2022/10/02 by Andrew Gould, Gould, Andrew · 2 voices
Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics of Galaxies (astro-ph.GA) #Earth and Planetary Astrophysics (astro-ph.EP) #FOS: Physical sciences #Gamma-ray bursts and supernovae #Instrumentation and Methods for Astrophysics (astro-ph.IM) #Physics and Society (physics.soc-ph) #Popular Physics (physics.pop-ph) #Pulsars and Gravitational Waves Research #Solar and Stellar Astrophysics (astro-ph.SR) #astro-ph.EP #astro-ph.GA #astro-ph.IM #astro-ph.SR #physics.pop-ph #physics.soc-ph
paper · pdf · doi:10.48550/arxiv.2210.10622
openalex publication_date 2022/10/02 · arxiv published 2022/10/02 · arxiv updated 2022/10/02 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
I show that a gravitational slingshot using a stellar-mass black hole (BH) orbiting SgrA* could launch robotic spacecraft toward M31 at 0.1 c, a speed that is ultimately limited by the tensile strength of steel and the BH mass, here conservatively estimated as m\rm bh=5 M_\odot. The BH encounter must be accurate to \lesssim 1 km, despite the fact that the BH is dark. Navigation guided by gravitational microlensing can easily achieve this. Deceleration into M31 would rely on a similar engagement (but in reverse) with an orbiting BH near the M31 center. Similarly for a return trip, if necessary. Colonization of M31 planets on 50 Myr timescales is therefore feasible provided that reconstruction of humans, trans-humans, or androids from digital data becomes feasible in the next few Myr. The implications for Fermi's Paradox (FP) are discussed. FP is restated in a more challenging form. The possibility of intergalactic colonization on timescales much shorter than the age of Earth significantly tightens FP. It can thereby impact our approach to astrobiology on few-decade timescales. I suggest using a network of tight white-dwarf-binary "hubs" as the backbone of a 0.002 c intra-Galactic transport system, which would enable complete exploration of the Milky Way (hence full measurement of all non-zero terms in the Drake equation) on 10 Myr timescales. Such a survey would reveal the reality and/or severity of an "intergalactic imperative".