As The Toast searches for its one true Gal Scientist, we will be running a ton of wonderful one-off pieces by female scientists of all shapes and sizes and fields and education levels, which we are sure you will enjoy. They’ll live here, so you can always find them.
I really did not mean to end up on a dark energy project.
In fact, the year I applied for jobs, it was a running joke. Inevitably every year there is some “cool” topic that you must insert into your job applications. My year it was dark energy. Studying planets? Better mention dark energy. We all chortled as we applied for all the jobs we would not get, and figured out how to include a paragraph about the inevitably far reaching vague overlap with dark energy.
I took a job on a dark energy project.
I love building things. I am an instrumental astrophysicist. I build spectrographs. These instruments take light, and turn it into rainbows. We use spectrographs to measure properties of stars, planets, and galaxies. We can learn how fast objects are travelling, and in which direction. We can measure how hot they are and deduce how long they’ve existed. We can measure all the different gases that make up the objects and in what ratios. We can watch solar systems be born and watch stars die. Not just pretty pictures, but the physics that governs the universe.
You did read that correctly. I build rainbow-making machines. Don’t judge.
I was drawn to my project because I think it is outrageous – we are using a novel instrument technique to measure dark energy, a truly mysterious piece of cosmology. By the end of this I want you to have a grasp of what dark energy is – but more importantly, I want you to have some idea how we do this wacky thing that is science.
One of the most misused and misunderstood words is “Theory.” In general use, “theory” tends to mean “an idea I had once while I spent an extended time in the bathroom.” Scientists, on the other hand, mean “a deeply developed and tested framework that has consistently passed observational tests and fits into our larger understanding.” This mismatch leads to people showing up to every talk I’ve ever given with very intriguing ideas as varied as a new way to make warp drives work, why our universe is actually very tiny but deceptive, or why Einstein was wrong (this one is exceedingly popular.) Usually they ask that I be able to disprove their “theory” in five sentences or less, ideally with no math.
This is sometimes a bit challenging.
I introduce this dilemma because dark energy comes out of a slew of interleaved theories. Many of which are elegant, all of which are a bit mathy. If you find yourself intrigued, I would invite you to come audit a class at your local university. No joke. Most instructors are happy to have you, you’ll be able to learn a ton more about cosmology, and you are not even required to have your own theory of everything. So let’s jump right in.
What is dark energy?
Dark energy is. Or rather, we think it is. Dark energy is a placeholder for something we haven’t discovered yet, but in our current understanding of the universe ought to be there. Is there. Depending on what it is. You see now why this is difficult. But intriguing because we can talk a little bit about how theory and observation help us build an understanding of physics.
(As a brief aside, here is what dark energy is not: dark energy is not dark matter. Dark matter does exist, and we have measured it. This stunning picture of the Bullet Cluster is an elegant demonstration of the existence of dark matter. We don’t quite know what dark matter is either, but it interacts gravitationally and so we can “see” it, even if it doesn’t radiate like “normal” (baryonic) matter. It was foolish to end up with dark matter AND dark energy, and it is confusing and unhelpful linguistically. Thanks, astronomers. If you think that’s impressive, you should check out our acronyms.)
The cosmic microwave background (CMB) is one of the most beautiful physics results, which not only has expanded our physical knowledge every time we’ve improved its measurement, but has resulted in one of my favorite comics. I love it because the theory and the measurement demonstrate such clear and tight symbiosis.
The CMB is radiation from the very early universe. Sometimes called “a baby picture of the universe,” it is a heat signature that has cooled throughout time. It was predicated initially by Alpher & Herman, and then “rediscovered” by Robert Dicke. His group was working on an experimental project to search for the signal when they got summarily scooped by two experimental physicists battling pigeon poop at a lab down the road. While trying to bring a radio antenna online, Penzias and Wilson found a background signal they couldn’t eliminate, no matter what. In a last ditch effort to get at their data, they climbed up and scrubbed off pigeon poop they thought might be interfering. It wasn’t, and they measured the CMB for the first time (and received a Nobel Prize for their troubles.) Measuring the CMB also confirmed the expansion of our universe.
This idea that everything is moving away from everything else that we call centerless expansion is a surprising enough result. But then it begs the question. What happens next? Does the universe expand forever? Does it collapse back on itself? What does an expanding universe look like?
