Astronomers discover dark matter 'bridge' linking colliding galaxies: 'This is the missing piece we've been looking for.' / Ancient cosmic collisions may have birthed the universe's most monstrous galaxies / Gruesome clash of galaxies give terrifying glimpse into how earth could die / 2-million-mile-per-hour galactic crash reawakens a dangerous 'cosmic crossroads' / Webb Telescope provides another look into galactic collisions