How scientists discovered helium from sunlight over a decade before seeing it on Earth

Breaking down sunlight and why the sun appears yellow despite emitting green light the most

This peak intensity is produced alongside a spectrum of other colors, which, when combined, make the sun appear white in space. Since Earth's atmosphere scatters bluer and greener wavelengths of light more than red and orange wavelengths, sunlight reaching Earth's surface appears yellow, while the sky appears blue. (Some readers may experience a paywall.)

Cecilia Payne-Gaposchkin discovered stars are mostly made of hydrogen and helium

At 25, her doctoral thesis challenged the then-common belief that stars were composed similarly to Earth. Several years later, Henry Norris Russell, who had initially dismissed her findings, independently made the same discovery and received credit for it.

An overview of helium, the nonrenewable resource that's lighter than air

The second element in the periodic table naturally forms deep underground over the course of billions of years through the decay of radioactive elements, but it is used and lost to space at rates faster than it is generated. Because of this and its extensive applications in scientific technologies, scientists continue to seek avenues for its exploration, storage, and recycling.

How scientists determine elemental composition based on the light emitted by cooling atoms

When electrons within an atom drop to a lower energy level closer to the nucleus, they lose energy and produce light with energy equal to the difference between the two energy levels. Because these levels and the corresponding emitted light are unique to each element, the light serves as a unique signature that can be compared to known lab samples for identification.

Radioactivity was accidentally discovered when uranium left marks on photographic plates

In 1896, Henri Becquerel had been exploring phosphorescence—the emission of light of one color after an object is exposed to another color. He expected these emissions to come from objects exposed to sunlight, but he observed emissions after an overcast day.

Ernest Rutherford's gold foil and nitrogen experiments revealed nuclear structure

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.

The history of helioseismology, which studies seismic waves traveling within the sun

Following World War II, scientists began studying the sun's influence on radio waves, the most popular form of mass communication at the time. NASA missions to study the sun's interior have since helped develop explanations for various phenomena in its atmosphere and protect digital infrastructure.

Galileo's Jupiter discovery shattered Earth-centered universe beliefs

Using a telescope inspired by Dutch designs, Galileo spotted four moons orbiting Jupiter in 1610, providing undeniable evidence against geocentrism and fueled support for the heliocentric model. Galileo’s original telescope design stretched 20 meters long—a feat of optical engineering for its time.

Why the ratios of helium isotopes are analyzed to investigate ocean circulation

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.

The greenhouse effect was discovered by analyzing Earth's temperature

Using mathematical techniques developed to analyze heat transfer, Jean-Baptiste Joseph Fourier showed that Earth should be significantly cooler if solar radiation were the only contributor to its surface temperature. By considering that the atmosphere could amplify the sun's warming effect, he formulated what became known as the greenhouse effect.

Metallic hydrogen exists in Jupiter and Saturn due to high pressure and temperature

This state of hydrogen has metallic properties, including conductivity, which powers these planets' magnetic fields. First theorized in the 1930s, its existence was confirmed through indirect evidence before being created in a Harvard lab in 2017.

Light has been modeled as a wave and a stream of particles throughout history

Isaac Newton first identified white light as composed of a spectrum of colors, which he believed consisted of particles of different hues. Various light phenomena, including refraction, led Christiaan Huygens to develop an alternative wave model. Quantum mechanics validated both models through the concept of wave-particle duality.

How helium greatly improves the efficiency of barcode-scanning lasers

Rather than directly energizing neon atoms, electrical discharge at lower, more practical power levels can excite helium atoms to energy levels nearly equal to those in neon atoms. Within a helium-neon laser, these gases are present in a 10-to-1 ratio, enabling helium to efficiently transfer energy to neon, which is then discharged as red light.

How a quantum quirk allowed neutral atoms to form soon after the Big Bang

At the beginning of the universe, high-energy photons prevented atomic nuclei from combining with electrons to form neutral atoms. Rather than waiting for the universe to expand and cool completely, a rare quantum phenomenon—a two-photon transition—allowed neutral hydrogen atoms to form sooner, expediting the formation of stars, planets, and life.

The Google Doodle honoring Jan Ingenhousz, who discovered oxygenic photosynthesis

Born in 1730, the Dutch scientist expanded on existing knowledge that plants produce and absorb gases in his 1779 paper, which detailed that light was necessary for the biochemical processes that produce oxygen in plant leaves. He also identified that all parts of plants produce carbon dioxide at night.

Explaining why solving the solar neutrino problem revealed that neutrinos could transform

Electron neutrinos are byproducts of the nuclear reactions within the sun's core. Based on the sun's energy output, scientists modeled reaction rates and predicted neutrino production, but the observed values were consistently one-third the predicted values. Experiments later showed that these neutrinos could change into other types on their way to Earth, causing the discrepancy.

First-ever image of the sun's south pole

For the first time, we have clear images of the sun's mysterious south pole. Captured in March 2025, by ESA and NASA's Solar Orbiter, this footage reveals magnetic chaos that could unlock answers about solar storms, the sun's strange 11-year cycle, and why its atmosphere is hotter than its surface.

Albert Einstein's equations predicted black holes decades before their discovery

For nearly 50 years, scientists dismissed black holes as implausible oddities, despite solutions to the equations indicating their existence. But the 1970s discovery of intense X-rays from Cygnus X-1 and its massive hidden companion flipped the consensus.

