Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: thedoc on 23/09/2013 21:56:39

Title: How can massless photons impart momentum on objects?
Post by: thedoc on 23/09/2013 21:56:39

How can massless photons impart momentum to objects like asteroids?
Asked by John, Norfolk

Visit the webpage for the podcast in which this question is answered. (http://www.thenakedscientists.com/HTML/podcasts/naked-scientists/show/20120715/)

or [download as MP3] (http://nakeddiscovery.com/downloads/split_individual/12.07.15/Naked_Scientists_Show_12.07.15_10479.mp3)

Title: Re: How can massless photons impart momentum on objects?
Post by: thedoc on 23/09/2013 21:56:39

We answered this question on the show...

Dominic -   This is actually a very common misconception because at school, of course, you’re taught a lot of Newtonian physics where something without mass can't exert a force.  It doesn’t have momentum.  But, in fact, a photon is a relativistic particle; and in relativity, energy and mass are equivalent to another. 

So, although the photon doesn’t have any mass, it has momentum still, which is associated with its energy and that’s significant because the photon is traveling at this relative speed of the speed of light. 

Einstein’s theory of relativity has completely taken over from Newtonian physics.  And that explains how the photon can have this momentum which it can impart to an asteroid...