Also, if it has negligible mass, how is it possible that it has energy?
For answers, please visit following pages (interesting explanations are there)
http://hubblesite.org/reference_desk/faq/answer.php.id=58&cat=exotic
a photon has energy, which is equivalent to mass, and therefore interacts via gravity with everything else. https://van.physics.illinois.edu/qa/listing.php?id=16351
http://physics.stackexchange.com/questions/34352/how-is-light-affected-by-gravity
http://www.reddit.com/r/askscience/comments/2ltjpg/if_gravity_acts_upon_objects_with_mass_and_light/
Anirudh,
Light has no mass. It always follows the shortest path between two points - but around very massive objects that path is not a 'common-sense' straight line.
As for having energy but no mass, well, does a ripple on a pond have mass? It's just the same stuff as the rest of the pond, but it is somehow excited, and travels at a given speed. Light's (almost) the same thing. There is energy by virtue of its motion, but no *thing* is moving.
Ah I see... So essentially light is neither a wave nor a particle (as it is just pure energy). But where does the wave-particle duality fit in?
Anirudh,
Light can be shown to have particle-like properties (Compton scattering, the photoelectric effect, etc.) and also wave-like properties (interference).
The 'duality' arises because it depends on the choice of experiment as to which behaviour it will show.
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