In the fourth installment of my “Top arXiv papers of the week” column you can read about quantum foam, whether GW190425 is the first neutron star-black hole merger ever detected, the H0 tension and strong lensing time delays, how to efficiently parametrize the spacetime around black holes, and finally whether microlensing of quasars might point towards primordial black holes. Also, I will at least try to come up with a nice name for this blog before next week’s column!