latest stories:  Wireless Device Helps Illuminate the Role of
Light on Human Health  Researchers are testing a small, ear-
mounted meter to help gauge exposure to light  Courtesy of
Rensselaer Polytechnic Institute's Lighting Research Center
During a 24-hour period humans experience a rise and dip in the
production of most hormones and neurotransmitters (the chemicals
that relay signals between nerve cells). This daily cycle is
referred to as the body's circadian rhythm and is regulated by
both internal systems and external stimuli, the most powerful of
which is visible light.  In an effort to gauge exactly how light
affects our body clocks, Rensselaer Polytechnic Institute's
Lighting Research Center (LRC) in Troy, N.Y., has developed a
device called a Daysimeter. Small and ear-mounted—like a
wireless cell phone headset—it has three sensors that measure
head movement, bright light (or lux, a measurement of the light
used for daytime vision), and blue visible light (also known as
circadian light). Circadian li