The reason you often wake up groggy is because your body is still secreting melatonin, the hormone that gets you ready for sleep. It's controlled by the amount of ambient light and because we use so much artificial light, your body clock can easily get out of sync with your alarm clock.
But Professor Kenneth Wright of the University of Colorado did an experiment that proves you can quickly reset your body clock to help you wake up alert. He recruited eight volunteers to spend one week undergoing an intensive type of natural light therapy called camping.
"People slept in tents but there were really no restrictions on them with the exception that they couldn't be exposed to any electrical lighting," said Wright. "So we took away all cell phones, no flashlights whatsoever."
And look at this: After one week outdoors, even the night owls started going to bed as much as two hours earlier and come morning, they would leap out of their sleeping bags.
After the trip, back in the laboratory, he checked his subjects' melatonin levels and found that in just that one week, the body's natural clock had reset itself. And the key was being outside because even on a cloudy day, sunlight is so much more intense than anything you can easily create indoors.
"Your normal indoor light is normally 200 lux - sunrise and sunset is 10,000. And a cloudy day is much brighter than that," said Wright.
Of course, in most cities, you can't live in a tent. That's called homelessness; our culture discourages it.
But starting the morning with a brisk sunrise walk in 10,000 lux of light can do the same thing. As for those of us who have to wake up before sunrise, we're pretty much hosed.