I don’t think his idea actually relies on intergalactic travel being difficult, just the way he stated it. If, say, intergalactic travel is easy, but not intercluster, then the idea could still apply, just at the galactic cluster level rather than at the galaxy level.
I don’t think his idea actually relies on intergalactic travel being difficult, just the way he stated it. If, say, intergalactic travel is easy, but not intercluster, then the idea could still apply, just at the galactic cluster level rather than at the galaxy level.