The total solar eclipse is returning to the United States — better than before

On April 8, 2024, millions of Americans will be able to see a rare celestial occurrence: a total solar eclipse.

It’s going to be awesome. If you’re in the center of the moon’s shadow, known as the totality, the sky will go dark for a few minutes in the middle of the day. The temperature will drop, stars will appear, and birds will become confused and start chirping their nighttime songs.

And it’s all because of a cosmic coincidence: From the Earth, the moon and the sun appear to be roughly the same size.

By many measures, April’s event will (please excuse the pun) eclipse the last total solar eclipse that passed over the United States in 2017. There are few reasons. The shadow of totality will be twice as wide as that of the 2017 eclipse (more on why below), so it will be easier to find a place to view it in any given state. The time of totality — how long the moon is completely covering the sun — will also be almost twice as long, at over four minutes in many locations.

“And I think even more importantly, 2024 passes over a much bigger population,” says Ernie Wright, who works in NASA’s Scientific Visualization Studio. He did the eclipse calculations underlying many of the maps and illustrations you’ll see in this article. “More than twice as many people actually live in the path and don’t have to go anywhere to see it.”

If you live anywhere in the path from Kerrville, Texas, to Houlton, Maine, you’re in luck. If you want to travel to see it, book accommodations now! Hotels in many areas are filling up. But even if you can’t get to the path of totality, you’ll be able to view at least a partial solar eclipse (which is pretty cool) from any location in the lower 48 United States. It will be the last total solar eclipse in the lower 48 United States until 2045. So, if you’ve been eager to see one in the US, now is your last chance for 21 years.

Here’s everything you need to know about the upcoming eclipse.

Why do we have solar eclipses?

There’s a simple answer: The moon occasionally covers the sun in its path across the sky. But it’s more complicated than that. Three cosmic conditions have to be met to produce the shadow.

First, there has to be a new moon.

One side of the moon is always lit by the sun, but the lit side isn’t always facing the Earth. This is how we get the phases of the moon. For a solar eclipse to occur, it needs to be in its “new moon” phase.

During the new moon, the dark side of the moon is directly facing the Earth.

Ernie Wright/NASA

Then, the moon has to cross the plane of Earth’s orbit.

If the dark side of the moon has to be facing the Earth for a solar eclipse to occur, why don’t we have them every new moon? The moon’s orbit isn’t perfectly matched up with the Earth’s.

That’s because the moon is tilted on a 5-degree axis. No one is completely sure why the moon is slightly skewed, but it might have to do with how it was likely formed: from a massive object smashing into Earth.

NASA

This means during most new moons, the shadow misses the Earth.

But there are two points in the moon’s orbit where the shadow can fall on the Earth. These are called nodes.

Joss Fong/Vox

For a total eclipse to occur, the moon needs to be at or very close to one of the nodes.

Joss Fong/Vox

Finally, whether the entire sun is covered depends on the moon’s distance to the Earth.

You might remember this from middle school science: The moon’s orbit around the Earth is not a perfect circle. It’s an ellipse.

Wikipedia

There’s a point in the orbit where the moon is the farthest it gets from the sun and a point where it’s the closest. For a total eclipse to occur, the moon needs to be near its closest approach to Earth.

If the eclipse occurs when the moon is close, it will totally block out the sun. If it’s farther away, we get what’s called a “ring of fire” eclipse.

How do we know when eclipses will happen?

The three conditions that conspire to create eclipses — the new moon, the moon crossing the plane of Earth’s orbit, and the moon’s distance to the Earth — all recur on slightly different time scales.

It takes the moon 27.212 days to return to a node (this is called a draconic month). Every 27.554 days, the moon returns to its closest approach to Earth (an anomalistic month). The moon finishes cycling through all its phases once every 29.530 days (a synodic month).

The system that keeps track of all three months and when they overlap is called the Saros cycle, and it predicts both solar and lunar eclipses. Saros is ancient: The Babylonians discovered it in the few centuries before the start of the common era. And they worked it all out just by making careful observations of the moon for hundreds of years.

