The absence of dark
To give you a brief synopsis of the current popular theories on the modern science concerning light: nobody really knows, we're all just guessing.<br />
Einstein coined the equation Energy = Mass times the speed of light squared. Meaning that all mass is relative to a certain amount of energy. So theoretically, energy (including electromagnetic energy, or light) can be converted into matter and vice versa. But that doesn't tell us anything about what light actually is - just a physical principle noting how matter and energy tend to govern themselves.<br />
That's the thing about science- it's just a desc<x>ription of the observable universe. There's a very limited amount that can be observed with our sense of sight- all of which is ba<x>sed on detecting visible light.<br />
For all we know, light may be some kind of interface with sentient extra-spacial entities trying to communicate with us by breaching space-time, but we're too dumb to understand the meaning so we erroneously assume that everything we see is there for our amusement. Who knows?
The opposite of dark
Light is a spectrum of heat/radiation. What we percieve as light is really just a spectrum of heat that we have evolved to see as a visible radiation. It's both a particle and a wave so that should tell you light doesn't give a ****. Light is also the fastest thing in the universe, but when we look up into the sky we're looking at old photographs. <br />
Since we are only working off what our eyes interpret, that means that nothing looks like what you think it does. If we saw things in the ultraviolet spectrum or infrared, I'm pretty sure not only art would be different our whole society would be foreign. Of course I could be wrong and that some colors or interpretations of colors were universal.
It's not an element, light is a coincidental effect of a chemical reaction causing heat. the sun is a perpetual fusion explosion. The light we see is just a visible spectrum of the heat radiation from that fusion reaction. So it's not really something, but more the byproduct of something happening. After all nothing emits light unless it has lots of heat, right?
I wasn't speaking biologically, only astronomically. There are many animals and plants with bioluminescence, but outside of living things with evolutionary advantages without heat there is no light. Especially in space. Just because your flashlight isn't hot doesn't mean the filament isn't burning white hot.
I doubt it. If light itself was an element or actual kind of matter I'm pretty sure a physicist or Chemist would have noticed that.
Since most of the world's recent advances have been made by utilizing the discovery that light acts as both a particle and a wave, chances are that it's a unique form of radiation. Of course I'm not an expert, but that's just my two cents.
Light is both a particle and a wave. Particles of light are called photons. They have no mass.