South 고등학교 3학년 Convergent Science
Chapters: 6
1. Origin and evolution of the universe
Hubble's law · Particles after the Big Bang · Hydrogen and helium spectra · Life cycle of stars · Galaxies · Molecules in space
- Cosmology: The Expanding Universe and the Big Bang – Cosmology is the study of the whole universe: its structure, history and future. Galaxies gather in groups, clusters and filaments around huge voids. Distant galaxies are moving away from us, faster the farther they are (Hubble's law, v = H₀d), because space itself is expanding. Running the expansion backwards leads to a hot, dense beginning about 13.8 billion years ago, the Big Bang. The main evidence is redshift, the cosmic microwave background and the amounts of hydrogen and helium. Most of the universe is dark matter and dark energy.
- Towards Bohr's Model: Light, Photons, Spectra and Bohr's Atom – Light is an electromagnetic wave: c = νλ, and wavenumber ν̄ = 1/λ. But some facts need particles: Planck said energy comes in packets (quanta) E = hν. Einstein used photons to explain the photoelectric effect: an electron comes out only if hν is above the work function W₀ = hν₀, and its kinetic energy is hν − hν₀. Atoms give line spectra, which means electron energies are fixed. Bohr put the electron on fixed orbits with angular momentum nh/2π; energy Eₙ = −2.18 × 10⁻¹⁸ Z²/n² J, radius rₙ = 52.9 n²/Z pm. A jump between orbits gives a photon, and 1/λ = R_H(1/n₁² − 1/n₂²) gives the Lyman, Balmer, Paschen, Brackett and Pfund series. Bohr works only for one-electron species.
- Stars and Galaxies: From Starlight to the Big Bang – Everything we know about stars comes from their light. Splitting starlight into a spectrum shows dark lines that tell us which elements a star has; the colour tells us its temperature (blue = hot, red = cool) and stars are sorted into classes O B A F G K M. The H-R diagram plots true brightness against temperature: most stars, including the Sun, lie on the main sequence, with giants top right and white dwarfs bottom left. A star is born in a nebula and its mass decides its life: a Sun-like star becomes a red giant and then a white dwarf; a star of more than about 8 solar masses becomes a supergiant, explodes as a supernova and leaves a neutron star or black hole. Stars gather in galaxies, which are spiral, elliptical or irregular. Distances are huge, so we use the astronomical unit, the light-year and the parsec. Galaxies are moving apart, faster when farther (Hubble's law), which together with the cosmic microwave background supports the Big Bang about 13.8 billion years ago.
- The Interstellar Medium: Gas, Dust and Molecules Between the Stars – The interstellar medium (ISM) is the thin gas and dust that fills the space between stars. About 99% of it is gas (mostly hydrogen and helium) and about 1% is tiny solid dust grains. In cold, dense clouds atoms join into molecules such as H₂ and CO. Dust absorbs and scatters starlight, blue light more than red, so a star behind dust looks fainter (extinction) and redder (reddening).
2. Solar system and Earth
Formation of the solar system · Kepler's laws · Earth-Moon motions · Escape velocity and atmospheres · Evolution of Earth · Elements and compounds of Earth · Magnetosphere and ionosphere
- The Solar System – The Solar System is the Sun and everything its gravity holds: 8 planets, their moons, dwarf planets, asteroids, comets and dust. The inner four planets (Mercury, Venus, Earth, Mars) are small and rocky. After the asteroid belt come the giants: gas giants Jupiter and Saturn, ice giants Uranus and Neptune. Gravity pulls planets towards the Sun while they move sideways, so they travel in orbits; closer planets move faster and have shorter years. It all formed about 4.6 billion years ago from a spinning cloud of gas and dust.
- Kepler's Laws of Planetary Motion – Kepler gave three rules for how planets move. 1) Each planet moves on an ellipse with the Sun at one focus. 2) The line from the Sun to the planet sweeps equal areas in equal times, so the planet moves faster when it is near the Sun. 3) The square of the time for one round (T²) is proportional to the cube of the semi-major axis (a³). The second law is really conservation of angular momentum. The third law follows from Newton's law of gravitation.
- Gravity – Gravity is the pull between all masses. Earth pulls every object towards its centre. A freely falling object speeds up by about 9.8 m/s every second (g), and this does not depend on its mass. Weight is the pull on your mass, W = m × g, so it changes from world to world while mass does not. A ball thrown sideways fast enough keeps missing the Earth and goes into orbit (about 7.9 km/s); at about 11.2 km/s it escapes.