If you humour me, and we accept that this weird expansion is happening, you might next assume that we’re expanding but slowing down. Gravity exists and even if the universe is expanding, an obvious answer is that gravity acts as a cosmic brake.
Ok, but we’re scientists, so let’s go measure it. That’s usually how we do it. We have some idea, using what we know and what we have measured before, and then we go check. Fantastic.
Several teams set about measuring the expansion of the universe in different ways, to see what the heck was going on. This is challenging because we have to observe further and further away from us (back in time.) This means studying fainter and fainter objects, which perhaps unsurprisingly can get hard. In 1998, scientists studying supernovae discovered that not only was the universe expanding but the universe was actually accelerating in its expansion. How is that even possible?
Well, that’s a bit of a kick in the pants for our intuition.
Everything in space is moving away from everything else. And it keeps going faster and faster all the time.
The universe didn’t always behave this way. That’s the even weirder part. The interaction between matter (dark & “normal” matter) and dark energy has changed throughout time. In early times, the universe was matter-dominated universe. That means the overall behavior of the universe was dominated by matter (and therefore the effects of gravity.) Now we live in a dark energy dominated universe. That means the effect of dark energy is the stronger, and causes our universe to expand and accelerate rather than contract. Understanding how and why the universe has evolved is one of the key questions in cosmology today.
So that’s what we’re doing. With a bucket full of theories to test, we’re going back to the measuring. There are quite a few projects using different techniques to measure this dark energy and its evolution throughout time. Our measurements will look at different times throughout cosmic history and measure the evolution of dark energy. We do this by measuring almost a million Lyman alpha emitters (LAEs.) These are young galaxies that are very bright at a particular wavelength of light that is often caused by star formation. Imagine these LAEs spread over time and space like a net. We measure the distribution of these galaxies, looking at the distortions in the net to understand the underlying peaks and valleys of the dark matter distribution. Our survey will take three years to complete, and net not only LAEs but a wide range of galaxies and stars. Astronomers are waiting to pluck those objects up and study them in more detail.
If this sounds like a lot, it is. Our project has taken over a decade from its initial bar napkin sketch to installing hardware on the telescope. We collaborate with institutions and companies around the world. There are hundreds of people involved at all different levels, from undergraduates to senior faculty. The budget is tens of millions of dollars, and that’s academic money – the amount of shared effort that isn’t “counted” in dollars would make that number look small.
We have started working out in West Texas, at the Hobby Eberly Telescope. We expect to start taking survey data in the Spring of 2015. And then the data analysis starts.
In the meantime, I’m just building 156 rainbow-making machines. Because who can resist looking up and discovering the universe?
APPLAUSE
SO COOL
This mismatch leads to people showing up to every talk I’ve ever given with very intriguing ideas as varied as a new way to make warp drives work, why our universe is actually very tiny but deceptive, or why Einstein was wrong (this one is exceedingly popular.) Usually they ask that I be able to disprove their “theory” in five sentences or less, ideally with no math.
OMG so true and also you are hilarious!
How is that so many people are convinced Einstein is wrong? I have paper and email files full of multifont/multicolor “proofs” people have sent me, and I’m not even a physicist–I just work at a famous science place as an office lady.
Also, do you want to build a perpetual motion machine? Cuz I’ve got diagrams. Lots and lots of diagrams.
I work as a student assistant in the physics department at my university and we get some of those, too! EINSTEIN WAS WRONG I FIGURED IT OUT HERE’S SOME CRAZY STUFF GIVE ME ONE MILLION DOLLARS
I’m going to throw out a wild guess about the gender of most of these people – are they perchance dudes?
I listened to an episode of This American Life once, and it was about some electrician dude who thought he had disproved Einstein, with NO PHYSICS BACKGROUND. And the episode was all about the REPORTER trying to get a physicist to check the theory, and the REPORTER getting all put out when physicists were all “Nope, not having anything to do with that.” The reporter was all “Why aren’t they interested, close minded academics,” clearly expecting the audience to agree.
I hate-listened, just waiting for the guy to get shut down. And… he got shut down, and refused to believe it.
Obvious ending much? Aaaah, so much rage!
It’s like creationists who get all pissed off when biologists refuse to “debate” them.
Fascinating! You are my science spirit animal.
Also, nice work on the off-hours job.
Right? I just saw that. So rad. Space rainbows and affordable, accessible abortions for all!
