Eclipse Central: All you need to know about the eclipse

SPRINGFIELD, Mo. (KY3/CNN/AP) -- On August 21, the sun will disappear across America.

It is being called the "Great American Eclipse." And you can mark it on your calendar, down to the millisecond. It's been 99 years since a total solar eclipse crossed the country from the Pacific to the Atlantic. The total solar eclipse on June 8, 1918, crossed from Washington to Florida.

During the celestial event, the moon will pass between the sun and the Earth, appearing to block the sun for almost an hour and a half. You can replicate an eclipse by holding a flashlight and waving your hand slowly across it.

When the moon blocks the sun, it will cast two types of shadows. The umbral is the small shadow cast on Earth where people will be able to see a total eclipse. Others will experience the penumbral shadow, where they will experience a partial eclipse.

We wanted to make your eclipse experience the best. Check out these links:

-NASA has built its own interactive map for the eclipse. You enter your city. Then it shows what how much of the eclipse you will see. Click HERE to see NASA's interactive map.

-How do you view an eclipse. NASA shares what to do and not to do. Click HERE to watch NASA's YouTube video.

-We all want that special social media picture of the solar eclipse. Read these tips to shoot the eclipse on a regular camera, a smartphone or video. Click HERE.

-The United States has prime seating for this eclipse. Click HERE.

-The United States Postal Service is celebrating too. It has a series of stamps to commemorate the eclipse. Click HERE.