It’s one of the most fascinating things about a solar eclipse: dazzling crescents of light appear under trees. But why does this happen and what’s the science behind it?
- During a solar eclipse, the light from the Sun becomes more focused, creating clearer images of the Sun around us and...
- As the Moon passes in front of the Sun, the apparent shape of the Sun is changed to a crescent, or -- in the case of an annular eclipse -- a donut!
- This produces numerous images of the solar eclipse in the shadows all around us.
The everyday, made extraordinary
You may not realize this, but there are nearly perfect projections of the Sun every day all around us. Need proof? Step outside on a sunny day and look under a tree. You’ll notice fuzzy circles of light --that’s a projection of the circular image of the Sun! Here’s a picture of a driveway on Sunday, a regular sunny day without a solar eclipse:
Notice the fuzzy circles of light? Those are projections of the circular Sun onto my driveway through the gaps in the leaves of a tree! The gaps in the leaves of the tree act as pinhole projectors -- just like the ones people make to view solar eclipses.
But how, during a solar eclipse, do these images change?
Less sunlight, clearer projection
On a regular sunny day, our star produces so much light it bounces and refracts off of many sources. This means that there are multiple points of light all around us other than the Sun. This is called ambient light. Ambient light causes shadows to become fuzzy.
During the partial phases of a solar eclipse, the amount of sunlight is reduced slightly, but the amount of ambient light is reduced greatly. So, projected images of the eclipsed Sun and shadows become sharper and clearer. Notice the shadows in the picture below, during an eclipse. Not only are the projections of the Sun sharper, but the shadow of the tree trunk is clearer, too!
Finally, we see crescent-shaped projections of the Sun because the apparent shape of our light source changes as the Moon moves in front of the Sun. In the case of the Oct. 14 annular eclipse, these projections were donut-shaped during the “ring of fire” peak of the eclipse!
Check out some of the pictures sent in to us on KSAT Connect:
Read more from the meteorologists on the Whatever the Weather page
Download KSAT's weather app for customized, accurate forecasts in San Antonio, South Texas or wherever you are
Find the latest forecasts, radar and alerts on the KSAT Weather Authority page