Stephen Hawking explained blackholes and the radiation coming from blackholes. He mentioned that the light jets coming out from blackholes are the photons that are captured by the blackholes near its event horizon and then part of those photons are re-radiated and coming out as light jets and part of them are absorbed by the blackholes. Yes he was right, because, it was established that blackholes re-radiates like a blackbody from the residual energy after the supernova and cools down further. The frontal re-radiation is the future light cone, the event horizon is the world line and the backside re-radiation is the past light cone. That's how past, present and future are related in a blackhole. Therefore time travel is possible through blackholes.