Let's do a mind experiment. You are in Miami on the beach and you have a nice 12 foot long model boat equipped with GPS, long range remote control (500 miles), but no cameras or imaging devices. Your control box has a map display so you can see where it is, what direction it is going and it's speed.
You put the boat in the water and start it off heading due east at 12 knots, it's full speed. As the boat reaches the horizon it disappears from sight but you continue to follow on your remote control box display screen. As the boat reaches 150 miles offshore you notice that it's speed has increased to 35 knots, positioning on the GPS map display confirms it. You scratch your head; What caused the speed increase?
The boat could have been hauled aboard a cigarette boat. Maybe a helicopter. Swallowed by a whale? There seems to be many possibilities that could explain it but which is correct? Could the Bermuda triangle be the cause?
Suddenly your signal is lost and so is your boat. Now you have two things to consider. Scientific explanations and impossible explanations. No boat, no evidence. Science can only guess. The unknown is also a guess. The two are equal. One guess and only one guess is the correct guess.
Now consider the Pioneer Spacecraft. The one with the speed change that science is having difficulty explaining. "We've been working on this problem for several years, and we have accounted for everything we could think of." and... "The unexplained force appears to be acting on four deep-space probes scattered around the Solar System."
Except one thing, the obvious. As the deep-space probes violated the laws of physics, at least to the 'trained eye', what is left to consider about this "unexplained force"? Is this UF phenomena explainable in other terms?
Men make crop circles. Apparently other crop circles arise that outdistances the ability of men to make. UC - unexplained circles.
What if: Men make KC - known circles, and something else responds with other circles, UC? UF, UC are related?
What if: UFO picked up deep-space probes, examined them, put them back without proper speed adjustments to fool the scientists?
Was it a helicopter or cigarette boat that examined your model boat?
Note: about crop circles, read this.