Atlas Obscura’s Wondersky columnist Rebecca Boyle is an award-winning science journalist and author of the upcoming Our Moon: How Earth’s Celestial Companion Transformed the Planet, Guided Evolution, and Made Us Who We Are (January 2024, Random House). Throughout the summer, she’ll be sharing the stories and secrets of our wondrous night sky.
It may seem obvious to say that stargazing is, at its heart, a visual hobby. You sit outside in the darkness, and allow your pupils to dilate, letting in as much faint light as possible—and then you can see the universe. As much as I love to look at the night sky, I am happy to disabuse new stargazers of this notion. Stargazing is multi-sensory. As you visually time travel, seeing light that is hundreds, thousands, or even millions of years old, your body is aware of your immediate surroundings. You can smell the night air; feel the chill on your skin; hear the crickets, the hydraulic brakes of the city bus, or the wind in the trees; touch the drops of condensation that form in your tent or on your porch. Taste is really the only sense missing, unless you’ve planned ahead and have s’mores on hand, in which case, good job.
Professional astronomy is no different. We think astronomy is a visual science because that is the primary way that most people experience the world. But the truth is, most astronomy is not stargazing, at least not anymore. Astronomy is about translating information from the universe into data, and then interpreting that data. Beautiful pictures are just one way to represent that data.
Several groups of astronomers and astrophysicists are developing ways to communicate their findings through other sensory means. A program under development called Astronify uses math software to translate astronomical data into sound. Astronomers working with the Chandra X-Ray Observatory, which observes very hot objects, produced a series of 3D models that you can make. If you don’t have a 3D printer, check your local library; it might. You can make a 3D-printed model of famous stargazing targets like the Crab Nebula, Supernova 1987A, and the Tycho Supernova Remnant.
These projects are educational and awesome, but they’re just the beginning. Professional astronomy is also moving into other sensory realms. In just the past few years, astronomy has transformed from a science built on light to a science that can use any kind of information. Newly possible “multi-messenger” astronomy is like using all available senses to perceive the universe.
In June, astronomers thrilled to a new finding that gives a fresh perspective on this point of view: The universe is awash in low-frequency sound, like the hum of people at a cocktail party.
This discovery is hard to understand without visiting Albert Einstein at least briefly, so bear with me.
Probably Einstein’s most consequential breakthrough was his general theory of relativity. It holds that gravity is not really an invisible force, but a distortion. Large objects warp the fabric of space and time around themselves—this looks like the work of gravity. Objects respond relative to each other because the space they are in is shifting. One (simplified) way to think about this is using playground equipment.
Imagine a trampoline with a bowling ball in the middle. The trampoline will sag under the bowling ball. Put another way, the ball warps the fabric of the trampoline, pushing it down. Now, imagine rolling some marbles around the bowling ball. They will spiral in toward the bowling ball, because the ball’s presence has shifted the path the marbles can take. They seem to be pulled in, the same way a planet is pulled in toward its star, or a galaxy is pulled in toward its central black hole. The bowling ball is not sucking in the marbles or anything; they spiral in because the trampoline they’re on has been altered.
In 1916, Einstein realized that this idea also implies ripples in space-time. Imagine dropping the bowling ball into a pond; the water would ripple outward from the impact site. Scientists found these space-time ripples, called gravitational waves, for the first time in 2016. This is not something they interpreted with light. Instead, the waves were interpreted through sound.
The first detection was a whomp! caused by the titanic collision of two distant black holes. The newer detection, which was announced June 29, was on a smaller scale but was in some ways more shocking. The universe is teeming with these waves. Humongous black holes at the centers of galaxies spiral together and then combine, sending out gravitational waves. These can be detected, and expressed, as a low-frequency hum.
If you go out sometime this week to experience the stars, I invite you to think about all this. Gravitational wave detection really is one of the most incredible discoveries in the last few years, and still has physicists buzzing, if you will. You and I and other stargazers can’t hear the universe ringing like a bell. But that does not mean that it isn’t happening. The universe is full of light we cannot see and sound we cannot hear; our ability to perceive it just depends on our representation. I think this is useful to remember, just like remembering that people with visual impairments can still fully appreciate the summertime experience of being outside at night, beneath and among the stars.
Is there something you’d like to know about our brilliant night sky? Share your stargazing questions with us and you may see them answered in a future Wondersky column!