Fredric Brown

Mars and Earth make first contact through a rocket landing, with Martians hoping to learn from Earth's technology and Earth hoping to learn from Mars' social sciences and parapsychological sciences.

A man finds himself transported to a future time and must make a decision about the use of a time machine.

A dictator, known as Number One, finds himself alone and hunted on a destroyed world. He seeks refuge among the natives but is ultimately betrayed and left to face his own madness.

A group of colonists on Mars, who have been genetically modified to adapt to the planet's harsh conditions, plan to kill the Earthmen and take over the planet.

Two Timer by Fredric Brown. A small-scale time machine experiment and a soldier fighting aliens on a distant planet.