When Cooper, Brand, and Doyle go to Miller's planet in Interstellar, Romilly stays behind to study the black hole.
After their arrival, Romilly says that he tried to send information to Prof. Brand but nothing goes out only information (messages) comes in.
But they at first decide to go to these three planets (Edmund's, Miller's and Mann's) because they received signals from these planets when they were on Earth.
How can they receive messages from Earth from near a black hole but cannot send messages to Earth from near a black hole?