By Bengt O. Hallberg

Sunlight, physics, and photonics shape vast areas from optics to defense. The text urges society and politicians to prioritize STEM expertise.

Without the Sun, We'll Die

Life on Earth would cease without the sun. The constant flow of photons it emits is essential to us. The travel takes about five hundred seconds. The extremely brief time that we, Homo sapiens, have existed—in the grand scheme of things—is so short that it is virtually insignificant. However, we, Homo sapiens, are not insignificant. We are the most accomplished species ever to have lived on Earth. However, we also have the capacity to destroy it if we do not manage our resources properly.

Physics and Mathematics

In addition to language, physics and mathematics are powerful tools that we humans use and that have made all of this possible. Together, they comprise the outer framework of what I consider to be part of STEM for example: biology, chemistry, computer science, earth sciences, and electronics. The beauty of the humanities is that they are open to speculation and everything that does not fall within the scope of STEM.

STEM vs Humanities

What distinguishes STEM from the humanities is the strict objectivity built on scientific method, mathematical modeling, and empirical experimentation. A hypothesis must be verifiable, repeatable, and quantitative by multiple independent sources.

One good example is the theories of the renowned physicist Albert Einstein, which were published in the early 1900s. Einstein lived from 1879 to 1955. Throughout the 20th century, many independent experiments were conducted to either prove or disprove his theories.

This applies to both applied and theoretical physics, where advanced mathematics is of great help. It turns out that, in the vast majority of cases, he was correct, even though some questions remain to be resolved now in the 21st century.

Their applications in technology and engineering are the most important. For example, fiber-optic communication would not be possible without them.

Photons

What are photons? Photons are elementary particles that carry energy in discrete packets. They can be absorbed and emitted by matter. The shorter the wavelength of such a packet, the higher is its energy. Long radio waves have low energy; infrared photons have higher, which we perceive as heat; visible wavelengths ranging from red to blue have progressively higher; and beyond the blue spectrum come X-rays and even higher-energy photons that can harm humans and other living things.

Our Vision

Our eyes perceive photons ranging from red to blue in a range of approximately 700–400 nm. When the entire spectrum of these photons reaches our eyes, we perceive it as white light. Using a prism or a holographic grating, it can be broken down into its components, just as we see in a rainbow. In that case, it is water droplets that create the same effect.

What is Color?

Photons have no color; they simply contain energy. What you see in the beauty of nature are photons that have been reflected or emitted by matter. When they reach your eyes and are transmitted to your brain, it is your brain that creates the colors you think you see.

Sunlight and blue skies

We perceive the direct light from the sun as white, but why does the surrounding sky appear blue? It comes down to a phenomenon known as Rayleigh scattering.

The intensity of this scattering is inversely proportional to the fourth power of the wavelength, ~1/λ⁴. Because light with a shorter wavelength (like blue) has a smaller value for λ, it ends up in the denominator of that mathematical relationship, making the resulting scattering dramatically higher than for longer wavelengths like red. As sunlight passes through the atmosphere, this blue light is scattered in every direction by molecules, filling the sky with the blue hue we see.

While Rayleigh scattering gives us our blue skies, it is actually atmospheric absorption—primarily by the ozone layer and upper atmospheric gases—that acts as our shield, blocking high-energy ultraviolet radiation and X-rays before they reach the surface.

Science in politics

If we carelessly release harmful particles into the atmosphere, it will be negatively affected. This exposes us to the risk of injury from high-energy photons when they reach the Earth’s surface. Unfortunately, this has already happened, along with many other harmful things to nature, despite warnings issued by American author and environmentalist Rachel Carson in the mid-20th century. She lived from 1907 to 1964. Her most famous book, Silent Spring, was published in 1962.

Paradoxically, it is in her home country, the United States, where people have had among the hardest times accepting her message, maintaining some of the highest per capita emissions in the world. It is rarely easy to be a prophet in one’s own land.

Yet, the need for evidence-based decision-making is just as urgent today as it was in Carson’s time. As this blog post goes live, election campaigns are in full swing in Sweden ahead of the vote on September 13, 2026. While traditional debates center on economics, healthcare, and education, the geopolitical landscape has shifted dramatically. Alongside new domestic security challenges, we are seeing an unprecedented military buildup.

After the Election

Regardless of the election results, it would be desirable for STEM issues to take on greater prominence among politicians. Given the enormous resources available to politicians and other decision-makers, it is important that they have sufficient knowledge of the tools that control them and the moral principles that guide them for the good of all the world's people.

That is not the case today. As a voter, I call for ministers in these fields who possess deep expertise and extensive professional experience, and I also hope that more members of the Riksdag will have these qualities.

I'm delighted that the trend has reversed and that STEM programs have become popular again in the Swedish universities, in addition to medical programs, which have been attractive for a very long time. This year, the Engineering Physics program at KTH Royal Institute of Technology required the highest gymnasium (high school) grades for admission among all.

Next Blog

After this political digression, I’ll return to the subject of this blog I’m knowledgeable about, photonics and its promising future. The definition of photonics is the physical science and technology, focusing on the generation, manipulation, and detection of photons.

As usual, the next post will be published on Tuesday in two weeks, which means September 15, 2026.