common out there [...but...] The possible existence of intelligent aliens and extraterrestrial civilizations [...] remains much more controversial and is scarcely funded at all. [...] SETI chiefly looks for chatty cosmic cultures that might be beaming messages around [...] But its interstellar eavesdropping has yet to detect any signals that withstand close scrutiny.

[...] Now, new results suggest this loneliness may extend out into the universe far beyond our galaxy or, instead, that some of our preconceptions about the behaviors of alien civilizations are deeply flawed. After examining some 100,000 nearby large galaxies a team of researchers lead by The Pennsylvania State University astronomer Jason Wright has concluded that none of them contain any obvious signs of highly advanced technological civilizations. [...] it is by far the largest of study of its kind to date.

[...James Annis:] “In some sense it doesn’t matter how a galactic civilization gets or uses its power because the second law of thermodynamics makes energy use hard to hide. They could construct Dyson spheres, they could get power from rotating black holes, they could build giant computer networks in the cold outskirts of galaxies, and all of that would produce waste heat. Wright’s team went right to the peak of the curve for where you’d expect to see any sort of waste heat, and they’re just not seeing anything obvious....”

[...] Annis suspects galaxy-sterilizing astrophysical explosions called gamma-ray bursts, which were more frequent in the cosmic past, until recently suppressed the rise of advanced civilizations and that we inhabit “the beginning of history.”

But as rich as the scientific literature is with ideas, some of the most fascinating ones come instead from science fiction. [...In author Karl Schroeder's] view the future of technology would not consist of star-hopping civilizations spreading like wildfire through galaxies, disassembling planets and smothering suns, but rather of slow-growing cultures becoming more and more integrated with their natural environments, striving for ever-greater efficiencies and coming ever-closer to thermodynamic equilibrium. Simply put, profligate galaxy-spanning empires are unsustainable and therefore we do not see them. “SETI is essentially a search for technological waste products,” Schroeder has written. “Waste heat, waste light, waste electromagnetic signals—we merely have to posit that successful civilizations don’t produce such waste, and the failure of SETI is explained....”

[Mr Doodlebug]

We could never detect an alien civilisation from waste heat. It would be a piddling amount.
Like looking for a fading torch light in a blast furnace.

Solar Luminosity---huge energy output!

The first basic question about the Sun is how bright is it? It puts out A LOT of energy every second. How much? The answer from our measurements is 4 × 10 to the 26 watts. Such a large number is beyond most of our comprehension, so let's put the Sun's total energy output (ie., its luminosity) in more familiar units. It is equal to 8 × 10 to the 16 of the largest power plants (nuclear or hydroelectric) on the Earth. Our largest power plants now can produce around 5,000 Megawatts of power. Another way to look at this is that the sun puts out every second the same amount of energy as 2.5 × 10 to the 9 of those large power plants would put out every year---that's over two billion!

http://www.astronomynotes.com/starsun/s3.htm

As for not finding signs of Alien life.
I put it down to Dark Matter. Or Dark energy.
That explains all the other stuff we don't know too.

[Yazata]

Does the "alien supercivilizations absent" conclusion really follow from the evidence?

I gather that somebody decided that "supercivilizations" means civilizations that have encased their star in a 'Dyson-sphere', a spherical shell that surrounds a star and captures all of its radiant energy. That's doubtful assumption #1.

Then they calculated that a Dyson sphere should have a distinctive infrared signature. That's doubtful assumption #2.

Then they assumed that their observation methods were capable of detecting that kind of infrared source not only in this galaxy, but in other galaxies as well. Doubtful assumption #3.

None were found. So q.e.d., no superciviliations exist in those 100,000 galaxies. At least if one accepts the assumptions. I certainly don't.

[Mr Doodlebug]

The nearest solar system to us is Alpha Centauri. 4 light years away.
Say there was a civilisation much the same as ours in it.
Would we be able to pick up their radio programmes?
Or would the signals be drowned in background radiation?
Their strength would be the square root of the distance wouldn't it?
In the UK, we can barely pick up US long wave radio signals, and that's only a few thousand miles.

I can't understand what signals SETI are hoping to detect.

RE the Dyson sphere. Worth a look. An Enterprise encounter with a Dyson Sphere would have been an excellent basis for a Star Trek episode.

Every now and again one of these "out of the box" ideas works, and the unexpected solution thereafter looks obvious.