Planeterrellas create artificial auroras that mimic the atmospheric displays of light by setting up an electric field between two metal balls in a jar filled with a small amount of air.

Scientists turn alchemists, transforming transform lead into gold

Fulfilling alchemists' dreams, scientists at the Large Hadron Collider (LHC) transmute lead into gold. While the 86 billion gold nuclei produced were short-lived, the experiment sheds light on how electromagnetic fields can play a critical role in nuclear transmutation.

Stars appear to twinkle because turbulence in the motion of molecules in Earth's atmosphere causes light to bend and wiggle rapidly on its way to the surface—a phenomenon called scintillation.

Planeterrellas create artificial auroras that mimic the atmospheric displays of light by setting up an electric field between two metal balls in a jar filled with a small amount of air.

Early Earth lifeforms likely made energy via mineral reactions, not sunlight

Earth's initial atmosphere was filled with carbon dioxide, methane, and water, with most oxygen locked away in the rocky crust. Over time, bacteria evolved to slowly release that oxygen into the atmosphere by breaking down rock.

The team responsible for the first interplanetary sundials included Bill Nye

While reviewing designs for instruments to be carried by future Mars rovers, Nye suggested adapting the function of a calibration tool, which would be used by the Spirit and Opportunity rovers to help calibrate the brightness and color of their panoramic cameras on the Martian surface.

Why the Antarctic climate enabled British scientists to discover the ozone hole

In the Antarctic stratosphere, polar conditions facilitate the formation of polar stratospheric clouds, which allow chlorine compounds from chlorofluorocarbons to accumulate. In 1985, British Antarctic Survey scientists detected massive springtime losses over Antarctica, as accumulated compounds destroyed significant amounts of ozone once sunlight returned.

Pineapple research helped scientists solve Los Angeles' smog mystery

In the 1950s, chemist Arie Haagen-Smit applied methods he'd used studying pineapple plant chemistry to smog-filled air—discovering that sunlight reacting with car exhaust produced photochemical smog from hydrocarbons and nitrogen oxides, not factory smoke.

Cloud 9 is a dark-matter-dominated failed galaxy

Identified in 2023, the starless, gas-rich object is the first of its kind seen by astronomers and provides a window into the early stages of galactic formation without observations relying on visible matter as a proxy. The existence of such REHLICs, or Reionization-Limited-H I Clouds, was predicted by cold dark matter cosmological models.

All rainbows are 'raincircles' caused by water droplets separating white sunlight into a spectrum of colors, but Earth's surface blocks the bottom half of the circle from our line of sight.

Learn more about the history of fireworks, which dates back to an accidental invention during an alchemist's quest for information about immortality.

The first image of a black hole was captured by creating an Earth-sized virtual observatory from a network of eight radio telescopes.

Scientists can determine Earth's past climate conditions by analyzing air trapped in microscopic bubbles within ice cores—columns of compressed snow layers that build up over hundreds of thousands of years.

See the 25 of the best photos of auroras from around the world.

Massive blooms of microscopic plankton called dinoflagellates produce the neon blue light seen in glowing tides.

Dirty lightning is a thunderstorm created from friction between rising and falling flows of ash and smoke during volcanic eruptions.

In 2009, the nation was gripped by the story of a missing young boy who was believed to be floating over Colorado in a homemade balloon, until it was revealed that he was at home the whole time.

While atoms are normally made of protons, neutrons, and electrons, exotic ones have been built with antimatter—alternate versions of normal matter that live for fractions of a second and are about a billion times as rare.

Sunflowers have long been a symbol of nuclear disarmament because they can extract large amounts of radioactive cesium from soil.

Clever Hans was a 1900s horse that was believed to be able to solve math equations, tell time, and read and comprehend German, until a psychology student discovered how he got his answers.

El Niño, Spanish for 'the boy,' was named after Jesus Christ because the phenomenon resembled the weather changes observed around Christmastime.

The first line of 'immortal' human cells, which can divide indefinitely and are used in scientific research, was nonconsensually taken from a Black woman.

As of 2025, the most cited papers in science include a review of graphene, methods to improve image recognition, streamlining electron density calculations, and optimizing protein studies.

The Great Salt Lake's distinct dual coloration results from high-salinity organisms that only live in the northern portion and produce a purple protein.

The Mona Lisa's celebrity status and repeated restorations have obscured what made the painting so revolutionary for its time

Explore fun facts from the USPS, including unique post office buildings, a stamp that traveled past Pluto, and more.

An investigation suggests a Scottish island became awash in forever chemicals via seafoam and seaspray—raising questions about what that means for the safety of other coastal areas.

The name 'Silicon Valley' arose from the founding of Shockley Semiconductor Laboratory in Fairchild Semiconductor in 1956-57, founded near Stanford University in Palo Alto

The word 'jazz' evolved from 'jasm,' 19th-century American slang for 'energy'

Budweiser stores yeast derived from the original 1800s strain in a secret bunker, which only the Head of Yeast Management can access—not even the CEO

Meet the 56 signers of the Declaration of Independence—most of whom didn't put pen to paper until August 2, 1776—and see their original signatures.

Sony set the standard for cylinder-shaped batteries when it repurposed manufacturing equipment used to make rolls of magnetic recording tape.