If a person invented something new but didn't file a patent:
Is it legal for other people to file a patent for it?
Is it possible for other people to be granted a patent for it if they are not the original inventor?
If other people file a patent and claim they invented it independently at about the same time, what evidence do they need to show?
If the original inventor has clear evidence to prove his/her originality, is there a way to stop other people from patenting this invention?