Every day science

Spring/Summer 2023 issue

The discipline of science is influenced by the world around us. These small glances into how the ordinary and everyday have inspired major breakthroughs and discoveries offer insight into the way the scientific mind works.

Light showing through clouds on a blue sky.

Blue-sky thinking

Associate Professor and Chair Raphael Slawinski, PhD
Department of Chemistry and Physics

Why is the sky blue? It’s the kind of question a child — or a scientist — might ask.

White light is a mixture of different colours, conventionally taken to be red, orange, yellow, green, blue, indigo and violet. An object appears blue because it reflects that colour and absorbs the others. So, maybe microscopic water droplets or dust particles reflect sunlight and make the sky appear blue? But this hypothesis can't be right, however, as the sky looks bluest when the air is clear and dry and the high clouds that foretell the arrival of bad weather turn the sky whitish instead of a deeper blue.

Still, the particle hypothesis points us scientists in the right direction. To quote Sherlock Holmes, “When you have eliminated the impossible, whatever remains, however improbable, must be the truth.”

And what remains is air itself. Air molecules, nitrogen and oxygen, less than one-thousandth the size of the wavelengths of light, scatter sunlight. Light with shorter wavelengths (more scattered) is perceived as blue, while longer wavelengths (less scattered) are perceived as red. Midday, when we look up at the sky, we see the colour that’s been scattered from white sunlight the most: blue. At sunset, when we look where the sun just dipped below the horizon, we see what colour remains in the sunlight: red.

Isaac Newton knew light was composed of different colours in the late 17th century, but he didn't know those corresponded with different wavelengths. That connection was clarified with the work of people like Thomas Young and his famous double-slit experiment in the early 1800s. The main development to come out of this insight is likely the development of spectroscopy in the 19th century, which is the science of identifying different substances by analyzing the light from them. Today its applications range from analyzing the images from the James Webb Space Telescope to studying the structure of chemical compounds.

A repeating pattern of soap bars on wooden soap dishes.

How does soap work?

Assistant Professor Jeella Acedo, PhD
Department of Chemistry and Physics

“Like dissolves like” is a rule of thumb in solubility that indicates that polar solvents dissolve polar solutes. Chemical polarity can be explained using the electronegativity scale developed by Linus Pauling in 1935, which describes the attraction an element has for electrons in a chemical bond. If the electronegativity difference between two atoms falls between 0.5 and 2.0, the bond is considered polar. We then look at the overall molecular structure and ensure that bond dipoles don't cancel out due to geometry. If they cancel out, even if there are polar bonds, the molecule as a whole becomes non-polar.

This is the reason why water will not wash away grease or oil. Water is polar while grease and oil are nonpolar. However, soapy water effectively washes off grease, oil and even microbes such as bacteria and viruses.

Soap acts as a good cleaning agent because of the hybrid structure of soap molecules, wherein each molecule contains a long, nonpolar, hydrophobic tail attached to a polar, hydrophilic head group.

The hydrophobic tail adheres to dirt, grease, fats and oils. Similarly, the protective covering, or cellular membrane, of microbes such as bacteria and viruses is composed of hydrophobic molecules that allow the hydrophobic tail of soap molecules to interact, penetrate and destroy these membranes, thereby killing the microbes.

Soap molecules that are now bound to such hydrophobic materials as fats, oil or microbial fragments subsequently cluster together to form a spherical assembly called a micelle. In a micelle, the hydrophobic tail of soap molecules along with the dirt adhering to it is buried inside the sphere, while hydrophilic head groups of soap molecules are left exposed on the surface. These exposed hydrophilic head groups interact with water molecules, allowing the washing off of the “dirt-containing” micelles.

Illustration and more information

An image split in half down the middle. On the left an aerial photo of a solar farm with panels in rings. On the right a sunflower with similar rings in the center of the flower.

Better design with biomimicry

Associate Professor Sarah Hewitt, PhD
Department of Biology

When was the last time you were inspired by a slime slug, a termite or a snake? Scientists continually observe nature to develop new technologies or solve problems. It’s called biomimicry — mimicking what’s observed in the biological world on a macro or micro scale to answer complex questions. Researchers have used biomimicry to make advances in areas as varied as renewable energy, structural design and materials, medical procedures, city planning and sustainable agricultural systems.

The best known example of biomimicry is Velcro. In 1941, a Swiss engineer named George de Mestral was hunting with his dog when he noticed how the burrs from a burdock plant clung to his dog’s fur. He inspected the burrs closely and eventually developed the hook and loop system that we now know as Velcro.

A common problem in medicine is closing wounds. Adhesives need to be strong enough to stick to wet surfaces on our insides, but also withstand friction and movement. Enter the slime slug, also known as the Dusky Arion ( Arion subfuscus). The mucous it secretes on its skin is so sticky predators can’t pry it off rocks or leaves — even wet, slippery ones. Seeing this, Harvard scientists recreated the proteins in the slug’s mucous and synthesized a substance that sticks powerfully to moving tissues like a beating heart.

Slugs aren’t the only slimy systems inspiring scientists. Studying how slime moulds move and grow to acquire food helped city planners in Japan design more efficient roads and railways. And to design the fastest bullet trains between cities, researchers used the shape of a kingfisher’s head as a model.

There are countless other examples of biomimicry. Researchers studied the scales of a snake’s skin to design grippier soles for shoes to help prevent falls — a major source of injuries in elderly people. And they studied air flow in termite mounds to develop more efficient heating and cooling systems in buildings. For every problem we have, nature has solutions. We just need to observe carefully to find them.

Read more Summit

The chemistry between us

A study based on the behaviours of atoms and molecules invisible to the human eye, chemistry is everywhere and everything.