Physics

science-lives-here:-take-a-virtual-tour-of-the-royal-institution-in-london

Science lives here: take a virtual tour of the Royal Institution in London

a special kind of place —

No less than 14 Nobel laureates have conducted ground-breaking research at the Institution.

The exterior of the Royal Institution

Enlarge / The Royal Institution was founded in 1799 and is still located in the same historic building at 21 Albermarle Street in London.

If you’re a fan of science, and especially science history, no trip to London is complete without visiting the Royal Institution, browsing the extensive collection of artifacts housed in the Faraday Museum and perhaps taking in an evening lecture by one of the many esteemed scientists routinely featured—including the hugely popular annual Christmas lectures. (The lecture theater may have been overhauled to meet the needs of the 21st century but walking inside still feels a bit like stepping back through time.) So what better time than the Christmas season to offer a virtual tour of some of the highlights contained within the historic walls of 21 Albemarle Street?

The Royal Institution was founded in 1799 by a group of leading British scientists. This is where Thomas Young explored the wave theory of light (at a time when the question of whether light was a particle or wave was hotly debated); John Tyndall conducted experiments in radiant heat; Lord Rayleigh discovered argon; James Dewar liquified hydrogen and invented the forerunner of the thermos; and father-and-son duo William Henry and William Lawrence Bragg invented x-ray crystallography.

No less than 14 Nobel laureates have conducted ground-breaking research at the Institution over the ensuing centuries, but the 19th century physicist Michael Faraday is a major focus. In fact, there is a full-sized replica of Faraday’s magnetic laboratory—where he made so many of his seminal discoveries—in the original basement room where he worked, complete with an old dumbwaiter from when the room was used as a servant’s hall. Its arrangement is based on an 1850s painting by one of Faraday’s friends and the room is filled with objects used by Faraday over the course of his scientific career.

The son of an English blacksmith, Faraday was apprenticed to a bookbinder at 14, a choice of profession that enabled him to read voraciously, particularly about the natural sciences. In 1813, a friend gave Faraday a ticket to hear the eminent scientist Humphry Davy lecture on electrochemistry at the Royal Institution. He was so taken by the presentation that he asked Davy to hire him. Davy initially declined, but shortly afterwards sacked his assistant for brawling, and hired Faraday to replace him. Faraday helped discover two new compounds of chlorine and carbon in those early days, learned how to make his own glass, and also invented an early version of the Bunsen burner, among other accomplishments.

  • Painting of the Royal Institution circa 1838, by Thomas Hosmer Shepherd.

    Public domain

  • Michael Faraday giving one of his famous Christmas lectures.

    Royal Institution

  • A Friday Evening Discourse at the Royal Institution; Sir James Dewar on Liquid Hydrogen, by Henry Jamyn Brooks, 1904

    Public domain

  • The Lecture Theatre as it looks today

  • Faraday’s magnetic laboratory in the basement of the Royal Institution

    Royal Institution

  • A page from one of Faraday’s notebooks

    Royal Institution

Faraday was particularly interested in the new science of electromagnetism, first discovered in 1820 by Hans Christian Ørsted. In 1821, Faraday discovered electromagnetic rotation—which converts electricity into mechanical motion via a magnet—and used that underlying principle to build the first electric motor. The Royal Institution’s collection includes the only surviving electric motor that Faraday built: a wire hanging down into a glass vessel with a bar magnet at the bottom. Faraday would fill the glass with mercury (an excellent conductor), then connect his apparatus to a battery, which sent electricity through the wire in turn. This created a magnetic field around the wire, and that field’s interaction with the magnet at the bottom of the glass vessel would cause the wire to rotate in a clockwise direction.

Ten years later, Faraday succeeded in showing that a jiggling magnet could induce an electrical current in a wire. Known as the principle of the dynamo, or electromagnetic induction, it became the basis of electric generators, which convert the energy of a changing magnetic field into an electrical current. One of Faraday’s induction rings is on display, comprised of coils of wire wound on opposites sides of the ring, insulated with cotton. Passing electricity through one would briefly induce a current in the other. Also on display is one of Faraday’s generators: a bar magnet and a simple cotton-insulated tube wound with a coil of wire.

In yet another experiment, Faraday placed a piece of heavy leaded glass on a magnet’s poles to see how light would be affected by a magnet. He passed light through the glass and when he turned on the electromagnet, he found that the polarization of the light had rotated slightly. This is called the magneto-optical effect (or Faraday effect), demonstrating that magnetism is related not just to electricity, but also to light. The Royal Institution has a Faraday magneto-optical apparatus with which he “at last succeeded in… magnetizing a ray of light.” In 1845, Faraday discovered diamagnetism, a property of certain materials that give them a weak repulsion from a magnetic field.

