Twinkle Khanna has reacted to Zomato CEO Deepinder Goyal's claim that gravity is the reason ageing happens. "If gravity were the kryptonite stopping us from turning into Superman, we might consider astronauts like Sunita Williams, who returned to Earth...after spending nine months floating in microgravity," Twinkle wrote. "She returned...with weaker bones, muscles, and heart," she added.