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The Grabby Aliens Model

This visualization implements the model from Hanson, Martin, McCarter & Paulson (2021), which offers an explanation for the Fermi Paradox.

The Hard Steps Model

Life's origin required passing through n "hard steps" — extremely unlikely evolutionary transitions.

If each step has a very low probability per unit time, then the time t for a civilization to emerge follows a power law:

t = u1/(n+1) · Tmax where u ~ Uniform(0,1)

Grabby Expansion

Once a civilization becomes "grabby" it expands at ~50% of lightspeed, claiming territory:

v ≈ 0.5c

Territories expand until they meet. The boundary between two civilizations forms where their expanding wavefronts collide.

The Simulation

This implements the algorithm from Paulson's simulation code:

1. Generate N candidates with t = u1/(n+1)
2. Sort by emergence time
3. Prune candidates reached by earlier civs
4. Territories expand and tessellate space

Scale: 1 unit = 1 billion light years. Observable universe ~100 Gly across.

Paper: arXiv:2102.01522

Civilizations emerge after n evolutionary "hard steps." More steps means later, rarer emergence.

"Grabby" civs expand at ~50% lightspeed, claiming territory until they meet neighbors.

Hanson et al. 2021

Earth
Other civilizations
Contact with Earth
Civilizations: 0
Volume claimed: 0%
Not yet expanding
10 Gly
Hard steps (n) 6
Time