📚 IB & OCR Science: Earth and Space Key Points | IB与OCR科学：地球与太空考点精讲
Earth and space science forms a captivating core module in both the IB Middle Years Programme and OCR GCSE specifications. This bilingual guide breaks down the essential concepts—from the layers of our home planet to the life cycles of distant stars—helping you prepare efficiently for exams while building a solid conceptual foundation.
地球与太空科学是IB中学项目以及OCR GCSE课程中一个引人入胜的核心模块。这篇双语指南梳理了从我们家园行星的圈层结构到遥远恒星生命周期的核心概念，帮助你有针对性地备考，同时构建扎实的理解基础。
1. Earth’s Internal Structure | 地球的内部结构
Earth is composed of four main layers: the solid inner core, liquid outer core, mantle, and crust. The inner core is primarily iron and nickel, with temperatures exceeding 5000 °C, yet it remains solid due to immense pressure.
地球由四个主要圈层组成：固态内核、液态外核、地幔和地壳。内核主要由铁和镍构成，温度超过5000°C，但由于巨大的压力仍保持固态。
The outer core is molten metal that generates Earth’s magnetic field through its convective motion. The mantle is a thick layer of semi-solid rock that flows very slowly, driving plate tectonics.
外核是液态金属，通过对流运动产生地球磁场。地幔是一层厚厚的半固态岩石，极其缓慢地流动，驱使着板块运动。
The crust is the thin, brittle outermost layer, divided into oceanic crust (denser, thinner) and continental crust (less dense, thicker). Seismic waves provide evidence for this layered structure.
地壳是薄而脆的最外层，分为洋壳（密度较大、较薄）和陆壳（密度较小、较厚）。地震波为这种层状结构提供了证据。
2. Plate Tectonics | 板块构造
The lithosphere is broken into tectonic plates that float on the asthenosphere. Convection currents in the mantle cause these plates to move, giving rise to earthquakes, volcanoes, and mountain building.
岩石圈分裂为若干个构造板块，漂浮在软流圈之上。地幔中的对流驱动板块运动，引发地震、火山活动和造山运动。
At divergent boundaries, plates move apart and magma rises to form new crust, such as at the Mid-Atlantic Ridge. Convergent boundaries involve plates colliding; subduction can create deep ocean trenches and volcanic arcs.
在离散边界，板块相互分离，岩浆上涌形成新地壳，例如大西洋中脊。汇聚边界涉及板块碰撞；俯冲作用可形成深海沟和火山弧。
Transform boundaries, like the San Andreas Fault, occur where plates slide past each other, often causing earthquakes. The distribution of seismic and volcanic activity strongly correlates with plate margins.
转换边界，如圣安德烈亚斯断层，出现在板块相互滑动之处，常引发地震。地震和火山活动的分布与板块边界高度吻合。
3. The Rock Cycle | 岩石循环
Rocks are classified into three families: igneous, sedimentary, and metamorphic. The rock cycle describes how any rock type can be transformed into another through processes driven by Earth’s internal heat and surface conditions.
岩石分为三大类：火成岩、沉积岩和变质岩。岩石循环描述了如何通过地球内部热量和地表条件的作用，将任何一种岩石转变为另一种。
Igneous rocks form when magma cools and solidifies, either below the surface (intrusive, e.g., granite) or above (extrusive, e.g., basalt). Sedimentary rocks result from the compaction and cementation of weathered fragments, fossils, or chemical precipitates.
火成岩由岩浆冷却凝固形成，可发生在地表以下（侵入岩，如花岗岩）或以上（喷出岩，如玄武岩）。沉积岩由风化碎屑、化石或化学沉淀物经压实和胶结而形成。
Metamorphic rocks are created when existing rocks are subjected to high temperature and pressure without melting, causing recrystallisation (e.g., marble from limestone). The rock cycle illustrates that all rocks are interconnected and constantly recycled.
变质岩在高温高压但不熔融的条件下，由原有岩石发生重结晶形成（例如石灰岩转变为大理岩）。岩石循环说明所有岩石相互联系并不断循环。
4. Earth’s Atmosphere and Greenhouse Effect | 地球大气与温室效应
The atmosphere is layered: troposphere (weather), stratosphere (ozone layer), mesosphere, thermosphere, and exosphere. Gases are held by gravity and the composition is approximately 78% nitrogen, 21% oxygen, with trace gases like carbon dioxide and water vapour.
