Scientist and broadcaster Professor Brian Cox will give a special one-off talk at the Meres Leisure Centre on Saturday 22 September - and only 380 of 1,200 tickets remain.
Tickets for all events at the spectacular five-day festival are now available.
Gravity Fields is South Kesteven District Council's biggest event, with spectacular outdoor arts, top-drawer speakers making science fun, well-known names from television adding celebrity sparkle, and an education programme highlighting events for schools.
The festival, from 26-30 September, celebrates Sir Isaac Newton's close links with the area, and the outdoor arts will be taken to another level thanks to a £89,500 grant from Arts Council England.
Science, arts and heritage events are being held in and around Grantham, including Newton's birthplace at Woolsthorpe Manor.
"Gravity Fields is truly exciting," said the Leader of SKDC Cllr Matthew Lee. "We have a world class festival here on the doorstep with something for everyone and for all ages.
"Arts Council funding over the years has allowed us to build a reputation for innovation in the arts. The sheer spectacle of a show-stopping event on the Saturday night is the icing on the cake of an amazing festival and we are truly proud of staging such a great event.
"We are expecting a huge amount of interest and would advise anyone planning to attend one of the ticketed events to book their place early to avoid disappointment."