  • Equipment used by Faraday to make glass

  • Drawing of Faraday’s electromagnetic rotation experiment.

    Public domain

  • Faraday motor (electric magnetic rotation apparatus), 1822

    Royal Institution

  • Faraday’s dynamo (generator), October 1831

    Royal Institution

  • Faraday’s induction ring

    Royal Institution

  • Faraday’s magneto-optical apparatus

    Royal Institution

  • One of Faraday’s iron filings (1851) showing magnetic lines of force

    Royal Institution

  • Faraday’s original gold colloids are still active well over a century later

  • Shining a laser light through a gold colloid mixture produces the Faraday-Tyndall Effect.

    Royal Institution

Faraday concluded from all those experiments that magnetism was the center of an elaborate system of invisible curved tentacles (electric lines of force) that spread throughout space like the roots of trees branching through the earth. He was able to demonstrate these lines of force by coating sheets of paper with wax and placing them on top of bar magnets. When he sprinkled powdery iron filings on the surface, those iron filings were attracted to the magnets, revealing the lines of force. And by gently heating the waxed paper, he found that the iron filings would set on the page, preserving them.

In the 1850s, Faraday’s interests turned to the properties of light and matter. He made his own gold slides and shone light through them to observe the interactions. But commercial gold leaf, typically made by hammering the metal into thin sheets, was still much too thick for his purposes. So Faraday had to make his own via chemical means, which involved washing gold films. The resulting faint red fluid intrigued Faraday and he kept samples in bottles, shining light though the fluids and noting an intriguing “cone effect” (now known as the Faraday-Tyndall Effect)—the result of particles of gold suspended in the fluid that were much too small to see.

One might consider Faraday an early nanoscientist, since these are now known as metallic nanoparticles. The Institution’s current state-of-the-art nanotechnology lab is appropriately located right across from Faraday’s laboratory in the basement. And even though Faraday’s gold colloids are well over a century old, they remain optically active. There’s no way to figure out why this might be the case without opening the bottles but the bottles are too valuable as artifacts to justify doing that.

Plenty of other scientific luminaries have their work commemorated in the Royal Institution’s collection, including that of Faraday’s mentor, Humphry Davy, who discovered the chemical elements barium, strontium, sodium, potassium, calcium and magnesium. Early in the 19th century, there were several explosions in northern England’s coal mines caused by the lamps used by the miners accidentally igniting pockets of flammable gas. Davy was asked to come up with a safer lighting alternative.

  • Schematic for the Davy lamp

    Public domain

  • Humphry Davy’s miner’s lamp (left) displayed alongside his rival George Stephenson’s lamps

    Royal Institution

  • Schematic for John Tyndall’s radiant heat apparatus

    Royal Institution

  • Tyndall’s radiant heat tube

    Royal Institution

  • Tyndall’s blue sky tube, 1869

    Royal Institution

  • Title page of Tyndall’s Heat: A Mode of Motion

    Paul Wilkinson/Royal Institution

After experimenting with several prototypes, Davy finally settled on a simple design in 1815 consisting of a “chimney” made of wire gauze to enclose the flame. The gauze absorbed heat to prevent igniting flammable gas but still let through sufficient light. The invention significantly reduced fatalities among coal miners. Davy had a rival, however in a mining engineer named George Stephenson who independently developed his own design that was remarkably similar to Davy’s. Samples of both are displayed in the Institution’s lower ground floor “Light Corridor.” Davy’s lamp would ultimately triumph, while Stephenson later invented the first steam-powered railroad locomotive.

Atmospheric physicist John Tyndall was a good friend of Faraday and shared the latter’s gift for public lecture demonstrations. His experiments on radiation and the heat-absorptive power of gases were undertaken with an eye toward developing a better understanding of the physics of molecules.  Among the Tyndall artifacts housed in the Royal Institution is his radiant heat tube, part of an elaborate experimental apparatus he used to measure the extent to which infrared radiation was absorbed and emitted by various gases filling its central tube. By this means he concluded that water vapor absorbs more radiant heat than atmospheric gases, and hence that vapor is crucial for moderating Earth’s climate via a natural “greenhouse effect.”

The collection also includes Tyndall’s “blue sky apparatus,” which the scientist used to explain why the sky is blue during the day and takes on red hues at sunset—namely, particles in the Earth’s atmosphere scatter sunlight and blue light is scattered more strongly than red light. (It’s the same Faraday-Tyndall effect observed when shining light through Faraday’s gold colloids.)

  • James Dewar in the Royal Institution, circa 1900

    Public domain

  • A Dewar flask

    Royal Institution

  • The x-ray spectrometer developed by William Henry Bragg.

