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Yuri Milner (left) and Stephen Hawking (right).
We don't yet know the details, but there are some strong clues.
Hawking has said in the past that humanity needs to colonize space if we are going to survive as a species long term. And as Space.com points out, April 12 is the 55th anniversary of human spaceflight. (The first man in space was cosmonaut Yuri Gagarin - who Milner has said he was named after.)
Milner has spent big money on science initiatives before, saying he wants to celebrate "intellectual achievement" in the same way we celebrate artistic and athletic prowess.
The Russian billionaire philanthropist has also collaborated with Hawking in the past. In July 2015, the two announced a $100 million plan, called "Breakthrough Listen," to search the stars for intelligent extraterrestrial life.
Milner's interest in science runs deep. He was working on a PhD in physics before becoming a Silicon Valley investor. He earned his fortune investing in companies like Facebook, Twitter, Spotify, and Groupon, and now funds some of the biggest science prizes out there, including the Breakthrough Prize, which Mark Zuckerberg also supports.
Watch the live video feed below of the announcement, which should start by 12 p.m. ET.
Also check back with Tech Insider - we'll be at the top of One World Trade Center to bring you the details directly.