Well, if you want to get technical, the major problem with this theory is that MACHOs are not a good candidate for dark matter: https://en.wikipedia.org/wiki/Ma

Well, if you want to get technical, the major problem with this theory is that MACHOs are not a good candidate for dark matter: https://en.wikipedia.org/wiki/Massive_compact_halo_object#Theoretical_considerations https://en.wikipedia.org/wiki/Massive_compact_halo_object#Th... Even if you imagine they were all hiding, their previous effects on the universe are missing.