In all fields of science, sometimes more is learned when you fail at what you’re trying to do than when you succeed. So what new science discoveries have failed expectations given us in astronomy?
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Female Speaker: This episode of Astronomy Cast is brought to you by Swinburne Astronomy Online, the world’s longest running online astronomy degree program. Visit astronomy.swin.edu.au for more information.
Fraser Cain: Astronomy Cast episode 417: Expectation Failed. Welcome to Astronomy Cast, our weekly facts-based journey through the cosmos, where we help you understand not only what we know, but how we know what we know. My name is Fraser Cain. I’m the publisher of Universe today. And, with me is Dr. Pamela Gay, a professor at Southern Illinois University, Edwardsville, and the director of Cosmo Quest. Hey Pamela, how are you doing?
Dr. Pamela Gay: I’m doing well. How are you doing, Fraser?
Fraser Cain: I’m doing great. Just to let everyone know, this is the penultimate episode of this season of Astronomy Cast. So, we have this episode, and then we have one more episode, Title Unknown. And then, we will take the summer off, as we always do, and then we’ll be back right after Dragon Con in early September.
So, if you’re wondering why episodes aren’t showing up on your podcatching software, that would be why. We’ll be back, don’t worry. Don’t cry.
Dr. Pamela Gay: So, in looking at what would be possible for the next show episode, we’ve been taking somewhat advantage of the HTTP error codes since we hit number 400 because it’s fun. And, error code 418 is, “I’m a teapot.”
Fraser Cain: Whoa.
Dr. Pamela Gay: And, we need to figure out how to turn that into an episode.
Fraser Cain: Well, I mean, obviously when you talk about some kind of quantum mechanics –
Dr. Pamela Gay: Tempest in a teapot?
Fraser Cain: No. Well, either. We could talk about sort of – anyway, there’s a ton. Seriously? That’s the 418 error code?
Dr. Pamela Gay: That’s the 418 error code.
Fraser Cain: I love it. I’ve got a million ideas. We’ll talk after the show.
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Fraser Cain: Got a theory? Great. Now, go out and test it. Today, we talk about what happens when you turn up the unexpected, from dark energy and relativity to the heliocentric model of the universe.
So Pamela, today we’re gonna talk – this is sort of one of your recommendations. We are gonna talk about when you have a theory, and then you try to go test it out, and what happens when, perhaps, nature doesn’t conform to what you were expecting, either in the good way or in the bad way.
So, let’s go all the way back to the beginning of, I guess, modern science, ancient Greek science, and talk about one of the first situations of this.
Female Speaker: I think the best example of, “Well, that didn’t work,” was poor Kepler kept trying to come up with equations to map out the planetary motions assuming circular orbits. And it turns out planets, they really don’t move in circles. They move in ellipses: slightly flattened circles. And so, there was a whole lot of expectation failed in terms of making careful observation, careful observation, putting together the equations, putting together the equations, predicting what should be seen, and not seeing it.
Fraser Cain: Right, but this all sort of comes on the original model of the universe developed by Ptolemy, right? Was that the Earth was at the center of the universe, and there were all these crystal spheres surrounding us, including the sun, and that all of these spheres would turn. And, it would pretty well explain the motion of the universe.
And then, Copernicus flipped things around and put the sun at the center of the solar system, and had the earth just be another planet. And, that also made sense. But, it didn’t predict –
Dr. Pamela Gay: It didn’t work.
Fraser Cain: It didn’t work. It didn’t predict the motions of the planets as well as the Ptolemaic system did that people had been grinding away on for hundreds, and even thousands, of years.
And so, you’ve got this expectation that all the planets are going in these perfectly circular orbits around the sun, didn’t work. How did they get that resolved?
Dr. Pamela Gay: Well, so once poor Kepler figured out – well, and he started from the supposition that Earth is not the center of the solar system. He did start from the Copernican notion that the sun is in the center.
And, because he was working from math, he eventually just had to have that leap of ingenuity, that leap of creativity, to try a different shape. Once he tried an ellipse, suddenly everything fell into working. He could make accurate predictions of everything, except for one annoying little world.
Fraser Cain: Which annoying little world?
Dr. Pamela Gay: Mercury.
Fraser Cain: Okay, so what was wrong with Mercury?
