A-Level WJEC Science: Earth and Space Revision | 地球与太空考点精讲

📚 A-Level WJEC Science: Earth and Space Revision | 地球与太空考点精讲

This revision guide covers the essential topics of Earth and Space for WJEC A-Level Science. From the structure of our solar system to the mysteries of the expanding Universe, each concept is broken down with clear explanations and key facts. Understanding these principles is crucial for mastering astronomy and physics in your exams.

本复习指南涵盖了WJEC A-Level科学中地球与太空的核心主题。从太阳系的结构到宇宙膨胀的奥秘，每个概念都通过清晰的解释和关键事实进行分解。理解这些原理对于在考试中掌握天文学和物理至关重要。

1. Our Solar System | 我们的太阳系

The Solar System consists of one star, the Sun, and all the objects gravitationally bound to it. These include eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. There are also dwarf planets like Pluto, numerous moons, asteroids, and comets. The inner planets are rocky and smaller, while the outer planets are gas giants or ice giants.

太阳系由一颗恒星——太阳，以及所有受其引力束缚的天体组成。包括八颗行星：水星、金星、地球、火星、木星、土星、天王星和海王星。还有像冥王星这样的矮行星、众多卫星、小行星和彗星。内行星是岩石质、较小的，外行星则是气态巨行星或冰巨行星。

All planets orbit the Sun in elliptical paths, as described by Kepler’s first law. Their orbital periods increase with distance from the Sun, following Kepler’s third law: T² ∝ r³, where T is the period and r is the semi‑major axis.

所有行星都以椭圆轨道绕太阳运行，如开普勒第一定律所述。它们的公转周期随着离太阳的距离增加而增加，遵循开普勒第三定律：T² ∝ r³，其中 T 是周期，r 是半长轴。

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2. Earth’s Rotation and Revolution | 地球的自转与公转

Earth rotates on its axis once every 24 hours, causing day and night. This rotation is from west to east, which is why the Sun appears to rise in the east and set in the west. The speed of rotation at the equator is about 1670 km/h.

地球每24小时绕地轴自转一次，产生了昼夜交替。自转方向是自西向东，这就是太阳看起来东升西落的原因。赤道处的自转速度约为1670公里/小时。

Earth also revolves around the Sun in an elliptical orbit, taking approximately 365.25 days to complete one revolution. This motion, combined with the axial tilt, leads to the changing seasons.

地球还以椭圆轨道绕太阳公转，完成一次公转大约需要365.25天。这种运动与地轴倾斜共同导致了季节的变化。

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3. The Seasons and Axial Tilt | 季节与地轴倾斜

Earth’s axis is tilted by about 23.5° relative to its orbital plane. This tilt means that during different parts of the year, either the Northern Hemisphere or the Southern Hemisphere receives more direct sunlight. When the North Pole tilts toward the Sun, the Northern Hemisphere experiences summer with longer days and higher solar intensity.

地轴相对于其轨道平面倾斜约23.5°。这一倾斜意味着在一年中的不同时间，要么北半球、要么南半球接收到更直接的阳光。当北极向太阳倾斜时，北半球是夏季，白昼更长，太阳辐射更强。

The solstices mark the longest and shortest days, while the equinoxes occur when day and night are roughly equal in length globally. These astronomical events are directly linked to the axial tilt and orbital position.

至日标志着最长和最短的白天，而分日则昼夜大致相等。这些天文现象与地轴倾斜和轨道位置直接相关。

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4. The Moon: Phases and Tides | 月球：月相与潮汐

The Moon orbits Earth in about 27.3 days (sidereal month), but the cycle of phases (synodic month) takes about 29.5 days due to Earth’s motion around the Sun. The phases—new moon, first quarter, full moon, last quarter—are caused by the changing relative positions of the Sun, Earth, and Moon, affecting how much of the Moon’s illuminated side we see.

月球绕地球公转大约需要27.3天（恒星月），但由于地球绕太阳运动，月相周期（朔望月）约为29.5天。月相——新月、上弦月、满月、下弦月——是由太阳、地球和月球相对位置的变化导致的，影响了我们能看到多少被照亮的月球面。

Tides on Earth are primarily caused by the gravitational pull of the Moon and, to a lesser extent, the Sun. The Moon’s gravity creates bulges of water on the side facing the Moon and the opposite side, resulting in high tides roughly every 12 hours. Spring tides occur during full and new moons when the Sun, Earth, and Moon align, while neap tides occur during quarter moons when the gravitational forces partially cancel.

地球上的潮汐主要由月球的引力引起，太阳的引力也有较小影响。月球引力在地球面向月球的一侧和背向的一侧产生海水隆起，大约每12小时出现一次高潮。当太阳、地球和月球排成一线（满月和新月）时发生大潮，当月球处于上弦或下弦时引力部分抵消，发生小潮。

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5. Eclipses: Solar and Lunar | 日食与月食

A solar eclipse happens when the Moon passes directly between the Sun and Earth, casting a shadow on Earth. This can be total, partial, or annular depending on alignment and distances. A lunar eclipse occurs when Earth is between the Sun and the Moon, so Earth’s shadow falls on the Moon. During a total lunar eclipse, the Moon appears red due to Rayleigh scattering of sunlight through Earth’s atmosphere.

日食发生在月球恰好经过太阳和地球之间，将影子投到地球上时。根据对齐情况和距离，日食可以是全食、偏食或环食。月食发生在地球位于太阳和月球之间，地球的影子落在月球上时。在月全食期间，由于阳光穿过地球大气层时的瑞利散射，月球呈现红色。

Eclipses do not happen every month because the Moon’s orbit is tilted about 5° relative to Earth’s orbital plane, so the alignment required for an eclipse is less frequent.

食并非每个月都发生，因为月球轨道相对于地球轨道面倾斜大约5°，因此形成食所需的对齐不是很频繁。

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6. Gravity and Orbits | 引力与轨道

Newton’s law of universal gravitation states that every mass attracts every other mass with a force proportional to the product of their masses and inversely proportional to the square of the distance between their centres. This is expressed as:

牛顿的万有引力定律指出，任何两个质量都会相互吸引，引力的大小与两质量的乘积成正比，与它们中心之间的距离平方成反比。公式为：

F = G m₁ m₂ / r²

This force keeps planets in orbit around the Sun and moons around planets. For an object in a circular orbit, the gravitational force provides the required centripetal force, so we have:

这个力使行星绕太阳运行，卫星绕行星运行。对于圆形轨道的天体，引力提供了所需的向心力，因此得到：

G M m / r² = m v² / r → v = √(G M / r)

This relationship shows that orbital speed decreases with increasing orbital radius. Kepler’s laws can also be derived from these principles.Published by TutorHao | A-Level Science Revision Series | aleveler.com

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