The tree
81 things that have to happen, and a test for each
The number on the home page is built from 81 events: breakthroughs, decisions, and milestones. Each one has a plain name and a written test, so that anyone can check later whether it happened, with no judgment call. If an event can't be tested that way, it doesn't get in.
- 25could be decided either way by 2031
- 3already happened
- 6deliberate long shots, kept on the board because they make the goal vivid
- 2are my own decisions, not things that happen to the world
For human industry to reach beyond Earth and Mars
four milestones, each building on the lastThe Expanse is a story. To say whether it is coming true, the project uses four milestones, from a first permanent base to millions living out there with their own economy and politics. Each milestone is a short list of events that all have to happen. The third one, Slow Expanse, is the bar the headline is counted against: human industry reaching beyond Earth and Mars.
1 Outpost
Permanent crewed presence at the Moon, Mars, or a permanently crewed station, hundreds of people, fully supplied from Earth.
Needs:
2 Settlement
Thousands living off Earth at one or more sites, partial local self-sufficiency in air, water, and food.
Needs:
- everything in Outpost
- Mass to low Earth orbit is sold for less than two hundred dollars a kilogram
- Humans can live off Earth long term, by partial gravity or by a spinning habitat
- A crew off Earth lives for a year with most of its food produced on site and its water and air recycled
- A major operation under anaesthesia is performed off Earth and the patient survives
3 Slow Expanse · the bar
Tens of thousands off Earth, including at least one site beyond the Earth-Moon system. Transit times in months. Something mined or made off Earth sold at a profit. Transit fast enough that people go out there to work. This is the bar for the headline.
Needs:
- everything in Settlement
- A site beyond the Earth-Moon system is crewed without a break for a year
- Three missions in one year reach the asteroid belt within twelve months of leaving Earth
- Something mined or made off Earth is sold at a profit
- The United States and China both recognise the same rules for owning what is mined off Earth
- A shielding system flown in space cuts the deep-space radiation dose to a crew by half
- A hundred tonnes of material dug or made on the Moon are delivered to orbit in one year
- A space traffic authority among the major powers can enforce rules on manoeuvres and launch windows
4 Full Expanse
Millions off Earth, transit times in weeks on constant-acceleration drives, children born and raised off Earth, a Belt population with its own political identity and economy.
Needs:
For me to live and work out there
four rungs, from contributing on Earth to living out there"Live and work off Earth" could mean a lot of things, so the project spells out four rungs. The headline number on the home page is the third rung: working off Earth for months at a time. The fourth, living there permanently, is reported beside it as the stretch.
1 Contributes from Earth
Works in or for the off-world industry without leaving.
Needs:
2 Has flown
At least one trip to space, suborbital or orbital, as passenger or crew.
Needs:
3 Works off Earth on rotation · the headline
Months at a time living and working at an off-world site. The headline number.
Needs:
- everything in Slow Expanse
- Holding a role whose holders go on off-Earth rotations
4 Lives off Earth
Permanent residence at an off-world site. Reported beside the headline as the stretch. Requires A2 plus a site that accepts permanent residents; the choice to stay is a future choice point, not a world event.
Needs:
- everything in Works off Earth on rotation
- An off-Earth site accepts people as permanent residents
The whole tree as one picture
every event, coloured by link, arrows from what it needsThree columns by how soon an event could be decided (within five years, within twenty, or only over a lifetime), rows grouped by link. Each box carries the event's chance by 2071, by 2095 and with no deadline, given what it depends on. Dashed boxes are my own decisions; filled boxes have already happened. It is drawn from the same tree and the same run as every number on this site, so it cannot disagree with them. Open it full size.
All 81 events, by link
the seven links from the home page, and the one beside themEvery event belongs to one of the seven links in the chain. Open a link to see its events, each with its test, its current probability, and what it depends on.
Window
That I am alive on the date in question.
8 events · 7 with a number · 1 already happened
LLaunch
That the cost of putting mass into orbit falls below the threshold that makes everything else affordable.
11 events · 11 with a number
EEnergy
That cheap, abundant power exists off Earth, from fusion or an equivalent.
11 events · 10 with a number · 1 already happened
DDrive
That propulsion puts the solar system within reach on human timescales.
8 events · 8 with a number
BBiology
That humans can live, and eventually reproduce, in partial gravity and deep-space radiation.
11 events · 11 with a number
MMotive
That there is an economic reason for large numbers of people to be out there.
5 events · 5 with a number
RRegime
That the political and legal conditions let a multi-decade build survive elections, downturns, and wars.
8 events · 8 with a number
AAccess
That I personally have a pathway in, given my training, health, and career.
14 events · 11 with a number · 1 already happened
Beside the chainContact Clause
That we meet a mind that is not ours, whether a machine that has outgrown us or something of non-human origin. The dream underneath the project, published beside the equation and never multiplied into it.
5 events · 5 with a number · never multiplied in