Oh, and then you have to ask if whoever sent the signals still exists as a civilisation now.
Astronomers heard two mysterious radio signals from outside our galaxy - unexplained blasts of radio energy which last a few milliseconds then are never heard again.
Scientists using the Parkes radio telescope in Australia heard two ‘Fast Radio Bursts’ this month - separated by just 2.4 milliseconds, according to researchers at the Max Planck Institute.
Radio telescopes have detected Fast Radio Bursts since 2001 – incredibly short, high-energy pulses which last for a few milliseconds and erupt with the energy the sun releases in a day.
But follow-up searches by non-radio telescopes have come up empty - leaving the source of the high-energy signals a mystery.
Astronomers have previously speculated the signals could come from evaporating black holes, or even from distant alien civilisations.
The new ‘double flash’ rules out some of the sources astronomers previously thought might cause Fast Radio Bursts.
For instance, the bursts could not be caused by neutron stars colliding - as they can collide only once.