When I was 8, I noticed an atlas on the bookshelf in my room. I had just started amassing large art books from family museum trips but this was the first abnormally sized book in my posession — it was so oddly shaped its pages spilled over the edge of the shelf. One day I used all my strength to wiggle it down off the bookcase. I sprawled on my bedroom floor and began sifting through the long pages. It must have been from the ’50s or ’60s. It smelled old but it was clearly a book that had been cared for over the years. Its pages were a mix of pastels so dizzying and complex; in how pinks separated from light green and the skinniest blue rivers cut across the pages. Once I was old enough to read, my grandpa started ceremoniously gifting me books from his shelves.
One by one, every time I saw him, a piece of his library became mine. He had travelled all over the world and knew how much it could change a person. And whenever I’d visit him, I’d browse the books on the lower shelves and run my fingers along the spines like a car’s wheels over speedbumps, each cover sort of yellowed from years of his cigarette smoke and constant reading. Once this book and I were formally introduced, I began having regular dates with the atlas. Each day I would lay on my stomach and then sit cross-legged hunched over the pages, running my fingers down the rivers in Africa — the Nile, Limpopo, I’d take a trip to France or Chile. I would attempt to pronounce Czechoslovakia and many other long words that threw me into a joyous tizzy. Every mountain range, every body of water, every large city I would look at longingly wondering one day when I got older, how many of these mysterious places I would see with my own eyes. My wanderlust grew as I grew. There was so much to be explored, there was so much space that existed around my little home in Los Angeles. There was so much I didn’t know.
For as long as we have existed, humans have been trying to understand themselves in the context of their physical location. Granted we associate value and identity with where we come from, where we live, and even many times where we know we are going. One of the oldest maps of the world on record in human history comes from the 7th or 6th century in Mesopotamia. The Imago Mundi is a simple clay tablet carved with cuneiform writing. Its eight sections describe a region around the Euphrates River in Babylon. But it is much more than a physical representation of where the Babylonians lived. Surrounding the Euphrates is a circle meant to symbolize the ocean or “bitter river.” The sections outside the circular ocean are called “nagu” or distant regions, some of which are also mentioned in the Babylonian Epic of Gilgamesh. This relationship between the parts of the map shows us that the ancient Babylonians were trying to place themselves and their location into the greater unknown regions beyond their understanding. By this time human civilizations had spent many years examining the stars and planets and marking down the movements of these objects in the sky. But the Imago Mundi is our first record of a map of our direct surroundings. “It’s a really unique text because we have a lot of descriptions of the world, but we don’t have a lot of drawings of it,” says Assyrian scholar Dr. Moudhy Al-Rashid. “We have drawings of buildings, building plans, that sort of thing but not an attempt to explain the world visually,” she says. “There are drawings of stars, there are star maps but not maps of the world.”
Two scissor lifts, with men strapped to the metal banister, flank the side of the telescope. There’s an oil leak near where the 5,000 robots are supposed to move around and they can’t stare at galaxies if there’s an oil leak. My visit to the Mayall 4-meter telescope at Kitt Peak National Observatory in Arizona came on a very regular working day in September 2019. The drive up the mountain started clearly, with no other cars in sight. There is a long narrow highway that drives straight toward the mountain, with two lanes that cut through the middle of the Tohono O’odham National Reservation. At first I could make out the greenery of shrubs and trees and rock layers folded together like neapolitan ice cream with milky chocolate ripples, rosey-tan, and white. These features were formed during the Triassic period, some 200 million years ago.
Each passing minute up the 6,883 foot climb became more and more opaque — I was driving into a cloud. When I parked and got out the wind knocked me onto my car, and when I looked up to stare at the dome, I couldn’t see the top. At 18 stories high, the dome housing the Mayall 4-meter disappeared into the sky above.
The Kitt Peak team were nearly done installing the DESI instrument that would search the universe for dark energy — the elusive force responsible for expanding our universe outward at speeds of tens of thousands of miles per second — 70 kilometers per second per megaparsec, to be precise. DESI, the Dark Energy Spectroscopic Instrument was being attached to the telescope to officially hunt galaxies in the early days of 2020. On October 22nd, 2019, they opened the double doors of the dome and the telescope collected its first official light as the DESI mission officially began. Their goal is an ambitious one — to make the most detailed 3D map of the universe. They will do this by looking back in time as far as 11 billion years ago when the universe was very young, galaxies were just beginning to form, and the contents of the universe were nestled much closer together.
For thousands of years people have climbed mountains and crossed rivers to create maps to understand their place in the context of things. In a way this 3D map of the universe is the last map humans can make. Sure it won’t be the last map of the universe, but we’ve traced the boundaries of land, marked rivers and oceans, countries and species. We’ve mapped Mars, the Moon, the solar system, even our own galaxy. Which means there is only one thing left to understand in this symbolic way and that is the entirety of the cosmos.
