That flag is cool, but here's an alternative that uses some of the same ideas. 

The black background represents the vastness of space, and its current emptiness. The blue dot represents our fragile home. The ratio of their sizes represents the importance of our cosmic potential (larger version here).

It's also a reference to Carl Sagan's Pale Blue Dot - a photo taken of Earth, from a spacecraft that is now further from Earth than any other human-made object, and that was the first to leave our solar system.

Sagan wrote this famous passage about the image:

Look again at that dot. That's here. That's home. That's us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every "superstar," every "supreme leader," every saint and sinner in the history of our species lived there-on a mote of dust suspended in a sunbeam.

The Earth is a very small stage in a vast cosmic arena. Think of the endless cruelties visited by the inhabitants of one corner of this pixel on the scarcely distinguishable inhabitants of some other corner, how frequent their misunderstandings, how eager they are to kill one another, how fervent their hatreds. Think of the rivers of blood spilled by all those generals and emperors so that, in glory and triumph, they could become the momentary masters of a fraction of a dot.

Our posturings, our imagined self-importance, the delusion that we have some privileged position in the Universe, are challenged by this point of pale light. Our planet is a lonely speck in the great enveloping cosmic dark. In our obscurity, in all this vastness, there is no hint that help will come from elsewhere to save us from ourselves.

The Earth is the only world known so far to harbor life. There is nowhere else, at least in the near future, to which our species could migrate. Visit, yes. Settle, not yet. Like it or not, for the moment the Earth is where we make our stand.

It has been said that astronomy is a humbling and character-building experience. There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it underscores our responsibility to deal more kindly with one another, and to preserve and cherish the pale blue dot, the only home we've ever known.

I think this is a fun idea and want to reward that. I also support the project of trying to come up with longtermist images and symbols. The EA lightbulb logo has been very powerful, it would be good to find similar things for longtermism. (Though I'm less sure about flags in particular, which feel very political.)

Unfortunately, I don't like this particular instantiation at all, and would be pretty sad if it became more widely used. I think I would be some nontrivial % less likely to want to hang out in longtermist spaces if they used this flag.

I'm hesitant to whale on this here since it's clearly to some extent a fun personal project. Also, design is hard and I'm not convinced I could do better. But I do also think it's important to give feedback in case anyone does decide to take this project forward more seriously. Sorry Cullen.

In my opinion:

• The colour scheme is jarring and IMO ugly. There are also a lot of colours for a flag.
• I don't like the sun aesthetically (I also don't like it on Malawi's flag). I also don't think we should be including symbols that are very distinctive to particular countries.
• In general the design doesn't give me good vibes. It doesn't make me feel excited or at home. (I acknowledge that it's going to be very hard to design a flag that does well on that last point for everyone, but this is my feeling.)

I think if the utilitarian flag were a national flag it would be in my top 15% favourite national flags,  while this would be in the bottom 30%. 

In general I think homages and symbolism should come a firm second after aesthetics in flag design. You can generally make any colour or pattern stand for anything you want, so it's not very constraining. But to be honest I'm pretty sceptical about loading a flag down with loads of symbolism and double meanings, as opposed to just trying to embody one or two big things.

Upvoted. 

While I didn't like the initial design for various reasons others have stated, I think the ensuing discussion has been really fun, and this is the kind of content I'd like to see more of on several levels (covers art/design, aims to bring community together, is light and playful). Given its overall impact, I'm very glad the post was published.

Personally, I like the symbolisms and explanations for the flag, but I like the aesthetic appeal and simplicity of the utilitarian flag a lot more.

I have two somewhat nitpicky comments on the aesthetics:

1. Some people might not understand that what's on the flag is a sun (without seeing the explanation). It looks like a red, Chinese fan to me. The sun could be made to look simpler and more like a sun, i.e. fewer rays and being a circle instead of a semicircle.
2. It's hard for me to like or get used to these colors, but I think the symbolism behind them means they should stay as is.

Nevertheless, even if the two aesthetic comments I said above aren't done, I think this is good enough!

Continuing to play with the space, light cone, time, warning light, and blue dot elements, here's another. I'm not trying to symbolize longtermism specifically here, but I do think this arrangement fits something present.  

