Equinoxes and solstices. In each of the images, Earth’s rotational axis is perpendicular (straight up and down), with the North Pole at top and South Pole at bottom. Earth at the equinoxes shown at right; Earth at solstices shown at left. Images via Geosync.
The sun crosses the celestial equator - moving from north to south - on September 23 at 01:54 UTC; translate UTC to your time. The equinox happens today for clocks in North America. Details here.
How is it possible for an equinox sun to rise due east - and set due west - for everyone around the world? How can you visualize it? Illustrations here.
Conventional rockets - with their onboard fuel - are expensive and dangerous. A new concept called quantized inertia might make rocket launches cheaper and safer. The concept has just received $1.3 million in new funding. Read more.
A new study suggests that the Large and Small Magellanic Clouds - small satellite galaxies to our Milky Way - might have once had a 3rd companion. Read more.
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"As twilight brightens before the equinox sunrise at the South Pole, the blue-grey shadow of the Earth descends to the horizon, the last vestige of the polar night." Twitter photo via Robert Schwarz (@iceman_90South)/The Antarctic Report (@AntarcticReport).
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