Can you tell me what the first two lines mean in the poem "She Walks in Beauty"?George Lord Byron's "She Walks in Beauty"

Lord Byron's poem "She Walks in Beauty" is a beautifully
lyric poem in praise of a woman that history holds was a cousin of his, Anne Wilmot. 
Supposedly, attired in a black dress with spangles, she inspired his Romantic perception
of beauty as a mixing of lights and darks.  And, rather than possessing beauty herself
as filled with it, the woman is possessed, or graced, by beauty.  This dynamic notion is
expressed in the first two lines which are actually one enjambed line, a line that runs
over into the next with no punctuation:

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She walks in beauty, like the
night

Of cloudless climes and starry
skies;

In these
first two lines there is the union of light and dark; further, the night of a lightened
sky that has stars and is cloudless creates a duality to the woman as opposites join in
her.  This duality is one that later in the poem appears to be the duality of mind and
body.