Last week, physics had a rare moment in the headlines after scientists announced they had made the first direct observations of gravitational waves, ripples in the fabric of spacetime predicted by Albert Einstein’s theory of general relativity. It was an astounding technological and scientific feat, decades in the making. Taking a page from our colleagues on the politics desk, who gather round to chat regularly, we asked some of our favorite astrophysicist-types to join us for a chat about the waves, what they mean for science, and what may come next.
- Christie Aschwanden: Lead science writer at FiveThirtyEight.
- Alan Lightman: Physicist, novelist and professor of the practice of the humanities at the Massachusetts Institute of Technology. His most recent book on science is “The Accidental Universe.”
- Katie Mack: Theoretical astrophysicist at the University of Melbourne, researching dark matter, particle physics and the early universe.
- Derek van Westrum: Physicist with NOAA’s National Geodetic Survey, specializing in terrestrial gravity measurements and their applications.
Christie: The big gravitational wave announcement happened about a week ago now, and the hoopla has mostly died down. I’ve gathered you all here today to discuss what’s next. How does this discovery frame our thinking about the universe? And where will it take us? What can we do now that we couldn’t do before?
Alan: No one doubted the existence of gravitational waves. We absolutely but indirectly inferred their existence with the binary pulsar a couple of decades ago.
Katie: And that won a Nobel Prize!
Alan: Yes, the new discovery — the direct detection — will also win a Nobel, probably for Thorne, Weiss and Drever. [That’s Kip Thorne, Rainer Weiss, and Ronald Drever, the founders of the Laser Interferometer Gravitational-wave Observatory (LIGO) that detected the waves.]
Christie: So given that this is anything but a surprise, what makes it such a big deal? And, maybe what I’d like to know even more: Why has this captured our imagination?
Derek: I think it’s literally a whole new kind of telescope. We can “see” (or maybe “hear” is better) things that were invisible before.
Alan: Better to use “hear” than “see” because this is not electromagnetic radiation, like light and X-rays. It is the vibrations of space, more like sound waves.
Katie: I think that the discovery, as a discovery, is immensely exciting. But the part that makes this thing game-changing and truly revolutionary is that it’s the start of gravitational wave astronomy. An entirely new field!
Christie: So a new tool AND a new field!
Katie: Yes, absolutely.
Alan: It’s a big deal for at least two reasons. As Derek says, it is a new kind of telescope. But also, it is a triumph of technology. It is the most sensitive instrument ever created by humankind. We will be able to see things we couldn’t see before — like oscillating black holes, quiet supernova, lumps in the early universe.
Katie: Up until now, we’ve been able to observe the universe with light and with certain kinds of cosmic particles. But this is fundamentally different — we’re looking at spacetime itself.
Derek: As an instrumentalist myself, that was the truly astonishing part. That this thing remotely worked! It’s incredible technology.
Katie: Yeah, the technological achievement is mind-blowing. I also love how much just came together perfectly for this. Until a decade or so ago, we didn’t have reliable simulations of black hole collisions. People had tried to get black holes to merge in numerical simulations and had to fudge something or the code would break. It was only in something like 2005 that a simulation was really successful, and what LIGO saw was pretty much exactly what the simulations predicted.
Alan: That was only a problem with the simulations, We knew that black holes would have to spiral in and merge.
Christie: I love the idea that we can use this to hear the early universe.
Derek: So I’ll let you both go for it on the astronomy side of things, but there is a separate chapter to Christie’s question: Are there important outcomes of this closer to home?
Alan: Closer to home might be a matter of coaxing the National Science Foundation and the National Institutes of Health to fund long-term projects without immediate payoff.
Derek: I would just add, as a taxpayer, I would pay cold, hard cash to know that the equivalent of three solar masses “disappeared” into gravity waves, and that was brighter than the visible universe. Incredible. But, that may just be me.
Alan: I wish all taxpayers were like you.
Christie: Me too!
Katie: I’m not sure how universal that is, but I definitely think there will be spinoffs to both the technology and the discovery itself that will have benefits we can’t even imagine yet.
Alan: Certainly to the technology. But I don’t think we need spinoffs to justify this. It is the same as justifying ballet.
Katie: I don’t need spinoffs to justify this, but it doesn’t hurt to point out to taxpayers that fundamental physics leading to new technology is a long and proven tradition!
Derek: That’s what I found so interesting about this particular announcement: It’s mind-blowing in itself, but if you wanted to “justify” it in terms of an investment, there really are things we can point to in the sensors that will have great payoffs. In manufacturing, for example.
Christie: I’ve noticed that gravitational waves seem to have captured the public’s imagination in a way that many basic science discoveries don’t. Do any of you have theories as to why?
Alan: For one thing, people love black holes, like dinosaurs. Also, the scientists were very very media savvy and orchestrated this with the press for months in advance.
Katie: I think a lot of people are picking up on how excited the physicists are, so that might be part of it. (I mean everyone I know who is involved in this stuff is positively giddy.) But also, people love black holes. And spacetime.
Derek: And they made it audible!
Alan: Yep. But when we detect much bigger black holes, they won’t be audible.
Christie: Yeah, I couldn’t stop listening to the chirps!
Derek: I still like to think of them like whale songs …
Katie: One of the things that makes this exciting for me is that it’s evidence of a massively violent event in the distant universe, but we’re not just seeing some vague image in the telescope. The instrument is actually being deformed by the gravitational waves. This is gravity coming to your house and moving your stuff.
