Hubble's first light test produced an underwhelming photograph

An imperfection 1/50th the width of a human hair blurred Hubble's initial images

Not all parts of the space telescope's primary mirror focused incoming light to the same location, an effect known as spherical aberration. Because Hubble was designed to reside in low Earth orbit and be serviced by astronauts, service missions were deployed in the years after its launch to conduct repairs.

Hubble overcame early optical failure and became a critical scientific instrument

The flaw in Hubble's mirror was smaller than the width of a human hair, but fixing it required a space mission as complex as a Hollywood rescue story—with astronauts installing corrective optics like contact lenses for a giant eye in the sky.

Watch a firsthand account of Hubble's first service mission to repair its faulty mirror

Hubble senior project scientist David Leckrone recalls initial public ridicule over the microscopic manufacturing error that put NASA's reputation at stake. In this behind-the-scenes interview, he breaks down the innovative fix deployed by space shuttle astronauts during Hubble's first servicing mission.

The Hubble Space Telescope uses curved mirrors to collect and focus light

Classified as a Cassegrain reflector, the observatory bounces incoming visible light and some infrared and ultraviolet light off a primary mirror with a diameter of 2.4 meters. The reflected light is directed to a secondary mirror, which reflects it through a tiny hole in the primary mirror and onto detectors.

Fly through the deepest image of space ever taken by the Hubble Space Telescope

Taken over 11 days between 2003 and 2004, when the space telescope was aimed at a seemingly empty patch of the sky, the Hubble Ultra-Deep Field revealed about 10,000 sources of light, most of which are entire galaxies. This visualization expands the 2D image into a 3D view spanning 12 billion years.

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

The scattering of light in the early universe prevents seeing the beginning of time

A "cosmic fog" of elementary particles in the early universe prevented light from traveling far before being absorbed. Only 380,000 years after the big bang, when the first atoms formed, was light free to travel and reach telescopes for study.

The breakthrough that changed our perception of the universe

In the 1920s, the Hooker Telescope helped Edwin Hubble make a discovery that forever changed how we see the universe. Building on the work of astronomers like Henrietta Leavitt and Harlow Shapley, Hubble used the telescope to prove that galaxies exist beyond the Milky Way—revealing a vast and expanding universe.

The first-ever image of a black hole

The Black Hole at the center of galaxy M87 is ready for its close-up, becoming the first black hole to have its image directly captured. The Event Horizon Telescope caught the distant yet massive object—it's more than 55 million light years away—recording its gravity's effect on nearby hot gases.

Space telescope development was driven by a desire to bypass Earth's atmosphere

The most important figure in the effort to create what would become the Hubble Space Telescope was Lyman Spitzer, who first proposed a telescope in orbit in 1946. The nearly 50-year endeavor led to space-based observatories, which are not limited by Earth's atmosphere absorbing or distorting most wavelengths of light.

Infrared vision gives Webb telescope access to the oldest light in the universe

To peer into the universe’s earliest moments, the Webb had to solve several immense engineering challenges: deploying a massive sun shield, surviving extreme cold, and stabilizing ultra-sensitive instruments. The telescope’s mirrors can adjust themselves in steps 10,000 times smaller than a human hair.

An early burst of dark energy may resolve discrepancies in the universe's measured expansion

The Hubble tension refers to mismatches in the calculated rate of expansion of the universe derived from different methods, such as supernova data and the cosmic microwave background. By allowing dark energy to become active at a different time, models of the universe on which some of these methods depend are revised, altering the calculated values.

Hubble's average used power is less than half the power generated by its solar arrays

The space telescope's components use about 2,100 watts, or about as much power as five refrigerators. When exposed to sunlight, the solar arrays can generate over 5,200 watts for the observatory, which was engineered by a team that included Judith Love Cohen, mother of actor Jack Black.

Published photography from JWST are false-color images

The James Webb Telescope captures invisible light, not photos. Scientists then color-map wavelengths of infrared light to show us the invisible universe.

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.

The European Space Agency's Euclid telescope maps dark matter

As light rays travel near massive objects in space, their paths can be distorted on their way to Earth, causing objects to appear displaced, magnified, shrunken, or sheared. By simulating these effects for various mass distributions, astronomers can match the distortion to a simulated mass and compare it with the observed visible matter to infer the presence of dark matter.

A breakdown of the experimental test results supporting the general theory of relativity

Besides accurately explaining the slight wobble observed in Mercury's orbit, general relativity predicted that light would bend around massive objects by an amount matching what was observed when background starlight bent around the sun during an eclipse. The theory also predicted the existence of gravitational waves and black holes decades before they were found.

The iconic photo of the Wright brothers' first flight was the photographer’s first

Using a then-state-of-the-art Korona V, rescue member John T. Daniels was tasked with squeezing the device’s rubber bulb the moment the plane left the wooden track on the sand. The camera produced negatives on 5 by 7 sheets of glass.

Hubble revealed that planet-forming disks are common around young stars

One of Hubble’s early images captured 30 young star systems in the Orion region, each surrounded by material that looked like it was forming planets. These systems increased the number of data points scientists had to test planetary formation models.

Observations of Jupiter's moons first demonstrated that light was not instantaneous

In 1676, Danish astronomer Ole Rømer noticed that eclipses of the moons occurred several minutes later when Earth and Jupiter were farther apart, reasoning that light needed more time to travel the greater distance. Lacking knowledge of Earth's orbital diameter, he was unable to calculate the speed of light.