Today, NASA doesn’t have to rely on the Saros cycle alone to predict eclipses. “It starts with knowing where the Earth, the moon, and the sun are,” Wright says of making eclipse prediction and maps. “But then you need to calculate, based on the geometry, what the shape of that shadow is and where it’s going to hit the Earth.”

The GIF below, produced by Wright and colleagues, demonstrates how the moon casts it shadow.

NASA Scientific Visualization Studio

To make extremely accurate maps and projections of the eclipse, Wright says, he even takes into account how the moon isn’t a perfect sphere. The edge of the moon “has mountains and valleys on it, and that actually affects the shape of the shadow,” he says. “And so with some extra calculation, you can take that into account. It’s the reason, when you look at my map, the shadow shape on the ground is not a perfect oval. It’s kind of a potato shape.”

You can see that potato shadow shape in Wright’s animation of the shadow passing over Arkansas, Indiana, and Ohio. (See the entire video of the shadow’s path here.)

Ernie Wright/NASA Scientific Visualization Studio

Can eclipses happen anywhere on Earth?

Eventually, every spot on Earth will see an eclipse. Wright made a map overlaying all the paths of every total solar eclipse that has occurred since the year 2000 BCE and will occur up to the year 3000 CE. The brighter the color, the more eclipses have occurred in that spot. Every spot on his map is colored in by at least one eclipse, Wright says — the map below comprises 14.6 million pixels, and they all are colored in.

NASA Scientific Visualization Studio/Ernie Wright

Do some places see more eclipses than others?

Interestingly, with the map above, Wright finds more eclipses have occurred and will occur in the Northern Hemisphere than in the South. There’s a reason for this. During the summer months in the Northern Hemisphere, the Earth is slightly farther away from the sun than when it is summer in the Southern Hemisphere. “During Northern Hemisphere summer, we’re a little bit farther away from the sun, so the sun looks slightly smaller in the sky,” he explains. “That makes it a little easier for the moon to cover the sun.” And eclipses are more likely in the summer “just because the Sun is up longer then,” he explains in his post on the NASA website.

Which places are going to get totality? When? And for how long?

In the United States, the total solar eclipse in April will cut a path from Texas all the way up to Maine. What time the eclipse starts and how long it lasts are dependent on the spot you choose to observe it. For example, in Kerrville, Texas, the totality will start at 1:32 pm local time and last for 4 minutes and 24 seconds. In Houlton, Maine, the totality starts at 3:32 pm local time and only lasts for 3 minutes and 20 seconds.

For all the information on when the eclipse starts, check out NASA’s great interactive Eclipse Explorer. Click on any city on the map there to see local eclipse information, including start times and lengths of totality.

NASA

Why will this eclipse last longer than the 2017 one?

In 2017, the length of totality for most places in the US hovered around the two-minute mark. This year’s eclipse will last around three or four minutes, depending on the location.

Why is this one so much longer? Again, it all has to do with the moon’s slightly elliptical orbit around the Earth. The oval shape of the orbit means “every month there are times when the moon is closer and times when it’s farther away,” Wright says. “We can only get total eclipses when the moon is pretty close to us.” Otherwise the result is that annular “ring of fire” eclipse, where the sun isn’t completely blocked out. But during the 2024 eclipse, the moon will be nearer to the Earth than it was in 2017.

The closer the moon is, the bigger it appears to us in the sky and the larger the shadow it casts, including during an eclipse. And a bigger shadow takes a longer time to clear an area.

Outside the totality, what will the rest of the country see?

The entire lower 48 United States will be able to observe at least a partial eclipse, where just a portion of the sun is covered by the moon. (You’ll need special solar eclipse glasses to view it safely — more on those below.) The Pacific Northwest will see about a quarter of the sun obscured, while the Southeast will see around 75 percent. For exactly what you’ll see in your area and when, check out NASA’s Eclipse Explorer.

NASA Scientific Visualization Studio

Are there any places in the US that got totality in 2017 and have it again in 2024?

Carbondale, Illinois, and the surrounding area in southern Illinois are getting a repeat total solar eclipse. Way to go! Wright says that, on average, an area should see a repeat eclipse once every 365 years. “To have two of them happen within seven years is, you know — it’s pretty lucky for Carbondale,” he says.

Do we know where the next total solar eclipse is going to be?

