Sarah Williams (December 1837 –April 25, 1868) was an English poet and novelist, most famous as the author of the poem "The Old Astronomer". She published short works and one collection of poetry during her lifetime under the pseudonyms Sadie and S.A.D.I., the former of which she considered her name rather than a nom de plume. Her posthumously published second poetry collection and novel appeared under her given name.
Williams was born in December 1837 in Marylebone, London, to Welsh father Robert Williams (c. 1807–1868) and English mother Louisa Ware (c. 1811–1886). She was very close to her father and considered her "bardic" interests to come from him. As a young child unable to pronounce 'Sarah', she inadvertently gave herself the nickname 'Sadie'. An only child, she was educated first by her doting parents and later governesses.
Although Williams was only half Welsh by birth and never lived outside London, she incorporated Welsh phrases and themes in her poems and Sadie was considered a Welsh poet.
Robert Williams died in January 1868 of a sudden illness. Already suffering from cancer and devastated by the loss of her father, Sarah's condition deteriorated. After three additional months of hiding the cancer from her friend and mother, she agreed to surgery despite knowing it might kill her. She died in Kentish Town, London during surgery on April 25, 1868.
Her second book of poetry, Twilight Hours: A Legacy of Verse, was published in late 1868. The collection included "The Old Astronomer" (also known as "The Old Astronomer to His Pupil", as it was titled in a 1936 U.S. reprint), now the most famous of her poems. The second half of the fourth stanza is widely quoted:
Though my soul may set in darkness, it will rise in perfect light;
I have loved the stars too fondly to be fearful of the night.
Ian Rankin titled his Inspector Rebus novel Set in Darkness after the lines and quoted them in the introduction. In an interview, Rankin linked the quote to the rise of a restored Scottish Parliament and the redemption of the Inspector in the novel. The poem is written from the perspective of an aged astronomer on his deathbed bidding his student to continue his humble research. The lines have been chosen by a number of professional and amateur astronomers as their epitaphs.