Waves and Particles: Musings after the National Science Teachers Convention

I was staffing one of the walk-by tables in a gizmos and gadgets "Share-a-thon" session last week at the National Science Teachers Association (NSTA)'s annual convention in St. Louis. My demo showed how an inexpensive photocell could detect both visible light from a flashlight, and invisible near-infrared radiation from a TV remote-control unit, which is one of the four activities in our SOFIA (Stratospheric Observatory for Infrared Astronomy) Active Astronomy kit. As hundreds of teachers filed by during two hours, I hawked my wares and handed out teacher guide on CD-ROMs plus web address cards to those who lingered for a conversation.

One person stopped in surprise as I said, "Light is just one form of radiation." We talked for a few minutes, during which I found out she was a pre-service teacher working toward certification in biology and environmental science. She asked, what does light have to do with radiation? -- by which she meant the type of radiation she had learned about, capable of mutating DNA. I explained that type of radiation usually refers to particles, flying bits of unstable atoms that have come apart. She wanted to know more about the mutating radiation from space she had also heard about. I guessed she meant cosmic rays, also particles (sometimes entire atomic nuclei) that were ejected from exploding stars and subsequently accelerated almost to the speed of light by our galaxy's magnetic field.

Her curiosity further piqued, she asked again about light and infrared radiation. I displayed an electromagnetic spectrum on my laptop computer and said, all of these types of radiation, from gamma rays to radio waves, including visible light, are energy traveling at the speed of light in the form of vibrating electric & magnetic fields. They differ in wavelength and frequency, I continued, but otherwise are the same physical phenomenon (and noted that the highest-energy varieties, gamma rays, X-rays and UV radiation, can also damage DNA, leading perhaps to some confusion with particle radiation). I pointed to the electric lights in the ceiling chandelier, saying, up there, electrons are vibrating about 600 trillion times per second, creating a disturbance that travels to us and makes the electrons in our eyes vibrate at the same frequency - like wiggling a cork at one end of a water tank and making a cork at the other end respond - and so we see the light. She asked, "Does it travel by making the electrons in the air in between vibrate?" "Good question!" I said, "the air electrons do respond a little, but that is not necessary for light to travel." It's hard to picture, a wave that is its own medium. 125 years ago, scientists made up a name, ether, for the strange substance they believed must permeate all locations in heaven and Earth as the necessary medium to carry the vibrations of light across outer space from the sun, planets, and stars to us. But, it turns out, there is no such thing: electromagnetic radiation does not need a medium, it can travel across vacuum.

My new friend looked thoughtful, and asked how she could work this information into lessons on environmental science. I suggested it could connect well to topics on sunlight, photosynthesis, energy in general, and even global warming, which is caused by the fact that carbon dioxide is transparent to incoming sunlight but opaque to the Earth's infrared emission trying to escape back to space. She thanked me, and moved on to the next Share-a-thon table.

Back at the SETI Institute booth in the exhibit hall, I talked with my booth partners, teacher alumnae of the SETI Institute's Voyages Through Time high school integrated science curriculum workshops. Am I na?ve, I asked, to wonder how a pre-service teacher, so obviously curious and quick on the uptake as my radiation questioner, could have missed learning about electromagnetic radiation versus particle radiation? These experienced teachers assured me that someone certified in biology and environmental science could easily have finished without required physics courses, and taken chemistry courses that never ventured into mention of EM radiation.

This is not meant as a "woeful state of U.S. education" story. We can spin this instead as a story of the value of having scientists interested in public education attending and delivering content at teacher meetings. Perhaps she did hear EM radiation distinguished from particle radiation, but in a lecture format -- an inefficient means of conveying information at best. It seems the Active Astronomy demo was a better way to engage her attention - and maybe this will be how she will choose to help pass the concepts on to her students.

I do know she is the type of educator I hope will apply to fly onboard SOFIA in our Airborne Astronomy Ambassadors program, in which we will train classroom teachers, museum docents, and even avid amateur astronomers to understand the research project of a group of astronomers and then join the astronomers as partners on a research flight. But more about that in a later space.com article ...

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• Video: Mars Life?