Starts With A Bang

Ask Ethan: do gravitational waves exhibit wave-particle duality? (Synopsis)

Image credit: NASA.

“You asked me how to get out of the finite dimensions when I feel like it. I certainly don’t use logic when I do it. Logic’s the first thing you have to get rid of.” -J.D. Salinger

Now that gravitational waves have been verified to exist, and the first black hole-black hole merger has been definitively detected by LIGO, it’s time to start thinking of the next steps in gravitational wave astronomy. The biggest one we can dream of, perhaps the holy grail of this field of study, is to go beyond General Relativity itself, and to find evidence that gravitation is a truly quantum theory at its core.

Image credit: Dave Whyte of Bees & Bombs, via

If that’s true, then these gravitational waves should exhibit wave-particle duality, just like all the other quantum entities we know of. In this case, detecting the wave-like phenomenon, which took a century to do, was the easy part; detecting the particle nature of gravitons will be the hard part. Nevertheless, even though this is likely beyond the reach of LIGO, future missions will have a chance to see these quantum effects down the road.

Image credit: Wikimedia Commons users Dr. Tonomura and Belsazar. Note how the interference pattern becomes discernible with enough particles, even though they’ve been passed through the double slit one-at-a-time.

Go get the whole quantum gravitational story on this week’s Ask Ethan!