The Cosmic Man (1959)

Starring John Carradine, Bruce Bennett, Angela Greene, Paul Langton, Scotty Morrow
Directed by Herbert S. Greene
(actor & director credits courtesy IMDB.com)

The American military track the descent of a UFO and try to seize its secrets, but also bring in a civilian astrophysicist who has a less aggressive and more peaceful approach.

I've seen this film knocked for being a rip-off of The Day The Earth Stood Still, and while thematically it does use similar characters and ideas, I think it stands on its own two feet, and have been charmed by it.  It of course doesn't compare to that classic film, but Arthur C. Pierce's screenplay has something of its own to say about scientists and a more reasoned approach to the unknown.  Carradine is a welcome presence as the film's titular alien, in a nod perhaps to The Invisible Man, appearing as both a shadowy partly transparent figure, and disguised in bulky clothing, allowing his rich voice to tell the background of the aliens who visit Earth.  Bennett, a frequent co-star to Humphrey Bogart in the 1940s, is perfectly cast as the cool-headed and reasoning Professor Sorenson.  The music score by Paul Sawtell & Bert Shefter adds weight to the tale, and there's some clever photography and editing on display that make the film ascend above its budget.