    Royal Institution

  • Bragg’s rock salt model

On Christmas Day, 1892, James Dewar exhibited his newly invented Dewar flask at the Royal Institution for the first time, which he used for his cryogenic experiments on liquefying gases. Back in 1872, Dewar and Peter Tait had built a vacuum-insulated vessel to keep things warm, and Dewar adapted that design for his flask, designed to keep things cold—specifically cold enough to maintain the extremely low temperatures at which gases transitioned into liquid form. Dewar failed to patent his invention, however; the patent eventually went to the Thermos company in 1904, which rebranded the product to keep liquids hot as well as cold.

As for William Henry Bragg, he studied alpha, beta, and gamma rays early in his career and hypothesized that both gamma rays and x-rays had particle-like properties. This was bolstered by Max Von Laue‘s Nobel Prize-winning discovery that crystals could diffract x-rays. Bragg and his son, William Lawrence—then a student at Trinity College Cambridge—began conducting their own experiments. Bragg pere invented a special “ionization spectrometer,” in which a crystal could be rotated to precise angles so that the different scattering patterns of x-rays could be measured. The pair used the instrument to determine the structure of crystals and molecules, winning the 1915 Nobel Prize in Physics for their efforts. That spectrometer, the prototype of today’s x-ray diffractometers, is still housed in the Royal Institution, as well as their model of the atomic structure of rock salt.

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X-ray imaging of The Night Watch reveals previously unknown lead layer

The latest from Operation Night Watch —

Rembrandt may have used lead-rich oil to prep his canvas and protect it from humidity.

The Nightwatch, or Militia Company of District II under the Command of Captain Frans Banninck Cocq (1642)

Enlarge / Rembrandt’s The Night Watch underwent many chemical and mechanical alterations over the last 400 years.

Public domain

Rembrandt’s The Night Watch, painted in 1642, is the Dutch master’s largest surviving painting, known particularly for its exquisite use of light and shadow. A new X-ray imaging analysis of the masterpiece has revealed an unexpected lead layer, perhaps applied as a protective measure while preparing the canvas, according to a new paper published in the journal Science Advances. The work was part of the Rijksmuseum’s ongoing Operation Night Watch, the largest multidisciplinary research and conservation project for Rembrandt’s famous painting, devoted to its long-term preservation.

The famous scene depicted in The Night Watch—officially called Militia Company of District II under the Command of Captain Frans Banninck Cocq—was not meant to have taken place at night. Rather, the dark appearance is the result of the accumulation of dirt and varnish over four centuries, as the painting was subject to various kinds of chemical and mechanical alterations.

For instance, in 1715, The Night Watch was moved to Amsterdam’s City Hall (now the Royal Palace on Dam Square). It was too large for the new location, so the painting was trimmed on all four sides, and the trimmed pieces were never found (although in 2021, AI was used to re-create the original full painting). The objective of Operation Night Watch is to employ a wide variety of imaging and analytical techniques to better understand the materials Rembrandt used to create his masterpiece and how those materials have changed over time.

As previously reported, past analyses of Rembrandt’s paintings identified many pigments the Dutch master used in his work, including lead white, multiple ochres, bone black, vermilion, madder lake, azurite, ultramarine, yellow lake, and lead-tin yellow, among others. The artist rarely used pure blue or green pigments, with Belshazzar’s Feast being a notable exception. (The Rembrandt Database is the best resource for a comprehensive chronicling of the many different investigative reports.)

Earlier this year, the researchers at Operation Night Watch found rare traces of a compound called lead formate in the painting. They scanned about half a square meter of the painting’s surface with X-ray powder diffraction mapping (among other methods) and analyzed tiny fragments from the painting with synchrotron micro X-ray probes. This revealed the presence of the lead formates—surprising in itself, but the team also identified those formates in areas where there was no lead pigment, white, or yellow. It’s possible that lead formates disappear fairly quickly, which could explain why they have not been detected in paintings by the Dutch Masters until now. But if that is the case, why didn’t the lead formate disappear in The Night Watch? And where did it come from in the first place? 

Hoping to answer these questions, the team whipped up a model of “cooked oils” from a 17th century recipe, which called for mixing and heating linseed oil and lead oxide, then adding hot water to the reacting mixture. They analyzed those model oils with synchrotron radiation. The results supported their hypothesis that the oil used for light parts of the painting was treated with an alkaline lead drier. The fact that The Night Watch was revarnished with an oil-based varnish in the 18th century complicates matters, as this may have provided a fresh source of formic acid, such that different regions of the painting rich in lead formates may have formed at different times in the painting’s history.

This latest paper sheds more light on the painting by focusing on the preparatory layers applied to the canvas. It’s known that Rembrandt used a quartz-clay ground for The Night Watch—the first time he had done so, perhaps because the colossal size of the painting “motivated him to look for a cheaper, less heavy and more flexible alternative for the ground layer” than the red earth, lead white, and cerussite he was known to use on earlier paintings, the authors suggested.

