Bakerian Lecture - X-rays and crystal structure - Willam Henry Bragg (1915)

Imagine standing at the edge of a massive, dense forest. From the outside, it looks like a solid, impenetrable wall of green wood and leaves. But what if you could shine a brilliantly bright, perfectly tuned beam of light into the trees? If you moved the light around, it would slip through the exact, repeating gaps between the tree trunks, casting a highly specific shadow pattern on the ground. Suddenly, without ever walking into the forest, you would have a perfect map of exactly where every single tree was planted.

Welcome to a story about how science forces us to look past the surface of the physical world, and how shedding old, comfortable ideas is the only way to find the truth. We call this radical stewardship: the brave act of discarding old dogmas to illuminate human progress.

For a very long time, the absolute dogma of chemistry—our Null Hypothesis—was that the internal world of solid matter was an impenetrable mystery. Scientists knew crystals like salt and diamond were incredibly structured because of their beautiful outer shapes, but they believed the inside was a black box. The arrangement of the atoms was a guessing game based purely on external geometry. We simply could not see inside.

But in 1915, a scientist named W. H. Bragg looked at crystals and wondered if humanity was clinging to a blind illusion. Building on the idea that X-rays were waves, he proposed a brilliant Alternate Hypothesis: The atoms inside a solid crystal are arranged in perfectly spaced, repeating planes. Because of this, we don't have to guess. If you shoot a beam of invisible X-rays into the crystal, those atomic layers will act like a series of microscopic mirrors. If the angle is just right, the reflections will overlap and bounce back with immense power.

To prove this using the careful, step-by-step Baconian method, Bragg needed an undeniable experiment. He built a machine that fired a fine pencil of X-rays into different crystals, and placed a gas-filled chamber on the other side to "listen" for the invisible reflections.

Here, practicing radical stewardship, we must ruthlessly discard the complex trigonometric equations of reflection, the exhaustive charts of sine angles, and the dense Fourier series of harmonic wave calculations Bragg recorded. What matters is the beautiful, elegant core of his work.

Bragg slowly turned crystals of rock salt, diamond, and copper in the path of the X-ray beam. As the crystals rotated, the X-rays slipped through the gaps in the atoms. At very specific, mathematically perfect angles, the invisible rays hit the layers of atoms and bounced back into his detector, proving they had been perfectly reflected! By simply measuring the angles of these reflections and how strong they were, Bragg could instantly calculate exactly how far apart the layers of atoms were. He even proved that atoms weren't just solid dots, but fuzzy clouds of material. The forest had been mapped.

The Impact: Bragg’s discovery was a stunning triumph of radical stewardship. To accept this beautiful truth, the scientific world had to ruthlessly discard the dogma of the impenetrable solid. What can be discarded must be discarded. By clearing out the old assumption that crystal structures were just unprovable guesses, Bragg gave humanity X-ray vision.

This beautifully simple method, known as X-ray crystallography, became the ultimate skeleton key for modern science. It is the exact technique scientists eventually used to discover the double-helix structure of DNA, map dangerous viruses, and design the modern medicines that save our lives. By letting go of the past, humanity finally learned how to see the invisible architecture of the universe. And for every curious family out there, it stands as a powerful reminder: human progress isn't just about the new things we build, but about the old dogmas we have the courage to leave behind.

Bakerian Lecture - On some chemical Agencies of Electricity - Humphry Davy (1806-11-20)

Imagine a magician’s top hat sitting on an empty table. The magician taps it with a sparkling wand, and suddenly, two colorful birds fly out. Did the tap of the wand miraculously create those birds out of thin air? Or were they simply hiding inside the hat all along?

Welcome to a story about how science forces us to look past magical illusions, and how shedding old, comfortable ideas is the only way to find the truth. We call this radical stewardship: the brave act of discarding old dogmas to illuminate human progress.

In 1806, electricity was a mysterious, almost magical force. The absolute dogma of the day—our Null Hypothesis—was that electricity could literally create matter. Scientists observed that zapping pure water with electric currents made chemical acids and alkalis suddenly appear. They concluded the electricity was magically spawning these chemicals directly from the water. It was an unquestioned magic trick.

But Humphry Davy wondered if humanity was clinging to a broken illusion. He proposed a beautiful Alternate Hypothesis: Electricity is not a magic wand creating matter; it is a powerful invisible wedge. He suspected the sudden appearance of these chemicals was just the electricity tearing apart hidden impurities already hiding in the water, the containers, or the air.

To prove this using the careful, step-by-step Baconian method, Davy needed a flawless experiment to catch nature in the act. He had to systematically remove every possible hiding place for these mysterious chemicals.

Here, practicing radical stewardship, we must ruthlessly discard the complex lists of animal threads, exhaustive mineral weights, and the dizzying array of chemical salts Davy recorded. What matters is the elegant core of his work: he ruthlessly stripped away the variables.

