Show potential detection ranges.
 Show detectable only.

Viewport:	0,0 0x0
Zoom Factor:	0:1
1 pixel on screen:	~0 ly ~0 pc
Closest civilization to Sol:	0 ly 0 pc
Age of closest civilization:	0y
Detectable Civilizations:
Cursor Position:	0 , 0
Galactic Longitude:	0°
Distance To Sol:	0 ly 0 pc

Where:	Estimate:
R* = the average rate of star formation per year in our galaxy
fp = the fraction of those stars that have planets
ne = the average number of planets that can potentially support life per star that has planets
fl = the fraction of the above that actually go on to develop life at some point
fi = the fraction of the above that actually go on to develop intelligent life
fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space
L = the length of time for which such civilizations release detectable signals into space
N =

Welcome to the Galactic Population Simulator!

• The What?

  The Galactic Population Simulator: a way to visualise the galaxy's estimated population

  In 1961, a nerd god named Frank Drake came up with the Drake Equation: a mathematical equation to figure out how many detectable civilizations exist in a galaxy. The equation is simple, but involves many factors, most of which are not known accurately or are totally unknown.

  This means that we can only put in estimates for several factors, and depending on the estimates you put in, you come up with wildly varying results, ranging from 'zero civilizations (just us!)' to 'hundreds of thousands'. The original figures Drake plugged in ranged from 20 to 50,000. Modern estimates tend to range between 0 and 10,000.

  Click to Show the Equation

  The equation is:

  N = R^* × f_p × n_e × f_l × f_i × f_c × L 

  Where:

  • R^* = the average rate of star formation per year in our galaxy
  • f_p = the fraction of those stars that have planets
  • n_e = the average number of planets that can potentially support life per star that has planets
  • f_l = the fraction of the above that actually go on to develop life at some point
  • f_i = the fraction of the above that actually go on to develop intelligent life
  • f_c = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space
  • L = the length of time for which such civilizations release detectable signals into space
  • N = The result: the total number of detectable civilizations in the galaxy today.

  With this in mind, This project has a few goals:

  • To examine the probability of extraterrestrial contact

    An estimate of 10,000 technological civilizations might sound like a lot, but is it really??

    The Galaxy is a big place: current figures indicate that it's about 100,000 light-years across and 1000 light-years thick. It contains more than 100 billion stars, perhaps as many as 400 billion. Recent data from Kepler indicates that the milky way has at least 100 billion planets, and up to 40 billion of them may be earth-like (i.e with liquid water).

    The nearest star, Proxima Centauri, is 4.2 light-years away. According to the theory of relativity, the speed of light is a universal speed limit. This means that if we send a message to Centauri, it will take more than four years to arrive. Similarly, it would take tens of thousands of years for any message to reach the every point the galaxy.

    One of the terms of the drake equation is "the length of time for which such civilizations release detectable signals into space". Given the size of the galaxy, we need to take this into account when we estimate the probability of extraterrestrial contact: If the nearest civilization is 1000 light-years away, but the average civilization only exists for a few hundred years, then we're not likely to make contact with them.

    To this end, the simulator also gives each generated civilization a random age between 0 and the provided L term of the drake equation, and indicates how many civilizations are detectable based on age and distance. Note that 'age' represents the length of time that the civilization has been detectable, not the actual age of the civilization.

    There's also an option to show the possible detection ranges for each civilization. This will be represented by a yellow circle surrounding each civilization. Note that Earth's civilization is young, so Sol's circle is invisible even at the highest zoom level.

    A galaxy with 10,000 civilizations is not all that densely populated: according to the simulations, the nearest civilization is likely to be anywhere between 100 and 1000 light-years away in this scenario.

    The SETI program has been running for a few decades. One of the goals Of the Galactic Population Simulator is to show that this effort is likely going to be a multi-lifetime project which should run for as long as possible and deserves continuing funding despite decades of no results.

  • To "give meaning to the numbers"

    To provide a way to visualise the implications of the wildly varying estimates the drake equation provides: it provides a way to see the relative population density of the galaxy given a number of civilizations output by the drake equation.

    To provide a way to visualise the size of the galaxy - it's a big place! even at the maximum zoom level, 1 pixel will be more than 20 light-years! Remember that there are hundreds of billions of galaxies in the universe!

  • To hone my skillz

    My js-foo is strong, but I hadn't done much with the canvas or with large datasets in javascript before. This is an exercise in learning the canvas model and optimization tricks for dealing with a relatively heavy load. Rendering is not as fast as I'd like, but panning should be smooth. I'll be making refinements.

  TL;DR: The Galactic Population Simulator takes a picture of our galaxy and draws N civilizations (mostly) randomly, with the location of the Sun (Sol) and earth highlighted.

• OK, so how do I use it?

It provides panning and zooming, so you can get a closer look at the simulation. This works somewhat like Google Maps: you can drag with your mouse and use the wheel to zoom. There are also pan/zoom buttons in the control bar to the right of the simulation.

The controls on the right also allow you choose presets or put your own numbers into the drake equation, changing the number of civilizations. You can also see statistics for the simulation and the point in the galaxy your mouse is pointing at.

