Perhaps it's actually Von-Neumann probes, or unmanned craft collecting data and observing. I would find this much more likely, but even still, why would they need to keep traveling on earth?

Personally, I keep an open mind about everything, regarding what is possible. I just imagine some civilization thousands or millions of years ahead of us could do things that would seem like magic. It certainly seems plausible in terms of the fermi paradox that we would be being visited. It's just incredibly odd that it would happen this way, and I have very basic questions as to the nature of what this phenomenon even is.