: In the United States, once an alien gains admission and develops ties, their constitutional status changes, according them a "generous and ascending scale of rights".
ArtI.S8.C18.8.7.2 Aliens in the United States - Constitution Annotated : In the United States, once an alien
: NASA uses a multi-level scale to verify alien life. Reaching "level seven" would mean ruling out all non-biological explanations and having secondary evidence, like a radio signal. : The term is often used metaphorically in
: The term is often used metaphorically in literature to describe the feeling of being "not quite one of us" or surviving in a foreign land. 3. Pop Culture and Science Fiction : Modern astronomers use telescopes to scan the
In science, an "alien" is any organism that did not originate on Earth.
: Modern astronomers use telescopes to scan the atmospheres of distant planets for "biosignatures"—gases like oxygen and methane that might indicate life.
Outside of space, "alien" has a specific legal meaning regarding human movement and national borders.