First, Davy realized the cotton threads connecting the water created acid, so he threw them out. Next, he noticed his glass cups were corroding and leaving behind soda. He switched to agate rock, but even those left mineral traces! He tried cups of wax, resin, and marble. He even realized the open air was dissolving into the water to create acid.

Finally, Davy went to the absolute extreme. He distilled his water slowly and perfectly. He placed it inside small cones made of pure, unreactive gold. And to eliminate the air, he placed the whole setup inside a vacuum chamber. He turned on the electricity.

The result? The pure water inside the pure gold cones in a vacuum produced absolutely nothing! No acid. No alkali. The grand illusion was shattered.

The Impact: Davy’s experiment was a triumph of radical stewardship. To accept his findings, the scientific world had to ruthlessly discard the dogma that electricity could spontaneously create matter. What can be discarded must be discarded. By clearing out this old assumption, Davy revealed the spectacular nature of chemistry: all elements that combine chemically are held together by natural electrical energies.

When you zap a substance, the electricity acts like a wedge, overpowering natural bonds and forcing hidden ingredients to separate. This beautifully simple realization gave birth to modern electrochemistry. It is the reason we know how to separate elements, analyze complex materials, and build the batteries powering our cellphones and electric cars.

By letting go of the magical past, humanity learned to unlock the hidden chemical bonds of our world. And for every curious family out there, it stands as a powerful reminder: human progress isn't just about the new forces we discover, but about the old dogmas we have the courage to leave behind.

Source: https://royalsocietypublishing.org/rspl/article/doi/10.1098/rspl.1800.0137/104910/The-Bakerian-Lecture-on-some-chemical-agencies-of

On the Theory of Light and Colours by Thomas Young (1802)

Imagine, for a moment, a perfectly still pond. You drop two pebbles into the water. *Plip. Plip.* Ripples spread out, expanding in circles until they meet in the middle. Where two wave peaks collide, the water jumps higher, and where a peak meets a valley, the water goes completely flat.

Now, what if the light shining on that pond is doing the exact same thing? Welcome to a story about how we see the universe, and how science sometimes forces us to throw away old, comfortable ideas to find the truth. We call this radical stewardship: the brave act of shedding old dogmas to illuminate human progress and discover simple, uniform laws of nature.

Our story begins in 1801 with a scientist named Thomas Young. At the time, the scientific world was deeply under the spell of the great Isaac Newton, whose older experiments on light were considered completely unrivaled. Because of Newton's massive influence, the absolute dogma of the day—our Null Hypothesis — was that light was made of tiny, microscopic bullets, or "projected corpuscles," shooting out in straight lines.

But Young looked at nature and wondered if humanity was clinging to a broken idea. He proposed a beautiful Alternate Hypothesis: Light is not a stream of bullets; it is a series of overlapping waves, or "undulations," traveling through the universe. To Young, the world was a grand symphony. He suggested that different colors of light are simply waves of different frequencies, exactly like different musical notes played on an instrument.

To prove this using the step-by-step Baconian method, Young needed an undeniable experiment. He had to show that light waves could crash into each other and cancel out, just like those water ripples.

The Experiment: Young took a piece of glass scratched with microscopic, perfectly parallel lines—a device called a micrometer. He shined a beam of light onto these tiny scratches. If light were made of solid bullets, it would simply bounce off the scratches in a chaotic, random spray. But if light were a wave? The waves reflecting off the tiny ridges would overlap. If the paths of the waves synced up perfectly, their power would combine to create bright, vivid colors, but if their timing was slightly off, the forward motion of one wave would crash into the backward motion of another wave, completely destroying each other and leaving total darkness.

When Young measured the reflected light, he didn't find a random spray. He found bright red light appearing only at very specific, mathematically perfect angles. It was a stunning success! He compared this magical overlapping of light to the everyday experience of hearing a musical note magically created by sound waves bouncing off an evenly spaced row of iron fences. Light was definitively a wave.

The Impact: Young’s discovery was a triumph of radical stewardship. To accept this beautiful truth, the world had to ruthlessly discard the old Newtonian "bullet" dogma. What could be discarded *had* to be discarded. By clearing out this old assumption, Young revealed simple, uniform laws of nature that dramatically improved human intellect. His wave theory opened the door to modern physics, eventually helping us realize that visible light and the invisible heat you feel from a campfire are actually the exact same thing—differing only in the speed of their waves.

By letting go of the past, humanity finally learned how to see the light. And for every curious family out there, it is a powerful reminder: progress isn't just about the new things we discover, but the old dogmas we are willing to leave behind.

The Bakerian Lecture: On the Theory of Light and Colours

Author(s): Thomas Young

Source: Philosophical Transactions of the Royal Society of London, Vol. 92 (1802), pp. 12-48

Published by: The Royal Society

Stable URL: https://www.jstor.org/stable/107113