UFO researchers have long been on a search for physical evidence of postulated alien technology. A fellow named Bob White has spent years writing and talking about a very odd-looking bit of metal he ways was deposited by an alien spaceship. There's no question it's odd, looking like an elongated pine cone and containing an amalgam of metals that didn't make any sense. In this case, though, it eventually did make sense when the right person saw it. The result:
"The object in question is made of accreted grinding residue. It forms in a manner similar to a common stalagmite when metal castings are “cleaned” on large stationary grinders."
COMMENT: I think there are unexplained aerial phenomena, but most likely they are natural. There's no question the concept of alien visitors is compelling: No one would be more fascinated than I to learn "they" were actually here. But I haven't seen anything that convinces me yet.