A solar eclipse occurs when the Moon passes directly between the Sun and Earth, casting a shadow on our planet and temporarily blocking the Sun’s light. Viewers situated in the path of totality, where the Moon fully covers the Sun, witness the full spectacle. Those outside this narrow track will only observe a partial eclipse, where the Sun appears to have a crescent shape. The entire event unfolds over several hours, but the most dramatic visual and physical changes happen in the final moments before the Sun is completely obscured.
The Visual Progression of the Eclipse
The initial phase begins subtly, with the Moon taking a small “bite” out of the Sun’s disk. Over the next hour, the Sun gradually transforms into a thinning crescent as the Moon continues its slow transit. During this period, the ambient daylight begins to take on a strange, muted quality.
As the eclipse progresses past 80% coverage, noticeable physical changes occur in the surrounding environment. The air temperature can drop significantly, often by 5 to 10 degrees Fahrenheit, creating a sudden chill akin to a rapid sunset. Shadows on the ground become remarkably sharper, and the small spaces between tree leaves act as natural pinhole cameras, projecting hundreds of tiny crescent-shaped sun images onto the ground.
In the final minutes before totality, two fleeting phenomena may appear. Just before the last sliver of sunlight vanishes, faint, rapidly undulating lines of light and shadow, known as shadow bands, may ripple across plain, light-colored surfaces. These wavy lines are caused by the refraction of the thin solar light source through pockets of atmospheric turbulence high above the ground. Simultaneously, the sky darkens rapidly to a deep twilight, and observers may spot Venus or Jupiter appearing in the unusual daytime darkness.
Distinct Features Visible During Totality
The total phase is the only time the Moon completely blocks the Sun’s blinding disk. Immediately before totality, the last rays of sunlight stream through the valleys and craters along the Moon’s irregular edge, creating brilliant spots known as Baily’s Beads. When only a single bead of light remains, it creates the “Diamond Ring” effect, resembling a dazzling jewel set into a dark ring.
Once totality begins, the Sun’s faint outer atmosphere, the corona, becomes visible as a wispy, pearly white halo surrounding the Moon’s silhouette. This ethereal glow is composed of superheated plasma that is millions of degrees hotter than the Sun’s surface, extending millions of miles into space. The corona’s shape is entirely dependent on the Sun’s current magnetic activity, appearing either spiky and uniform or elongated with long streamers.
You may also glimpse the chromosphere, a thin layer of the Sun’s atmosphere. This layer appears as a vibrant, reddish-pink arc just above the Moon’s limb, a color caused by hydrogen-alpha emissions. Around the entire horizon, a 360-degree sunset effect is visible, marking the edges of the Moon’s shadow cone, which creates a dome-like effect over the landscape.
Essential Safety Practices for Viewing
Viewing the Sun directly without proper protection can cause permanent eye damage, known as solar retinopathy. For all phases of a partial solar eclipse, you must use certified solar viewing glasses or handheld viewers that comply with the ISO 12312-2 safety standard. These devices are thousands of times darker than regular sunglasses and are designed to filter out intense visible light, along with harmful ultraviolet and infrared radiation.
Standard sunglasses, polarized lenses, or smoked glass are insufficient and will not protect your eyes. The only time it is safe to remove your certified eye protection is during totality, when the Moon completely covers the Sun. The moment the Diamond Ring or the first bright point of the Sun reappears, you must immediately replace your eclipse glasses to prevent injury. Alternatively, indirect viewing methods, such as using a pinhole projector to cast an image of the eclipsed Sun onto a surface, offer a safe way to observe the partial phases.