We know how we are handling space exploration. We send robot probes. So once you get good at space travel. You set up automated factories on an asteroid and just churn out probes. Scattering them all over the universe looking for radio waves, nuclear explosion and polluted planets.
Imagine what it must have looked like to the swarms of interstellar probe cruising between the stars, when we detonated Ivy Mike or when the Russians detonated the Tsar Bomba. They would all come running like moths to a flame.
https://en.wikipedia.org/wiki/Ivy_Mike
https://en.wikipedia.org/wiki/Tsar_Bomba
I feel I should point out that the civilizations who did this are probably long dead or just don't care what the probes found. After thousands of years they are gone or have moved on. The probes are just on auto pilot.
I've never looked at the stats but I've always understood that UFO sightings increased "dramatically" after WWII. So the porch light in that case may have been the extensive explosions.
Sightings really spiked in the 70s, there were lots of reports of strange triangle shaped spaceships that looked like nothing of this world. Many sightings were near UFO activity hotspots, like area 51, or Roswell New Mexico.
Then in the early 80s, the F-117 officially entered service.
Most UFO sightings are totally mundane objects and people not having any idea what they're looking at. The rest are legitimately strange aircraft, because they're cutting edge military projects (not aliens).
I may be off on when the sightings increased and therefore hurt my question. Then again we don't know how long between observation and investigation it would take them.
As far as cutting edge military, I find it impossible to believe that the astounding physics required to validate those reports would not already be in use in todays world, if true.