To sail on winds of sunlight has long been a dream of rocket scientists.

The Planetary Society, a nonprofit that promotes space exploration, announced Monday that it would send the first of two small spacecraft testing the technology of solar sails into orbit this May, tagging along with other small satellites on an Atlas 5 rocket.

“We strongly believe this could be a big part of the future of interplanetary missions,” said William Sanford Nye — better known as Bill Nye the Science Guy — the chief executive of the organization. “It will ultimately eventually take a lot of missions a long, long way.”

When photons — particles of light — bounce off a shiny surface, they impart a tiny bit of momentum, an effect that comes directly from the equations of electromagnetism published by the physicist James Clerk Maxwell in the 1860s. In his 1865 novel, “From the Earth to the Moon,” Jules Verne appears to have been the first to realize that this force could be harnessed for travel through the solar system. The bombardment of sunlight over a large area can gradually but continuously accelerate a spacecraft.

On launching, the Planetary Society’s craft, LightSail, is about the size of a loaf of bread — 4 inches by 4 inches by 1 foot. In orbit, the spacecraft will undergo a month of testing before it extends four 13-foot-long booms and unfurls four triangular pieces of Mylar, less than 1/5,000th of an inch thick, to form a square sail that spans almost 345 square feet.