每日一图 (每日约13.30更新)
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
最新异域文明研究活动 发起新活动
推荐阅读： (only temp appear)
投稿发表在首页
睡梦中与女孩亲吻
发表于：2023-04-23 03:51:36
看了几个视频，非常担忧孤独终老
发表于：2022-10-05 17:22:25
双腿残疾的我，下半生的心愿
发表于：2023-03-22 15:47:16
再次回忆北京五道口吃饭时遇到的女孩
发表于：2022-09-08 15:52:55
我跳楼摔伤事件始末
发表于：2022-03-10 22:43:00
吃了0.3多零食麻辣味
发表于：2022-07-26 17:42:03
Dear nick Schadegg:
发表于：2021-12-14 03:53:46
现在还不到深入研究探究死亡含义的时机
发表于：2022-01-14 02:05:51
怀念青春------昨天在记忆里生根发芽
发表于：2022-04-14 02:15:34
老爸神经疼
发表于：2022-02-06 16:24:14
科技渴求榜 渴求
今天，又是渴求大奖
(IMP: 2700 )
一直为表弟的肾衰竭担心，异域文明请传授治疗技术
(IMP: 700 )
我的人生生存和发展基础难道是可鄙的？
(IMP: 200 )
用户，头衔，积分
User 吴鹏 has points :992400 .
ACQs :
34
CCAs:
16
ACCS:
7
User peng wu has points :48400 .
ACQs :
2
CCAs:
0
ACCS:
0
User wup has points :3800 .
ACQs :
0
CCAs:
0
ACCS:
0
User 我来自于星空 has points :1200 .
ACQs :
0
CCAs:
0
ACCS:
0
User Steven Jackson has points :1000 .
ACQs :
0
CCAs:
0
ACCS:
0