The first interferometric gravitational wave detector was invented in 1972

Robert Weiss completed the designs after his students asked about an earlier apparatus that used stretched aluminum cylinders to detect passing gravitational waves. Unfamiliar with general relativity and hoping to keep the course focused on experimental tests rather than mathematics, Reiss later asked his students to consider his device for homework. (Some readers may experience a paywall.)

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

In 1868, using tools that dispersed light into its constituent colors like a prism, astronomers Pierre Jules César Janssen and Joseph Norman Lockyer independently identified a bright yellow line in the solar spectrum that didn't match any known element. Fourteen years later, amid continued skepticism over the existence of a new element, the same spectral signature was observed in lava on Earth.

Light echoes are expanding shells of reflected starlight

Just as sound waves reveal the location of obstacles by reflecting off them, pulses of light emitted by stars illuminate rings of interstellar dust, giving the appearance of ejected material as the light travels outward.

The discovery of neutron stars by Jocelyn Bell Burnell, who was not awarded the corresponding Nobel Prize

During her doctoral program in radio astronomy at Cambridge University, Bell Burnell's first two observations of a neutron star were initially dismissed as interference by Antony Hewish, her advisor. He and Martin Ryle, head of the research group, were jointly awarded the Nobel Prize in physics, the first awarded for astronomical research.

Most of the observable universe's volume consists of voids and supervoids—enormous regions of space with little to no galaxies, stars, or light.

Holograms are produced by shining light through recordings of interference patterns

When one half of a split laser beam that was reflected off the surface of an object recombines with its other, unreflected half, the two produce an interference pattern that becomes etched onto holographic film. When light shines through the back of the film, it reacts with the pattern to create the reflected light, projecting the original object.

View media of the sun's south pole, taken for the first time in 2025

Captured in March 2025 by the Solar Orbiter—a satellite developed by ESA and NASA—the images and video are the first to be taken by an object not moving around the sun's equator. The orbiter moved outside the plane of the planets by using Venus to slingshot it into a tilted orbit, and the data it collected will help scientists better understand the sun's magnetic activity.

The first horror movie is believed to be George Méliès' 1986 short 'The Haunted Castle,' which pioneered the use of special effects

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.

After NASA's Voyager 1 captured Earth as a single pixel as it left the solar system in 1990, astronomer Carl Sagan used the image to reflect on humanity's fragility and the responsibility to protect 'the only world we've ever known.'

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

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

Objects can be 3D printed with light by projecting 2D computerized tomography (CT) scans onto rotating cylinders of resin, which solidify upon exposure.

Before humans, the Soviet Union and the United States sent animals—including apes, dogs, and cats—to space during the Space Race.

The original copy of the Declaration of Independence is not a pristine document, and even features a smudged anonymous handprint in the bottom left corner.

'Grand Canyon of the Yellowstone,' a work by American painter Thomas Moran, inspired Congress to establish Yellowstone National Park.

Explore the animals that populate the depths of the ocean, from fish and coral in the first few hundred feet, all the way down to the bottom of the Mariana Trench.

Take a 3D tour of the Hajj, Islam's annual pilgrimage to Mecca, undertaken by over 1.5 million Muslims.

Long before Major League Baseball began allowing instant replay for balls and strikes, an umpire reluctantly used the technology to determine whether a hit was a home run, a move that inadvertently ushered in a new era for the sport.

The Beatles' US label rejected the band's first two singles, 'Please Please Me' and 'From Me to You,' with one executive calling the band 'dead in the water.'

See 33 images that became central to huge scandals, including a young Charles and Camilla, Michael Jackson's baby on a hotel balcony, and Hugh Grant's mugshot.

SpaceX's S-1 or 'prospectus' revealed many previously unknown details about the company, including its unprofitability despite doing $18.7B in revenue in 2025, exactly how many voting shares Elon Musk will have in the company (roughly 85%), and more.

While the first exchange-traded fund (a 'basket' of different assets that can be bought and sold on a stock exchange) in the US only launched in 1993, the global ETF market has grown to more than $10T in the short time since.

Georgia O'Keeffe's flower paintings are often assumed to be sexual, though the artist claimed she was simply interested in highlighting the beauty of flowers that most people neglect

Double world record holder Hunter Ewen helped conquer his fear of balloons, called globophobia, by training to win Guinness World Record titles for balloon inflation.

When you complete a CAPTCHA on a website to prove you are human, you may be unknowingly training algorithms for self-driving cars, whose systems require training data to help identify crosswalks, bicycles, and other outdoor objects.

In 1984, Operation Smash Hit intentionally crashed a 239-ton train into a nuclear waste canister at 100 miles per hour to prove the canister's safety, which remained completely intact and lost just 0.29 of its 100 pounds of pressure.

Fear or disgust related to clusters of holes and cracks, called trypophobia, may stem from evolutionary processes to help us avoid pathogens.

In its famous catalog, Sears sold $600 DIY house kits from 1908 through the 1940s, resulting in an estimated 100,000 'Sears and Roebuck homes.'

Elk Cloner, the first computer virus to spread in public, was written as a practical joke by Richard Skrenta, a Pittsburgh high school student.