Why Can't We Walk on Water: Beyond Newton's Third Law

Humans have long fantasized about the idea of walking on water, a concept that has been explored in literature, movies, and even in mythological and religious stories. While Newtons Third Law plays a role, the primary reason we cannot walk on water involves more complex physical principles, including buoyancy, surface tension, and the forces exerted by our bodies on water. This article explores these concepts and explains why, despite our attempts, we cannot walk on the surface of water as effortlessly as some insects or in the image of the mythical characters like Jesus Christ.

Buoyancy: The Principle of Floating

To understand why we cannot walk on water, it is essential to first comprehend the concept of buoyancy. Buoyancy is the upward force exerted by a fluid (in this case, water) on a submerged object. For an object to float, it must displace a volume of water equal to its own weight. Humans, unfortunately, are denser than water. This means that when we try to walk on water, we do not displace enough water to provide sufficient buoyancy to support our weight. As a result, we sink.

Surface Tension: The Thin Skin of Water

Another key factor to consider is surface tension. Surface tension is a phenomenon that allows small objects, like insects, to walk on the surface of water due to the cohesive forces between water molecules. However, surface tension is not strong enough to support the weight of a human. Insects can stay on the surface of water because they are much lighter than humans, and the surface tension provides enough support for their weight. This is why molecules can dance on the surface of water but we cannot.

Newton's Third Law: Action and Reaction

Many people mistakenly believe that Newton's Third Law, which states that for every action, there is an equal and opposite reaction, means that we can walk on water as easily as we can walk on the ground. This is a common misconception. Newton's Third Law explains the forces at play but does not change the fundamental fact that our weight exceeds the support that water can provide. When we push down on the water with our foot, the water exerts an upward force, but this force is insufficient to counteract our weight, resulting in us sinking rather than walking.

Science Unraveled: Why We Fall

The concept of "falling" due to gravity is a natural phenomenon that we experience daily. The Earth's gravity pulls objects towards its center, and this is what causes us to fall when we step off a cliff or lose our balance on the ground. The same principle applies when we try to walk on water. However, it's important to note that the mass of objects significantly affects how they interact with gravity. When we throw a stone, we can see the effects of gravity because the stone has a relatively small mass compared to the Earth. Conversely, when we consider the Earth's mass, the force we impart would be negligible and would not significantly alter its motion. This is why, even if we could exert a force equal to our weight on the water, the water would not move enough for us to lift ourselves.

Conclusion: The Combined Forces at Play

In summary, the inability to walk on water is primarily due to our density being greater than water, insufficient surface tension, and the limits of buoyancy. Newton's Third Law describes the forces at play but does not change the fundamental fact that our weight exceeds the support that water can provide. The principles of buoyancy and surface tension, along with the laws of gravity, combine to explain why we cannot walk on water as effortlessly as some insects or in the mythological image of having the ability to walk on water.

While Newton's laws and other physical principles provide us with a deep understanding of why we cannot walk on water, they also highlight the fascinating and complex nature of the natural world. It is through such principles that we can appreciate the beauty and intricacy of our surroundings and the physics that govern our every movement.