UW-La Crosse Planetarium director Bob Allen on all things solar eclipse

“It is the most unearthly experience you can have on the Earth,” explains UW-La Crosse Planetarium Director Robert Allen, describing a total solar eclipse.

During a total solar eclipse, the sun falls behind the moon, leaving only a sign of the outermost atmosphere of the sun — the solar corona. This corona appears like a glowing ring perched high in the sky. Daylight succumbs to an eerie twilight with only a thin sunset all around the horizon. Birds go to roost and certain flowers close as if nightfall has truly come. Planets and some of the brighter stars come into view. Then, within minutes the moon’s shadow has moved on and world returns to a normal day.

People will have a chance to see a total solar eclipse this Monday, April 8, if they live in any communities along the projected direct path of the moon’s shadow or “path of totality” that will move diagonally across the North American continent, stretching from Mexico’s Pacific coast to Newfoundland, Canada. This dark shadow will travel across portions of various U.S. states including Texas, Oklahoma, Arkansas, Missouri, Illinois, Kentucky, Indiana, Ohio, Pennsylvania, New York, Vermont, New Hampshire, Maine and small parts of Tennessee and Michigan.

This will be the first total solar eclipse to cross the continental U.S. since 2017.

Wisconsin doesn’t fall within the path of totality, so the state will experience a partial solar eclipse, along with nearly all of North America. A partial solar eclipse is noticeable if you know what you’re looking for, but not nearly as spectacular, explains Allen.

Allen will be traveling to Arkansas, along with a host of other local astronomy buffs to see the total solar eclipse — a phenomena he’s witnessed only three times in his life: In 1979 in Canada, in 1991 in Hawaii, and in 2017 in Nebraska.

Below Allen answers common questions about total and partial solar eclipses.

What is a solar eclipse? 

During a solar eclipse, the moon comes between the sun and the Earth, blocking out the sun’s rays. This is possible because the moon and sun appear to be roughly the same size in the sky when viewed from the Earth’s surface. In reality, the sun is much larger than the moon — about 400 times larger. However, coincidentally, the sun is about 400 times farther away than the moon, making the two appear roughly the same size from the Earth. This phenomena makes a solar eclipse possible.

During a solar eclipse, the moon’s shadow is projected onto the Earth, causing those on Earth to experience dawn or dusk-like surroundings despite it being daytime. However, not all shadows are created equal. Two types of shadows are projected on Earth, and one is much darker than the other.

• Umbral shadow: A smaller, darker shadow cast on the Earth. The umbral shadow is considered the “path of totality” and those in this path experience a total solar eclipse. The width of this umbral shadow can be up to about 150 miles wide. During the April 2024 eclipse it will span about 115 miles, creating a dark and truly otherworldly experience for viewers below. Being in the umbral shadow is a rare opportunity considering the path of totality is fairly narrow when considering the Earth’s full diameter is nearly 8,000 miles.
• Penumbral shadow: A much broader and lighter shadow cast on the Earth by the moon. Many more people experience the penumbral shadow of the moon during a solar eclipse, which means they are experiencing a partial solar eclipse. The darkness they experience ranges, depending on how far they are from the path of totality. La Crosse, Wisconsin, for instance can expect to be at 85% of totality for the April 2024 solar eclipse.  See a video demonstrating umbral and penumbral shadows. 

Why don’t we have a solar eclipse every month?

The moon takes about one month to orbit Earth, so one could reason that a solar eclipse should occur every month — each time the moon makes its round to orbit Earth and comes in front of the sun. That would be true if the moon’s orbit around the Earth was perfectly aligned with the Earth’s orbital plane around the sun. However, the moon’s orbit is not perfectly aligned — it is inclined a few degrees north or south in relation to the Earth. Because of its inclined orbit, the moon sometimes doesn’t block the sun at all, and, at other times, it is only partially blocking it. 

During a total solar eclipse, orbiting planes of the Earth and moon intersect, and the moon lines up perfectly in front of the sun. This happens relatively infrequently. Consider that eclipse season — a 35 day period when the new or full moon happens and a solar or lunar eclipse is possible — occurs only about twice a year. But the chance of seeing a solar eclipse during this period is even less frequent as it must happen in locations on the Earth that is possible to get to. Eclipses over the oceans, arctic tundra and deserts often go unseen. That’s why seeing a solar eclipse is so special. It is truly a once in a lifetime opportunity — and potentially more depending on how far you’re willing to travel.

