The Great Filter

We know now that our galaxy is filled with rocky planets, a percentage of which will almost certainly fall within the category of ‘earth-like’.  (100 billion stars mean even a 1:1000000 chance allows for 100 000 earth-like planets).  If we ever do find evidence of microscopic life on Mars the odds will go way up as well – meaning that life is much more likely to exist elsewhere.   And yet, we see no evidence of extraterrestrial life in our observations of the galaxy, a fact known as the ‘Great Silence’.

There could be many explanations for this phenomenon.  A short and not at all comprehensive list includes:

  1. We are leading the development curve.  Other life has not yet reached or surpassed our current development level, and those who have are so far away the evidence still has not arrived (1000 light years is really far away).  This theory makes the assumption that humans are outliers, which is always possible but statistically less likely.
  2. We are well behind the development curve, and would not recognize evidence of extraterrestrials because we haven’t developed far enough yet.  Just as an Amazon tribesman might not grasp the significance of a Predator drone at 20,000 feet, we might not recognize or understand what we are looking at.  For a long time we assumed that radio transmissions would be evidence of life, but would a 1970s SETI researcher have recognized a typical WiFi or cell phone transmission as evidence of sentience, or merely dismissed it as noise? Even if an ET civilization did have recognizable transmissions at some point, it wouldn’t have been obvious to anyone on Earth until the middle of the last century.  It is possible that ETs developed beyond us while we were bashing away at each other with clubs or muskets.  The thought that irrefutable evidence of ETs might have been readily available in the form of recognizable radio transmissions during the Spanish Inquisition makes me chuckle for some reason.
  3. Life is harder than we think.  Just because it happened here doesn’t mean that it is easy.  Perhaps the places where it might happen number in the dozens.  Add in some random elements like planet killing asteroids, and we have a quiet galaxy.
  4. The Great Filter.  The notion that some point in the development of a civilization is very hard to overcome, and that most species do not actually succeed.  If this filter is in the past, something like the development of language or writing, then we may be outliers leading the pack.  If it is in the future, like developing into a star-faring civilization before we destroy our own planet, then we might be in trouble.  We certainly aren’t doing well at planet management so far, it isn’t hard to imagine humans entering a downward spiral long before leaving the solar system.

Whatever the situation, our current rush of exoplanet discoveries and the dawn of private space travel make me hopeful that humans will be able to explore at least our own solar system, with an eye to exploring further in some capacity (biological or not).  Meanwhile we should really be trying to find ways to avert civilization killing catastrophes like war and climate collapse.


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Can we go to Alpha Centauri?

Alpha Centauri

This artist’s impression made available by the European Southern Observatory on Tuesday, shows a planet, right, orbiting the star Alpha Centauri B, center, a member of the triple star system that is the closest to Earth. Alpha Centauri A is at left. The Earth’s Sun is visible at upper right. Searching across the galaxy for interesting alien worlds, scientists made a surprising discovery: a planet remarkably similar to Earth in a solar system right next door. Other Earth-like planets have been found before, but this one is far closer than previous discoveries. Unfortunately, the planet is way too hot for life, and it’s still 25 trillion miles away. (AP/ESO, L. Calcada)

The recent confirmation of a planet circling our nearest stellar neighbour is nothing short of thrilling.  Sure, it isn’t habitable, circling Alpha Centauri B in something like 3.2 days, but the fact it exists at all is a major breakthrough.  If we can find a few more planets over there, we might seriously start thinking about actual space exploration.  Kudos to the European Southern Observatory team for making the discovery, and having the scientific self-discipline to spend three years confirming it before the announcement.

So, what are the realistic considerations of a potential interstellar mission?  In my opinion, the barriers are enough that we won’t be doing it for a very long time, if at all – barring some black swan scientific discovery like a warp drive or other FTL technology.  No doubt we have much to learn about physics and the universe, but we cannot assume that future scientific discoveries will help us indulge our urge to explore.


One of the biggest barrier to such travel is time.  If it takes 100 years to reach another star, nobody is going to want to go.  And if we might find nothing of worth and have to set off somewhere else, the incentive is too small to bother, especially assuming a significant cost in energy and resources to send a viable ship that far and for that long.

So, how can we address the time barrier?  Nobody wants to live our their lives (and the lives of the next 40 generations) in a spaceship – there haven’t been many human societies that have lasted anywhere near that long.  But what if a human lifespan was dramatically longer, even functionally immortal?  It seems unlikely now, but no more so than warp drives and wormholes.  In fact, we spend significantly more resources and energy studying health than we do on space.

A thousand-year old person, or a person who might live for 10,000 years, might be much more willing to undertake an interstellar voyage.  It is hard to know what humans would be like if they had lifespans on that scale, but I imagine patience would be much more common.  Some people would no doubt appreciate an opportunity to spend a few centuries working on something that interests them.  Maybe they could finally finish the Harry Potter novels, or read those impenetrable Tolkein books that aren’t LOTR.


The other big barrier to interstellar travel is cost.  Not in dollars but in resources and energy.  It will take a lot of energy to send even a tiny ship to another star, and a lot of resources to support even a tiny crew for thousands of years.  And the more resources needed, the more energy as well, a vicious cycle that could well make interstellar travel impossible.

However, there are some resources that weigh nothing, like technical and scientific knowledge.  Far better to send a few small machines capable of making anything on arrival as needed than to try to send everything in advance.  Similarly, it would be a lot easier to send some raw materials for the manufacture of humans on arrival (i.e. genetic material and the means to grow and educate people when they get there).  Trying to send actual grown humans might be impossible and absurdly expensive, but sending a tiny ship with all it need to build on arrival might actually be viable.

Of course, we don’t have the scientific knowledge to build a person from scratch right now, but we much closer than we are to an FTL drive (if such a thing is possible).  It may be that humans who arrive at another star will be born of that star, and any further exploration would be similarly done by their descendents.  Von Neumann Machines, but organic.

All of this is a long way off, barring the black swan event that changes everything.  (My personal favourite would be friendly contact from somewhere else once we reach a certain level of development).  Nonetheless, the discovery of planets in the neighbourhood makes me optimistic that someday, someone will go for a closer look.



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