Albert Einstein first predicted the existence of gravitational waves 100 years ago as part of his General Theory of Relativity, but even he had doubts about whether they might ever be detected.
Last Thursday, in an announcement that has scientists giddy with excitement, their existence was confirmed.
Three local scientists Vicky Kalogera, Shane Larson and Daniel Holz were among the more than 1,000 scientists from around the world who worked to develop the Laser Interferometer Gravitational-Wave Observatory (LIGO), the instrument that made this discovery possible.
Vicky Kalogera is a chaired professor of physics and astronomy at Northwestern University and the founding director of the astrophysics research center CIERA. She has worked on the gravitational waves project for more than 15 years.
Shane Larson is a research professor of physics and astronomy and part of Kalogera's CIERA research team at Northwestern University. He is also an astronomer at the Adler Planetarium.
Daniel Holz is an assistant professor at the University of Chicago where he is studying astronomical phenomena including black holes, supernovae and dark matter. He also works on the LIGO project.
The discovery has literally opened up a new way for scientists to look at the universe and may one day enable us to see the very moment of creation itself, the Big Bang.
We spoke with Kalogera, Larson and Holz by phone on Monday afternoon. Below, some highlights from the conversation.
Why is the science community so excited about this discovery?
Shane Larson: If I had to list the most important discoveries of the last 100 years in astronomy, this has got to be right up there at the top of the list. It’s as important as discovering that the universe is expanding, it’s as important as discovering that there are other galaxies outside our own.
Gravitational waves are a way of looking at the universe in a way that we are physiologically incapable of sensing. The idea that we can see the universe in gravity is something that is completely enabled by technology and by this great discovery that Einstein made 100 years ago.
Daniel Holz: What is most exciting for me is that it really is opening a new window; this is a whole new way to learn about our universe. We can turn on this new kind of telescope – it’s like an ear – and it’s like we are listening to the universe for the first time. And we’ve just turned this on and the first thing we hear are these two black holes crashing into each other. But now we’re going to hear all sorts of things. We are venturing into this unknown … it’s really just incredibly exciting and really is a sea change in physics.
Explain how this is a new window on the universe. Is it analogous to the difference between and optical and radio telescope?
Holz: I would say that is probably not the right way to think about it in the sense that they are both part of the same spectrum – it’s all light, just different frequencies and colors. So radio is light with very long wavelengths … What’s interesting here is that it’s a whole different new spectrum that we’ve never had before.
It seems that one of the most amazing aspects of this discovery is that we are able to build machines sensitive enough to be able to detect gravitational waves.
Vicky Kalogera: It is amazing. In fact LIGO is the most precise measurement humans have ever made. There is nothing else anywhere in science that beats the precision with which these detectors are working – not just in the field of gravitational waves, but across all fields of science. So it is an amazing feat. And in terms of technology development, many things were pioneered within the LIGO project that down the road will affect many different disciplines.
What’s the possibility of seeing the moment of the big bang?
Larson: Gravitational waves are very, very hard to detect, and the reason they’re very hard to detect is because they don’t interact with ordinary matter very readily – they go right through us without us knowing because the effect they have on us is so tiny. The fact that they don’t interact with matter is why they are so useful for the study of astrophysics.
The reason you can’t see back more than about 400,000 thousand years after the big bang is that the matter is so dense that photons of light can’t get out. But gravitational waves don’t care about all that. We can go all the way back to the beginning and no matter how dense the matter gets the gravitational waves still get out. So the holy grail for all of us would be to detect gravitational waves from the big bang.
Holz: … We don’t expect the waves from the big bang to be strong enough to detect with this detector.
Do you think future scientists will be able to get that picture of the first moments of the creation of our universe?
Holz: Yes. We believe those gravitational waves are there. All we have to do is build more sensitive instruments. We don’t know how much more sensitive they need to be because we don’t know how strong the waves will be. But we will certainly look, and I would hope that at some point in the future we will be able to measure those gravitational waves from just a tiny fraction after the big bang – which would be amazing.
I understand there are some 1000 scientists from 16 countries working on this project. Is that correct?
Kalogera: Correct. It is a big team involving scientists in many disciplines. In fact astrophysicists are not the majority within the collaboration; it is mostly scientists who work on the instrument because making the detector able and sensitive enough to detect these signals was an incredible challenge and an amazing success for the collaboration. There are also many scientists working on the data analysis.
Below, Kalogera and Larson discuss the first detection of gravitational waves by LIGO on Sept. 14, 2015.
Learn more at Adler Planetarium
Want to learn more about this exciting discovery? The Adler Planetarium has a temporary exhibit called "LIGO Discovers Gravitational Waves," which continues through Feb. 29. The Adler's website states the following about the exhibit: "In the Adler’s Clark Family Welcome Gallery, visitors will be able to watch a video explaining this direct observation in more detail while also enhancing their knowledge on LIGO." For location and ticketing information, visit Adler's website.