You can also see the Moon’s shadow by making a pinhole projector, holding up a colander, or by looking at the dappled shade from a tree.
The quality of light
As more and more of the Sun gets eclipsed, you’ll notice some strange lighting effects.
Normally, the edges of your shadow under the full Sun are fuzzy. That’s because our big, round star generates light rays at an infinite number of angles. But as the Sun gets eclipsed into a crescent, it behaves more like a glow stick, putting out light in a more uniform direction. Objects aligned to the axis of the Sun’s crescent will cast sharper shadows.
You may also notice daylight starting to fade. What began as a bright, sunny day may start to appear overcast as the Moon blocks more and more sunlight.
Shadow bands
A rarer phenomenon to look for near totality is shadow bands. Shadow bands are undulating shadows that are most easily seen on plain surfaces. They are subtle, but may appear for a few minutes before and after totality, as seen in this enhanced video.
Scientists are not certain what causes shadow bands, and their appearance is unpredictable. One theory is that they are created by the same turbulent air in the upper atmosphere that makes stars twinkle. As the Sun shrinks into a thin crescent — the same crescent that makes shadows sharp — the light may organize into twinkling lines.
The racing shadow
After observing the Moon’s leisurely progression across the Sun, you may be tempted to forget that the Earth, Moon, and Sun are locked in a high-speed orbital dance.
The Moon’s average speed around the Earth is around 3,700 kilometers per hour (2,300 miles per hour), meaning the darkest part of its shadow, the umbra, travels just as fast. The Earth’s rotation changes the shadow’s effective speed depending on where you live, but it’s still quick. If you’re watching from a spot where you can see a long way in the direction of the oncoming shadow, you may be able to see it racing toward you on the ground or in the clouds.
Baily’s beads
As the last of the Sun’s rays disappear, you may see what looks like a string of beads along the Moon’s limb. These beads are caused by sunlight slipping through lunar valleys — you’re actually seeing the Moon’s topography!