Final answer:
The origin of the most energetic cosmic rays is still unknown, despite various clues from observations and research. These high-energy particles reach Earth from both within and outside the solar system, and their properties can be studied through direct capture or atmospheric reactions.
Step-by-step explanation:
The origin of the most energetic cosmic rays is unknown. While there are clues as to where cosmic rays might be generated, such as supernova explosions and the material ejected by them, the exact source of these high-energy particles is still a topic of ongoing research. Cosmic rays reach Earth from both within and outside the solar system, and their properties can be determined by capturing them directly or observing the reactions that occur when they collide with atoms in our atmosphere.