Image description: A team of astronomers using NASA’s Hubble Space Telescope is reporting the discovery of another moon orbiting the icy dwarf planet Pluto. The moon is estimated to be irregular in shape and 6 to 15 miles across. Learn more about the discovery.
Image from NASA; ESA; M. Showalter, SETI Institute
On Saturday, the Naval Observatory will add a “leap second” to the world’s clocks at 23 hours, 59 minutes and 59 seconds Coordinated Universal Time (UTC). This corresponds to 7:59:59 pm Eastern Daylight Time.
Time, including seconds, has historically been defined by the rotation of the Earth around other objects in space. The invention of atomic clocks allowed us to more precisely define time.
In 1970, an international agreement established two timescales: one based on the rotation of the Earth and one on the atomic clock. These timescales are not exactly the same so extra seconds are added or removed to keep them within 0.9 seconds of each other. Saturday’s “leap second” will help sync the two timescales.
The Naval Observatory and National Institute of Standards and Technology are responsible for determining the time in the United States.
Learn more about the addition of this leap second to the clock. (PDF)
From NASA’s Earth Observatory:
There have been many images of the full disc of Earth from space – a view often referred to as “the Blue Marble” – but few have looked quite like this. Using natural-color images from the Visible/Infrared Imaging Radiometer Suite (VIIRS) on the recently launched Suomi-NPP satellite, a NASA scientist has compiled a new view showing the Arctic and high latitudes.
Image description: An animated gif that creates a three dimensional illusion by alternating between two photographs of the White House from the late 19th century.
Did you know that many libraries have 3D images that are over 100 years old? These images are called stereographs. The Library of Congress explains that “stereographs consist of two nearly identical photographs or photomechanical prints, paired to produce the illusion of a single three-dimensional image, usually when viewed through a stereoscope.”
Browse over 8,000 stereographs from the Library of Congress.
Or use the New York Public Library’s Stereogranimator to make your own animated gifs from stereographs.
Image courtesy of the New York Public Library.