IB Science: Earth and Space – Core Revision Notes | IB 科学：地球与太空核心考点精讲

📚 IB Science: Earth and Space – Core Revision Notes | IB 科学：地球与太空核心考点精讲

This comprehensive guide covers the key topics in IB Science related to Earth and Space. Whether you are preparing for the Physics option in astrophysics or the ESS unit on Earth systems, these concise yet detailed notes will help you master the essential concepts.

本综合指南涵盖了 IB 科学中与地球和太空相关的核心主题。无论你是在准备物理学科的天体物理选项，还是环境系统与社会中的地球单元，这些精要的笔记都将助你掌握关键概念。

1. Earth’s Shape and Motion | 地球的形状与运动

Earth is an oblate spheroid, slightly flattened at the poles and bulging at the equator due to its rotation. The equatorial diameter is about 12,756 km, while the polar diameter is 12,714 km.

地球是一个扁球体，因自转作用两极略扁、赤道隆起。赤道直径约 12,756 公里，两极直径约 12,714 公里。

Evidence for a spherical Earth includes: ships disappearing hull-first over the horizon, the curved shadow of Earth on the Moon during lunar eclipses, and the change in visible constellations with latitude.

地球是球形的证据包括：船只出海时船身先消失在海平面下，月食时地球投在月球上的圆弧形阴影，以及不同纬度所见星座的变化。

Earth rotates from west to east once every 24 hours, causing diurnal cycles and the Coriolis effect. It revolves around the Sun in an elliptical orbit with a period of 365.25 days, giving rise to seasons due to the 23.5° axial tilt.

地球自转方向自西向东，周期为 24 小时，产生昼夜交替和科里奥利效应。地球以椭圆轨道绕太阳公转，周期 365.25 天；地轴倾角 23.5°，由此产生四季。

2. Gravitation and Kepler’s Laws | 引力与开普勒定律

Newton’s law of universal gravitation states that every mass attracts every other mass with a force given by F = G M₁ M₂ / r², where G = 6.67 × 10⁻¹¹ N m² kg⁻².

牛顿万有引力定律指出，任何两个质量间都存在引力，大小为 F = G M₁ M₂ / r²，其中 G = 6.67 × 10⁻¹¹ N m² kg⁻²。

Kepler’s three laws of planetary motion: (1) Planets move in elliptical orbits with the Sun at one focus. (2) A line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time. (3) The square of the orbital period T is proportional to the cube of the semi-major axis a: T² ∝ a³.

开普勒行星运动三定律：(1) 行星沿椭圆轨道运动，太阳位于其中一个焦点。(2) 行星与太阳的连线在相等时间内扫过相等的面积。(3) 轨道周期 T 的平方与轨道半长轴 a 的立方成正比：T² ∝ a³。

These laws allow us to calculate planetary distances and masses. For a satellite orbiting Earth, the centripetal force is provided by gravity: m v² / r = G M m / r², which simplifies to v = √(G M / r).

利用这些定律可计算行星距离与质量。对于绕地球运行的卫星，引力提供向心力：m v² / r = G M m / r²，化简可得 v = √(G M / r)。

3. Eclipses | 日食与月食

A solar eclipse occurs when the Moon passes between the Earth and the Sun, casting a shadow on Earth. It can be total, partial, or annular depending on the alignment and distances.

日食发生在月球运行到太阳和地球之间，在地球上投下阴影时。根据对齐情况和距离，日食可以是日全食、日偏食或日环食。

A lunar eclipse occurs when the Earth is positioned between the Sun and the Moon, and the Moon passes through Earth’s shadow. It is visible from the entire night side of Earth and appears red due to atmospheric scattering (blood moon).

月食发生在地球位于太阳和月球之间，月球穿过地球的影子。月食在整个夜半球可见，因大气散射呈现红色（血月）。

Eclipses do not happen every month because the Moon’s orbit is tilted about 5° relative to the ecliptic plane, so the alignment (syzygy) is exact only occasionally.

日月食并非每月发生，因为月球轨道相对黄道面倾斜约 5°，只有在偶尔精确对齐时才会出现。

4. Earth’s Atmosphere and the Greenhouse Effect | 地球大气与温室效应

Earth’s atmosphere is composed primarily of nitrogen (78%) and oxygen (21%), with trace gases including argon, carbon dioxide (0.04%), and water vapor. It is divided into layers: troposphere, stratosphere, mesosphere, thermosphere, and exosphere.

地球大气主要由氮气（78%）和氧气（21%）组成，含有微量氩气、二氧化碳（0.04%）和水蒸气。大气层分为对流层、平流层、中间层、热层和外逸层。

The natural greenhouse effect is essential for life: atmospheric gases like CO₂ and H₂O trap infrared radiation emitted by Earth’s surface, raising the average surface temperature to about 15°C. Without it, Earth would be a frozen -18°C.

自然温室效应对生命至关重要

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