大气层是分层的：对流层（天气现象）、平流层（臭氧层）、中间层、热层和散逸层。气体受重力吸引，成分大约为78%氮气、21%氧气，以及微量气体如二氧化碳和水汽。
The natural greenhouse effect is essential for life, keeping Earth’s average temperature around 15°C. Shortwave solar radiation passes through the atmosphere, warms the surface, and longer-wavelength infrared radiation is partly absorbed by greenhouse gases.
天然的温室效应对生命至关重要，使地球平均温度保持在约15°C。短波太阳辐射穿过大气，加热地表，较长波长的红外辐射部分被温室气体吸收。
Enhanced greenhouse effect, caused by human activities like burning fossil fuels, increases the concentration of CO₂, methane, and nitrous oxide, leading to global warming and climate change. The carbon cycle illustrates the movement of carbon between reservoirs.
由燃烧化石燃料等人类活动引起的增强温室效应，提高了CO₂、甲烷和氧化亚氮的浓度，导致全球变暖和气候变化。碳循环展示了碳在储库之间的迁移。
5. Seasons and Earth’s Axial Tilt | 季节与地轴倾斜
Earth’s axis is tilted at an angle of about 23.5° relative to its orbital plane. This tilt, rather than the distance from the Sun, causes the annual cycle of seasons as different hemispheres receive more direct sunlight at different times of the year.
地轴相对于轨道平面倾斜约23.5°。正是这一倾斜而非距太阳的远近，造成了周年的季节循环，因为不同半球在一年中不同时段接收到更直接的阳光照射。
During the June solstice, the Northern Hemisphere is tilted towards the Sun, resulting in longer days and summer, while the Southern Hemisphere experiences winter. The December solstice brings the opposite situation. Equinoxes occur when the Sun is directly above the equator, giving roughly equal day and night.
六月冬至时，北半球向太阳倾斜，导致昼长夜短，进入夏季，而南半球则经历冬季。十二月冬至则相反。当太阳直射赤道时出现二分点，昼夜大致等长。
The intensity of solar radiation per unit area varies with the angle of incidence, explaining why polar regions are colder. This geometric effect is a key practical consideration in IB and OCR exam questions on insolation.
单位面积的太阳辐射强度随入射角变化，这解释了为什么极地更冷。这一几何效应是IB和OCR考试中关于日射量问题的关键实际考量。
6. The Solar System: Planets and Features | 太阳系：行星与特征
Our solar system consists of the Sun, eight planets, dwarf planets, moons, asteroids, and comets. The inner planets (Mercury, Venus, Earth, Mars) are rocky and smaller; the outer planets (Jupiter, Saturn, Uranus, Neptune) are gas or ice giants with multiple moons and ring systems.
太阳系由太阳、八大行星、矮行星、卫星、小行星和彗星组成。内行星（水星、金星、地球、火星）是岩质的，体积较小；外行星（木星、土星、天王星、海王星）是气态或冰态巨行星，拥有众多卫星和环系统。
| Planet | Type | Key Feature |
| Mercury | Terrestrial | Smallest planet, no atmosphere |
| Venus | Terrestrial | Hottest surface, retrograde rotation |
| Earth | Terrestrial | Liquid water, life |
| Mars | Terrestrial | Red planet, Olympus Mons |
| Jupiter | Gas giant | Great Red Spot, strongest magnetic field |
| Saturn | Gas giant | Extensive ring system |
| Uranus | Ice giant | Tilted sideways, blue-green colour |
| Neptune | Ice giant | Strongest winds, deep blue |
| 行星 | 类型 | 关键特征 |
| 水星 | 类地行星 | 最小行星，无大气层 |
| 金星 | 类地行星 | 最热表面，逆向自转 |
| 地球 | 类地行星 | 液态水，存在生命 |
| 火星 | 类地行星 | 红色行星，奥林帕斯山 |
| 木星 | 气态巨行星 | 大红斑，最强磁场 |
| 土星 | 气态巨行星 | 宽阔的环系统 |
| 天王星 | 冰巨行星 | 侧向自转，蓝绿色外观 |
| 海王星 | 冰巨行星 | 最强风，深蓝色 |
Asteroid belt lies between Mars and Jupiter, containing rocky remnants. Dwarf planets like Pluto reside in the Kuiper Belt. Comets originate from the Oort Cloud and develop tails when approaching the Sun.
小行星带位于火星与木星之间，包含岩石残余物。矮行星如冥王星位于柯伊伯带。彗星起源于奥尔特云，靠近太阳时会形成彗尾。
7. Gravity, Orbits and Kepler’s Laws | 重力、轨道与开普勒定律
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.