There is a mode which allows you to run multiple simulations for the current drake equation, and see statistics over many runs. To use this, press the '...' button after choosing your terms for the drake equation, then enter the desired number of simulations and press 'go'.

Important Note: There are no limits in place on the simulator - you can plug in ridiculously large numbers and it will valiantly attempt to generate thirty million civilizations, or do ten billion iterations. If you plug in large numbers, expect it to be slow, and maybe to even crash your browser. Soft-limit numbers: ~100,000 civilizations, ~1000 iterations.

Also note that the Galactic Population Simulator is a work in progress and some things might not work quite right! If you're having trouble, feel free to email me at antisol (at) antisol (dot) org.

• I want to know more! What are your assumptions and how does it work?

  Obviously, This isn't a scientific model of a real place: there are several incorrect assumptions being made for the sake of simplicity. This is a toy, not a proper scientific investigation. The idea is that you'll press "simulate" a few times, and compare the 'closest civilization to Sol' figures. In scientific terms, it uses a very simple model, but I have tried to make reasonable and fairly conservative assumptions:

  • Perhaps the biggest margin for error is the fact that I have ignored the galaxy's "depth" when calculating distances: all calculations are two-dimensional rather than three-dimensional. This means that distances displayed will be somewhat shorter than actual distances in a three-dimensional galaxy, however given that the galaxy's 'depth' is only about 1% of it's width and height, this margin for error should always remain less than 1%.
  • Another big assumption this model makes is that once a civilization starts being detectable, they continue to be detectable for the rest of their lifetime. This is not necessarily true - civilizations might start using new technology which is not detectable from space. For example, Earth is less detectable today than we were a few decades ago, as we are (generally speaking) using far lower-power and more-directed radio signals than we used to, and large numbers of people have also switched to cable TV (which does not emit radio signals at all).
  • I'm not taking dead civilizations into account. Some of these might be detectable as their signals propagate into space after they're gone. These civilizations would have a hollow circle for their detection area.
  • We're placing civilizations randomly on a galaxy image. That means that we're not dealing with actual star chart data. The simulator may e.g suggest that a civilization is 4.9 light years away, even though there is no star at that distance.
  • The randomizer will not generate any civilizations closer than 4.2 light years, since there are no stars within that distance.
  • I've made an assumption that 4120 pixels in the original (large) galaxy image is 100,000 light-years, and made my distance calculations based on that scale. This is wrong, since I've done it by eye, but it's close enough for my purposes.
  • I have assumed that a civilization can't live without a star, so my randomizing algorithm requires a certain level of brightness in the image to be able to place a civilization at a given point. This means that civilizations will appear 'on the galaxy', not out in empty space at the corners. This fails to take into account the possibility of a civilization emerging on a rogue planet or in orbit of a brown dwarf. It seems that the general consensus at this time is that neither is likely.
  • I have assumed that the televised opening ceremony of the 1936 olympics was the first broadcast strong enough to reach space, thus when I calculate humanity's "age", I use 1936 as the starting year for our detectability (our "age" is the current year minus 1936). An Alternate year may be 1895, when radio was invented, which would add ~40 years to our 'age' and ~80ly to the diameter of our "detection zone".
  • I've provided a mode, on by default, that assumes that the galactic core is hostile to life, and excludes that area from the simulation.
  • Apart from the above, I've assumed that any part of the galaxy is as habitable as any other. This may not be the case.
  • I've assumed that "einstein is right" - that what we currently know about the universe is correct, and that the speed of light is indeed a universal speed limit: I'm discounting the possibility of godlike aliens with wormhole technology showing up on the white-house lawn tomorrow. The probability of that happening is a separate exercise.
  • We don't have a complete map of the Milky Way, and there's even been some debate as to how many spiral arms there are. It's particularly hard to get data about the other side of the galaxy because the galactic core is in the way. This image of the galaxy is an artists conception, taken from NASA, which attempts to be fairly close to current scientific knowledge. The location of Sol is also approximate.
  • I have not taken into account any of the practical considerations of actually detecting extraterrestrial civilizations, e.g signals get weaker the further away a civilization is, other things (like the galactic core) might be in the way and make detection even more difficult, and of course we would need to have a radio telescope pointed at the correct patch of sky at the correct time.
  • This model assumes that a civilization which develops radio will keep using it. It does not take into account the possibility that some other technology may replace it once a civilization has been around for long enough. It could be that on average a civilization only emits radio for a relatively short time (say, 100-200 years). If this is the case, detecting these civilizations becomes much more difficult.

• j0o Ar3 Teh Aw3s0m3! I want to give you money!

• j0o Ar3 Teh Sto0P1d! I want to ask question / challenge an assumption!

  • email antisol (at) antisol (dot) org

• It broke my computer! I'm going to sue you!

  • No responsibility is taken for computers, people, psyches, extraterrestrial civilizations, galaxies, space-time continuums, furry animals, or anything else damaged by using this page. By viewing this page, you have agreed that nothing bad that happens is my fault.