Hey there, Monet :)
A metaphor is a type of figurative language that compares two things, but unlike a simile, it doesn't use the words "like" or "as".
This is comparing our Earth to perhaps the vastness of our universe, which is done often- perhaps the most prominently in Carl Sagan's Pale Blue Dot speech, which I think could really help you make some connections.
Hope this helps! :)