This is awesome and I want to know more.
Here’s what I don’t get: We can see the expansion of the universe by measuring the motion of galaxies that are billions of light years away, which means we are seeing how they moved billions of years ago. How then, do we know what they’re doing NOW? Is it all just math that I gave up on trying to comprehend years ago?
So, uh. Any Young Wizards fans out there feeling distinctly unsettled right now? Because as far as I can tell Wizards at War is 100% real based on this and probably that explains this horrible summer, maybe.
okay that aside THIS WAS REALLY COOL and building rainbow machines sounds like an impossibly, unassailably cool job. You must have the best time meeting new people and waiting for the “so what do you do” part.
Yay for the Young Wizards Series!
It is wonderful to meet new people and talk about science. The only time it isn’t is:
1) On airplanes when I’m very tired. Usually someone senses that, and also asks about God. or
2) At parties, several drinks in, when people want me to do physics on napkins.
That being said, a shocking amount of astrophysics is done on napkins, while mildly intoxicated. (Don’t quote me.)
A shocking amount of all inspired thinking happens that way, I think.
Man, I hope the Toast picks you as their Gal Scientist. I love physics and you explain things so clearly. Like, Feynman’s-QED-lectures-clearly.
Is this the Bullet Cluster pic? It’s fantastic and I need to learn about gravitational lensing now.
That is exactly it! The link didn’t make it, but well done! The composite image of the Bullet is fantastic because it is SO BEAUTIFUL and also *chock full* of physics.
I love rotating through various deep-space photographs as my desktop background. Because of SCIENCE.
awesome article, thank you
*pretend there’s a clever gif here with the caption reading “CONTINUE….” Maybe someone has their fingers steepled.*
I love all this stuff. It’s so amazing and fascinating (just learned something about the etymology of that word today and now I feel a little odd whenever I type it…) and a combination of humbling and empowering. We are going through the new Cosmos series with our kids…uhh that’s kind of related, right? Science (and rainbows)!
This article is awesome. The content is great, and more than that, you’re a fantastic communicator. I suspect this stuff is way more complex than I realize, but you did an amazing job telling us about it. Thank you, and please keep writing about science. You’re really, really good at it, and we always need good scientific communicators.
And now I’m sorry I didn’t follow through on my childhood dream of being an astrophysicist. No one told me there were rainbow machines!
There’s a Heimdall joke in here somewhere, I just know it…
Yes and no! Sometimes I think the easiest way to think about it is to surrender to this fact: The only now relevant is what we can measure. Yes, true, when we look back in time we’re also looking back in space. But we truly have no way to *observe* those galaxies at high redshift at any other times, right?
But you bring up one of the trickiest parts of studying cosmology. We can’t “set galaxies going and see how they evolve” except with simulations. We measure *different* galaxies at *different* times and compare them. So we see how those Lyman alpha emitting galaxies moved many millions/billions of years ago – and we can measure galaxies that are local and see how they move now, and compare them.
There is some incredible work being done in “forensic astronomy” – For example, we can study faint streams of stars around the Milky Way and study how dwarf galaxies might have accreted or interacted with our galaxy in the past. We’re getting better at “measuring” the past. Slowly but surely.
In general use, “theory” tends to mean “an idea I had once while I spent an extended time in the bathroom.” Scientists, on the other hand, mean “a deeply developed and tested framework that has consistently passed observational tests and fits into our larger understanding.”
…which nevertheless began as an idea had once during an extended visit to the bathroom. I’ve been on to you scientist types and your ways for a while now–long enough to even have one of them scientifical PhDs and all (but in math, so not really a science). I can confidently state as a fact that virtually all of the conceptual progress I made on my thesis happened while I was showering, or while I was unable to get out of bed in the morning (for suitably math-grad-student values of morning like, say, 2pm), wracked by guilt that I hadn’t made enough progress on my research lately.
My best dissertation-related decision was the result of me screwing up monumentally and writing down the name of the wrong guy to look up in the library. The one I wrote down by accident turned out to be a far more important figure than the one I intended to focus on.
It's like creationists who get all pissed off when biologists refuse to "debate" them.
My best dissertation-related decision was the result of me screwing up monumentally and writing down the name of the wrong guy to look up in the library. The one I wrote down by accident turned out to be a far more important figure than the one I intended to focus on.