What exactly is swimming?
Although it appears to be a simple question, it is important to be specific. Moving your body through water (a moderately viscous fluid) that is either still (as in a swimming pool) or turbulent (as in the ocean) or somewhere in between is what swimming is all about. If you’re swimming completely beneath the surface (as in scuba diving), you’ll be moving through relatively calm water; at other times, you’ll be moving along at the more turbulent interface between air and water, with your legs, arms, head, and body moving from one element to the other and back again, speeding up or slowing down as they cross the border between the two elements.
Water vs. air is a debate that continues to this day.
Before we can understand the science of swimming, it is important to remember that air (a gas) and water (a liquid) are very different (a liquid). The most significant difference is that water is significantly more dense (a given volume of water weighs significantly more) and viscous (in other words, thicker—in the same way that treacle is viscous relative to water).
The difference between air and water has a significant impact on our ability to move through the air and on land. For most people who walk on land, the most difficult thing for their bodies to do is to fight gravity (by lifting their legs, swinging their arms, and preventing them from falling over by making constant adjustments to their balance). There is also a small amount of friction where your shoes meet the ground. The force of air resistance becomes more important than the force of gravity when you move more quickly (for example, when riding a bicycle); however, unless you’re walking into a particularly strong wind, you barely notice the wind while you’re walking. In water, gravity is significantly less important because your buoyancy (proclivity to float) more than compensates for it. As a swimmer, the most important force to consider is drag, also known as water resistance. After that, we’ll discuss it further.
In addition, if you swim outdoors, particularly in the winter months, you should be aware of the following differences between water and air: water is much more dense than air (more precisely, it contains many more molecules per unit of volume, and those molecules are bonded together), and as a result, it removes heat from your body approximately 25–40 times faster than air at the same temperature. (This is why surfers and “wild” outdoor swimmers frequently wear wetsuits to protect themselves from hypothermia, a potentially fatal cooling of the body’s core that can occur.) As a result of the fact that water is denser than air, it takes significantly longer to warm up. As a result, in countries such as the East Coast of the United States and the United Kingdom, the ocean temperature typically lags behind the land temperature by 2–3 months on average (where the ocean is often warmest in September).
Newton’s laws of swimming are as follows:
If you enjoy science but are intimidated by the prospect of swimming, you will find it extremely helpful to think about Newton’s three laws of motion, as I did when I was learning to swim. These three fundamental principles of physics, which are among the most fundamental rules of physics, are sufficient to explain completely the movement of almost every single object you’re ever likely to come across.
The concept of inertia is defined in the first law of motion. It states that unless something pushes or pulls them, things will remain stationary or move steadily (at the same speed) (unless some kind of a force is applied). The second and third laws are the ones that pique my interest the most. The second law of motion explains the relationship between force and acceleration: if you push or pull something, it starts moving (if it wasn’t already moving) or accelerates (if it was already moving); the greater the force applied, the greater the acceleration obtained; and the longer the force is applied, the greater the change in momentum that can be achieved.