Science to Live By: Our Senses (Part Five): Touch

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© J. Dirk Nies, Ph.D.

Touch is our most intimate and encompassing sense. Touch is more physical, solid and corporeal than our more ethereal senses of sight, hearing, taste and smell. Nothing says ‘I am here for you’ as much as does a heartfelt handshake, a friend’s arm over our shoulder, or the loving embrace of a mother comforting her child. Our sense of touch affects in profound ways our physical, emotional and spiritual wellbeing, which in turn leads to its many meanings. When we are in a dicey situation or critically ill, these circumstances often are described as “touch and go.” When we are mentally confused or lose connection with the world, we are “out of touch” with reality. A person who is easily convinced, especially to give or lend money, is considered “a soft touch.” When artists or athletes perform with a high degree of skill and finesse, we say they showed “great touch.” Poems such as Maya Angelou’s “Touched by an Angel “and the fresco painting by Michelangelo in the Sistine Chapel showing the hands of Adam and God reaching towards each other capture how important the touch of love is to our lives.

At a fundamental level, everything physical thing that we touch is made of atoms: Atoms of hydrogen, carbon, nitrogen and oxygen and the other elements that have combined together in myriad ways to make the clothes we wear, the food we eat, the air we breathe, the water we drink. And yet, from the point of view of atoms, it’s a miracle that we can touch, feel or manipulate any of these things. Why do I say this? Because atoms, and the molecules and substances made from them, are almost completely empty spaces. For example, if all vacant space could be stamped out from each and every atom that makes up my body (like flattening empty cardboard boxes), I would stand less than 0.1 millimeters tall. I would become microscopic–although I would still weigh as much as I do now.

To comprehend this thought, we need an understanding of the structure of atoms. Atoms are made of two distinct parts that possess mass, positively charged nuclei and the much smaller, negatively charged electrons. Not unlike how the orbits of the planets around the sun define the size of the solar system, the orbits of electrons as they swirl around the nucleus define the size of the atoms. And like our solar system, there is a huge amount of unoccupied space between the parts.

To get an inkling of the overall volume occupied by an atom compared to the volume of its solid parts, consider this. Hydrogen, the simplest of all elements, consists of a single proton (its nucleus) and a single electron. If the proton at the center of a hydrogen atom were enlarged to the size of a basketball, its associated electron would grow to the size of a grain of pollen. Correspondingly, the volume of the hydrogen atom, that is, the sphere defined by the outer extent of the electron’s orbit, would balloon from its nanoscale dimensions to more than 9 miles across!

If this make-believe, basketball-sized proton were positioned at the intersection of Three Notch’d Road and Crozet Avenue, its pollen-grain-sized electron would wiz around an area bounded by Greenwood, White Hall, Ivy Corner and Batesville. And since the electron’s orbit is three dimensional, it also would travel to depths as deep as the ocean floor and soar as high as the highest peaks of the Andes.

So with this inflated atom now pictured in your mind, how likely would it be for me to physically bump into either the stationary ‘nuclear’ basketball or its orbiting ‘electronic’ grain of pollen if I am out for a stroll at Crozet Park? I contend not very likely at all. So it is with all matter under ordinary conditions; the nuclei and electrons of adjacent atoms never touch one another.

What is it then that we feel when we touch something solid? What makes concrete concrete? Force fields.

Four fundamental forces are at work in the universe. They are the gravitational, electromagnetic, strong nuclear, and the weak nuclear forces. The everyday phenomena that we experience are controlled by the first two, gravity and electromagnetism. The two nuclear forces show up in the strange, quantum behavior of the subatomic world of elementary particles of quarks, leptons, bosons and gluons, which are the fundamental building blocks and glue of matter. (For example, a proton consists of 2 ‘up’ quarks and 1 ‘down’ quark held tightly together by the strong nuclear force (gluons).

From the point of view of physics, commonplace interactions between our bodies and external objects, such as when we hold hands, are understood primarily as interactions among electromagnetic forces (and the quantum mechanical Pauli exclusion principle, which we happily will ignore for now).

Keep in mind that opposite charges attract each other while like charges repel. So the first action that happens when we begin to touch another object is repulsion. For example, when I reach to shake your hand, the aggregate electric fields, created by the electrons of my hand, repulse and are repulsed by the aggregate electric fields established by the electrons of your hand. And this, along with the innate stability of molecules, is a very good thing if we are to maintain our physical integrity. Otherwise, given all the empty space available, our hands would meld and blend.

The power of these repulsive negatively charged force fields is attenuated, however, by the simultaneous attraction of the positively charged nuclei to the negatively charged electrons of each other’s hands. And this, too, is fortuitous, otherwise we might not have sufficient strength to overcome the repulsive force and shake hands, or to touch anything else for that matter.

Changing our point of view from physics to physiology, our sense of touch arises from our body’s complex somatosensory system comprising thermoreceptors and mechanoreceptors geared to recognize temperature, pressure, vibration, pleasure and pain and then send these messages to our brain. This marvelous system, which covers and embeds the skin, skeletal muscles, bones and joints, internal organs, and the cardiovascular system, helps us properly monitor and interpret the physical world within us and around us. As remarkable as it is, it is nevertheless susceptible to paresthesia, those unreal sensations we experience when we strike our funny bone and suffer the stings of “pins and needles” or when a limb goes numb and “falls asleep” due to restricted blood circulation.

The human hand is our most important touch-sensor of the world. The 18th century German philosopher Immanuel Kant once said that “the hand is the visible part of the brain.” Handshakes affirm good faith and verify the lack of a handheld weapon. The hand is so important that it often denotes the entire person, as in “I’ll lend a hand” or when we refer to a laborer as a “hired hand.” When chaos erupts, we say that things have gotten “out of hand.” When the hero comes riding in to save the day, we know that the townsfolk are in “good hands.”

Research on premature infants receiving intensive care shows that those who are frequently handled by their caregivers gain weight and thrive better than those deprived of touch. A study of patrons of a university library who were subliminally touched on the hand by the librarian as they checked out books reported much higher satisfaction with the library than those who weren’t. Touching a person can even increase honesty and altruism. Investigators have consistently found that the likelihood of lost money being returned to the rightful owner significantly increases if the one who found the money, when asked for help, was lightly touched on the elbow.

Touch conveys that we believe passionately in what we are saying; a liar seldom touches the person he is deceiving. Culturally appropriate touch makes us feel better and perceive the world as friendlier. We feel emotionally closer when we touch. Bumper stickers that ask “Have you hugged your kids today?” convey much wisdom. Thanks for reading, let’s stay in touch.

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