Of Eclipses and X-rays
Experiencing wonder at phenomena, both rare and commonplace, both natural and man-made, as a citizen of the world and as a radiologist.
How many of you got to witness the recent solar eclipse along the line of totality? I traveled with my family to Clemson, South Carolina, for the event, equipped with a solar telescope, a handful of eclipse glasses, and lots of sunblock and cold beverages. My husband focused primarily on looking through his solar telescope and those belonging to other skywatchers, picking out sunspots, locating solar prominences, tracking the moon's march, and discussing all things astronomical. My children and I spent the hour and a half between first contact and totality alternating between doing crossword puzzles and playing card games. We paused to peek through the telescope at the moon's transit and occasionally engaged in other solar-centric activities, like piercing a small hole in the bottom of a paper cup to make a primitive camera obscura.
Dappled sunlight spread through a tangle of limbs and leaves of a stately tree, its shade our sanctuary from the oppressive midday heat. But instead of the expected spots of light beneath our feet, we saw parallel crescents of collimated sunlight mimicking the small portion of sun unobscured by the moon. I took the above photographs* of this phenomenon along a brick path, slightly before (left) and soon after totality (right).
In the last few minutes before totality, an eerie coolness and preternatural quiet enveloped us. As if a heavenly stagehand was controlling a dimmer switch, the gradual darkening was at first nearly imperceptible. Then, just as we could tell unequivocally that sunlight was diminishing, there was an urgent crescendo in the final moments. We threw off our eclipse glasses and...boom!...totality.
The site of the black disc crowned by silvery tendrils of the corona caused a momentary mass paralysis, mouths and eyes gaping in awe as the star of the show (pun intended) took center stage. The crowd took its first breath and erupted in cheers, joined by the sounds of nighttime creatures. There it was, our very own ball of hydrogen and helium, the sun, twinkling in the firmament with its starry brethren, revealing Venus's and Jupiter's daytime hiding spots. Soon a tiny burst of light at one edge of the disc confirmed the moon was moving on and the sun reasserting its threat to our retinas.
We beheld the power of the moon, a lifeless rock, with no light of its own, visible at night only by reflecting the sun's light, yet able to insinuate itself between the earth and sun and thereby attenuate the sun's radiant energy. Sure, I ascribe power and deliberateness where there are none. After all, an eclipse is just a predictable physical phenomenon based on the periodic intersection of the orbital paths of heavenly bodies. Still, it's fun to just imagine the lowly little moon as David getting the chance to overpower his fireball, Goliath.
Look around, look around at how lucky we are to be alive right now.
Look around, look around...
- from the song "That Would Be Enough" in the musical "Hamilton"
What a rare and wonderful phenomenon is a solar eclipse. But there are other amazing phenomena we experience yet take for granted. Take a minute to just look at a radiograph, resisting the temptation to read it. Appreciate the interplay of light and shadow, the illumination of normal structures and disease. Picture x-ray photons penetrating fat, soft tissues and air-filled structures, perhaps those of your own body, while being prevented from travelling further by bone, iodinated contrast, and metallic foreign bodies. Imagine the latent pattern of photons that have successfully reached detectors. Reflect on how our retinas and brains perceive and decode photon patterns. Notice radiological optical phenomena, like Mach bands, and appreciate the limitations of our perceptive abilities.
The marvel that is a radiograph has been around little more than a century. The scientific experiments of the past and early experiences with ionizing radiation for medical applications laid the groundwork for the modern practice of radiology. So as you look at a radiograph, remember how lucky you are to have the opportunity to practice radiology. Not many people on this planet get to say that they are radiologists.
On April 8, 2024, another total solar eclipse will occur across a portion of the United States. Whether or not you get to experience it, you will still get to look at radiographs and other medical imaging studies and contemplate the phenomena involved in creating them. We have been afforded the rare opportunity to interpret shadow and light to make a difference in the lives of many people. We will soon witness the power of machine learning and increasing diversity to further enhance the practice of radiology. We are so lucky to be radiologists right now.
*In the left-hand image, the photograph was taken about 30 minutes before the eclipse and the crescents are wider and have more ill-defined margins compared to the right-hand image, taken less than 15 minutes after the eclipse. Note also the opposite direction of convexity of the waxing and waning crescents of sunshine.