It's been shown in studies on humans that getting bright light in your eyes in the first hour after waking, or as soon as possible after waking, increases the peak of that cortisol pulse by 50%, five zero. And that cortisol pulse, yes, increases mood, yes, increases alertness, but it does one other very important thing, which is that... it can clear out any residual adenosine that might be present in your system when you wake up in the morning.