Absolutely. There’s a total solar eclipse roughly once every 18 months.

The next total solar eclipse will be on August 12, 2026, and it will pass over Spain, Iceland, and Greenland.

NASA keeps a catalog of all the eclipses (both solar and lunar) that have occurred or will occur from 1999 BCE to the 3000 CE. That’s five millennia, mind you.

That’s why we know, for instance, that on January 27, 2837, a total solar eclipse will pass over southern Mexico. (Will any humans be around to see it?)

The next solar eclipse over the United States will be visible in Alaska in 2033. And the next one in the lower 48 states will be in 2045.

Great American Eclipse

Okay, enough with the astronomy. What happens on the ground during a total solar eclipse?

If you’re in the path of the total solar eclipse, expect to do a fair amount of waiting around for the big moment.

The eclipse goes through a few phases. In Kerrville, Texas, the partial eclipse phase starts around 12:14 pm, but the totality doesn’t begin until 1:32 pm.

For anywhere in the path of totality, the first thing you’re going to see is a partial eclipse: the moon slowly starting to obscure the sun. For this part of the eclipse, be sure to wear special eclipse glasses (more on them below).

Sijori Images/Barcroft India/Barcroft Media via Getty Images

During a partial solar eclipse, shadows form eerie crescent shapes.

fdecomite/Flickr

When totality nears, that’s when the show really begins. There are a couple of awesome phenomena that you can look out for.

Right before totality, the last glimpse of light from the sun will form a “diamond ring” in the sky.

SSPL/Getty Images

You’ll also be able to see “Baily’s beads” (named after astronomer Francis Baily): bits of light poking through canyons and craters on the roughed-up surface of the moon.

SSPL/Getty Image

Insider tip: Wright says if you want to see more Baily’s beads, choose to watch the eclipse near the edge of the totality zone on the map. “The edge of the moon is grazing the edge of the sun at that point on the path,” Wright says.

Then comes totality: when the moon is fully covering the sun. This is what you’ve been waiting for. When the totality happens, the sky goes dark. Stars come out. You can see the corona — the sun’s wispy outer atmosphere. This is normally too faint to see, even if you are wearing solar eclipse glasses. But with the moon blocking the sun’s light, it shines through in an almost ghostly manner.

Carlos Avila Gonzalez/San Francisco Chronicle via Getty Images

While you’re dazzled by the corona, consider this: The sun’s atmosphere is actually hotter than its surface, but no one really knows why.

What’s so awesome about totality?

Photos can’t really capture the awesomeness of totality.

“Anytime you’ve ever taken a picture of the full moon, it never captures how it felt in your eyes and in your heart, you know what I mean?” Rhonda Coleman, an eclipse chaser, told me in 2017. “It seems to fill the sky, but your photograph will only be a memory.”

I saw the 2017 eclipse in South Carolina. Here’s how I described it at the time:

When the shadow fully took over the sun, the crickets chirped, the kids screamed, Venus appeared bright in the sky next to the sun, and I lay down before a black, black disc that was surrounded by the most angelic white light I’ve ever seen. It must be the color Renaissance painters yearned for when painting pictures of God in heaven — sublime, gentle, powerful, and singular.

So yeah, viewing the eclipse might bring out overwrought prose in you too. You’ve been warned!

Will it change my life?

Many people report feeling a profound sense of awe during and after a total solar eclipse. “You suddenly feel as though you can see the clockwork of the solar system,” Wright told me back in 2017.

He continued:

We kind of know — in the back of our minds — that we live in a giant ball and it revolves around a hot ball of gas, and we’re floating in space. But you don’t really believe it until you see something like a total solar eclipse, where everything is all lined up and you go whoaaa. Other planets pop out. You got instant nighttime. And you can see Mercury and Venus usually. And sometimes Mars and Jupiter. ... It looks like the pictures from the textbook. It’s not entirely a science thing anymore. ... It’s mostly a thing where you have a better appreciation of where you are in the solar system.

Your experience may vary.

Do normal laws apply during totality, or am I allowed to do weird, wolflike things without the fear of repercussions?

Arguably, you can do weird, wolflike things any day of the year. But check your local and federal laws before proceeding.

Will my pets freak out?

