The Earth, the Sun and the Moon · 地球、太阳与月球
| English | 中文 | Pinyin · 拼音 |
|---|---|---|
| Moon/muːn/ | 月球 | yuè qiú |
| orbital speed/ˈɔːbɪtl spiːd/ | 轨道速率 | guǐ dào sù lǜ |
| rotates/rəʊˈteɪts/ | 自转 | zì zhuàn |
| orbits/ˈɔːbɪts/ | 公转 | gōng zhuàn |
| seasons/ˈsiːznz/ | 季节 | jì jié |
| phases/ˈfeɪzɪz/ | 月相 | yuè xiàng |
| period/ˈpɪərɪəd/ | 周期 | zhōu qī |
Days, months and years
- A day, a month and a year all come from motion in space.
- The Earth spins, the Moon 月球 circles us, and we circle the Sun.
- Let's see what each motion gives us — and how to find an orbital speed 轨道速率.
日、月和年
- 一日、一月和一年都来自空间中的运动。
- 地球自转,月球绕我们转,而我们绕太阳转。
- 让我们看看每个运动给我们什么——以及如何求一个轨道速度。
The spinning, orbiting Earth
- The Earth rotates 自转 on its axis once in about $24$ hours — giving day and night.
- It orbits 公转 the Sun once in about $365$ days — one year.
- Its axis is tilted, so each half of the Earth leans toward the Sun for part of the year — giving the seasons 季节.
The full Moon, Earth's natural satellite
自转、绕行的地球
- 地球在它的轴上每约 $24$ 小时自转一次——给出昼和夜。
- 它每约 $365$ 天绕太阳一次——一年。
- 它的轴是倾斜的,所以地球的每一半在一年的一部分朝太阳倾斜——给出季节。
满月,地球的天然卫星
Why the Moon changes shape · 为什么月球改变形状
The Sun always lights half the Moon; the phase is simply how much of that lit half faces us as the Moon orbits — it is not Earth's shadow. · 太阳总是照亮月球的一半;相只是当月球绕行时那被照亮的一半有多少面对我们——它不是地球的阴影。
What causes day and night? · 什么造成昼和夜?
The Earth rotates once in about 24 hours, so each place faces the Sun (day) then faces away (night). · 地球约每 24 小时自转一次,所以每个地方面对太阳(昼)然后背对(夜)。
What causes the seasons? · 什么造成季节?
The tilted axis means each hemisphere leans toward the Sun for half the year (summer) and away for the other half (winter). · 倾斜的轴意味着每个半球在一年的一半朝太阳倾斜(夏天),在另一半远离(冬天)。
The Moon
- The Moon orbits the Earth once in about one month.
- As it goes round, we see different amounts of its lit side — the phases 月相 (new, half, full).
- From shortest to longest: day (Earth's spin) < month (Moon's orbit) < year (Earth's orbit).
The Moon's lit half always faces the Sun, so as it orbits we see different amounts of it — new, half and full
Saturn and its rings, photographed by the Cassini spacecraft
月球
- 月球每约一个月绕地球一次。
- 当它绕行时,我们看到它被照亮一面的不同量——相(phases,新月、半月、满月)。
- 从最短到最长:日(地球的自转)< 月(月球的轨道)< 年(地球的轨道)。
月球被照亮的一半总是朝向太阳,所以当它绕行时我们看到它的不同量——新月、半月和满月
土星和它的环,由卡西尼号航天器拍摄
Put these from the shortest time to the longest. · 把这些从最短的时间到最长的排列。
Day (~24 hours) < month (~1 Moon orbit) < year (~365 days). · 日(~24 小时)< 月(~1 个月球轨道)< 年(~365 天)。
The phases of the Moon happen because we see different amounts of its lit side as it orbits. · 月球的相发生,因为当它绕行时我们看到它被照亮一面的不同量。
As the Moon orbits Earth, the fraction of its sunlit side that we can see changes, giving new, half and full moon. · 当月球绕地球时,我们能看到的它被阳光照亮一面的分数变化,给出新月、半月和满月。
Orbital speed
- One full orbit covers the circumference $2\pi r$, where $r$ is the orbit radius.
- The orbital speed is that distance divided by the period 周期 $T$ (the time for one orbit):
- The same equation works for planets, moons and satellites.
Mars, the red planet, one of the rocky inner planets
轨道速度
- 一个完整轨道覆盖周长 $2\pi r$,其中 $r$ 是轨道半径。
- 轨道速度是那个距离除以周期 $T$(一个轨道的时间):
- 同样的方程对行星、卫星和人造卫星都起作用。
火星,红色的行星,岩石内行星之一
A satellite orbits at radius $r = 7.0 \times 10^6\ \text{m}$ with a period $T = 5800\ \text{s}$. What is its orbital speed, in m/s? · 一颗人造卫星以半径 $r = 7.0 \times 10^6\ \text{m}$、周期 $T = 5800\ \text{s}$ 绕行。它的轨道速度是多少,以 m/s 计?
$v = \dfrac{2\pi r}{T} = \dfrac{2\pi \times 7.0 \times 10^6}{5800} \approx 7600\ \text{m/s}$. · $v = \dfrac{2\pi r}{T} = \dfrac{2\pi \times 7.0 \times 10^6}{5800} \approx 7600\ \text{m/s}$。
Compared with planets close to the Sun, the outer planets orbit: · 与靠近太阳的行星相比,外行星绕行:
The Sun's gravity is weaker further out, so the outer planets move more slowly in their orbits. · 太阳的引力在更远处更弱,所以外行星在它们的轨道中移动更慢。
You've got it
- Earth spins → day/night; orbits the Sun → year; tilt → seasons
- the Moon orbits Earth in ~1 month, giving its phases
- day < month < year
- orbital speed $v = \dfrac{2\pi r}{T}$
你掌握了
- 地球自转 → 昼/夜;绕太阳 → 年;倾斜 → 季节
- 月球约 1 个月绕地球一次,给出它的相
- 日 < 月 < 年
- 轨道速度 $v = \dfrac{2\pi r}{T}$