Forrest M. Mims III (forrestmims.org), an amateur scientist and Rolex Award winner, was named by Discover magazine as one of the "50 Best Brains in Science." His books have sold more than 7 million copies.

Take me to the Steps

Six years ago, I described in these pages how to build a twilight photometer (Figure A below) to determine the presence and altitude of overhead layers of smoke, dust, and smog ("Build a Twilight Photometer to Detect Stratospheric Particles," Make: Volumes 44 and 45).

That two-part article has become a serious project to detect and measure the elevation of stuff in the sky, including dust arriving from Africa's Sahara Desert, smoke from agricultural fires in Mexico and Central America, and most interestingly, high-altitude cosmic dust that accompanies meteor showers as Earth orbits the sun. Some of this "dust" might actually be space debris -- manmade junk orbiting the Earth.

My twilight photometers are much simpler than professional versions, and that original Make: article has been read by 76 scientists who are members of the ResearchGate community and 719 non-members (and, hopefully, many Make: readers). It hasn't yet been cited in a peer-reviewed scientific paper, but at least one is on the way. Maybe you can build a twilight photometer and cite it in your research. This article can be considered Part 3. Here I describe how the original project, which uses an LED as a photodiode to detect the very weak twilight glow, has been expanded to detect particles high above those in the troposphere and stratosphere. I close with a description of a new kind of low-noise LED twilight photometer.

Project Steps

Micrometeors

Space Debris

The Atmosphere