The electric fluid travels at the mean rate of 20,000 miles in a
second under ordinary circumstances; therefore, if it were possible to
establish a telegraphic communication with the star 61 Cygni, it would
require ninety years to send a message there.
Professor Henderson and Mr. Maclear have fully confirmed the annual
parallax of α Centauri to amount to a second of arc, which gives about
twenty billions of miles as its distance from our system; a ray of
light would arrive from α Centauri to us in little more than three
years, and a telegraphic despatch would arrive there in thirty years.