水星上的一天为什么比一年还长？
Why is a day on Mercury longer than its year?
水星绕太阳公转一圈约88个地球日，而它自转很慢，一个太阳日（从日出到下一次日出）约176个地球日。这是因为水星自转周期约59天，加上公转造成的视角变化叠加，使太阳日拉长到一年的两倍。所以它上面一天确实比一年还长。
Mercury orbits the Sun in about 88 Earth days, but it spins slowly, so one solar day (sunrise to sunrise) lasts about 176 Earth days. Its rotation period is about 59 days, and the motion around the Sun stretches the apparent solar day to twice the year. So on Mercury a day really is longer than a year.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 来源待核验 · Source pending review
来源 · Source
出处备注：著录含书名，但缺版次 / 出版社 / 年份中的一部分，需编辑补全后才能做独立比对。
Pettengill 与 Dyce 1965 年《自然》雷达测得水星3:2自转-公转共振；NASA 水星数据表
Pettengill & Dyce (1965, Nature) radar detection of Mercury's 3:2 spin–orbit resonance; NASA Mercury Fact Sheet
#水星 #自转 #公转
水星为什么白天酷热、夜晚极寒？
Why is Mercury scorching by day and freezing by night?
水星几乎没有大气来储存和传递热量，向阳面温度可超过400摄氏度，背阳面则降到约零下180摄氏度。它自转又慢，一个水星日相当于约176个地球日，昼夜持续时间极长。缺少大气调节是温差惊人的根本原因。
Mercury has almost no atmosphere to store and move heat, so its dayside exceeds 400 degrees Celsius while the nightside drops to about minus 180. It also rotates slowly, with one Mercurian day lasting about 176 Earth days. The lack of an atmospheric blanket is the root cause of the huge swing.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
苏宜,《天文学新概论》第5版,科学出版社
Su Yi, Introduction to Astronomy, 5th ed., Science Press
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787030620477（豆瓣书目条目: 天文学新概论）
#水星 #温差 #大气
水星有大气吗？
Does Mercury have an atmosphere?
水星几乎没有真正的大气层，只有极稀薄、不断逃逸又被补充的『外逸层』，主要成分是氧、钠、氢等。由于水星质量小、引力弱且离太阳近，气体很容易被太阳风剥离。这使得水星表面昼夜温差极大。
Mercury has essentially no real atmosphere, only an extremely thin 'exosphere' of oxygen, sodium and hydrogen that constantly escapes and is replenished. Because Mercury is small, weakly gravitational and close to the Sun, gases are easily stripped away by the solar wind. This leaves its surface with extreme temperature swings.
难度 入门 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
苏宜,《天文学新概论》第5版,科学出版社
Su Yi, Introduction to Astronomy, 5th ed., Science Press
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787030620477（豆瓣书目条目: 天文学新概论）
#水星 #大气 #外逸层