How long does a solar eclipse last?

A solar eclipse can last from several seconds to a maximum of just a little over seven minutes. The 2024 eclipse will last a maximum of about six minutes in some places and less in others.  

How do you safely observe a solar eclipse?  

One should never look directly at the sun with the naked eye or other tools such as binoculars or a telescope, except during totality, as it can instantly cause severe eye injury. Use special-purpose solar filters or other devices created to view a solar eclipse indirectly. 

• Eclipse viewing glasses – Many libraries, museums, and planetariums provide eyewear specifically created for solar eclipse viewing. Eclipse glasses should meet all ISO 12312-2:2015 standards for direct solar observation. They block 99 percent of UV light, 97 percent of IR radiation and only allow a transmission of roughly 0.0003 percent of visible light through them.
  Indirect ways to watch –
• Pinhole projection – The simplest way to view a partial solar eclipse is to poke a small hole in a piece of cardboard and project the image onto a second piece of cardboard behind the first one. A piece of white paper taped to the cardboard makes the image brighter.
• Colander – A colander with multiple holes in it can also be used to project images of the crescent sun onto the ground.
  https://youtu.be/cxrLRbkOwKs?si=fLlNQuq10qAqtXPA

When is the solar eclipse in 2024? 

The 2024 eclipse will be on Monday, April 8 at varying times depending on where you are located.

Where is the solar eclipse in 2024? 

The 2024 solar eclipse path or “path of totality” includes portions of Mexico, Texas, Oklahoma, Arkansas, Missouri, Illinois, Kentucky, Indiana, Ohio, Pennsylvania, New York, Vermont, New Hampshire, Maine, Canada, and small parts of Tennessee and Michigan. Most of North America will experience a partial solar eclipse. 

Even if you are in the path of totality, you are not guaranteed to see the total solar eclipse as it requires a clear sky. The clearest skies for the 2024 eclipse are predicted to be in southwest Texas and Mexico.
Even if you are not in the “path of totality” you can view the partial solar eclipse, which may create a noticeable darkness and create a crescent shape on the sun when viewed through a filter. Check your community for local viewing events.

Former astronomy teacher at Logan High School Jim Konichek will be set up at La Crosse’s Riverside Park, if the sky is clear, around 1 p.m. Monday, April 8 to view the partial solar eclipse. Peak coverage will be at 2 p.m. with the outgoing partial eclipse over by 3 p.m. Everyone is welcome to come and view. Viewing glasses will be provided.

Solar eclipse 2024, can you see it in Wisconsin?

We will see a partial solar eclipse of varying degrees in Wisconsin. La Crosse, Wisconsin, for instance, will experience an 85 % solar partial eclipse.  This may produce a noticeable darkening of the sky and the moon will come partially in front of the sun, but not fully cover it. For comparison, Allen says La Crosse had an 92 % partial eclipse in 2017, and it became dark enough that the street lights came on. He doesn’t expect an 85 % partial eclipse to cause street lights to turn on.

When can we expect to see the solar eclipse in Wisconsin?

Times will vary. In La Crosse it will begin to be visible at 1 p.m. with a peak at 2 p.m. and wrapping up at 3 p.m.

Why does a lunar eclipse last so much longer than a solar eclipse?

A lunar eclipse is typically several hours long while a solar eclipse lasts only minutes. Why the difference? Remember during a solar eclipse the moon casts a shadow on the Earth and during a lunar eclipse, the Earth casts a shadow on the moon. The Earth is much larger than the moon, and so is its shadow, meaning it takes much longer for the Earth’s full shadow to pass across the moon’s surface. The moon is one fourth the diameter of the Earth, so its shadow quickly makes its trek across the Earth’s surface.  

Solar eclipse 2024 myths, theories and legends

Various myths, theories and legends have been associated with solar eclipses over the centuries of human existence. Early and even more modern day humans have pondered whether they signal the end of the world. These stories likely gained popularity in early times as humans had no scientific explanation for why the world was suddenly growing an eerie dark.

In ancient China it was thought that a dragon was swallowing the sun. In ancient Hindu mythology, the deity Rahu is beheaded by the gods for capturing and drinking Amrita, the gods’ nectar. Rahu’s head flies off into the sky and swallows the sun causing an eclipse. Traditionally, people in many cultures get together to bang pots and pans and make loud noises during a solar eclipse. It is thought that making a noise scares the demon causing the eclipse away.

— Story by UW-La Crosse