Colors

I like the thinking behind the color choices in the original, so I tried to do that too.

- Eigengrau instead of black: Eigengrau is the almost-black color humans see when we close our eyes in darkness, darkness as perceived by human vision. It's black with visual artifacts of uncountably many points of light. It rhymes with how we see space, and represents the eyes-closed opposite of enlightenment.

- pale yellow instead of white: stark white feels lifeless/barren/rhetorical, while sunlight is a human universal. Technically that color would be rather more blue, but I didn't want 3:1 in cold's favor, and our experience of sunlight is "warm".

- global blue : I like ocean blue, but global blue is traditional and recognizable.

- almost-red shocking pink: this color was tricky and unsatisfying. True traditional red is associated with the vigorous bloodshed of war. Amber felt slower, like plasma seepage and electronic running lights. But comparing them side by side, this weird in-between color feels more right. I don't know from whence it comes and it's troubling me, and that feeling seemed to fit, so I went with the red-pink. And disagreeing about whether this particular shade is red or pink would be the kind of moving-concepts-around time-wasting disagreement that so often distracts resources from problem-solving.

Shapes

Four-pointed star: a focus, or flaw that draws focus
- orienting star 
(compass star, North star, Star of Bethlehem, LessWrong, Alcor, Quaker star)
- how stars or points of light appear to us, for reasons I'm not competent to explain 
- Once I saw the bright "shadows" created by bubbles on the surface of water concentrating sunlight on the stone below, and at a certain depth the anti-shadows looked like curved four-pointed stars. 
- the shape of a wound created by an X-shaped cut

Semicircle: the known world
- as a sphere: planet, sphere of influence
- as a hemispherical bubble: habitat, growth, celestial heavens of antiquity
- as an arc: arc of history/narrative, rise and fall

Arrangement/assembly/explication

The darkness is unknown. Can contain risk, ignorance, space, void, death, etc. as you like.

Enlightenment is a growing buffer between the world and the unknown. Can contain hope, mercy, knowledge, skill, empathy, consciousness, energy etc. as you like.

Darkness holds three corners, and light one. However, darkness holds less than half the area.

The expansion of hope/mercy/enlightenment has both a linear and a non-linear growth aspect.

This star/wound/pain/warning/flaw connects the three, or is in all three. It sometimes obscures what's going on between the other three. It's the central focus. It's in the middle of everything.

From left to right, there's a progression in time from the beginning in void to the post-world end where enlightenment dominates, yet cannot eliminate the unknown.

Does the story arc get interrupted, or obscured? 
And is this burst of pain an event in time, or a constant element? 
Is the wound in the middle opening or closing? 
Does pain orient or distract?

Reflection

In retrospect, I may be guilty of being quite influenced by other brands I like. I was not consciously thinking of these when I was working on this design, so I'm not sure how much is my fault and how much is convergence/overlap. 
- Black triangle on top-left, yellow on the right: I have previously considered myself anarcho-capitalist. 
- red and black Quaker star: I don't know what the Quaker star symbolizes, but I like the connotations of humility, principles, service, and insistence on a kinder future. I don't "identify" as anything religious, but I occasionally attend the local Friends' Meeting.

The result also reminds me of Jordan Peterson's work: in a world made of chaos, order, suffering, and matter, one needs a negative motivation, a positive motivation, a foundation to stand on, and a direction in which to go. "Life is suffering," but what you do about that is up to you.

Made using Amadine. An editable SVG version is here in case you want to build on it further.

Here's the link to the SVG. I don't think you should have to pay for an SVG. I downloaded the JPG and put it through vectorizer.io. 

https://www.dropbox.com/s/4fvviw1s3yveeri/Longtermist-Flag.svg?dl=0

And here's a TED talk I really enjoyed about flag design: https://www.ted.com/talks/roman_mars_why_city_flags_may_be_the_worst_designed_thing_you_ve_never_noticed

Very late to this thread, but here's a design for a longtermist flag:

The ring of seven 7-pointed stars represents the seven classical planets, from which the seven days of the week are derived. This in turn represents the vastness of time and space. The dark blue field represents the vastness of outer space.