I mean a primordial black hole with the size of a tennis ball would have 5 to 15 earth masses. It would not be invisible, but at that size it would be invisible to us even if it was in our solar vicinity.
If primordial black holes are things that exist, one could reason that they might be an explaination for masses we cannot see maybe?
It's an interesting idea. I suspect such a large population of these objects would generate enough x-rays from interactions with dust and gas that we'd be able to detect their presence. We'd also probably see micro-lensing of various observable phenomena if they were that populous. Just guesses though.
Indeed black holes and other dark stars are a reasonable option for dark matter [1], but apparently observations do not seem to match this model adequately.
[1] they are collectively called MACHOs, as opposed to WIMPs...
If primordial black holes are things that exist, one could reason that they might be an explaination for masses we cannot see maybe?