After the rollout of the spectacular first images from NASA’s James Webb Space Telescope, a fellow journalist emailed me a question: “Does Webb allow us to see the entire universe?”
I did what I always do when astrophysically befuddled: I emailed Garth.
Garth Illingworth is an astronomer at the University of California at Santa Cruz. He played a key role in dreaming up the Webb back in the late 1980s, knows everything there is to know about the telescope, and answers even my dumbest questions promptly and compassionately.
“We can only see the part of the universe that is within the light travel time from us for the age of the universe — so what we can see lies within a huge ball (monstrous ball!), but it is not all of the universe,” Illingworth responded. “The universe may be infinite, but regardless it is bigger than what we can ever see!”
He added a merciful postscript: “Really hard to get one’s head around this, I agree.”
Let’s put aside the brain-boggling size and possible infinitude of the universe for one moment. The successful launch, deployment and early scientific returns from the Webb are a big deal in astronomy. But make no mistake: The universe is not about to reveal all its secrets.
We Earthlings lug around a very long and daunting list of Things We Don’t Know. The new telescope can chip away at them, but most of the unknowns will have to be handled by future scientific instruments. And by future scientists — the ones currently in grade school, peppering parents with basic, and quite excellent, questions, such as:
Is there life beyond Earth?
Are there alien civilizations?
What is the fundamental essence of matter and energy?
What causes gravity?
Why is the universe expanding, and what will be its fate?
And then there’s the ultimate question (might want to loop in some theologians and philosophers): Why is there something rather than nothing?
The Webb telescope, orbiting the sun roughly 1 million miles from Earth and performing beyond expectations, is designed with certain unknowns in mind and isn’t optimized for solving some of the others. The telescope was dreamed up by scientists primarily as a tool for capturing some of the first light of the universe, emitted not very long after the big bang, when ungainly little galaxies were just starting to form and had not yet grown into majestic spirals like Andromeda or our own Milky Way.
Scientists describe those distant objects by their “redshift” — how far their wavelengths of light have been shifted toward the red end of the spectrum by the expansion of space since the big bang. The higher the redshift, the more distant the galaxy in space and time. There have been other infrared telescopes — the Spitzer Space Telescope explored that realm, and even the Hubble sees a little way into the infrared portion of the spectrum — but the Webb has a much bigger mirror. There has never been a telescope that could see in such detail those very early galaxies.
“It is like humanity just got a brand-new pair of eyeglasses for the distant universe,” planetary astronomer Heidi Hammel told me in an email. Like Illingworth, she has a gift for explaining things in ways we ordinary folks can understand. Her email continued: “We are suddenly seeing that those green areas on the tops of trees are actually made of thousands of individual leaves. We suspected it, but we are now seeing it for the first time.”
The universe has an amazing archival feature: light. It travels at a finite speed of about 186,000 miles per second. And it keeps going, and going — capable of crossing the cosmos until it encounters something, like a dust particle or the mirror of a telescope.
Astronomy is a form of cosmic archaeology, because everything we see is a snapshot of some point in the past. A light-year is a measure of distance — about 6 trillion miles. So when we see something that’s four light-years away, we’re seeing the light it emitted four years ago. Andromeda, the nearest large galaxy, is a couple million light-years away. The earliest galaxies emitted their light more than 13 billion years ago.
“The universe, it’s been out there, we just had to build a telescope to go see what was there,” project scientist Jane Rigby memorably declared at a news conference July 12 at NASA’s Goddard Space Flight Center, when the first batch of images were released.
To see that faint infrared light requires a telescope that can operate in ultracold temperatures. That means parking it far from our warmth-radiating Earth. It also means building a big mirror to serve as the light bucket. The engineers came up with a novel and risky design: 18 hexagonal, gold-plated mirrors that can be independently maneuvered and function as a single mirror about 21 feet across.
The mirror was so big the telescope had to be folded at launch in the nose cone of a rocket. While hurtling in space, it had to open up in a series of delicate deployments, like a flower blooming. That included the unfurling of a five-layer, ultrathin sun shield the size of a tennis court.
NASA and its partners — the European and Canadian space agencies — gambled that all this would work perfectly. There was virtually no margin for error. The engineers could command the telescope to shimmy and shake if something got jammed, but that was a crude emergency option. The Webb was on its own out there, too far away to be fixed by astronauts, and with no modular parts that could be swapped out, unlike the instruments on the Hubble.
The scientists were nervous. The engineers were nervous. The NASA bosses were nervous. Count this reporter among the people who thought this telescope had an excellent chance of becoming a $10 billion paperweight.
“It is impossible to convey how hard it really was,” John Mather, a NASA scientist who won a Nobel Prize in physics for his research on the early universe and is senior project scientist for the Webb, told the crowd on July 12.
