I've been working on my "Legends of the 23rd Century" series for quite some time now, but something my readers haven't given me feedback about is the "four elements" aspect of it. Taking a leaf out of the "Avatar: Last Air Bender" books, I've given key characters in my series power over four scientific "elements", namely Space, Time, Gravity and Energy. The characters have discovered these powers themselves, and as such there are no masters to learn from. The traditional fantasy elements are sometimes portrayed as being opposite to each other, such as Fire being described as hot and dry, while Water is cold and wet. By contrast, Earth is described as being cold and dry, while Air is hot and wet. With my four elements it isn't as easy to define them in this way, but I suppose the expansion of the universe counters the effects gravity over very long distances, while time causes differences in energy to even out. I know somebody will point out that real scientific elements have names like "Hydrogen", "Helium", etc, but I'm not sure how else else to call my set of four families of powers, other than to use the word "elements". So my question is, does having control over Space, Time, Gravity and Energy sound like interesting reading? It isn't the core focus of the first two books, though it is mentioned. It does become more important as the series progresses.