Olivia Newton-John, the Grammy-winning superstar who reigned on pop, country, adult contemporary and dance charts with such hits as “Physical” and “You’re the One That I Want” and won countless hearts as everyone’s favorite Sandy in the blockbuster film version of “Grease,” has died. She was 73. Newton-John, a longtime resident of Australia whose sales topped 100 million albums, died Monday at her southern California ranch, John Easterling, her husband, wrote on Instagram and Facebook. “Olivia has been a symbol of triumphs and hope for over 30 years sharing her journey with breast cancer,” he wrote.