Dr. Pamela Gay: Well, it was our next expectation failed kind of problem, and this is, Mercury is in so close to the sun that to fully understand its motion. You have to take into account not just Kepler’s equation of motion, not just what Newton came up with to explain the extra pulls and tugs that become apparent that Newton was able to explain. But, you actually have to have a relativistic correction to fully get at Mercury’s motion.
Fraser Cain: Right, and they had no idea about relativity. So, they did these really great observations of all the planets, got them all to within really accurate points, but then Mercury just kept drifting away. How off was Mercury?
Dr. Pamela Gay: It wasn’t a huge amount, in terms of, “Oh, Mercury is nowhere near where I expect it to be.” But, it was definitely a – the star it’s behind, or the star that’s behind it, rather, is not the correct star, by a small amount through a telescope eyepiece. If you were to very carefully watch Mercury year after year after year, you’d see that over the course of a century, it moved about 43 arc seconds off of where you’d expect it to be compared to the background stars.
Fraser Cain: Right, right. So, you’re sort of – I mean, with the other ones, you could say, “Maybe we’re making some observational error. We’re a little off.” But, Mercury was just completely not where it was supposed to be.
Dr. Pamela Gay: Right. And, so this works out to about half an arcsecond a year, and good telescopes can make out one or two arc seconds. So, over a matter of years, this becomes more and more and more noticeable, with more and more, “What the insert-expletive-of-choice is going on?”
Fraser Cain: So then, how did they finally resolve that?
Dr. Pamela Gay: Well, for about 300 years, there’s a whole lot of scratching of heads. Now, 300 years is a bit of an exaggeration because it wasn’t Kepler who immediately noticed the problems. Because, they were still working from not the best optical systems out there. And, in fact, a lot of the work that he was working from, it wasn’t telescopes they were using, it was very careful alignment circles, big old chunks of metal, where they’re measuring essentially with fixed sextants where things are on the sky.
With that kind of technology, it wasn’t Kepler who was noticing this, and data taken by Tycho Brahe. But, over the decades and centuries of telescopes, up until the early 1900s, when Einstein started working on his theory of relativity, which was able to predict and explain Mercury’s precession. Mercury is not quite in the right place, according to Newtonian physics.
It was Einstein, in the early 1900s, that fixed the problem with our expectations.
Fraser Cain: Right. And so, there was a couple of other experiments that they did as well around that time, to confirm Einstein’s theories on general relativity. In fact, they’re still attempting to directly observe. I guess we’ve wrapped up the final Einsteinian prediction with the direct detection of gravitational waves.
But, it’s just this sequence of new kinds of observations that they were able to do to prove both the movements of Mercury, as well as some of his other suggestions.
Dr. Pamela Gay: And, at a certain level, I think because relativity, like quantum mechanics, is so non-intuitive, that it’s going to be at least a few more generations, if not forever, that people are going, “And, we shall test general relativity in this new direction now.” Just to confirm, one more time, that your expectation is wrong, and reality is much trickier than –
Fraser Cain: Have you ever heard that anecdote with Eddington, where someone asks him, “Is it true, Dr. Eddington, that you are one of the three people in the world who understand relativity?” And he stopped, and thought for a while, and then someone’s like, “What’s wrong? No?” And he’s like, “No, I’m just trying to think about who the third person might be.”
Dr. Pamela Gay: Yes. When I was at Harvard, we had a professor who was introduced to me as one of the two people that understood string theory in the United States. And, I decided I didn’t want to ask who the other one was.
Fraser Cain: Right. So, okay. So we’ve got – turns out, looking for circular movements of the planets, and it turns out there are ellipses, and everything changes. And then, trying to use those elliptical motions of the planets, and it turns out that they’re under relativistic motion, and sorry, but not sorry.
So, what’s another example where you went looking for one outcome, and you got a completely different outcome?
Dr. Pamela Gay: So again, at the turn of the 1900s, technology in astronomy was going through the second renaissance. We went from having telescopes; to suddenly we started to be able to do amazing glass plate photography. And, this brought on a whole new set of things that we were finally capable of doing, with longer exposure times.
And, one of those things that we were finally able to do was take spectra to spread the light out through prisms, or diffraction gratings, so that we could see the individual emission and absorption lines produced by the atoms, the gas, in stars and galaxies.
