One of the biggest questions facing SETI, at least how we search now using radio, is
would an alien civilization choose to announce their presence to others using methods of
communication that require massive amounts of energy.
This is a problem for radio beacons, to be detected at a distance these have to have
some serious power behind them.
And the timing has to be right; you have to be looking at just the time when the signal
arrives.
Unless the signal is continuous and repeating, it may as well not have been sent.
Nevertheless, contact beacons are possible, so we should look for them.
But with other possible ways of detecting an alien civilization without a contact beacon
through radio, we run into problems.
A good example here would be directional radar, which can conceivably be very powerful.
Say a civilization is mapping asteroids in their system using radar, we ourselves have
done a bit of that and someone might have seen it, but because the signal is a one off
by nature and won’t repeat, no conclusions can be drawn.
Repeatability is key for determining if a signal is of alien origin and without a repeat,
we will be stuck with our current state of affairs: even if a signal appears to be of
alien origin, something like the Wow!
Signal, we can’t say so for sure without corroboration.
But, on the other hand, expensive intentional high power radio signals aren’t something
someone might put the resources into repeating, such as with our own Arecibo signal.
And then there is the question of period.
If a signal does repeat, you have no way of knowing the period of the pulses until you
actually observe it repeating.
So the signal may be detected once, but if it doesn’t repeat for, say 100 years, it
takes that long to verify it at least.
It may also be the case that we haven’t detected alien radio beacons because their
period may be far longer than we’ve been practicing SETI.
Because of these issues, it’s been suggested, increasingly so, that there may be better,
more efficient ways for aliens to communicate than radio.
This has led to a number of researchers rethinking just how aliens might be detected in recent
years.
One such addition to the growing number of alternative methods of SETI came out earlier
this month in the form a paper by Duncan Forgan, link in the description below.
This paper is interesting because it goes beyond just a simple method for communication
between alien species, but allows for a veritable intergalactic Internet to be formed.
It’s a variation on the concept of transit SETI, which is where a civilization blocks
a star’s light in an unnatural way.
The concept of building structures to block light from a star in order to announce your
presence to alien astronomers looking at planetary transits is not a new one.
It was originally advanced in a 2005 paper by Luc Arnold, link in the description below.
Also in that paper are several models of what baffles would look like in light curves, including
a triangle, but also louvered structures.
These could be made from anything, including something thin like Mylar, and might even
greatly outlast the civilization that created them, link to another Arnold paper in the
description below on that subject.
But one could also make such visual beacons into dual-use structures such as habitats,
making them less expensive.
And you could convey information with them, such as prime numbers and even data could
be sent employing something along the lines of Morse Code.
There are a lot of possibilities there.
But the Forgan paper details a second way, somewhat of a hybrid.
You could transmit your radio signal or laser pulse while your planet is in transit in front
of the star.
This would require much lower energy than a huge omnidirectional radio transmission.
It merely assumes, as does the baffle method, that astronomers in the universe will be looking
for planetary transits.
This is a reasonable assumption, since we ourselves are looking at them and have used
that method to detect hundreds of exoplanets.
But the problem with transit communications is that the planet, or megastructure, blocking
light from the host star must be aligned to the line of sight of the observer.
This is a serious issue, as most star systems are not going to be sufficiently lined up
for transits.
In fact, a majority of planets in the galaxy are undetectable right now due to the fact
that the transits aren’t lined up with earth.
Forgan took this into account in the paper and calculated that only a few civilizations
would be aligned properly at any given time.
However, given that each civilization will be aligned slightly differently, if Civilization
A sees Civilization B, Civilization B may be able to see civilizations that A cannot.
But given that A and B are in contact, B can simply relay communications between the other
two.
The idea is that ultimately, all civilizations present in a galaxy would discover each other
by relay eventually completing the galactic internet allowing everyone to communicate
by relay, and such a thing could be built within less than a million years.
A million years is not a long time in the geologic sense, the galaxy has been here for
billions of years, long enough for many advanced civilizations to have come and gone.
This opens the possibility up that the galactic transit internet could exist right now in
the Milky Way awaiting discovery by us, ultimately allowing us to connect ourselves by building
our own network of transit structures, and maybe making it easier for other civilizations
to communicate more easily if we’re aligned right.
This particular idea would represent a profound discovery even beyond the discovery of a single
alien civilization.
We would have access to information on many or most civilizations present in the galaxy.
And if the system has existed a while, say billions of years and everyone was collecting
data that whole time, we would know about civilizations that may have formerly been
present but no longer are.
Even though communications in the system would still be governed by the speed of light limit
no matter what we do, we would then by relay be able to very slowly communicate with any
civilization with a connection to the galactic transit Internet and they, in turn, may have
data, albeit outdated by nature, on most of the others, or at least ones that have been
around a while.
We could go from knowing little about intelligent life in our galaxy to knowing much of what
can be known from a data dump from an alien civilization that could take centuries, or
longer, to receive and read through.
That’s providing that we can figure out how to understand it at all, which is a subject
for a future video.
Thanks for listening!
I am futurist and science fiction author John Michael Godier and be sure to check out my
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explorations into the interesting, weird and unknown aspects of this amazing universe in
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