Credit & Copyright: Giuseppe Petricca
Explanation:
If you went outside at the same time every day and
took a picture that included
the Sun, how would the Sun's position change?
A visual answer to that question is an
analemma,
a composite image taken from the same spot at the
same time over the course of a year.
The featured analemma was composed from images
taken every few days at noon near the village of
Callanish in the
Outer Hebrides in
Scotland,
UK.
In the foreground are the
Callanish
Stones,
a stone circle built around 2700 BC during humanity's
Bronze Age.
It is not known if the placement of the
Callanish Stones has or had astronomical significance.
The ultimate causes for the
figure-8 shape of this and all analemmas are the
tilt of the Earth axis
and the
ellipticity of the
Earth's orbit
around the Sun.
At the solstices,
the Sun will appear at the top or bottom of an analemma.
The featured image was taken near the December solstice and so the Sun appears near the bottom.
Equinoxes, however,
correspond to analemma middle points -- not the
intersection point.
In two days there will be an
equinox ("equal night"),
when day and night are equal over all of planet Earth.
Many
cultures celebrate a change of season at an
equinox.
APOD's main NASA site is
moving:
From apod.nasa.gov to
science.nasa.gov/apod
1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 |
Январь Февраль Март Апрель Май Июнь Июль Август Сентябрь Октябрь Ноябрь Декабрь |
NASA Web Site Statements, Warnings, and Disclaimers
NASA Official: Jay Norris. Specific rights apply.
A service of: LHEA at NASA / GSFC
& Michigan Tech. U.
Based on Astronomy Picture
Of the Day
|
Публикации с ключевыми словами:
equinox
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