The Night Watch via the correlated synchrotron-based X-ray fluorescence and ptychographic tomography of a paint sample, supported by a macroscale X-ray fluorescence scan of the whole painting.” height=”439″ src=”https://cdn.arstechnica.net/wp-content/uploads/2023/12/nightwatch4-640×439.jpg” width=”640″>

Enlarge / A so far unknown lead-containing impregnation ‘layer’ was discovered in Rembrandt’s The Night Watch via the correlated synchrotron-based X-ray fluorescence and ptychographic tomography of a paint sample, supported by a macroscale X-ray fluorescence scan of the whole painting.

Fréderique Broers

Per the authors, this is the first time that 3D X-ray imaging techniques have been used: X-ray fluorescence and X-ray ptychographic nano-tomography applied to an embedded paint fragment comprised of only the quartz-clay ground. The authors maintain that microscale analysis of historical paintings usually relies on 2D imaging techniques (e.g., light microscopy, scanning electron microscopy, synchrotron radiation spectroscopy), which only yield partial information about the size, shape, and distribution of pigment particles below the visible surface.

The 3D methods capture more detail by comparison, revealing the presence of an unknown (and unexpected) lead-containing layer located just underneath the ground layer. The authors suggest that this could be due to using a lead compound added to the oil used to prepare the canvas as a drying additive—perhaps to protect the painting from the damaging effects of humidity. (Usually a glue sizing was used before applying the ground layer.)

The Night Watch originally hung in the “great hall” of a musketeer shooting range in Amsterdam and faced windows. The authors note that since the Middle Ages, red lead in oil has been used to preserve stone, wood, and metal against humidity, and one contemporary source mentions using lead-rich oil instead of the typical glue to keep the canvas from separating after years of exposure in humid environments. And that newly discovered lead layer could be the reason for the unusual lead protrusions in areas of The Night Watch with no other lead-containing compounds in the paint. It’s possible that lead migrated into the painting’s ground layer from that lead-oil preparatory layer below.

DOI: Science Advances, 2023. 10.1126/sciadv.adj9394  (About DOIs).

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Marbled paper, frosty fireworks among 2023 Gallery of Fluid Motion winners

Harvard University graduate student Yue Sun won a Milton Van Dyke Award for her video on the hydrodynamics of marbled paper.

Enlarge / Harvard University graduate student Yue Sun won a Milton Van Dyke Award for her video on the hydrodynamics of marbled paper.

Y. Sun/Harvard University et al.

Marbled paper is an art form that dates back at least to the 17th century, when European travelers to the Middle East brought back samples and bound them into albums. Its visually striking patterns arise from the complex hydrodynamics of paint interacting with water, inspiring a winning video entry in this year’s Gallery of Fluid Motion.

The American Physical Society’s Division of Fluid Dynamics sponsors the gallery each year as part of its annual meeting, featuring videos and posters submitted by scientists from all over the world. The objective is to highlight “the captivating science and often breathtaking beauty of fluid motion” and to “celebrate and appreciate the remarkable fluid dynamics phenomena unveiled by researchers and physicists.”

The three videos featured here are the winners of the Milton Van Dyke Awards, which also included three winning posters. There were three additional general video winners—on the atomization of impinging jets, the emergent collective motion of condensate droplets, and the swimming motion of a robotic eel—as well as three poster winners. You can view all the 2023 entries (winning and otherwise) here.

The hydrodynamics of marbling art

Harvard University graduate student Yue Sun was fascinated by the process and the resulting patterns of making marbled paper, particularly the randomness. “You don’t really know what you’re going to end up with until you have it printed,” she told Physics Magazine.

Although there are several different methods for marbling paper, the most common involves filling a shallow tray with water, then painstakingly applying different ink or paint colors to the water’s surface with an ink brush to cover the surface with concentric circles. Adding surfactants makes the colors float so that they can be stirred—perhaps with a very fine human hair—or fanned out by blowing on the circles of ink or paint with a straw. The final step is to lay paper on top to capture the colorful floating patterns. (Body marbling relies on a similar process, except the floating patterns are transferred onto a person’s skin.)

Sun was curious about the hydrodynamics at play and explored two key questions in the simulations for the video. Why does the paint or ink float despite being denser than the liquid bath? And why don’t the colors mix together to create new colors when agitated or stirred? The answer to the former is basically “surface tension,” while the latter does not occur because the bath is too viscous, so the diffusion of the paint or ink colors across color boundaries happens too slowly for mixing. Sun hopes to further improve her simulations of marbling in hopes of reverse-engineering some of her favorite patterns to determine which tools and movements were used to create them.

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