[LuxMaker]

and if light can be made to go backwards, down't that mean it has mass? and doesn't that destroy the conservation of matter thoery that says that mass cannot be created nor destroyed since one can turn a light off and on?

First off, light does have mass.

Second the conservation of matter theory could easily be said to be a conservation of energy theory as well because E=MC². Energy and Mass are directly proportional to each other. When you turn a light on, nothing is created as electrons are used to generate photons (light) both of which are different kinds of energy.

[MHGinTN]

Pesky bosons and leptons. They need to all be in a condensate ... Mmmm, think I'll get an ice cream.

[Physicist]

First off, light does have mass.

Not that we know of.