“Ping….ping…..p i n g…..”
We heard it in the U-boat movie Das Boot. And in Run Silent, Run Deep. And in the History Channel special about the Battle of the Atlantic. A single “ping” figures in a plot twist during The Hunt for Red October. The “ping” is the sound of underwater hunting.
It’s the sound of sonar.
When early U-boats threatened to cut off England in 1917, British scientists worked feverishly to invent a way of tracking submerged subs. The answers came in the between-war years. A machine would emit a metallic “ping” into the water. If there was a large object underwater nearby, the ping would echo back and be amplified by the machine. The time between ping and echo-ping told the distance; the strength of the echo told the direction.
Sonar went to war big time in 1939. Combined with the code-breakers who deciphered U-boat orders sent by radio, plus anti-sub aircraft, the Allies defeated the new U-boat offensives in 1943 and 1944.
What’s that got to do with our new fossil hall?
Our field crews have brought back the largest single fossil ever dug from the Permian Red Beds of north Texas. Check it out:
It’s the “Judy Block”, a slab of pond sediment 10 feet long and three tons in weight. Inside are dozens and dozens of complete skulls and jaws from a new species of Panzer Mudpuppy. These were bottom-living amphibians, distant cousins of frogs, who crowded onto the riverbeds and ponds all through the Early Permian 295 to 275 million years ago.
And our Judy Block is a dramatic lesson in Nature’s Passive Sonar.
Active Sonar is used by porpoises and whales — they make clicky noises underwater and use the echoes to find food and, in the mating season, each other.
Passive Sonar is more elegant and delicate. The sonar operator doesn’t ping or click — that would give away the operator’s position to enemies. Instead, the passive sonar operator listens with extremely sensitive microphones. The Hunt for Red October demonstrates how submariners avoid making any noise but just listen and listen and listen — every tiny sound being amplified by the best acoustic equipment. The fossils in our Judy Block show Nature’s equipment in the fossil amphibian.
Look at the skull:
Running across the bones are a system of sonar canals (technical label: “lateral-line canals”). Most fish have those canals today. Many frogs have a similar apparatus. Under the microscope you’d see a marvelous device. Tufts of tiny sensory hairs are clumped together inside jelly capsules (the jelly is secreted by the cells that hold the hairs). The capsules are connected to nerves that run to the brain.
Imagine you are a Permian Mudpuppy and glance at the three scenes here:
You sit still on your pond bottom. You are passive. But your sonar is super-alert. The water is so murky that you can’t see anything. Doesn’t matter. A fish wanders by above your head. It suspects nothing. But the fish’s tail sends out vibration waves through the water. Minute vibrations bump into the sensory hairs in your sonar canals. You’ve got thousands of the hair clusters, and so your brain knows where the fish is swimming and how fast it’s going.
Your fire-control computer in your brain knows instinctively what to do. Wait. Wait … wait … then FIRE!
You twist your head up. You open your jaws wide. The sudden suction draws the fish into your jaws. Chomp! Yum.
Sonar canals were features of most early amphibians. You can see them in the giant Gator-Headed Amphibian, Eryops, that ruled the waterways in the Red Beds times. In the new hall, we will display a complete Eryops across the pathway from the Judy Block.
When you come to the new exhibit, pause at the Judy Block. Stare at the sonar canals. Get lost in a time-travel reverie. Multitudes of those animals lived their lives through millions of years, each generation being successful through the high-tech acoustic machinery.