And, part of doing this included many different folks looking out at galaxies. And, the expectation was that we lived in a steady state universe that had kinda been around forever, would be around forever. It was neither expanding nor contracting, it was just steady.
And, if you live in a steady galaxy, it was assumed that about half the galaxies would be moving towards us, about half would be moving away from us, and it would be this nice, friendly, random distribution. And, it was a fellow by the name of Vesto Slipher, working out at Lowell Observatory, who was the first to notice, “No, most of the galaxies, they’re running away from us. Most of them have light that is shifted towards the red.
And, this meant that we were either in a special place that caused all the galaxies to run away, or we lived in a different kind of universe that we couldn’t understand at that moment. Now, the thing was, all he knew was the galaxies tended to be moving away from us.
Fraser Cain: Right, and so the expectation, and the perfectly natural expectation that you would think of, is that you would imagine something else that you’re familiar with. Like, imagine birds flying around you, or you’re out on a boat and there’s a bunch of other boats. And, some boats are moving toward you, and some boats are moving away from you. And, some boats are sort of hanging out at the same distance. And, by detecting those motions, you can start to get a sense of what’s going on.
And, the completely unexpected result is all these galaxies are all moving away from us. What’s wrong with us? Why do they hate us? Right? I’m sure it was a blow to his ego.
So, what was the sort of understanding that they came to?
Dr. Pamela Gay: Well, so Henrietta Leavitt, working at Harvard College Observatory, figured out that you could use pulsating variable stars to measure the distance to, well, anything that had a variable star we could observe in it. So using Cepheid variables, Hubble, the Hubble, Edwin Hubble, was with his colleague Milton Humason.
They took glass plate spectra and images of a variety of nearby galaxies, measured the distance using those pulsating variable stars, those Cepheids, with what we now call the Leavitt relationship, for their distance. And, he made a plot of the distance to the galaxies compared to their recession velocity, or their approach velocity, so their red-shift or blue-shift.
And, what he found was, the more distant something was from us, the faster it appeared to be going. And, it was the nearby stuff that had this random mix of moving away and toward us. And, the way we now understand this, thanks to Hubble, who actually put the idea forward, is the nearby stuff, it’s gravitationally bound to us. We’re all kind of in this local group together.
But, once you look beyond our local group, we start to see things getting carried away from us by the expansion of our universe. And, something that’s nearby doesn’t have enough stuff between us and it to do the expanding. But, the further something is away, the more stuff is between us and it. And all that extra stuff, all of it’s expanding.
Which means that further away stuff, with more expansion going on, is going to be carried away faster.
Fraser Cain: So, fine. That’s all fine, Hubble, and obviously this led to the concept of the Big Bang cosmology, and this understanding that the entire universe was once a singularity, and then it’s been expanding ever since. Don’t ask what came before the singularity. That is not a question that the Big Bang attempts to explain.
But, I know that just in the last, say, 20-ish years or so, astronomers tried to really get a good sense of exactly how fast the universe is expanding, and exactly when it’s going to slow down and stop.
Dr. Pamela Gay: Right. So, back in 1998 – and, I think most modern professional astronomers have this year etched into their brain. Because in 1998, two different supernova detection experiments, two different groups of observers, who were trying to measure the expansion rate of the universe by looking at super novae that have really bright spectral lines, that can be detected at these great distances. And, which also have a standard brightness.
Because, they’re just explosions of a set amount of material. If you consistently blow up the same amount of star, you end up with, essentially, the same brightness of explosion.
So, by being able to measure the expansion rate, using things with a set distance yet again, they were trying to get at, “How does the expansion rate of our universe change with time?” And, the thought was that three different things were going to be happening. We were either going to slow down so much that, eventually, gravity pulled the whole universe back together and crunched us, and we died by fire.
Or, perhaps the universe’s expansion was going to ever, just, slow. Until asymptotically, which is a fancy math word for, “In infinite time,” the universe, essentially, stopped. The final theory that we had was that it’d be enough that, while it was slowing down, it would never slow down so much that it stopped.
These were the only things that we really even considered. Because, to consider anything else was to say that when you took the integral of one of Einstein’s equations, you got an extra constant that changed the acceleration of the expansion rate. That it wasn’t just a single rate forever, but that it was a changing rate over time.
