Our Quiet Galaxy

Part of our surviving the great filter was our galaxy having especially few collisions with other galaxies:

The Milky Way and Andromeda are siblings, … we used to think they were near-twins. .. [But] the black hole at [Andromeda's] heart is more than a hundred times as massive as ours. And while our galaxy is strewn with about 150 of the bright galactic baubles known as globular clusters, Andromeda boasts more than 400. … Whereas Andromeda is a pretty well-adjusted spiral, the Milky Way is an oddball – dimmer and quieter than all but a few per cent of its peers. That is probably because typical spirals such as Andromeda are transformed by collisions with other galaxies over their lifetimes. …

The Milky Way must have lived relatively undisturbed. Except for encounters with a few little galaxies such as the Sagittarius dwarf, which the Milky Way is slowly devouring, we wouldn’t have seen much action for 10 billion years. Perhaps that is why we are here to note the difference. More disturbed spirals would have suffered more supernova explosions and other upheavals, possibly making the Milky Way’s rare serenity especially hospitable for complex life. (more)

So alien life is more likely to be found in our galaxy than in random galaxies. More generally, the more steps in the filter that are spatially correlated like this, the more likely that if life is anywhere out there, it is especially near to us.

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  • Eric Falkenstein

    So, the Milky Way has been around for 10B years, but supposedly the heavy elements like iron that make up the Earth involve at least a couple generations of stars exploding. Then there’s heavier elements that seem to involve different processes. The models that allow this seem rather quirky. Dark energy, dark matter…I’m skeptical this is anything but rationalization, especially considering the unanimity projected for a science that doesn’t allow much empirical testing.

  • Eric Falkenstein

    I’m not saying we are thus in The Matrix, merely there’s a lot of certainty in theories that seem to just be fitting the data.

    • JenniferRM

      Wait what?

      This news is has vast and mostly positive implications. This is the kind of big picture seemingly subtle post that I read Hanson for and it cuts in the opposite direction from The Matrix. It suggests that a significant chunk of “the great filter” is behind us, because we evolved in a physically exceptional location. (Which is great!)

      The only way this supports simulationist conclusions is if you already had a lot of prior probability backing the theory that we’re being simulated by an evil-demon-like simulator that has an interest in fooling us into thinking we’re in not in a simulation by providing a very detailed and internally consistent backstory for the universe that justifies our thinking that we’re one of the first sentient species ever to evolve (which somehow doesn’t intervene in many other ways that it could, such as by directly censoring the thought in everyone’s mind), which is a extra element to add to a simulationist theory beyond simply “we’re in a simulation” and thus expensive from the perspective of occams razor.

  • Mark Plus

    So the Copernican Principle doesn’t apply to our galaxy after all? How curious.

    • Captain Oblivious

      I don’t think the Copernican principle (“there’s nothing special about our location”) is being violated per se; it’s just being overruled by the anthropic principle (“life is more common in areas more hospitable to life”).

  • Jesper Östman

    If the universe is infinite in size, as Max Tegmark seems to claim is a pretty common assumption among astronomers, then is it not very unlikely that life is *not* anywhere else but here?

    • Poelmo

      We really don’t know if the universe is infinite or not, it could also just be very large. The only way we might ever find out is if the universe is finite and we can build a ship that goes faster than the expansion of the universe near it’s edge, then that ship could take of in front of an object, keep flying for a long time and end up behind the object. Then we’d know for sure that space is finite. If the universe expands to fast near it’s edge or if it’s infinite then we would never know for sure whether the universe is infinite or not.

      But I digress, if the universe is finite it’s still very large and of course there would be more civilizations far away from us than near us. However, what Robin was pointing to was that our Milky Way galaxy may be more rich in life than most other galaxies in our “neighborhood”. So you’ll be more likely to find a civilization at 500 ly than at 3 million ly. Of course there will be other “oases” like our galaxy out there so within a sphere with a radius of 3 billion ly centered around Earth there will be more civilizations than within a sphere with a radius of 500 ly.

  • http://www.gwern.net gwern

    How much of the Great Filter does this defuse? The calculations I usually see are for within this galaxy, so this wouldn’t affect Drake equations…

  • katesisco

    I kind of think the fact that NASA gives 10 million y age to the near by nova that disrupted our local gas field, or created it, or added to it is more significant. Over there by Centauri A & B and Proxima and the Coal Sack.
    Science has said our sun may be pulled out of M something on a pass, and our planets aren’t even supposed to be Sol’s. So this is more indicative of the creation of life I think. Otherwise we would be salps swimming under the ice whose only purpose is to consume carbon and die.