von Neumann probe

A sudden increase of UFO sightings during and after second world war

According to COMETA report, reliable UFO sightings began 1944 COMETA report (pdf page 22). I'm not sure if 1944 is the exact year or not but I must admit there seems to be very few notable UFO sightings in the 10's, in the 20's and in the 30's.

Then, suddenly, there was a foo fighter phenomena.

"These sightings were the cause of much concern to the Allied authorities" COMETA report (pdf page 46)

In those days military aviators started to see strange flying objects (at least) over Europe. Apparently both allied and axis considered it a possible secret weapon of the enemy.

There are many things that make these sightings interestning. They were reported by experienced military pilots, who (over Germany) definetly have better things to do than play pranks. This phenomena seemed

After foo fighters there were ghost rockets. And green fireballs. And so on. We must ask: could there be something that explains this sudden wave of sightnings?

V2 rockets: the human race enters the space age

V2 rockets were first human-made spaceborne objects

What this has to do with von Neumann probes

Let us assume that extraterrestial von Neumann probes have entered the vicinity of the Earth sometime in the past. This could have happened maybe 1,000 years ago, or 1,000,000 years ago, or maybe even 100,000,000 years ago. They have evaluated our planet and determined inhabitants of it are not capable to build von Neumann probes. What those probes would have done next? Maybe they went to a sleep mode. That means they only seldom investigate the level of technical capacity of earthlings. Another reason to keep eye on the Earth would have been to make sure no aggressive extraterrestial probe are trying to build factory there.

However, the probes would have been programmed so that a certain events on a planet they are watching will trigger them to increase their activity. What could these events be? One pretty obvious answer is reaching of the space age by a civilization they are monitoring. And it can be claimed human civilization achieved space age with V2 launches. It is interesting that especially continental Europe seemed to be a hotspot for foo fighters - the area where V2 rockets were launched.

Of course no civilization will launch von Neumann probe the day after it launched it's first space rocket. But as far as I can imagine, it is impossible to determine an universal minimum time required between these two events. Therefore it is logical to start intensified surveillance as soon as possible.

Conclusion

So let us still assume some of the UFO sightings are actually von Neumann probe sightings. On this hypothesis, the reason for a sudden increase of sightings during and after second world war was because our civilization reached an ability to launch objects, including von Neumann probes, to the space. Therefore we became a potential threat to the rest of the universe - a threat that need to be monitored. The easily observable atomic bomb explosions didn't certainly make us to look less threatening.

http://en.wikipedia.org/wiki/Project_Daedalus -> atom bombs