And, all of us just wanted to set that constant to zero. It made the math lovely. But, as Chris Impey once put it in a very strongly emotional talk, “No one ordered this constant up, but the universe put it there.” And, what was found in 1998 was all of our mathematical assumptions that you could set this constant to zero were completely wrong. And, our universe does indeed have an acceleration term, and that acceleration term is causing our universe to expand at an increasing rate forever. Forever.
Fraser Cain: Right. Thanks, Einstein.
Dr. Pamela Gay: Hey, the guys did get Nobel prizes for it.
Fraser Cain: You know what I find interesting, is that people find that outcome – the heat death of the universe, this accelerating expansion, this cold, quiet, long thing – I find people generally find that more sad and depressing than the big crunch. This idea, that the universe is gonna come to a stop, and then it’s gonna come smashing in, and everything’s gonna get mulched up. For some reason, that’s the one they were hoping for, as opposed to the one that we’ve got. And, I find that really weird because this one gives us more time.
Dr. Pamela Gay: Yeah. But the Big Crunch, we get to see everything later. It’s like a reverse diaspora. Everyone comes back to visit, and then kill you.
Fraser Cain: So, okay, so there’s dark energy. And, it really is the classic. I mean, it is the gold standard of completely opposite results that came from doing some kind of observational astronomy. I love it. Do you have any more for us?
Dr. Pamela Gay: Well, dark matter. You can’t mention dark energy without mentioning dark matter.
Fraser Cain: Then you just mentioned it. Begin. Proceed.
Dr. Pamela Gay: So, I guess it started with Vera Rubin going out and, while working on her graduate degree, measuring rotation rates. And finding, “Nope, doesn’t match the mathematics.” You can add up all the luminous light – and different experiments have shown that this works if you’re looking at spiral galaxies, doing the spiral galaxy rotation thing, if you look at a variety of galaxies in a galaxy cluster. No matter what it is that you’re looking at, the things in the outskirts of the system are moving way faster than our predictions that add up all the luminous stuff – way faster than our predictions say they should be moving.
So, this meant that there had to be stuff out there, stuff permeating our whole galaxy, permeating all of galaxy clusters. In fact, permeating a lot of space: stuff that we can’t see via the electromagnetic force. And, that’s just perplexing and difficult to think about.
And, again, expectations failed. The idea that there’d be something that didn’t reflect light, didn’t emit light, that was just out there being a gravitational suck, well, we didn’t predict that, but it’s sure out there. And, over the decades, over the scientific generations of discovery, we’ve been able to figure out it’s, at least in part – perhaps not all of it, but it’s at least in part, some sort of a particle that we haven’t fully identified yet.
Fraser Cain: Yeah. And I mean, the thing is, with dark energy – I mean, we know a little more about dark matter than we know about dark energy, in that what we know with dark matter is that it’s probably not gravity. It’s probably some kind of particle, and we probably have a sense about what its cross-section is, how big it is. But, that’s kinda it. And, we know that it doesn’t emit electromagnetic radiation. But, that’s about it. Dark energy, we’re like, “Uh-uh.”
Again, we know it’s there, and that’s all we got.
Dr. Pamela Gay: Right, and sometimes that’s that’s all the universe gives you. This is why we keep doing science, and keep building new and fancier detectors, to do new and interesting experiments to try and figure out not just what this crazy stuff is, but to keep looking for – well, our greatest discoveries seem to keep coming out of this expectation failed.
Fraser Cain: One of my favorite conversations to have with space scientists, some of the people that are running – like, the principle investigators for various missions – you talk to the people who are working on the Dawn mission, or the people who are working on New Horizons.
When they do the mission, they have a bunch of stuff that they’re looking for, but I think the part that tickles them the most is the stuff that they weren’t even expecting. And, so now we see these close-up pictures of Pluto, and we see these amazing mountains of ice, and these plains of ammonia and methane, this weird hydrological cycle. We look at Ceres and we see these bizarre salt deposits at the middles of these craters.
It’s like, every time that a new instrument is created, that gets out there and actually is able to start taking a look at a new region of space, or with more sensitivity, it turns up these surprises.
There’s one – we talked about the expansion of the universe. There’s one great story, that I know you probably know by heart, and this is the radio telescopes, back in the 1950s, that were working on –
Dr. Pamela Gay: Microwaves.
