On August 21, 2017, a total solar eclipse moved from the Pacific Ocean to the Atlantic Ocean, casting a narrow corridor through 14 U.S. states under the moon’s shadow in the first coast-to-coast totality in 99 years. On that day, Oregon’s shadow moved across the U.S. toward South Carolina, moving roughly northwest to southeast.
It’s going to happen again, with the total solar eclipse on April 8 again starting in the Pacific Ocean and ending in the Atlantic Ocean, but this time the path appears to be from southwest to northeast.
There are also other differences, including the maximum length of totality (2 minutes and 40 seconds in 2017 and 4 minutes and 28 seconds in 2024) and the width of totality’s path (about 70 miles in 2017 and about 115 miles in 2024). This time, many millions more people will experience totality – and that at a time when the sun is close to solar maximum.
Related: Total solar eclipse April 8, 2024: Live updates
Here’s how the 2024 total solar eclipse differs from the 2017 total solar eclipse:
Eclipse conditions
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“The eclipse conditions are just completely different,” says Dan McGlaun, an eclipse expert at Eclipse 2024that one interactive map and eclipse simulator for the upcoming solar eclipse, in an interview with Space.com.
“It’s all about the distance from the sun and the moon — just simple geometry.” Although Earth’s distance from the Sun changes, it is the closest perihelion in January and furthest at aphelion in July – that doesn’t affect these two eclipses because the Sun is about the same distance away.
What does differ greatly is the distance from Earth to the moon, which has a somewhat elliptical orbit.
The distance to the moon
During the height of the 2017 solar eclipse, the moon was 372,008 km away Soil, while on April 8 it will be 359,515 km away. On April 8, the moon will be a few thousand kilometers closer, making the cone-shaped shadow that falls on Earth a larger diameter. In 2017, the path of totality was 60 to 70 miles wide. according to NASAwhile on April 8 it will be between 100 and 120 miles wide, covering a much larger part of the Earth.
The path of totality – a projection of the moon’s shadow – moves from west to east, because that is the direction in which the moon orbits the Earth (and the moon moves much faster than the Earth rotates, visibly overtaking it during the solar eclipse). That partially cancels out the moon’s speed, but its shadow will remain stationary sweep over the earth from west to east at more than 1,500 miles per hour on April 8, according to NASA.
The position of the moon
The moon’s orbital path around Earth is tilted 5.1 degrees relative to Earth’s orbit around the sun. That means its orbit crosses the ecliptic – the sun’s apparent path through our daytime sky – at two points, which astronomers call nodes (ascending and descending). When this happens at a new Moonit causes a solar eclipsebut at which node it occurs makes a difference.
“In an ascending nodal eclipse the moon goes up, while in a descending nodal eclipse the moon goes down,” says McGlaun. However, because both the 2017 and 2024 are ascending nodal eclipses, there is something else that is much more important when looking at the different paths: the angle of the Earth.
The rotation of the earth
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The sun and the moon together create a shadow in space that is always there. Only when a planet orbiting an axis titled 23.4 degrees is in the way does a path of totality emerge. “As the year progresses, the Earth changes direction and spins in place, and this, more than anything, is why the shadow in 2017 is different than the shadow in 2024,” McGlaun said. In short, the Earth’s axis tilts in different ways during both eclipses.
“In 2017, it’s the Earth rotating during totality, which makes it look like the path is going down, but in reality it’s going up,” says McGlaun. Seen from the sun, North America appears to move up the Earth’s globe as the Earth rotates during the solar eclipse, as shown in McGlaun’s solar eclipse simulator. “For the 2024 solar eclipse, the moon’s shadow does the same thing, but the Earth leans the other way.” During the solar eclipse, North America appears to move along the globe as the Earth rotates.
Change the angle of the Earth’s axis and you can make the path of totality go wherever you want.
The ‘Eclipse Crossroads’
Another effect of all this is that the 2017 and 2024 paths will cross, creating an “Eclipse Crossroads” area of about 9,000 square miles in parts of southeastern Missouri, southern Illinois, and western Kentucky, which will soon experience a second totality in less than seven years.
The centerlines intersect in Makanda, Illinois, near Carbondale. Also in the happy quadrant are Paducah, Kentucky, Cape Girardeau and Farmington, Missouri. The Texas Hill Country, meanwhile, has its own 36,000-square-mile “Eclipse Crossroads” area — centered on Vanderpool — where a Ring of Fire annular solar eclipse on Oct. 14 was just a warm-up for the totality to come.
The solar cycle
Another big change between 2017 and 2024 is the sun’s magnetic activity. The sun has its own cycle, the solar cycle, which lasts about 11 years. During that time, the magnetic activity increases and decreases. The 2017 solar eclipse occurred close to solar minimum, when magnetic activity was low. Solar maximum is predicted to occur in 2024, meaning more will be visible on the Sun during the eclipse.
Use your solar eclipse glasses during the partial phases of the eclipse, and you will see sunspots — dark areas of magnetic activity — on the surface, close to the equator. If you are in the path of totality, totality will likely reveal a larger corona, streamers through the corona and prominences, which appear as bright, pink curls or loops coming from the sun.