These Whale Calls Appear to Break Physics, but the Truth Is Even Weirder

While tracking whale calls near Massachusetts, oceanographer John Spiesberger noticed that the software he was using was clocking speeds for whale calls greater than the speed limit for sound traveling in seawater. Spiesberger, of the University of Pennsylvania, initially thought there was something wrong with his program. After all, if the software wasn’t to blame, it would mean that those whale calls were “breaking” physics.

It turns out there wasn’t anything wrong with his coding, nor was there any violation of physics: what he was seeing was even weirder than that. The exceptional speeds seemed to have come from a physical effect caused by the hydrophone receiving not only the direct sound wave but also its echo, reflected against the ocean’s surface. Combined, these signals make it appear as if the whale calls went supersonic, when in reality, the observed phenomenon is an effect of wave interference, an unexpected finding predicted by Einstein’s theory of special relativity.

“Most of us don’t hear a whale call and think, ‘Wow, look at the special theory of relativity in action,’” Spiesberger said, who recently published his findings with co-author Eugene Terray, from the Woods Hole Oceanographic Institute, in Physical Review E. In a University write-up on the research, Spiesberger added that he’d “never guessed any connection existed.”

Most physicists will come to the rare agreement that general and special relativity reflect some of Einstein’s best, most consequential observations. Special relativity explains the relationship between space, time, mass, and energy (it’s also where the famous E=mc 2 equation comes from). In a vacuum, the speed of light is the same for any observer. But this is relative to an observer’s reference frame. For instance, a whale and a human swimming are subjected to the same laws of physics, but because they’re moving at different speeds, the two “frames” experience time and space differently.

To give a more practical example , GPS devices depend on a network of satellites with atomic clocks to precisely keep track of locations. But these satellites whiz around Earth’s orbit at blinding speeds, which means they—“relative” to the time we experience—tick an extra 7 microseconds each day. So, the atomic clocks on satellites must subtract 7 microseconds daily to keep things consistent with the time we experience here on the surface.

According to Spiesberger, oceanographers depend on hydrophones to track whales. These devices allow scientists to find whales from 62 miles (100 kilometers) away underwater. When the hydrophone picks up far-traveling whale calls, scientists then “can use them to pinpoint where an animal is by comparing when its sound reaches receivers spread across the seafloor,” Spiesberger explained.

But the sounds get mixed up when a whale is physically closer to the ocean surface. In the first place, a whale call isn’t a singular, neat wave packet that bounces off the hydrophone’s receiver.