✔ 最佳答案
Yes, this theory works. In fact, it is the theory of "photon pressure" or "radiation pressure"
The change of momentum of a photon when reflected from a surface indeed gives rise to an impulse to the surface. If the surface is large and there are quite a large number of photons hitting the surface in a unit time. This could provide a propulsion for space travel.
Suppose there are n number of photons, each of which with energy E, hitting a flat surface with area A in a unit time.
since momentum of photon p = E/c, where c is the speed of light
The change of momentum of a photon if it is reflected = 2p = 2E/c
hence, the total change of momentum in 1 second if all photons are reflected = 2nE/c
The force given by the photons on the surface F= 2nE/c
or the pressure exerted onto the surface by the incident photons
= 2nE/Ac
Therefore, if n is sufficient large (i.e. a large surface area is used so as to 'catch' a large number of photons), the force F could be good enough to propel a small spacecraft to move in space under an acceleration.
In fact, such principle has already been used in the design of "solar sails" that makes use of photons coming from the sun to propel sapcecrafts.
You may wish to look at the following interesting article about solar sail. There is also a calculation showing how an acceleration as high as 9 m/s2 (almost equal to that of the acceleration due to gravity) could be achieved on a small 1 kg spacecraft.
http://www.howstuffworks.com/solarsail.htm/printable