Alan: Everything about this discovery is theatrical: 40 years in the making, generations of grad students, two 2.5-mile long tubes, black holes, audible signal.
Christie: Alan, do you think there’s a novel in here?
Alan: There is certainly a movie in this. Janna Levin is about to come out with a nonfiction book on LIGO, where she interviewed all of the principals.
Derek: And Alan — it comes ~exactly 100 years after Einstein thought of it
Alan: Yes, that’s another part of the theater. It was made for Hollywood, but it’s serious stuff.
Katie: Everybody loves a story about Einstein being a genius.
Christie: Einstein had some uncertainty about gravitational waves, right?
Alan: Yes, he did. He thought that the wiggles might be wiggles of the coordinate lines, like wiggling latitude lines on a globe, rather than real wiggles in space.
Christie: Does this feel like a moment that will give physics some propulsion in the coming years? Not just for those in the field, but in the public’s mind? Do you expect this success will make it easier to get funding for the next big project?
Derek: I think this gets back to “justifying the ballet.”
Christie: Yeah, we shouldn’t have to! But the reality is, we do.
Katie: I think this will definitely give the LISA project some propulsion. (Possibly literally.)
Derek: The thing that it isn’t obvious at first is that this project is actually relatively easy to point to as an investment: The techniques with quartz fibers and interferometers will be very useful in all types of manufacturing. And talk about delayed payoff: 100 years after general relativity was invented, there are practical uses for it.
Katie: There are lots of examples of delayed payoffs from obscure fundamental physics. Antimatter has led to PET scans, quantum tunnelling to certain kinds of transistors, etc.
Alan: Yes. The history of science is full of pure ideas and discoveries that then turned out to have practical application.
Derek: Just imagine if LIGO never worked! *gulp*
Alan: Robert A. Heinlein wrote a book about a society that prided itself in funding projects that wouldn’t succeed for 100 years. Unfortunately, the society kept messing up, and the wild-idea projects had practical applications within a few years.
Derek: That is worth a try
Christie: Last year I wrote about this theory of creativity that says that following interesting ideas and seeing where they lead you results in bigger payoffs than working toward a concrete goal. Seems true of science too.
Alan: That to me is a big implication here. Our national funding agencies, like NSF, NIH, etc., need to put money into pure research even if they cannot see an immediate payoff.
Katie: Yes, that’s hugely important. It’s easier to think outside the box if you ignore the box entirely.
Alan: Actually, gravitational waves, among all other waves, can penetrate the box, any box.
Christie: Yeah, this looks like a brilliant example of the payoffs of basic research, which you can never predict in advance.
Derek: I’m with you, but as devil’s advocate: If LIGO was just a continuous disaster, never producing results, we’d be having a different conversation right now, for sure.
Alan: I don’t think LIGO could have been a continuous disaster. We knew from theoretical calculation the likely sources of gravitational waves, the likely strengths, and we knew how sensitive the device had to be. We slowly but steadily worked towards that sensitivity.
It’s not like when we searched for the decay of the proton, where we weren’t sure of the underlying theory.
Christie: I wonder though if it would be helpful to science if funders could embrace failure a little more. Sometimes it’s the best teacher.
Alan: Totally agreed. You have to risk failure to get results, certainly results like this one. There is a saying in Bridge, the card game: If you don’t lose half your slam bids, you are not bidding them often enough.
Derek: That’s a good point, and I’d say it speaks to the quality of the funding agencies: They seem to be able to recognize a plausible, even if difficult, idea. At least that’s my impression. It sounds like maybe you think they could be more daring?
Christie: So, Alan, how could funders adopt an approach that’s not afraid to fail?
Alan: Well, none of us are saying that funders should support failure. But we are saying that funders should take some chances on longer bets and not always be looking for quick payoffs. Funders should support very solid and dedicated scientists who they trust, like Thorne, Weiss and Drever.
Derek: I’d add that sometimes, if it’s “reasonable,” you can try things where you expect one outcome, but another would open lots of new science. The ether is the classic example: They all expected it to be there, and when it wasn’t, voila! Way more interesting stuff …
Katie: Funders should also support new investigators and new ideas, though. Can’t always be just the top established people. There’s a lot to be said for funding experiments based on expected value, right? High risk but high reward experiments are just as important as stuff that’s almost certain to pay off but isn’t revolutionary.
Christie: Katie, do you think this could inspire a new wave of physicists?
Katie: I definitely think young people will be inspired by this. Black holes and warped spacetime were the kinds of things that got me excited as a kid.
Alan: The astonishing thing is that the physical event was so clean. Two black holes spiraling into each other is far neater and more predictable than a black hole and a neutron star, for example.
Derek: Were there other, messier events that probably generated gravitational waves, but we just can’t tell? What are the chances that the “first” was so perfect? And from a direction where the Louisiana detector could so clearly ”hear” it first.
Alan: I believe that LIGO has been picking up other, smaller and messier events. Nothing is as clean as two black holes spiraling into each other. You don’t have to know anything about the crust of a neutron star, etc.
Christie: So we’re running out of time. Shall we wrap up with a few final thoughts?
Alan: It’s a great day for science, and the human civilization that has produced our science.
Derek: Agreed — this is an amazing achievement that is beautiful, interesting and will surely lead to things we can’t imagine now.
Katie: It’s the start of a whole new era — a new branch of astronomy! (I’ve been saying that a lot over the past few days, but it’s not at all an exaggeration.)
Alan: We are back in the time of Galileo, but looking forward.
Christie: Thanks so much for your time, all. It was a delight to have you here.
Alan: Until the next black hole collision!