G-HAT (Glimpsing Heat from Alien Technologies)

For those interested in the post about finding advanced civilizations in other galaxies by their heat emissions, Paul Gilster at Centauri Dreams has a write up about the study, including links to additional material as well as the actual paper.

I found that this part clarified the seeming contradiction in the Science Daily article.

The currently reported work tells us that none of the galaxies resolved by WISE in this study contain Type III civilizations that are reprocessing 85 percent or more of the starlight of their galaxy into the mid-infrared. And as mentioned above, out of 100,000 galaxies, only fifty show a mid-infrared signature that could be considered consistent with reprocessing more than 50 percent of the starlight.

These fifty point to the further investigations ahead.

The overall endeavor of which the study is a part appears to be named G-HAT (Glimpsing Heat from Alien Technologies).   Gilster links to a site that looks like it has lots of additional information on it, along with some interesting articles.

Searching for advanced civilizations in other galaxies: 50 possible candidates found?

At first, this article seems like a bit of a downer:
Search for advanced civilizations beyond Earth finds nothing obvious in 100,000 galaxies — ScienceDaily.

After searching 100,000 galaxies for signs of highly advanced life, a team of scientists has found no evidence of advanced civilizations there. The idea behind the research is that, if an entire galaxy had been colonized by an advanced spacefaring civilization, the energy produced by that civilization’s technologies would be detectable in mid-infrared wavelengths.

…”Whether an advanced spacefaring civilization uses the large amounts of energy from its galaxy’s stars to power computers, space flight, communication, or something we can’t yet imagine, fundamental thermodynamics tells us that this energy must be radiated away as heat in the mid-infrared wavelengths,” Wright said. “This same basic physics causes your computer to radiate heat while it is turned on.”

Theoretical physicist Freeman Dyson proposed in the 1960s that advanced alien civilizations beyond Earth could be detected by the telltale evidence of their mid-infrared emissions. It was not until space-based telescopes like the WISE satellite that it became possible to make sensitive measurements of this radiation emitted by objects in space.

However, somewhat contradicting the title of the article and its opening passage, we have this snippet:

Wright reports, “We found about 50 galaxies that have unusually high levels of mid-infrared radiation. Our follow-up studies of those galaxies may reveal if the origin of their radiation results from natural astronomical processes, or if it could indicate the presence of a highly advanced civilization.”

I’m not entirely sure what to make of this passage given the apparent contradiction, but it sounds like we have 50 possible candidate galaxies for advanced civilizations.  (Emphasis on the word “possible” here.)

Based on the information the article provides, it seems obvious that the scientists were looking for Type III civilizations on the Kardashev scale.  A Type I civilization has harnessed all of the energy on its native planet.  (We’re not a Type I civilization yet).  A Type II civilization has harnessed all of the energy of its native star, possibly using concepts like Dyson spheres or swarms.  And a Type III civilization will  have harnessed all of the energy in its galaxy, or, at least for purposes of this study, enough to be noticeable across intergalactic distances.

Of course, we have no real idea how possible a Type III civilization actually is.  It would involve engineering on scales that currently seem hard to imagine.  But given enough time (think hundreds of millions of years), there doesn’t seem to be anything in the laws of physics that prevent it.  We also can’t be sure that some observed astronomical phenomena that we’re chalking up to nature might not turn out to be mega-structures created by extraterrestrial intelligence.

But given the age of the universe, and the fact that there’s no evidence of Earth ever having been colonized in its 4.5 billion year history, it seems likely that if there are advanced civilizations out there, they’re too far away to have reached us yet.  50 out of 100,000 galaxies sounds like about the right number.  The nearest advanced civilization may be several hundred million light years away.

Unless they find natural explanations for the high levels of mid-infrared radiation.  Then the closest advanced civilization might might be billions of light years away, or even outside our visible universe.

Life on the Billionth Rock From the Sun | Seth Shostak

Seth Shostak has an article at HuffPost on asteroids.  Not the usual we-need-to-prepare-for-incoming, but discussing something I’ve noted before that the space age needs: an economic incentive.  As some of us have discussed, mining asteroids looks like it might be an excellent candidate.

These rocks are a resource. The fact that they’re in small chunks makes mining them as appealing as cat videos. And at least two companies are considering doing just that. The consequences could be mind-boggling. According to John Lewis, chief scientist for Deep Space Industries, if humanity can improve its recycling efforts, then ores smelted out of just the nearest asteroids will supply the needs of 80 billion of us until that distant day on which the sun dies.

That sure beats the slow and inevitable impoverishment that will be our fate if we confine mining to our own back yards (or preferably someone else’s back yard). The asteroids aren’t so much a renewable resource as an endless one.

via Life on the Billionth Rock From the Sun | Seth Shostak.

Shostak also discusses the possibility of us living on asteroids, and on the rocks further out from the sun in the Kuiper belt and scattered disk.

The only issue with these far out locations is their distance from the sun and the inability to use solar energy.  Shostak talks about Freeman Dyson’s idea of using mirrors near the sun to beam energy out to specific colonies.  But that seems like it would quickly grow cumbersome with large numbers of such colonies.  To be economically feasible, those outer colonies would probably eventually need to figure out a way to use the materials on hand to generate energy.

I suspect any such colonies would be “manned” by robots, or post-humans.  Maintaining natural humans that far out from the sun would probably be too energetically expensive.