- Origin and Evolution of the Earth: From Dust Cloud to Living Planet – Early thinkers said the planets formed from a spinning cloud of gas around the young Sun (nebular hypothesis) or from matter pulled out of the Sun by a passing star. Today scientists explain the universe with the Big Bang: about 13.7 billion years ago everything began from one tiny point and it is still expanding. Stars formed from clumps of gas; planets formed from dust around the Sun. The Earth, about 4.6 billion years old, was hot and molten; heavy iron sank to make the core and lighter rock formed the crust. Gases from volcanoes made the early air, water vapour rained into oceans, and life began in the oceans about 3.8 billion years ago.
- Interior of the Earth: Earthquake Waves, Layers and Volcanoes – Nobody can dig to the centre of the Earth, so we learn about the inside from direct sources (mine rocks, deep drilling, lava) and indirect sources (heat and pressure with depth, meteors, gravity, magnetism and, above all, earthquake waves). P-waves travel through solids and liquids; S-waves only through solids. Where the waves do not arrive, we get shadow zones, which prove the outer core is liquid. Earthquakes are measured by magnitude (Richter) and intensity (Mercalli). The Earth has a thin crust, a thick mantle with a soft asthenosphere, a liquid outer core and a solid inner core. Magma that reaches the surface builds volcanoes; magma that cools inside forms intrusive landforms like batholiths, sills and dykes.
- Earth’s Magnetic Field (Geomagnetism) – Earth has a magnetic field like a tilted bar magnet. It is made by moving liquid iron in the outer core (the dynamo). A compass lines up with it. The angle between magnetic and true north is declination; the angle the field makes with the ground is dip (0° at the equator, 90° at the magnetic poles). The field forms a shield, the magnetosphere, that bends the solar wind. Some particles slip in near the poles and make the aurora.
3. Evolution of life
Chemical evolution · Photosynthetic bacteria and oxygen · Fossils through time · From simple to complex life · Shared genetic code · Alleles and meiosis · Genes and evolution
- Evolution: Origin of Life, Mechanisms and Human Evolution – Life began on the early Earth from simple chemicals: Oparin and Haldane proposed it and Miller made amino acids in a flask. Evidence of evolution comes from fossils, homologous and analogous organs, embryos, molecules and changes we can watch (industrial melanism, drug resistance). Darwin explained it by natural selection acting on variation in populations; the modern synthetic theory adds genes: mutation, recombination, gene flow, genetic drift and natural selection change allele frequencies. If none of these act, frequencies stay constant: Hardy–Weinberg, p² + 2pq + q² = 1. Selection can be stabilising, directional or disruptive. One ancestor spreading into many habitats gives adaptive radiation (Darwin’s finches, Australian marsupials). Humans evolved from Dryopithecus-like apes through Australopithecus, Homo habilis, Homo erectus and Neanderthals to Homo sapiens.
- Origin and Evolution of the Earth: From Dust Cloud to Living Planet – Early thinkers said the planets formed from a spinning cloud of gas around the young Sun (nebular hypothesis) or from matter pulled out of the Sun by a passing star. Today scientists explain the universe with the Big Bang: about 13.7 billion years ago everything began from one tiny point and it is still expanding. Stars formed from clumps of gas; planets formed from dust around the Sun. The Earth, about 4.6 billion years old, was hot and molten; heavy iron sank to make the core and lighter rock formed the crust. Gases from volcanoes made the early air, water vapour rained into oceans, and life began in the oceans about 3.8 billion years ago.
- Evolution: How New Kinds of Living Things Arise – Variations arise during reproduction. Nature selects those that help survival, so over many generations populations change: this is evolution. Only inherited (DNA) changes pass on; acquired changes do not. Separated populations can become new species. Homologous organs, analogous organs and fossils help us trace who is related to whom, and complex organs evolved step by step.
- Chromosomes, Genes, Alleles and Polygenic Inheritance – Each cell nucleus holds chromosomes made of DNA. All the DNA of an organism is its genome. A gene is a stretch of DNA at a fixed place on a chromosome; its different forms are alleles. Chromosomes come in pairs, one from each parent. Meiosis puts one chromosome of each pair into each gamete, and fertilisation restores the pairs. Some traits, like height, depend on many genes together (polygenic) and so show a smooth range. All living things use the same four-letter DNA code.
4. ICT and new materials
Signals and sensors · Kinds of sensors · Digital storage · Colour vision and displays · Energy bands · Doping and devices · Polymers · Mineral resources
- Sensors: How Machines Sense the World – A sensor turns a physical quantity (light, temperature, distance, moisture, sound, pressure) into an electrical signal. Analogue sensors give a smooth voltage; an ADC turns it into a number the computer can use. A controller compares the number with a threshold and switches an actuator, often through a relay. Readings taken at regular times are data logging. Good sensors have the right range, sensitivity, accuracy and response time.
