Milner, who is an investor in Facebook and Alibaba, has partnered with Hawking for Breakthrough Initiative, a new push to look for intelligent life beyond Earth.
The ad in the FT says, "Are we alone? Now is the time to find out."
Scientists supporting the initiative and listed on page five of the FT include: Lord Martin Rees, the astronomer royal, fellow of Trinity College and emeritus professor of cosmology and astrophysics at the University of Cambridge; James Watson, the chancellor emeritus, Cold Spring Harbor Laboratory and a Nobel Prize laureate, and the cosmonaut Alexey Leonov.
Other people who have put their name to the ad include: Sarah Brightman, the soprano; Magnus Charlsen, the world chess champion, and Seth Macfarlane, the actor, writer and director.
Milner has personally put up the $100 million to find the search.
The two-part Breakthrough Initiative includes Breakthrough Listen, which is being billed as the "most powerful, comprehensive and intensive scientific search" for intelligent life, and Breakthrough Message, a competition to find messages representing humanity and Earth that could be sent to other civilizations.
Milner already operates the Breakthrough Prize Foundation, which gives out $3 million to the scientists who win its prize.
Mark Zuckerberg, Facebook's chief executive, and Sergey Brin, the Google co-founder, are among the Silicon Valley investors to fund Breakthrough Prize Foundation.