APOD: Equinox on a Spinning Earth (2017 Mar 19)

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APOD Robot
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APOD: Equinox on a Spinning Earth (2017 Mar 19)

Postby APOD Robot » Sun Mar 19, 2017 4:13 am

Image Equinox on a Spinning Earth

Explanation: When does the line between day and night become vertical? Tomorrow. Tomorrow is an equinox on planet Earth, a time of year when day and night are most nearly equal. At an equinox, the Earth's terminator -- the dividing line between day and night -- becomes vertical and connects the north and south poles. The featured time-lapse video demonstrates this by displaying an entire year on planet Earth in twelve seconds. From geosynchronous orbit, the Meteosat satellite recorded these infrared images of the Earth every day at the same local time. The video started at the September 2010 equinox with the terminator line being vertical. As the Earth revolved around the Sun, the terminator was seen to tilt in a way that provides less daily sunlight to the northern hemisphere, causing winter in the north. As the year progressed, the March 2011 equinox arrived halfway through the video, followed by the terminator tilting the other way, causing winter in the southern hemisphere -- and summer in the north. The captured year ends again with the September equinox, concluding another of billions of trips the Earth has taken -- and will take -- around the Sun.

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bjmb
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Re: APOD: Equinox on a Spinning Earth (2017 Mar 19)

Postby bjmb » Sun Mar 19, 2017 8:15 am

very good timr-lapse video. yet: "a time of year when day and night are most nearly equal. " - almost there: both poles and adjacent areas bathe in 24 hr sunlight, no night there.

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RedFishBlueFish
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Re: APOD: Equinox on a Spinning Earth (2017 Mar 19)

Postby RedFishBlueFish » Sun Mar 19, 2017 11:44 am

Wonderful visualization and demonstration of the origin of the seasons.

Wonderful if this clip would be shown in schools on the Quarter Days of the Wheel of the Year.

Somehow I missed seeing it in 2014 when it was posted: Showing value of APOD Sunday greats!

Thanks

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Re: APOD: Equinox on a Spinning Earth (2017 Mar 19)

Postby E Fish » Sun Mar 19, 2017 1:09 pm

That's amazing. While I know the definition of an equinox, I don't think I've ever seen a video showing the actual movement of the terminator. Definitely going to show this to my students. We're just about to start the astronomy unit anyway.

Guest

Re: APOD: Equinox on a Spinning Earth (2017 Mar 19)

Postby Guest » Sun Mar 19, 2017 1:17 pm

Very interesting. In addition to the terminator excursions, I found the cloud patterns fascinating. It appears the video is centered on Africa and one can sea the dearth of clouds throughout the year over the Sahara Desert.

Steve Dutch

Re: APOD: Equinox on a Spinning Earth (2017 Mar 19)

Postby Steve Dutch » Sun Mar 19, 2017 2:49 pm

And here I thought "equinox" mean all the cylinders in my car were misfiring equally badly!

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Chris Peterson
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Re: APOD: Equinox on a Spinning Earth (2017 Mar 19)

Postby Chris Peterson » Sun Mar 19, 2017 2:53 pm

Steve Dutch wrote:And here I thought "equinox" mean all the cylinders in my car were misfiring equally badly!

I checked Google the other day to find the exact time of the equinox, and the top three items that came up were for some car I've never heard of! That's just sad.
Chris

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Re: APOD: Equinox on a Spinning Earth (2017 Mar 19)

Postby De58te » Sun Mar 19, 2017 5:47 pm

I looked up the 'equinox definition' on Yahoo search and I got "a hybrid species resulting from the interbreeding of the horse family and the oxen family."

{Early April Fool]

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Re: APOD: Equinox on a Spinning Earth (2017 Mar 19)

Postby Guest » Mon Mar 20, 2017 11:33 am

I've understood intellectually about the tilt of the Earth's axis and the seasons "for ever", but to actually see it happening before my eyes is just amazing. Thanks!


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