repost: I ♥ axial tilt and elliptical orbits

Because without them we wouldn’t have seasons. Happy September equinox, all.

sun and star trails photographed over the equator at Ecuador

This picture combines daytime and night-time photography and uses the equatorial location to show both northern and southern hemispheres of the sky together. | Image credit: Juan Carlos Casado

Equinoxes occur when the Sun as viewed from Earth crosses the celestial equator, marking the astronomical change of seasons to longer thus warmer days in one hemisphere and shorter thus colder days in the other. The word equinox means equal night, because around the equinoxes we experience nearly 12 hours of sunlight and 12 hours of darkness.

Saturn only has an equinox every 15 years, because it’s orbital period is so much longer than Earth’s. When Saturn is at equinox, the rings disappear for observers on Earth, because they are directly edge-on to the Sun and thus very nearly edge-on to the Earth. My favourite spacecraft, Cassini, took this photograph of Saturn at equinox back in 2009.

Photograph of Saturn taken from spacecraft Cassini

Saturn at Equinox | Credit: Cassini Imaging Team, ISS, JPL, ESA, NASA



Categories: Life, Science

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5 replies

  1. I need a way to skip from the spring to the autumn equinox … anyone want my share of summer?

  2. I love Spring, but I hate hayfever….

    • The older I get, the more I hate hayfever. Currently only just getting through the day on my Loratidine. My mum’s hayfever got worse as she aged, I conclude that this is one more hereditary prank upon me. I do not approve.

  3. My eardrums hate hayfever. My boss has the most explosive Shouting Bloke Sneezes and I sit next to him.

  4. Ugh, tell me about it tigtog. Except I use fexofenadine instead. And no inheritance on my side either. I just seem to have an overclocked immune system. Still, better an allergy than another auto-immune disease.

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