Happy 167th birthday to us! The Interior Department was created on March 3, 1849, to take care of our nation’s internal affairs. Today, @usinterior is responsible for conserving America's treasured natural resources and public lands, like #Glacier #NationalPark (@glaciernps) in #Montana, pictured here on a spring day. Photo by Greg Chancey (http://ift.tt/18oFfjl). by usinterior

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Isolated in the mid #Pacific, the Hawaiian Islands are the most remote major #island group on earth. Formed by a volcanic "hot spot," they are 2,400 miles from the nearest continent. #Haleakala #NationalPark on #Maui is an International Biosphere Reserve that supports a unique, native ecosystem in this maturing volcanic landscape. Photo courtesy of Chris Archer (@archer357). #Hawaii by usinterior

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Unusual Clouds over Hong Kong Unusual Clouds over Hong Kong

What's that in the sky? Earlier this month, in the sky high above Hong Kong, China, not just one unusual type of cloud appeared -- but two. In the foreground was a long lenticular cloud, a cloud that forms near mountains from uprising air and might appear to some as an alien spaceship. Higher in the sky, and further in the background, was a colorful iridescent cloud. Iridescent clouds are composed of water droplets of similar size that diffract different colors of sunlight by different amounts. Furthest in the background is the Sun, blocked from direct view by the opaque lenticular, but providing the light for the colors of the iridescent. Either type of cloud is unusual to see in Hong Kong, and unfortunately, after only a few minutes, both were gone. via NASA http://ift.tt/1LUWz3j

These spiky, twisted Joshua trees look like they’re straight out of a Dr. Seuss book -- the iconic desert plant is rumored to have inspired his famous book The Lorax. One of the best places to see these unbelievable trees in real life is #JoshuaTree #NationalPark in Southern #California. If you visit @joshuatreenps this spring, keep an eye out for clusters of white-green flowers growing at the tips of their branches. Photo courtesy of David Bahr (http://ift.tt/18oFfjl). by usinterior

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The 72,000-acre Valentine National #WildlifeRefuge lies in the heart of the #Nebraska Sandhills, a vast area of grass blanketed sand dunes. Lakes, marshes and rolling prairie meadows provide habitat for many kinds of #wildlife and are an important stopping ground for migratory birds like #sandhillcranes pictured here. Every year, hundreds of thousands of sandhill cranes congregate on the Platte River during their spring migration north. It’s a must-see sight -- mid-April through early May is a great time to see the birds at the @USFWS refuge. Photo by Juancarlos Giese, USFWS. by usinterior

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One of the most noticeable animals at #BigCypress National Preserve (@bigcypressnps) in #Florida is the American #alligator. This large reptile is commonly seen during the winter dry seasons, when it has fewer places to hide. Growing up to 15 feet long, it’s a sight most visitors won’t forget after exploring this amazing 729,000-acre freshwater #swamp. Photo by Robert Sullivan (http://ift.tt/18oFfjl). by usinterior

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NGC 3310: A Starburst Spiral Galaxy NGC 3310: A Starburst Spiral Galaxy

The party is still going on in spiral galaxy NGC 3310. Roughly 100 million years ago, NGC 3310 likely collided with a smaller galaxy causing the large spiral galaxy to light up with a tremendous burst of star formation. The changing gravity during the collision created density waves that compressed existing clouds of gas and triggered the star-forming party. The featured image from the Gemini North Telescope shows the galaxy in great detail, color-coded so that pink highlights gas while white and blue highlight stars. Some of the star clusters in the galaxy are quite young, indicating that starburst galaxies may remain in star-burst mode for quite some time. NGC 3310 spans about 50,000 light years, lies about 50 million light years away, and is visible with a small telescope towards the constellation of Ursa Major. via NASA http://ift.tt/1TOrkyF

Happy 144th birthday, #Yellowstone #NationalPark! On this day in 1872, @yellowstonenps became the first national park -- starting a worldwide movement to protect special places. Today, the park preserves more than 2 million acres of mountain wilderness, amazing geysers and vibrant landscapes. Photo from Uncle Tom’s Trail 🌈 by Kallem Phillips (http://ift.tt/18oFfjl). by usinterior

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Yellows and purples hint at the fiery past of Skookum Volcano in this photo, taken just moments before a storm passed through Wrangell-St. Elias National Park & Preserve in #Alaska. From walking in the shadow of ancient volcanoes to navigating some of the biggest ice fields in North America, there’s so much to explore across this vast, rugged landscape. #wrangellstelias -- the largest #nationalpark in the U.S. -- boasts more than 13 million acres of scenic views and outdoor adventures for every season. Photo by National Park Service. by usinterior

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Julius Caesar and Leap Days Julius Caesar and Leap Days

Today, February 29th, is a leap day - a relatively rare occurrence. In 46 BC, Julius Caesar, featured here in a self-decreed minted coin, created a calendar system that added one leap day every four years. Acting on advice by Alexandrian astronomer Sosigenes, Caesar did this to make up for the fact that the Earth's year is slightly more than 365 days. In modern terms, the time it takes for the Earth to circle the Sun is slightly more than the time it takes for the Earth to rotate 365 times (with respect to the Sun -- actually we now know this takes about 365.24219 rotations). So, if calendar years contained 365 days they would drift from the actual year by about 1 day every 4 years. Eventually July (named posthumously for Julius Caesar himself) would occur during the northern hemisphere winter! By adopting a leap year with an extra day every four years, the calendar year would drift much less. This Julian Calendar system was used until the year 1582 when Pope Gregory XIII provided further fine-tuning when he added that leap days should not occur in years ending in "00", unless divisible by 400. This Gregorian Calendar system is the one in common use today. via NASA http://ift.tt/1QGtTw8