But it did work, and now the attention pivots from the amazing engineering to the amazing science.
Jane Rigby patiently walked me through what the Webb can and can’t do. One thing I learned: Even a million miles from Earth, with that sun shield providing the equivalent of SPF 1 million, the Webb isn’t in total darkness. The heavens glow in the infrared part of the spectrum because of sunlight bouncing off dust.
“It’s our stupid solar system,” Rigby said. “It’s the zodiacal cloud. It’s the light from our own solar system. We’re stuck in our solar system, and we can’t get out of it.”
The Webb probably won’t be able to see the very first stars, she said, “unless they’re kind enough to blow up for us.” But already, the Webb has detected a galaxy that emitted its light just 300 million years after the big bang — easily a record. The instruments on the telescope can do spectroscopy on that light to see what elements are present.
“How do we make us?” Rigby asks — and then explains what she means by that very simple question. “How do you make oxygen, carbon, nitrogen, iron? How do you make the periodic table? I think that’s going to be really important science that comes out of Webb.”
One of the most exciting tasks of the Webb will be to scrutinize exoplanets — planets that orbit distant stars. One tantalizing target is Trappist-1, a red dwarf star orbited by seven planets, several of which orbit in what is considered the habitable zone where water could be liquid at the surface.
Webb can’t see these planets directly — it gleans information from how they alter the light from the stars they orbit — but should be able to discern if they have atmospheres. Red dwarf stars periodically emit violent bursts of radiation, and astrophysicists want to know if planets around such stars can hang on to their atmospheres amid those stellar storms. Webb should answer that and potentially detect atmospheric water vapor, methane and carbon dioxide. That wouldn’t be proof of life but would refine our understanding of exoplanets. Future telescopes could possibly see not only atmospheres but surfaces, including “ocean glint,” said Knicole Colon, another astrophysicist at NASA Goddard.
Colon told me she is curious about whether the Trappist system has multiple habitable planets or, like our own solar system, just one. And she pointed out a basic truth about new astronomical tools: They always turn up something that wasn’t on the planning document.
“I don’t know that we’ll ever solve the universe, because every time we launch something new, we make new discoveries that are not expected — and then we have to figure those out,” she said.
Here’s a life-beyond-Earth question that scientists might someday be able to answer: Can a planet have just a little bit of life? Can life eke out an existence on superficially barren places like Mars? Or does life, when it gets a foothold, typically run riot, transforming its environment into a biosphere completely smothered in living things?
“There’s an idea that you’re either pervasively inhabited or you’re not. You’re not just a little bit alive if you’re a planet,” Shawn Domagal-Goldman, a NASA Goddard astrobiologist, told me. “But that’s an idea. The whole point of science is that we have to test that hypothesis.”
The fact that there are so many unknowns should not be confused with the silly notion that we don’t know anything at all. Everyone has heard some version of this idea, which is not an intellectual argument so much as a moral one, a kind of chastisement for arrogating to ourselves the belief that we can understand our physical reality.
Hogwash. If you lived a few centuries ago and asked an astronomer how many light-years distant is the Andromeda Galaxy, the answer might be “What’s a light-year?” (and also “What’s a galaxy?”). The power of science is that it tells us what is true — or at least gives us the best, provisional approximation of what is true — rather than what we’d like to believe or what seems apparent at first glance. When Copernicus overthrew the Ptolemaic model of the solar system and displaced us from the center, it was just one step in a long and stunning journey to discover how we fit into the universe.
Science, broadly speaking, has been so successful over the last half-millennium that it has raised the bar for young researchers, particularly in physics. Watching an apple fall from a tree just isn’t going to cut it anymore if you are working on a dissertation. You may need to analyze data from an entirely new tool — like the Webb telescope.
Maybe one reason it is so hard to understand some of the fundamental features of the universe is that it’s outrageous on its face. It is packed with untold trillions of stars and galaxies and planets and moons, as well as complex organisms that ask hard questions about why they exist. That’s a lot of stuff to decode. If the universe were much simpler — just a lot of hydrogen and helium floating around — it wouldn’t be as inscrutable. It would be just a big, boring gasbag. (And it would run for president!)
What will be the Webb’s greatest discovery? Its most significant contribution might simply be its successful deployment as a tool that produces prodigious amounts of science. Maybe someday we’ll figure out gravity, cosmic destiny and life on other worlds, but for now let’s just remember that we’re making progress on the great unknowns.
Technology almost surely cannot solve every one of our global problems; a fancy new telescope isn’t going to feed the hungry, promote justice, end war or suppress the worst effects of climate change. But when something like the Webb comes along — a collaboration of NASA, international space agencies, the private sector, and the collective genius of scientists and engineers across the world — it reminds us that we can still do the hard stuff.