For thousands of years, humankind has been enthralled by the solar eclipse. In centuries past, before people understood the basic science behind what causes a solar eclipse, the sudden blotting out of the sun in the middle of the day could be an event of extreme fright and sometimes caused public panic.
But today we know that a solar eclipse is caused when the moon passes in between the disk of the sun and Earth, creating a shadow that races across the surface of our planet. It’s an event of fun, wonder, and awe. If one is lucky enough to live in an area where the shadow passes, a total eclipse lasts an average of 71/2 minutes.
There are actually three kinds of solar eclipses: total eclipses, partial eclipses, and annular eclipses. In the first, the disk of the moon completely covers the sun creating night-like conditions. A partial eclipse is when the disk of the sun does not line up completely and the face of the sun is only partially covered. An annual eclipse happens when the moon happens to be at its furthest point from Earth. In this case, it cannot totally blot out the full surface of the sun’s disk.
1. Total Darkness vs. Reduced Light
So, the first major difference between a total solar eclipse and a partial eclipse is that a total eclipse produces almost nighttime-level darkness if one is directly in what astronomers call the “path of totality.”
During the 7+ minutes or so of a total eclipse, the stars will come out, a cold breeze may pass across the area where one is observing and even animals, such as birds and insects, will become suddenly quiet.
2. Noticeable Light Difference
During a partial eclipse, the average person may notice no change in daylight at all. Note that a partial eclipse can mean one-half the sun, one-quarter, or some other fraction of the sun being obscured by the moon.
If enough of the sun gets covered in a partial eclipse, the daylight may become noticeably dusky.
3. Rare vs. Common
A total solar eclipse happening in any given location on the Earth is relatively rare in terms of where a person lives at the time. Most people will not observe a total eclipse pass over their hometown or neighborhood in their lifetimes! However, many people choose to travel to where they can get inside the path of totality.
But there can be two to five partial solar eclipses that can be seen by everyone every year.
4. Danger to the Eyes
It’s extremely important to note that looking directly at either a total eclipse or partial eclipse with the naked eye is dangerous.
That’s why NASA recommends the use of special “safe solar viewer” glasses or handheld filters when observing an eclipse. Eclipse glasses are a thousand times darker than even the darkest kind of regular sunglasses. They comply with the ISO 12312-2 international standard for filters.
Although there’s a difference in the level of solar UV radiation exposure between a total and partial eclipse, both should be treated as the same when observing them.