- Basic Computer Organisation – A computer system has hardware (parts you can touch) and software (instructions). Input devices bring data in, the CPU (ALU + Control Unit + registers) processes it, and output devices give results. Memory forms a ladder: registers and cache are tiny and fastest, primary memory (RAM, ROM) holds running programs, and secondary storage (HDD, SSD, pen drive) keeps data permanently. Memory is measured in bits and bytes: 8 bits = 1 byte, and each bigger unit (KB, MB, GB, TB, PB) is 1024 times the one before.
- Light and Colour: Mixing, Seeing and Energy of Light – White light is a mix of colours (red to violet). Lights add: red + green + blue make white (additive mixing, used by screens). Paints take away: cyan + magenta + yellow make near-black (subtractive mixing). An object has a colour because it reflects some colours and absorbs the rest. Eyes use three kinds of cone cells. Light colour tells its energy: E = hf, blue photons carry more energy than red.
- Semiconductors and the p-n Junction Diode – A semiconductor has a small energy gap (about 1 eV), so a little heat frees some electrons. Pure silicon is intrinsic (electrons = holes). Adding a 5-valence atom makes n-type; a 3-valence atom makes p-type. Joining p and n makes a junction with a depletion layer and a barrier (about 0.7 V for Si). The diode conducts in forward bias, almost not in reverse bias, so it can change AC into one-way DC (rectifier).
- Polymers – A polymer is a giant molecule made by joining many small molecules (monomers) into a long chain. In addition polymerisation, monomers with a C=C double bond open up and link with nothing lost (ethene → poly(ethene)). In condensation polymerisation, two kinds of monomer with reactive groups at both ends join and give off a small molecule such as water at every link (nylon, polyester). Nature makes polymers too: starch, cellulose, proteins, DNA, rubber. Separate chains give thermoplastics that melt and can be recycled; cross-linked chains give thermosets that never melt. Most plastics do not rot, so we must reduce, reuse and recycle them.
- Natural Resources – Natural resources are useful things we take from nature: sunlight, wind, water, soil, forests, minerals, oil, gas and coal. Renewable resources come back in a human lifetime; non-renewable ones took millions of years to form and run out when used. Resources are spread unevenly because they form only where certain geological processes happened in the past (old seas, volcanoes, mountain building). Using them brings benefits such as energy, jobs and materials, but also costs such as pollution, habitat loss and hazards, so societies weigh costs against benefits and try to use them sustainably.
5. Human health and technology
Nitrogen fixation and fertiliser · Sustainable food resources · Cell-level health · Bacteria and viruses · Medical devices · Biodiversity value · Cancer
- Nitrogen: the Element, Its Compounds and the Nitrogen Cycle – Nitrogen (N₂) makes up 78% of air, but its triple bond is so strong that most living things cannot use it. Fixation (by root-nodule bacteria, lightning and the Haber process) turns it into ammonia. From ammonia we make nitric acid and fertilisers. In nature, nitrogen moves in a cycle: fixation → nitrification → absorption by plants → animals → decay (ammonification) → denitrification back to air.
- Food Security: Feeding Everyone, Every Day – Food security means every person, at all times, can get enough safe and nutritious food for an active, healthy life. It rests on four pillars: availability (food is produced or imported), access (people can afford and reach it), use (good nutrition, clean water, safe cooking) and stability (supply does not collapse in bad years). Food supply is uneven across the world. Demand keeps rising with population, incomes and changing diets, while climate change, water shortage, soil loss, conflict and waste limit supply. Food insecurity causes hunger, malnutrition, high prices, migration and unrest. Supply can be raised by irrigation, better seeds, new technology and cutting waste, but long-term answers must also be sustainable and fair.
- Infectious Diseases: How Germs Spread and How We Stop Them – An infectious (communicable) disease is caused by a tiny living thing called a pathogen: a bacterium, virus, fungus or protist. It passes from one person to another through air, water and food, touch, or a vector such as a mosquito. The body fights back with skin, mucus, stomach acid and white blood cells. Vaccines train the immune system in advance. Hand washing, clean water, cooking food well, mosquito nets and staying home when sick all cut the spread.
