Astronomy was my first teaching assignment at Weber State University. Hired just a few weeks before a fall semester, I was shown the planetarium and given a textbook, and members of the physics department went out of their way to share materials, give advice and answer questions. I was set up to succeed.

Except, I had never taken astronomy myself.

I learned a few things as I prepped that summer. I knew some physics, but I still needed to learn some astronomical context. At the time, robotic missions to Mars were being planned, a space shuttle program was still active, and the new Hubble Space Telescope was going through the process of being fully implemented after corrections to its optics were put into place.

The outputs of Hubble would reveal to me some of the most impactful images of my career, especially those known as “deep field” images. It revealed that the darkest pixels of the sky are actually flooded with distant galaxies, each different from one another but all fitting a mold of what galaxies do, each clumping together as an organized island of hundreds of billions of stars. It’s easy to feel physically lost and emotionally overwhelmed.

But, to be honest, this was not the most astonishing image I’d come across as I crammed to understand what I was going to be teaching. My favorite astronomical observation, then as now, is documented exactly like this:

*       *    O               *             *

This is Galileo’s 1610 depiction of what he saw when he peered through a telescope pointed at one of the brightest dots of the night sky. Jupiter, a bright wandering object in our skies, presumed to be one of the many points on a crystalline sphere surrounding our spherical Earth, is that “O.” Through this telescope that Galileo decided would be a good thing to turn skyward, it was curious that Jupiter looked bigger than other things we know as stars. But even more surprising were those other four dots, never before seen or reported on until this time. And, what’s more, these four dots moved around systematically, tracing paths back and forth on that straight line tied to Jupiter.

Galileo had seen, more or less directly, for the first time, objects orbiting one another. This idea wasn’t new, and certainly Galileo was building from others’ propositions that Earth along with other planets are physical objects orbiting the sun, but this was the first time an orbit could be seen from outside looking in. It suddenly made the sky something that was not so much a painting of dots as it was a three-dimensional space, a universe larger than had ever been imagined. Space had real, physical objects in it. And they moved.

Telescopes since then — Hubble, the James Webb Space Telescope, others of various size and diverse detection regimes — all have expanded our view and inspired awe. But seeing Jupiter next to the pinpoints of these Galilean moons strikes me as the most shocking, even in this day and age. Galileo thought it was important enough that he wrote about it not in Latin, but in Italian, a language more people would be able to read. The combination of an innovative use of glass to make lenses, the advent of the printing press, and the movement known as the Protestant Reformation all created a perfect storm for Galileo and this scientific revolution.

This fall, I get to teach astronomy for the first time in about 10 years. It’s an amazing course because our understandings change so rapidly and the experience is so audacious and self-minimizing at the same time. Many of us are pulled into astronomy headlines that advertise a newly discovered most-distant galaxy, a particularly bright moon, maybe new imagery of an explosively dying star. I can use images from the new Webb telescope and so many others to emphasize these points, but the first one I’ll bring up is this simple sketch of Galileo, four dots and one blob, tied together to help us realize there is so much more — and there always will be.

Adam Johnston is a professor of physics and director of the Center for Science and Mathematics Education at Weber State University, where he helps to prepare future teachers and provides support for classroom educators throughout Utah.

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