There’s a big hole in the Indian Ocean. It’s nothing you can actually see. And the ocean itself isn’t especially deep. Instead, it’s a hole in Earth’s gravitational field—the weakest pull across the entire planet.
The “hole” was discovered in 1948. It’s centered about 750 miles off the southwestern coast of India. It covers more than a million square miles—more than a third the area of the Lower 48 states. Gravity there is so weak that surrounding regions of the ocean pull water away from it. As a result, sea level above the hole is about 350 feet lower than the global average.
Sound travels farther in water than it does in the air, and acoustics are an important aspect of daily life for marine creatures ranging from whales to coral. In addition to communication, many marine animals rely on sound for navigation, hunting, avoiding predators, and choosing ideal places to live. Baby oysters are among the many species that depend on sound cues in their environment to determine where best to settle down. But researchers in Australia have discovered a growing challenge for oysters: the interference of human-created noise in the ocean.