牛顿万有引力定律指出，任何两物体之间都存在相互吸引的力，力的大小与它们质量的乘积成正比，与它们中心之间距离的平方成反比。
F = G m₁ m₂ / r²
where G = 6.674 × 10⁻¹¹ N m² kg⁻², and r is the separation. Planetary orbits are elliptical, with the Sun at one focus (Kepler’s first law). A line connecting a planet to the Sun sweeps out equal areas in equal time intervals (second law), and the square of the orbital period is proportional to the cube of the semi-major axis (third law).
其中G = 6.674 × 10⁻¹¹ N m² kg⁻²，r为距离。行星轨道是椭圆形的，太阳位于其中一个焦点上（开普勒第一定律）。连接行星与太阳的连线在相等时间内扫过相等面积（第二定律），轨道周期的平方与半长轴的立方成正比（第三定律）。
For a satellite in circular orbit, gravity provides the centripetal force: mv²/r = GMm/r². This leads to orbital speed v = √(GM/r), showing that inner planets move faster. Geostationary satellites have an orbital period of 24 hours and appear fixed above the equator.
对于沿圆形轨道运行的卫星，重力提供向心力：mv²/r = GMm/r²。由此可得轨道速度v = √(GM/r)，表明内行星运动更快。地球同步卫星的轨道周期为24小时，看似固定在赤道上空某一位置。
8. Earth-Moon System: Phases, Tides and Eclipses | 地月系统：月相、潮汐与食
The Moon orbits Earth approximately every 27.3 days (sidereal month). Its changing appearance—new moon, waxing crescent, first quarter, waxing gibbous, full moon, waning phases—results from the relative positions of Earth, Moon and Sun.
月球约每27.3天绕地球一周（恒星月）。其形状变化——新月、蛾眉月、上弦月、盈凸月、满月、亏缺阶段——源于地球、月球与太阳的相对位置。
Tides are caused by the differential gravitational pull of the Moon (and Sun) on Earth’s oceans. Spring tides with the largest range occur when the Sun and Moon are aligned (new/full moon), while neap tides with the smallest range occur at first and last quarters.
潮汐由月球（和太阳）对地球海洋的差异引力引起。当太阳与月球成一线（新月/满月）时，发生潮差最大的大潮；上弦月和下弦月时发生潮差最小的小潮。
A solar eclipse happens when the Moon passes between Earth and the Sun, casting a shadow on Earth. A lunar eclipse occurs when Earth is between the Sun and the Moon, with the Moon passing through Earth’s shadow. Eclipses do not occur every month due to the Moon’s inclined orbit.
日食发生在月球经过地球与太阳之间，在地球上投下阴影时。月食发生在地球位于太阳与月球之间，月球穿入地球阴影时。由于月球轨道倾斜，食并非每月都发生。
9. Life Cycle of Stars | 恒星的生命周期
Stars form from nebulae—vast clouds of gas and dust—that collapse under gravity. As the core temperature reaches millions of degrees, nuclear fusion ignites, converting hydrogen into helium and releasing energy. The star enters the main sequence, where it spends most of its life.
恒星形成于星云——巨大的气体尘埃云——在引力作用下收缩。当核心温度达到数百万度时，核聚变点燃，氢转化为氦并释放能量。恒星进入主序星阶段，在此度过生命的大部分时间。
| Mass | Main sequence | Post-main evolution | End state |
| Low-mass (like Sun) | Stable H fusion | Red giant → planetary nebula | White dwarf |
| High-mass (>8 M☉) | Rapid fusion | Red supergiant → supernova | Neutron star or black hole |
| 质量 | 主序星 | 主序后演化 | 最终状态 |
| 低质量（如太阳） | 稳定的氢聚变 | 红巨星 → 行星状星云 | 白矮星 |
| 大质量（>8 M☉） | 快速核聚变 | 红超巨星 → 超新星 | 中子星或黑洞 |
In low-mass stars, the core contracts and outer layers expand into a red giant. Fusion produces carbon and oxygen; eventually the outer layers are ejected as a planetary nebula, leaving
Published by TutorHao | IB Science Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
屏轩国际教育cambridge primary/secondary checkpoint, cat4, ukiset,ukcat,igcse,alevel,PAT,STEP,MAT, ibdp,ap,ssat,sat,sat2课程辅导，国外大学本科硕士研究生博士课程论文辅导