Imagine for a second an alternate reality where aliens have never visited the Earth at all. What would look different? Wouldn't we still have UFO's? What's stopping people from misidentifying balloons or camera artifacts? Surely we would still get tons of claims of hard to explain stuff, right? So the difference between this world and that one doesn't actually seem that great?
Putting a lot of confidence that some of the unexplained cases actually have an extremely interesting explanation seems like a bad bet.
I guess it just all depends on what a person finds interesting or exciting. I like science. I like things that haven't been figured out. I find it interesting when we discover a large aquatic creature swimming deep in the ocean. I found the slot experiment that basically broke open the gates to quantum research extremely exciting...
In the scenario you provide, you mention that the differences wouldn't seem that great, but it makes me wonder about a few things. One, I wonder what the probability is that we have been visited, however likely it is in this reality. There may be stark differences between those two realities if, in the other, they haven't ever been visited. We used to think that water was scarce in space, and that Earth having it was an exception. What if in their reality that's true, and the the rest of the solar system has very little water? That would make deep space observations very different from what we know in our reality, as the questions they would be asking would be quite different (ie. Are we possibly the only life in the universe? Can water even exist around most types of stars? Why isn't there more water? Did water happen accidentally? lol) In their reality, life on other worlds could be extra exceedingly rare, whereas in our reality we suspect it shouldn't be that incredibly rare -- we're looking for signs of it on Mars whereas 20 years ago it may have been a near-forgone conclusion that Mars was always very dead.
If I lived in that alternate reality, I would be very interested to find out what the objects are like the one the USS Nimitz encountered. The dark blob that appeared to
roll some coal in the one video from a different encounter has me very intrigued also -- what kind of boulder shoots through the air with its own propulsion? We've had opportunities to study metals and minerals from similar objects as these to try and determine whether they are terrestrial, ya know? I've read some great interviews and analysis on sites like Buzzfeed and such (mainstream), and the answers are nevertheless fascinating. They do seem to be terrestrial but they're not ordinary (that's the best way I can put it). So what were the objects? It's still a complete mystery. What can make a hunk of mineral do the things we're seeing? It's puzzling. Maybe it's not aliens. Maybe it's octopi. Maybe we'll learn there's huge cities of tentacle beings at the bottom of our oceans, and maybe these things are
their planes. They may be very interested to figure out a means of
first contact with us.
Or, maybe there's some sort of atmospheric charge that can send boulders flying into the atmosphere and hold them there, like electro-magnetic atmospheric anomolies, and while boulders are caught in this strange phase there's a state that enables them to zip as if they were pure energy (think lightning zipping and zapping in all manner of directions).
All of this excites me because it
means something. It can have practical application if we can figure it out. It doesn't have to be aliens to be very, very exciting stuff!
I'm such a nerd...
EDIT: One last thought... as it pertains to aliens, I have always been on the fence on whether I really want there to be aliens visiting us. The consequences of such a reality can be very jarring. It's not just about human society and longstanding cultural things such as religion, but it's also about concepts such as sovereignty, free will, and aspects of self-governing. If these craft do belong to aliens, what if we find out that they have occupied the rest of our solar system for resource harvesting? What if suddenly we have to get permission from them to do anything in space beyond basic exploration? We could find ourselves boxed in at the start of a massive 4x space strategy scenario. lol
Just understand that there can be consequences to the reality of aliens being here. They never really explain how it is that the aliens in Star Trek just kind of let the humans take the lead with the Federation, or the proposition is that we all learned warp travel at roughly the same time. We're on the brink of being a primitive culture discovered by someone who could be the Federation or they could be the Klingons or Romulans, or even the Cardasians. It can suck major butthole to be found by the wrong people.