Tag: seti

Great Filter Day

Assume that since none of the ~10^20 planets we see has yet given rise to a visible expanding civilization, each planet has a less than one in 10^20 chance of doing so. If so, what fraction of this 10^20 filter do you estimate still lies ahead of us? If that fraction were only 1/365, then we face at least a 12% chance of disaster. Which should be enough to scare you. To make sure we take the time to periodically remember this key somber fact, I propose that today, the day before winter solstice, the darkest day of the year, be Filter Day.

400b rogue planets

Japanese astronomers claim to have found free-floating “planets” which do not seem to orbit a star. They say they have found 10 Jupiter-sized objects which they could not connect to any solar system. They also believe such objects could be as common as stars are throughout the Milky Way. Using a technique called gravitational microlensing, they detected 10 Jupiter-mass planets wandering far from light-giving stars. Then they estimated the total number of such rogue planets, based on detection efficiency, microlensing-event probability and the relative rate of lensing caused by stars or planets. They concluded that there could be as many as 400b of these wandering planets, far outnumbering main-sequence stars such as our Sun

with this, my personal estimate for the drake equation goes to 8000.

Looking at the Kepler K2 data, the scientists documented 10s of short-duration microlensing events near the galactic core. Of these, 22 were previously detected during the OGLE and KMTnet ground-based campaigns, but 5 signatures hadn’t been seen before. Of these 5, 1 turned out to be a bound exoplanet, but the remaining 4 featured super-short microlensing events consistent with free-floating planets. 1 of the 4 candidate signatures was subsequently detected in ground-based data. The microlensing events, lasting for just several hours, suggest the discovery of unbound exoplanets no larger than Earth. It’s impossible to know what the conditions are like on these presumed rogue exoplanets, but they could be “cold, icy wastelands,” and, if similar in size to Earth, their surfaces would “closely resemble bodies in the outer Solar System, like Pluto.” The new paper suggests the presence of a large population of Earth-sized rogue planets in the Milky Way. It’s becoming clear that free-floating planets are common.

Interstellar Predation

It is often suggested that extraterrestial life sufficiently advanced to be capable of interstellar travel or communication must be rare, since otherwise we would have seen evidence of it by now. This in turn is sometimes taken as indirect evidence for the improbability of life evolving at all in our universe. A couple of other possibilities seem worth considering. One is that life capable of evidencing itself on interstellar scales has evolved in many places but that evolutionary selection, acting on a cosmic scale, tends to extinguish species which conspicuously advertise themselves and their habitats. The other is that — whatever the true situation — intelligent species might reasonably worry about the possible dangers of self-advertisement and hence incline towards discretion. These possibilities are discussed here, and some counter-arguments and complicating factors are also considered.

advertising our existence might be a suicidal mistake

Fermi Solutions

An enumeration of possible solutions to fermi’s paradox.

  • Aliens exist, but we see no evidence
    • Human limitations
      • Human beings have not been searching long enough (Freitas Jr 1983; Freitas Jr. 1985)
      • Human beings are not listening properly
    • Practical limitations
      • Communication is impossible due to problems of scale
      • Intelligent civilizations are too far apart in space or time (Wesson 1990)
      • Communication is impossible for technical reasons
      • They only recently emerged and have not yet had the time to become visible. This could for example be due to synchronization due to a declining rate of gamma ray bursts that sterilize much of the galaxy (Annis 1999; Cirkovic 2004).
      • Civilizations only broadcast detectable radio signals for a brief period of time before moving on to other media.
      • It is too expensive to spread physically throughout the galaxy (Landis 1998)
    • Alien nature
      • They are too alien to be recognized
      • They are non-technological and cannot be detected except by visiting them.
      • They tend to experience a technological singularity becoming unfathomable and invisible.
      • They develop into very fast, information-dense states that have no reason to interact with humans (Smart 2002; Cirkovic and Bradbury 2006)
      • They migrate away from the galactic disk for cooling reasons (Cirkovic and Bradbury 2006)
      • They tend to (d)evolve to a post-intelligent state (Schroeder 2002)
      • They choose not to interact with us
    • They are here unobserved
      • Earth is purposely isolated (The Zoo or “Interdict” hypothesis) (Ball 1973; Fogg 1987)
      • Earth (and nearby parts of space) are simulated (Baxter 2001; Bostrom 2003).
      • They secretly deal with the government or other groups.
  • No other civilizations currently exist
    • We are the lucky first civilization
    • Intelligent, technological life is exceedingly rare
      • Rare earth hypothesis
      • Life is very rare (Wesson 1990)
      • Intelligence is very rare
    • Intelligent, technological life is very short-lived
      • Intelligent life is wiped out by external disasters at a high rate
      • Technological intelligent life exhaust its resources and dies out or becomes nontechnological
      • It is the nature of intelligent life to destroy itself.
      • It is the nature of intelligent life to destroy others.

Neutrino Communication

Jolting the star with neutrinos could advance the pulsation by causing it to heat up and expand. Information could thus be shuttled around our galaxy’s network of 500 or so Cepheids – and out as far as the Virgo cluster of galaxies.

does this mean we’ll finally have internet in the subway?

Beams of neutrinos have been proposed as a vehicle for communications under unusual circumstances, such as direct point-to-point global communication, communication with submarines, secure communications and interstellar communication. We report on the performance of a low-rate communications link established using the NuMI beam line and the MINERvA detector at Fermilab. The link achieved a decoded data rate of 0.1 bits/sec with a bit error rate of 1% over a distance of 1.035 km, including 240 m of earth.

To make use of neutrinos an advanced civilization can use a gravitational lens as a focus and amplifier. The lens can be a neutron star or a black hole. Using wave optics one can calculate the advantage of gravitational lensing for amplification of a beam and along the optical axis it is exceptionally large. Even though the amplification is very large the diameter of the beam is quite small, less that 1 cm. This implies that a large constellation of neutrino transmitters would have to enclose the local neutron star or black hole to cover the sky. This means that such a beacon would have to be built by a Kardashev Type II civilization.