Reflections on academic life

Water waves and physics

UBC physicists and civil engineers have successfully tested a theory by eminent physicist Stephen Hawking. In 1974, Hawking posited that black holes emit a weak level of radiation even as they exert gravitational pulls so strong that little can escape, not even light. The UBC team published results in a recent issue of Physical Review Letters.

Study co-author Prof. Gregory Lawrence, who teaches in the Faculty of Applied Science, helped to design simple experiments that featured water flowing over an obstacle in a six-metre flume. Holder of a Canada Research Chair in Environmental Fluid Mechanics, Lawrence provided expertise in investigating an analogy between water waves and black holes.

How did you get involved in this study?

I was intrigued by [UBC theoretical physicist] Bill Unruh’s discovery that the mathematical equations describing some aspects of the physics of black holes are the same as those governing water waves in a moving fluid.

Were you surprised that you got the results you did?

It was a collaboration that you could never plan. Frankly, we achieved more than I had dreamed possible with such simple equipment in such a short period of time. It has been the most fulfilling research experience I’ve had.

What was one of the “aha” moments?

At one point, Bill and I were watching long waves in the flume and saw something we didn’t expect: a small group of short waves that appeared after the long waves disappeared. It was very subtle, but we had seen something new. We turned to each other and it was like “Did you see that, or was it a ghost?”

What made the research experience so fulfilling?

Several things. The experience of working with an interdisciplinary team on a problem that was completely new to me. The discovery of results of great interest to theoretical physics using simple experiments performed in a flume usually devoted to undergraduate teaching. The realization that these experiments also revealed new aspects of water wave mechanics that are counter to what I had been taught.

The prospect that our results are of engineering relevance, for example, to the study of flooding caused by tsunamis traveling up rivers. Finally, I used to stick my hand in the flume to illustrate waves travelling upstream. But it didn’t work because I wasn’t imposing long enough waves. In future I will ensure that I generate longer waves.

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