- Cancer: When Cells Forget to Stop Dividing – Our body makes new cells by mitosis only when needed: to grow, to heal or to replace worn-out cells. Genes in DNA control this: proto-oncogenes act like an accelerator (go), tumour-suppressor genes like a brake (stop), and other genes repair DNA or make a damaged cell self-destruct (apoptosis). Cancer starts when mutations build up in these genes in one cell. The cell ignores stop signals and divides again and again (1, 2, 4, 8…), forming a lump called a tumour. A benign tumour stays in one place inside a capsule; a malignant tumour invades nearby tissue and can spread through blood or lymph to other organs (metastasis). Mutations come from carcinogens (tobacco smoke, UV light, X-rays and other radiation, some chemicals and air pollution), some viruses (HPV, hepatitis B), lifestyle (alcohol, obesity, poor diet, inactivity), from copying errors with age, and some are inherited (for example BRCA genes). Many cancers can be prevented (no tobacco, sun protection, HPV and hepatitis B vaccines, healthy diet, exercise) and treated well if found early (screening, surgery, chemotherapy, radiotherapy, targeted therapy and immunotherapy).
6. Energy and environment
Forms of energy · The Sun as energy source · Efficiency of conversions · Atmosphere and ocean circulation · Fossil fuels and redox · Photosynthesis and carbon · Fossil and nuclear resources · Renewable sources · Solar cells, fuel cells, hybrids
- Solar Energy: From the Sun to Your Plug – The Sun makes energy by nuclear fusion: hydrogen nuclei join to make helium, and a little mass becomes a lot of energy (E = mc²). The hot surface (about 5800 K) radiates mostly visible light (Wien's law), and its total power grows as T⁴ (Stefan's law). About 1361 W reaches each square metre facing the Sun at the top of the atmosphere; about 1000 W/m² reaches the ground on a clear day. Sunlight hitting at a slant spreads over more area, which explains latitude and seasons. Solar cells turn light into electricity: P = intensity × area × efficiency × cos(angle). Solar water heaters turn light into heat.
- Energy Efficiency – Every machine changes energy from one form to another. Part of the energy becomes what we want (useful energy). The rest spreads out, mostly as heat (wasted energy). Efficiency = useful energy out ÷ total energy in × 100 %. No real machine reaches 100 %. Using efficient devices and wasting less energy saves money and cuts pollution.
- Atmospheric Circulation and Weather Systems – Air has weight, so it presses down: this is air pressure (about 1013 mb at sea level). Wind blows from high pressure to low pressure, pushed by the pressure gradient force, turned by the Coriolis force (right in the north, left in the south) and slowed by friction near the ground. Uneven heating makes pressure belts (equatorial low, subtropical highs, subpolar lows, polar highs) and three circulation cells, giving planetary winds: trade winds, westerlies and polar easterlies. Belts shift with the seasons, giving seasonal winds like the monsoon; local winds include land and sea breezes and mountain and valley winds. Big bodies of air with the same temperature and moisture are air masses; where two meet is a front. Cyclones are low-pressure storms: tropical cyclones form over warm seas; extratropical ones form along fronts. Thunderstorms and tornadoes are small but violent storms.
- Redox Reactions: From Oxygen to Electron Transfer – Oxidation first meant adding oxygen or removing hydrogen. Reduction meant the opposite. Today we use a bigger idea: oxidation is losing electrons and reduction is gaining electrons. Both always happen together, so we call them redox reactions. A more active metal gives electrons to the ion of a less active metal.
- The Carbon Cycle: Where Carbon Is Stored and How It Moves – Carbon moves between the air, living things, soil, oceans and rocks. These places are called stores (or sinks and sources), and the movements are called flows (fluxes). Photosynthesis takes carbon dioxide out of the air; respiration, decomposition and burning put it back. The ocean takes in and gives out huge amounts. Over millions of years carbon is locked into rocks and fossil fuels, and volcanoes and weathering slowly return it. People now burn fossil fuels and clear forests, adding carbon faster than natural sinks can take it up, so the CO₂ in the air rises and the Earth warms.
- Nuclear Fission and Fusion – Fission is the splitting of a large, unstable nucleus such as uranium-235 or plutonium-239. A slow neutron is absorbed, the nucleus splits into two smaller nuclei and releases 2 or 3 neutrons, gamma rays and a lot of energy. The new neutrons can split more nuclei: a chain reaction. In a nuclear reactor, a moderator slows neutrons and control rods absorb some, so the chain reaction stays steady. Fusion is the joining of two light nuclei, such as hydrogen, to make a heavier nucleus, such as helium. Some mass turns into energy. Fusion powers the Sun and stars, but it needs very high temperature and pressure.
- Renewable Energy Sources – Non-renewable sources (coal, oil, gas, uranium) are used faster than nature makes them, and fossil fuels release CO₂. Renewable sources are refilled by nature: solar (photovoltaic cells and solar heating), wind (P ∝ v³), hydroelectric (P = η ρ g h Q), tidal, geothermal and biomass. Hydrogen fuel cells turn hydrogen and oxygen into electricity and water. Because sun and wind change, we need storage (batteries, pumped hydro) and a mix of sources. Every source has costs: land, materials, cost and effect on nature.