If aliens are nearby and listening in on our spacecraft command signals, we could hear back from them as early as 2029.
Since 1972, NASA has used a system of radio antennae called the Deep Space Network (DSN) to track spacecraft and send powerful radio signals towards them.
Howard Isaacson at the University of California, Berkeley, and Reilly Derrick at the University of California, Los Angeles, worked out which stars these radio signals may have reached and when …