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When 99% isn't enough: Why it's so important to get inside the zone of totality for the eclipse

NASA map showing the path of totality across New York State for the April 8, 2024 solar eclipse
NASA's Scientific Visualization Surgery
The path of totality across New York State for the solar eclipse Monday, April 8

99 percent of the time, 99 percent is just about as good as 100 percent.

But when it comes to a solar eclipse, the math doesn't work that way.

“Going to an eclipse but not going into totality is like driving 99% of the way to Disneyland, looking at your kids in the back seat, and then turning around and driving home because it is not the experience,” says Deb Ross, chair of Rochester’s eclipse task force.

She picked up that analogy at the national eclipse meeting we both attended last fall in San Antonio.

Remember the Alamo, because it's one of the places where that 99 percent will make a huge difference come April 8th.

By now, you've probably seen all those maps that show the path of the eclipse with three lines. The one in the middle gets all the attention - it's the one that shows you where the exact center of the moon’s shadow will be, which means the longest possible time with the moon completely covering the sun.

You can fudge *that* one. If you're a few miles away from the center line, you'll still get plenty of the good stuff. You'll just be in totality for a few seconds less than your neighbors on the line.

The farther out you go from that center line, the shorter your totality will last, right up until you hit those two outer lines. And they have no room for error at all, because they mark the boundaries of totality, and the difference between a transcendent experience and just a somewhat interesting science lesson.

We don't need graduate level math here to understand that the sun is incredibly bright - so much so that even if you block out more than 99 percent of it, that remaining fraction of a percentage is still too bright to look at directly. That's the edge of the line. The difference between 100 percent totality and anything less. The difference between KNOWING with all your senses that you're in an eclipse, and having to make a point of noticing something's happening.

Even at 99.58%, it won't get dark out, the temperature won't fall, your eclipse glasses don't come off, and it won't be any different than the partial eclipses you might have experienced here in 2017 and other years. If you saw one of those and you're wondering what all the fuss is about this eclipse, that's why.

99.58%, by the way, is exactly how much eclipse the Alamo will see - which is why planners in San Antonio and other spots along the edge are loudly urging people not to watch from there.

There's an edge to the path up our way, too, and so you'll want to make sure you're on the right side of the line. The Finger Lakes are split - if you're in Canandaigua or Geneva you get at least some time in the magic of totality. If you're in Watkins Glen or Ithaca, you just get a few nice hours outdoors on a Monday. Rome is in. Utica is out. The southern Adirondacks fall right on the line. And for our Canadian friends, it's the drama of darkness from Hamilton to Niagara Falls, but in Toronto, it's just “ehhhh,” eh?

So that's the math of totality - there's 100 percent, and everything else rounds to zero.

When the shadow races our way from Texas… be sure you're on the right side of the line.

You'll hear Scott in various capacities on WXXI either as a reporter, or hosting Morning Edition or All Things Considered.