Gold can be dissolved by aqua regia—a combination of two acids that, on their own, cannot dissolve gold.

Although gold has been prized since its use in 40,000 BCE for decorative purposes, it has more recently served as a replacement for mercury in the production of PVC plastic. Because gold does not react with air or corrode, it has remained in circulation and reused in electronics and biomaterials.

Researchers have found that goldfish cause "regime shifts" in habitats as they search for food in places like lake beds, kicking up sediment that muddies the water and disrupts small invertebrates. They can also outcompete native species to further destabilize existing food webs.

Gold is a pretty expensive topping. Nonetheless, luxury menus around the world are offering food staples—think bagels, chocolate, and burgers—wrapped or dusted with gold. What's the deal with this fascination?

Earth's core, containing 99.999% of all known gold, is leaking trace amounts of precious metals into the mantle. Advanced isotopic methods have detected this leakage at volcanoes in Hawai'i, providing new insights into the movement of material beneath Earth's surface.

For centuries, the things people used as money had intrinsic value, such as precious metals like gold. In medieval Italy, giant wheels of parmesan cheese were once used as a store of value.

Out of the total above-ground stock of gold (weighing roughly 216,265 metric tons), the largest share is found in jewelry (97,149 metric tons).

In principle, this provides price stability as the amount of gold (and therefore the value of the currency) is limited, but also restricts the ability to modulate the money supply during economic downturns.

Those involved in the predecessor of the modern scientific discipline engaged in experimentation to develop recipes that would transform ordinary matter into gold and to create medicines, cosmetics, dyes, and alloys. Over the course of centuries, scientists identified unique elements, organized them based on their properties in the periodic table, and eventually developed the technology to discover the internal structure of atoms.

About 216 million metric tons—about 0.4% of the Great Pyramid of Giza's volume—have been extracted and used primarily for jewelry. The remaining reserves are estimated based on chemical analysis of rock samples extrapolated to the entire mass of Earth's crust.

"Gold bugs" often argue that fiat money allows governments to engage in financially reckless behavior (think: chronic borrowing). They also say the price of gold rises as the value of fiat currency falls.

Austrian artist Gustav Klimt's most iconic image, "The Kiss," can be seen today printed on tapestries, t-shirts, mugs, and more. The painting comes from a decade in his career where gold held a prominent place. Klimt's family business of goldsmithing, in tandem with inspiration from Byzantine churches, coalesced in his obsession with gold.

However, critics argue that globalization has made the gold standard impractical for modern economies, as it limits a nation’s ability to have a flexible monetary policy—hence, none of today's governments have a gold standard.

In shallow waters where sunlight can reach, photosynthetic reactions absorb water and dissolved carbon dioxide, producing bubbles of oxygen at the surface of plants. As these bubbles rise to the water's surface, a fizzy appearance is created.

It’s typically kept in the form of bars or ingots. Governments and central banks often keep bullion reserves on hand; they can use it as a hedge against inflation. One can invest in bullion via ETFs, among other financial vehicles.

This fortified vault, built in 1936, is part of the US Mint, but it doesn’t create any currency. Only a presidential order can open Fort Knox—there has not been an audit of its contents since 1953.

This approach, which is sometimes called flameless cremation, involves dissolving the body with water and chemicals. The remaining bone fragments can then be spread like ashes. It was reportedly incorporated into the funeral industry in 2011.

Through spherification, drops of a solution of sodium alginate and a flavored liquid are placed in a calcium lactate solution, which forms a chemical skin around them. This is because calcium replaces the sodium in the alginate chains, forming a gel around each drop's liquid interior.

A 2022 NBC news investigation of gold mining in the Peruvian Amazon rainforest. Much of the $3B in illegal gold is trafficked to the US every year.

Dutch engineer Thomas de Wolf created a car for a goldfish, or a water tank on wheels that is directed by the movements of the creature inside it. Using a motion-sensing camera, when Blub the fish moves to one side of the tank, the camera moves in the same direction.

Observing high-angle deflections when alpha particles were fired at gold foil led to an atomic model with a dense, positively charged nucleus. Firing those particles at nitrogen resulted in the emission of hydrogen nuclei—protons—leading to the discovery of the subatomic particle.

While massive stars naturally fuse elements as heavy as iron, an analysis of gravitational waves from the collision of two neutron stars revealed that more massive elements are created in this environment via rapid neutron capture—the r-process. This phenomenon sees existing iron nuclei absorb plentiful free neutrons, many of which decay into protons, creating new elements.

The extraction and processing of REEs requires significant amounts of water, and poorly regulated projects can contaminate groundwater with acids and heavy metals. Toxic waste spills have paused work in several US mines since the 1980s, despite growing REE demand.

While tap water is regulated by the EPA, environmental and infrastructural factors can introduce contaminants, which filtering can help to remove. Distilled water has had all of its mineral contaminants removed and may be used in laboratory settings, but mineral water has them added in for taste or to promote health.

Although Costco's gold bars often sell out, experts caution that the Costco gold rush was more "mob mentality" than sound investment. The bullion program is one way for retail investors to get exposure to the commodities market.

Pools use copper sulfate to control algae, which can bind to hair either damaged by the sun or recently bleached. Chlorine, which is often considered to be the culprit, weakens the hair structure to exacerbate the green coloration reaction, rather than causing it.

When sunlight enters water droplets, it can reflect from the inside and spread out into different colors, producing a series of colorful arcs—supernumerary bows—which we refer to as rainbows. For droplets a few hundredths of a millimeter in size, these arcs overlap onto each other, producing fogbows of white light.

Known for gruesome gladiatorial contests, ancient Rome's aquatic spectacles may have been even more over-the-top. This article dives into the art of synchronized swimming in ancient Rome. Lakes were dug and amphitheaters flooded to provide space for aquatic reenactments of naval battles and artistic performances. Swimmers playing the role of water nymphs would create elaborate shapes, including ships with billowing sails.

The gallery highlights major gold coin treasures from ancient to modern times, from the Saddle Ridge hoard in California in the 1800s (now worth $10M) to finds in Baltimore, Kentucky, and more. Each discovery reveals something about the period, with some buried and others left in vaults.

On Earth, oxygen naturally reacts with metals to form an oxide layer on their surface, which prevents two different pieces from fusing when they come into contact. If the layer is worn away without oxygen to replenish it, metals can instead stick together upon impact—a phenomenon known as cold welding.

Volcanic activity on the seafloor produces high ratios of helium-3 to helium-4, which can be tracked in ocean samples more easily than other elements because helium is nonreactive. Water from deep ocean currents can also be distinguished from air-exposed surface water sources by comparing these ratios, since atmospheric helium ratios are much lower.