(U. S. Postal Service)

On Aug. 21, a total solar eclipse will cross the United States for the first time in more than 20 years. To celebrate, the U.S. Postal Service is creating the best stamp they’ve ever designed — at least in my humble, science-loving, sky-watching opinion.

The new Forever stamp will change with the heat of your finger. It’s the first time this thermochromic ink has been used on a stamp. It will change from a dark image of the eclipse — with the sun’s corona still visible — to the moon with the sun’s corona behind it. The photograph itself is of the total solar eclipse over Libya in 2006, taken by astrophysicist Fred Espenak.

Pretty neat!

The big stamp reveal will happen on June 20 — the summer solstice — at the Art Museum at the University of Wyoming.

The Postal Service notes that thermochromic inks are vulnerable to UV light, so you can’t leave your mail out in the sun. To make sure your Forever stamps stay thermochromatically awesome forever — or at least for a very long time — they will offer special UV-blocking envelopes.

The solar eclipse begins around 9 a.m. Pacific on the West Coast and will be seen over 11 states before it ends on the East Coast around 4 p.m. Eastern. Nine major cities just happen to be in the path where the sun will be 100 percent covered by the moon, including half of Kansas City and St. Louis, most of Nashville and all of Columbia and Charleston, S.C.