Radiation Pressure

 
"Can light exert a force to move an object?" 
 
Excerpts from link (University of Cambridge Institute of Continuing Education)
 
"How can photons travel at the speed of light instantaneously without producing a force in the opposite direction? Why don't I get thrown backwards when I switch on my torch?"
 
Dr Anna Lombardi, Nanophotonics Centre, University of Cambridge
 
"By transferring their momentum, photons are able to exert a force on an object. Physicists refer to it as an optical force. The higher the frequency of the light, the larger its momentum and, therefore, a stronger force it can exert. This means that blue light will push you stronger than red light."
 
"While the push of light is so tiny that you don’t feel it in everyday life, we can observe it at the nanoscale in the world of the infinitely small. Arthur Ashkin, a scientist working at the Bell Labs in the seventies demonstrated that nanometer and micron sized particles can be accelerated, trapped and manipulated by radiation pressure of a highly focused laser beam."
 
"Nowadays, scientists use light quite literally like optical tweezers to manipulate objects from cells to single atoms"
 
Kirsten: Does that mean that we just need a superpower torch to move the big stuff?
 
Anna: If as a light source we don’t limit ourselves to a simple torch, but we consider the Sun, then the radiation pressure exerted is strong enough to push spacecrafts and even asteroids from their path.