[ExI] tabby's star dimming again

[Stuart LaForge]

John Clark wrote:
 ​
>> ​So in a observable universe ​ 27,600,000,000 light years in diameter the
>> only other technological civilization just happens to be only 1480 light
>> years away and Kepler just
>> ​ ​
>> happened to find it even though it was looking at 1/400 of the sky and it
>> ​ ​
>> just happened to find it when ET had the technological chops to build 5%
>> ​ ​
>> of a Dyson Sphere but no more? Doesn't seem very likely. ​

Irregardless of whatever explanation is found for it, Tabby's Star will go
down in history as one of the luckiest breaks in all of science. It
doesn't matter if it's aliens or some novel physical phenomenon that is
paradoxically both mundane and seemingly unique, the odds that a telescope
with a broken servo happened to be looking at it when it happened are
quite low. Maybe it was superdeterminism. ;-)

>​ Yes, too close to the galactic center and there is too much gamma
> radiation from Supernovas and the Supermassive Black Hole, and too far  
  > from the center and there are not enough elements other than
Hydrogen and > Helium to support life. But the Galactic goldilocks zone
is HUGE, it forms > a ring between 13,000 and 33,000 light years from
the center, Earth is    > 26,000 light years from our Galaxy's center. 
And there are at least 200   > billion Galaxies in the observable
universe.

Let's please constrain the search space to our own galaxy. Apart from the
closest galaxies in our own cluster, we would have very little chance of
noticing engineered galaxies in the rest of the universe. As Sophie
mentioned im her post, beyond a certain point, we are looking so far into
the past that nothing can be concluded about the present. Most of the
galaxies could have been Dysoned off back in age of the dinosaurs and we
would be none-the-wiser for a few billion more years.

With regard to the Milky Way then, we can assume we are somewhere in the
middle of the habitable zone. From our vantage point we are only able to
view at most about 1/2 of the goldilocks zone because the hot gas and
crazy radio sources in the galactic bulge would obscure any signal from
the far side of the ring of life. Furthermore radio signals and the
density of bright stars would likely screw up observation even of life in
the centerward direction along the radial line from the galactic core to
our solar system. Thus even having the galactic core in the background
could cause too much noise.

Therefore we are stuck looking for life in two relatively narrow swaths of
the life zone on either side of the galactic bulge. And even less if we
are on the outward edge of the life ring. Find the solar system and the
constellation of Cygnus at 90 degrees on the following galactic map:

https://astronomytopicoftheday.files.wordpress.com/2016/08/milky_way_arms_ssc2008-10-svg.png

Notice that Tabby's Star located in the constellation Cygnus is almost in
the same orbit as we are around the galactic nucleus. That's amazing!

> A planet 1480 light years away is our next door neighbor galactically   
 > speaking and even more so cosmically speaking. So I ask again, if ET
is   > real when we look into the night sky why isn't it obvious that
the        > universe has been engineered?

Because most of the galaxies we can see didn't have metals when the light
we observe left them. Without metals how do you engineer anything let
alone galaxies?      ​

> For intelligence to form on a planet life may have to
> start freakishly early, if not their sun might not give Evolution enough
> time to produce intelligence before it dies of old age. After all, in the
> nearly 4 billion year history of life on this planet Evolution only     
 > managed to come up with a technological civilization once, and it
only    > happened a few thousand years ago.

True but evolution is a stochastic process like a random walk. You might
never reach your destination or you might get lucky and reach it in the
first few steps. The point is that we don't know if we are early, late, or
somewhere in the middle. But drunk or not, the faster you walk, the more
places you can get to in a shorter amount of time.


​> Why [should photosynthesis occur more readily under a hotter star]? If 
  > it's a planet that can support liquid ​water and its sun is
> brighter than ours then it must be further from it's sun than we are from
> our sun. So from that planet the disk of the sun would look more intensely
> bright than what we see from our planet but it would also look smaller, so
> the total amount of solar energy reaching the surface would be the same on
> both planets.

Yes but not all solar flux is created the same. In photosynthesis it is
the blue wavelengths in the neighborhood of 450 nm that do most of the
heavy lifting. A hotter more massive star should have it entire spectrum
shifted blueward. Thus more "high calorie" light for the plants to gobble
up. The increased vigor of plant growth should cascade up the food chain
such that even apex predators should have more offspring and thereby
evolve faster.

I admit this is no more than informed speculation. I got no proof that
Tabby's star is an ET civ. But life is pretty damn good at long shots and
I can't think of any physical phenomenon that fits the description of
"mundane but unique" better than life.

Stuart LaForge