In 2017, I posed this question to Bill Kramer, a 16-plus-time eclipse viewer who runs Eclipse Chasers, an online community for, well, you know.

Kramer says pets get confused and will think it’s nighttime.

“Some dogs bark at the eclipse,” he says. “Some dogs detect the emotion of the moment, or anxiety beforehand, and react accordingly. Never heard of one reacting like some do to fireworks or gunshots. The eclipse is a silent thing, except for the ambient sounds and cheers. ... Cats, on the other hand, are cats.”

During the 2017 eclipse, zoos reported odd behavior with their animals. At a zoo in South Carolina, CNN recalled in a recent news story, “the giraffes gathered and broke into a gallop, the Galápagos tortoises began to mate, and the gorillas started to get ready for bed.”

How animals react to eclipses is still something of a mystery overall. This April you can sign up to be part of a National Science Foundation-funded citizens science project to help collect data. More information on that on the SciStarter website.

Will bad weather ruin the eclipse?

Always a risk.

If you’re feeling really anxious about picking out the “perfect” spot to view, you’ll want to find a place with little cloud cover. An eclipse on a cloud-covered day is still cool (it will get very, very dark), but you won’t be able to see the dark mask of the moon in front of the sun.

The weather, as you know, can be hard to predict. But the National Oceanic and Atmospheric Administration (NOAA) is here to help. The agency has created an interactive map (click for the full map; see a static version of it below) that projects the likelihood of cloud cover for many cities in the path of the eclipse based on historical weather data.

For example, in Cleveland, Ohio, there’s a 43 percent chance of it being overcast. That’s a relatively bad bet compared to Waco, Texas, where there is a 25.8 percent chance of it being overcast.

NOAA

Will I go blind?

Not if you’re careful! On a normal day, staring straight into the sun can harm your eyes. On eclipse day, it is no different.

NASA warns: “It is never safe to look directly at the sun’s rays — even if the sun is partly obscured.” So don’t look at the partial eclipse directly!

The intense light from the sun can damage your retinas and cause “permanent scotoma or ‘blind spot’ in the central vision,” according to the Lancet. Even when the sun is 99 percent obscured, it can still cause damage.

During the partial eclipse phases, and even through the eclipse’s “Baily’s beads” and “diamond ring” phases — when you can see the last bits of sun peeking through the craters of the moon — you need eye protection. You can only take the protective glasses off when the moon has completely covered the sun during totality.

Regular sunglasses won’t block enough light. You’ll need glasses that filter all but 0.003 percent of visible light and block out most ultraviolet and infrared as well. “Such filters usually have a thin layer of aluminum, chromium or silver deposited on their surfaces that attenuates ultraviolet, visible, and infrared energy,” NASA’s eye safety page explains.

You could grab a pair of the darkest available (No. 14) welder’s glasses. But this is even easier: Pick up a dirt-cheap pair of disposable eclipse glasses. The American Astronomical Society (AAS) points out there are several manufacturers that meet international standards for eclipse eye protection. They are:

Grafix Plastics Halo Eclipse Spectacles American Paper Optics/eclipseglasses.com Seymour Solar Flip’n Shades DayStar Filters Rainbow Symphony Thousand Oaks Optical

The AAS has more information on eclipse glasses retailers.

Importantly, the AAS does not recommend “searching for eclipse glasses on Amazon, eBay, Temu, or any other online marketplace and buying from whichever vendor offers the lowest price.” Be sure to identify the manufacturer of the glasses and see that they are on the approved list above.

The good news is you might be able to pick up a verified pair for free at a local library. The Space Science Institute has donated 5 million solar eclipse glasses to 10,000 libraries across the United States. Call your local library and ask whether they have any available.

What does a total solar eclipse look like from space?

In 1999, a French astronaut on the Mir space station snapped this photo of a total solar eclipse over Europe.

Via NASA

If you’ve made it this far, you might be thinking, “I can’t believe I just read more than 3,000 words on the total solar eclipse. Could you just show me some awesome eclipse photos now?”

Sure.

Sebastian Brogca/Anadolu Agency/Getty Images

Sebastian Brogca/Anadolu Agency/Getty Images

Jonathan Newton/Washington Post via Getty Images