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astronomy

The spacetime diagram (“a position vs time graph”) is a valuable tool for modeling and interpreting situations in relativity. As I like to say, “A spacetime diagram is worth a thousand words.” Many problems and “apparent-paradoxes” (or better “puzzles”) can be resolved by drawing a good spacetime diagram. However, because Minkowski spacetime geometry is not Euclidean, there

Free Astronomy Books - Primarily for education.Feel free to add your own links to free books. Let me know if there are broken links or copyright issues.A New AstronomyA Popular History of Astronomy During the Nineteenth Century, Fourth EditionA Simple Guide to Backyard AstronomyAdvances in Modern CosmologyAstronomical DiscoveryAstronomy for AmateursAstronomy To-DayAstronomy of To-day A

Explanation: Can you find which day is the winter solstice? Each panel shows one day. With 360 movie panels, the sky over (almost) an entire year is shown in time lapse format as recorded by a video camera on the roof of the Exploratorium museum in San Francisco, California. The camera recorded an image every 10 seconds from before sunrise to after sunset and

Image Credit & Copyright: Data - ESO / MPIA / OAC, Assembly - R.ColombariSculpted by stellar winds and radiation, the star factory known as Messier 17 lies some 5,500 light-years away in the nebula-rich constellation Sagittarius. At that distance, this 1/3 degree wide field of view spans over 30 light-years. The sharp composite, color image, highlights faint details of the region's gas and dust clouds against

Image Credit: ESA/Hubble and NASABeautiful island universe Messier 94 lies a mere 15 million light-years distant in the northern constellation of the hunting dogs, Canes Venatici. A popular target for earth-based astronomers, the face-on spiral galaxy is about 30,000 light-years across, with spiral arms sweeping through the outskirts of its broad disk. But this Hubble Space Telescope field of view spans about 7,000

Image Credit: NASA, Johns Hopkins U. APL, SwRIWhat do the moons of Pluto look like? Before a decade ago, only the largest moon Charon was known, but never imaged. As the robotic New Horizons spacecraft was prepared and launched, other moons were identified on Hubble images but remained only specks of light. Finally, this past summer, New Horizons swept right past Pluto, photographed Pluto and Charonin detail, and took the best