elemental

This is not really my point, but someone might find it interesting: http://motls.blogspot.com/2011/09/why-is-there-energy-and-what-it-isnt.html#more

Planck's constant has the dimensions of energy multiplied by time. h=6.62606957x10^-34 erg.s

pmb; You should have seen how far off my first try was. I had to edit to make the meaning clearer and still missed the mark. Max Planck's h is a discrete amount of energy, maybe fundamental was the wrong word to use. The v is of course the multipler. The OP asked a question. What is energy? With Max Planck's h we have a very small discrete amount of energy to consider. I read that Planck was disturbed by any physical interpretation of h. If someone can explain what h is instead of just being an amount, it would be an explanation for one manifestation of energy.

For optical photons E=hv, indicating a fundamental measure of energy.

I must have misread something along the way and took Max Planck's h ( a quantum of action ) to be more fundamental, more general, than the photon as a quantum of action. Planck's constant is a proportionality constant and as pantheory pointed out, the h is theoretical. It must be impossible to detect, or even emit one h, so it can't be verified as an entity. So, what is the lowest energy single photon that can be detected?

Isn't the quantum a smaller measure of energy than a photon? Can't photons be different multiples of quanta?