DESI is a conglomerate of 500,000 parts moving in a synchronized ballet. Collected in tubes that run 40 feet from the top of the telescope to the bottom are 5,000 fiber optic cables. These threads of pure glass are as thin as a strand of hair and act as conduits for light. At the top of the telescope all 5,000 strands fan outward where each single cable will be assigned to an individual galaxy. Every 20 minutes the team will point the telescope at a new patch of sky while each one of the 5,000 cables locks onto a different galaxy. It takes only a few seconds for each robot to do-si-do and swivel to a new object. On an average night the team expects to collect the light from 150,000 different galaxies and will rarely look at the same galaxy twice. While this might sound daunting, the tricky element with DESI isn’t mapping nearly 40 million galaxies over five years, but the 5,000 miniature robots that move each individual hair-like strand inside the telescope. “This is a very complicated instrument,” says Michael Levi, DESI Director. “It has a half a million moving parts.” Not unlike the way complex internal clock mechanisms work, DESI’s 5,000 robots are so small that if one thing goes wrong each time they shift, it risks the entire operation, and a setback in data collection.
We’ve mapped Mars, the Moon, the solar system, even our own galaxy. Which means there is only one thing left to understand in this symbolic way and that is the entirety of the cosmos.
DESI’s 5,000 eyes will spend five years looking back in time at ancient light to better understand the story of the universe. By collecting this data they will be able to decode the light’s journey across the void. While we don’t have any functioning DeLoreans just yet, we do have telescopes and telescopes are real time machines. It is easy to forget that the images we see of space are never from the present –– that light has taken billions or millions of years to reach us. When we study deep space, we are studying the past, objects as they once were, not as they are now. We do this by studying photons. A photon is one of the lightest particles in the universe which happens to be responsible for what we know of as light and they play a vital role in how DESI will help us understand dark energy and the expansion of the universe.
Because this light takes so long to reach us, each photon has a story to tell of where it comes from and where it’s been. These photons have spent billions and billions of years traversing the cosmos to get to Earth but when they enter the mirror of the Mayall telescope their journey isn’t quite finished. As the light enters each fiberglass cable, it will travel down the length of the telescope through each individual thread of glass another 40 feet and across the white tile floor into a room that houses 10 identical spectrographs. The instruments will break the light apart sort of like a mail sorting machine, only with the spectrum of light from each galaxy. Depending on the story of each individual collection of photons, it will appear in the instrument as either redshifted or blueshifted. As light travels, the colors within the spectrum appear at different wavelengths — if an object is moving toward us its light is crunched and appears toward the blue part of the spectrum, whereas if an object is moving away, the light is stretched out and appears red. After traveling many billions of years, the journey of the light from all 40 million galaxies will end in a clean room inside of a dome on a mountaintop in Tucson, Arizona.
After traveling many billions of years, the journey of the light from all 40 million galaxies will end in a clean room inside of a dome on a mountaintop in Tucson, Arizona.
In 1929 astronomer Edwin Hubble was studying the light spectra of galaxies and announced that his observations showed that many galaxies were redshifting — they were in fact moving away from us. But what he’d actually discovered was the expansion of the universe. Those galaxies weren’t just speeding away on their own, the very fabric of space-time itself was ballooning outward. He didn’t believe this was evidence of expansion; it would take another 70 years before scientists realized that not only was the universe expanding –– the expansion was speeding up.
Nearly a decade before Hubble took to the telescope, Albert Einstein proposed a theory called the Cosmological Constant in tandem with his theory of general relativity. The idea being that the universe was a static place and the density remained constant. When Einstein saw Hubble’s news about the redshifting galaxies he threw this theory away, except Einstein was sort of right, go figure. The universe is not a static place — we know it’s expanding rapidly, but the density in the universe still remains constant. Think of it like this, imagine you’re in your living room with a table and TV and some books and a cup of coffee. Now imagine if that room began to expand like a balloon and got bigger and bigger. The objects in your living room would not increase in density — they are what they are. This is the same with our universe, as it balloons out the density remains the same, hence, your cup of coffee is the cosmological constant.
This was a tricky thing for astronomers to accept for the longest time because there is a lot of matter in the universe. And because of gravity we know that matter clumps together, so shouldn’t the universe be contracting? Newer estimates by astronomers say that there could be up to two trillion galaxies in the universe which are made up of two types of matter. The matter made of “normal” things like you and me and your cat and desk and iPhone — represents only 5 percent of the matter in the universe. Dark matter, which we cannot see, is about 25 percent. That is a lot of mass, an