Fraser Cain: Yeah, on microwaves.
Dr. Pamela Gay: Right. So, people always teach little kids that when you make a discovery, it’s a “Eureka!” moment. But, I think most discoveries, that are unexpected like this, are actually deeply rooted in the, “Huh? Wait, that shouldn’t have happened. What did we do wrong?”
And, for two gentleman working at Bell Labs, Penzias and Wilson, they were trying to, basically, plot out what is all of the interference in the microwave band, that people building receivers for commercial communications would need to worry about.
So, when Penzias and Wilson built their big horn, and discovered that there was, essentially, this background noise no matter what direction they pointed their detector in, the first reaction was, “What the heck? Where’s the noise in our electronics? What did we do wrong? Is there something wrong with our horn?”
There was a great deal of scrubbing of pigeon poo, as one does, and the truth was, no matter how much pigeon poo they cleaned out of that horn, that noise was still there. Because, the noise is part of our universe. And, what they had discovered, what their expectations had failed to account for – I really love error code 418 – What they failed to account for, is our universe has this constant background of microwave light that had actually just been predicted by folks working up at Princeton University as being one of the natural outcomes of having a Big Bang, of having a singularity that expanded out from a hot, bright everything into the universe we have today.
So, what they found was something that, well, a few people had started to say, “Well, this is something we should detect,” but it wasn’t generally in the list of things that were being looked for. And, they just happened to find it a little bit ahead of their time.
Fraser Cain: Yeah, that one’s a great one. Okay, are there any fairly recent ones that spring to mind?
Dr. Pamela Gay: Pluto.
Fraser Cain: Pluto; that Pluto exists?
Dr. Pamela Gay: Well, no, we knew Pluto existed. But, it should not have active tectonics. I don’t think any of our basic expectations of what Pluto should look like came anywhere near reality. We had expected this ancient, pockmarked world, that was just gouged up with craters and fairly flat, other than what was created by the craters. Think moon, but icy.
And, what we found instead, was something that is geologically alive, that has active resurfacing, that has some sort of a heat generation mechanism that is causing convective cells. This so broke with all expectations that there’s probably going to be literal generations of researchers dedicating their lives to trying to model. How do you get what was seen in that far-too-swift fly-by?
And, unfortunately it will probably be the next, or the next next, generation of astronomers that finally gets us to return to that icy world.
Fraser Cain: Yeah. And, I mean, we’re starting to run out of time. We could do this all day long. We’ve got hot Jupiters. We’ve got pulsars, quasars. I mean, there’s so many things that turned up completely unexpectedly, and even some modern stuff. Yeah, this could go on forever.
And, I think when I talk to the anti-science people, a lot of the time they say that science is like a religion, and you don’t – you won’t – you’re not open-minded, and you don’t – and I think that’s ridiculous. Because, so often these outcomes happen, these discoveries are made. They completely change people’s expectations and their theories on what they thought they knew, and what they understood.
And, the scientists just go, “Okay. Well, this is the new world, now. Now, I understand it a little better. My old way of thinking was stupid, and didn’t fit, and I have rejected it. And now, I am thinking about this the new way.” They are open-minded.
And, there’s so many examples of these.
Dr. Pamela Gay: Neutrinos. We never talked about how neutrinos changed flavors.
Fraser Cain: Yeah, we can go on and on and on. So, that is the point, that I think there are so many of these events that you make one observation, and it overturns the current understanding of the world, and the universe as you knew it, and you’re into a new one, and that’s great. And, scientists love it. They love to be wrong.
Dr. Pamela Gay: And, I think it’s important to know that our great discoveries come from moments of, “Huh. That’s not right,” and discovering we’re what’s not right, because the universe is far more interesting than anything we could imagine.
Fraser Cain: Yeah, we just didn’t understand it yet. Well, thanks Pamela.
Dr. Pamela Gay: My pleasure.
Fraser Cain: Thanks for listening to Astronomy Cast, a non-profit resource provided by Astrosphere New Media Association, Fraser Cain, and Dr. Pamela Gay. You can find show notes and transcripts for every episode at astronomycast.com. You can email us at firstname.lastname@example.org. Tweet us @astronomycast. Like us on Facebook, or circle us on Google Plus.
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Duration: 33 minutes