Vigilant soldiers, when on night watch, sometimes insert the iron “cleaning rod” from their gun into the ground and place their ear against the end of the rod to detect movements on the ground within a range of two hundred steps.
Why is this? It’s because solids transmit sound much better than air. Scientific research has shown that sound travels ten times faster in steel than in air, and the ground also transmits sound faster and more clearly than air.
Dogs don’t understand this principle, but they instinctively apply it. At night, when they sleep, you’ll see them always pressing their ears to the ground. This habit has been passed down from generation to generation.
The ancestors of dogs are wolves. These ferocious beasts prey on other animals, but they are also hunted by many other animals. To protect their own lives, they must remain highly alert to their surroundings. While staying awake during the day is not a problem, it becomes an issue when sleeping at night. Fortunately, their keen hearing helps a lot. When they press their ears to the ground, they can hear any sound and wake up immediately. Thus, whenever a dog is startled awake, it will raise its head and look around to determine the direction of the sound.