Albert Einstein, whose theories exploded and reshaped our ideas of how the universe works, died on April 18, 1955, of heart failure. He was 76. His funeral and cremation were intensely private affairs, and only one photographer managed to capture the events of that extraordinary day: LIFE magazine’s Ralph Morse.

Armed with his camera and a case of scotch — to open doors and loosen tongues — Morse compiled a quietly intense record of a 20th-century icon’s passing. But aside from one now-famous image — of Einstein’s office, exactly how he left it, taken hours after his death — the pictures Morse took that day were never published. At the request of Einstein’s son, who asked that the family’s privacy be respected while they mourned, LIFE’s editors chose not to run the full story, and for more than five decades Morse’s photographs lay in the magazine’s archives, unseen and forgotten.

Now LIFE presents a selection of Morse’s photographs from that day, as well as Morse’s own memories of what it felt like 57 years ago, on a spring morning in Northern New Jersey, when he found himself racing around an Ivy League town trying to find out what became of the late, great scientist …