A strange issue in whale-tracking software off the coast of Massachusetts has led researchers to believe a fin whale's call may contain hints of the same mathematical limits that helped shape Albert Einstein's special relativity, suggesting that standard methods for locating nearby whales could be off by hundreds of meters.
Here's what to know
The effect was described in Physical Review E by John Spiesberger, a visiting scholar in the Department of Earth and Environmental Sciences at the University of Pennsylvania, and Eugene Terray of the Woods Hole Oceanographic Institution.
For researchers trying to find whales, acoustic monitoring can be more useful than waiting for a sighting from shore or from a boat. Spiesberger said in a school release, "Sound from a fin whale can be heard from 100 kilometers (62 miles) away underwater with a single hydrophone." He added, "Because those calls travel so far, we can use them to pinpoint where an animal is by comparing when its sound reaches receivers spread across the seafloor."
A receiver can pick up more than one version of the same call — one that arrives directly and another that reaches it after bouncing off the ocean surface. Because the reflected sound comes later, the signals can interfere with each other and change the apparent arrival time.
More background
The anomaly surfaced while Spiesberger was tuning a computer program used in whale-tracking calculations. Instead of returning the usual seawater sound speed of about 4,921 feet per second (1,500 meters per second), the code produced erratic results.
"The first time, we got a number that was around 1,000 meters per second," he says. "And then, further on, I got values that were sometimes 3,000 meters per second. I immediately thought there was a bug in my program."
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His review of the software led to a physical explanation rather than a coding fix, explaining that when a whale is close to the surface, a receiver may detect both the direct call and a surface-reflected echo. Physicists call that effect temporal interference.
If monitoring systems miscalculate a whale's location by even a few hundred feet (meters), that error can undermine efforts to understand animal movement and behavior with precision.
What's being done?
The researchers' work indicates that whale-tracking models can be updated to account for interference rather than treating each call as if it traveled along only one route.
Hydrophones remain one of the best tools for detecting whales across long distances — particularly in conditions when visual spotting is unreliable. Better math could help researchers use that existing equipment more precisely.
Accounting for that slight change in perceived arrival time could make it easier to map the positions of whales near the surface. Much can be hidden in a single ocean sound.
"Most of us don't hear a whale call and think, 'Wow, look at the special theory of relativity in action,'" says Spiesberger. "I would have never guessed any connection existed."
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