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The Sun’s Size, Heat, and Structure The Sun’s Size, Heat, and Structure Drawing the Sun’s Layers to Scale Layer Radius in km / Scaling Factor = Radius of Each Layer in cm Convective Zone 495,000/ 69,500 km = 695,000 km 1 cm Radiative Zone 190,000/ 69,500 km = 495,000 km 1 cm Core 0-190,000 km / 69,500 km = 1 cm = = = Characteristics (List these on drawing) The Solar Wind is the cause of geomagnetic storms and the Aurora Borealis (Northern Lights) The Aurora Borealis (Northern Lights) The Sun is powered by nuclear fusion. The Sun Burns Hydrogen and converts it to Helium + Energy Plasma is a fourth state of matter. Charged nuclei of particles fuse together. Plasma is a fourth state of matter. Charged nuclei of particles fuse together. Normal Hydrogen Atom with proton (+) and electron (-) In Plasma, electrons are stripped away from the nucleus. “Since nuclei are positively charged, they will repel other nuclei. Only tremendous heat and pressure will cause the nuclei to fuse. Such temperatures and pressures occur naturally in stars where they are ultimately caused by gravitational forces.” Summary of Fusion Reactions Solar Energy is derived from the conversion of mass to Energy. Albert Einstein is famous for his equation E=mc2. Assignment Your job is to draw the model of the sun on butcher paper using colored pens/pencils. You should describe all the layers and temperatures. You also need to discuss how the sun makes energy (fusion), how/when sunspots form, and the solar wind and what it does to Earth. Historical Observations of the Solar System “The idea that the Earth was stationary and the sun moved across the sky was the idea that prevailed for over two thousand years.” What is a geocentric model? It’s the idea that Earth was at the center of the Universe. The stars were thought to move around the Earth. The same constellations were noticed to be visible at the same time each year. A few points of light seemed to move however, or wander. What were these things? These were the planets! Planet means wanderer. The most perplexing of all was retrograde motion of Mars, the observation that it stopped moving eastward and moved westward for a few weeks. Retrograde Motion Ptolemy, a Greek Astronomer in the 2nd Century A.D., believed that the planets orbited Earth in Epicyles. This idea was accepted until the 16th Century. Copernicus (1473-1543), proposed the Heliocentric Model, the idea that the sun is the center of the solar system and the planets revolve around the sun. We use Copernicus’s model to this day. Enter Tycho Brahe in the th 16 Century. This Danish astronomer made very accurate observations of the movement of planets and their moons. Tycho Brahe in his observatory, Uraniborg. Brahe died in 1601. His work was extended by his assistant, Johannes Kepler. Kepler went on to make an unexpected discovery and formed Kepler’s Laws! What was this? The planets orbit in ellipses with the sun at one foci. This is Kepler’s First Law. Earth Sun Focus Focus The planets sweep out equal areas in equal times. This is Kepler’s Second Law. Earth 1 Sun Focus Focus Kepler’s Third Law says that the Period squared equals the average Distance 2 3 Cubed. P = D Earth 1 Sun Focus Focus Isaac Newton and His Physical Laws Newton invented calculus, studied the composition of light, and established classical physics. Newton’s First Law An object in motion will stay in motion unless acted upon by an outside force. An object at rest will stay at rest unless acted upon by an outside force. This is the foundation of space travel. Newton’s Second Law The Force on an object equals it’s mass X acceleration (gravity). Force = mass x acceleration F = ma Newton’s Third Law For every force, there is an equal and opposite force. The basis behind rocket propulsion. Force a on b = Force b on a Newton’s Law of Gravitation The gravitational force on two bodies (planet and sun) is proportional to mass and inversely proportional to the square of distance. 2 Forcegravity = Gm1m2/d Earth’s Rotation and Revolution Rotation is the spinning of Earth around its axis. It’s takes 24 hours for the earth to rotate on its axis. Evidence for Earth’s Rotation is given by a Foucault Pendulum. YouTube video of the Foucault Pendulum at the Griffith Observatory! We also know that the Earth rotates from west to east because the sun rises in the east, moves through the southern sky (in the northern hemisphere), and sets every day in the west. Time Zones are needed to account for the fact that the Sun is not in the same position everywhere at the same time. Revolution is the movement of Earth around the Sun. It takes 365 ¼ days to revolve around the Sun. Evidence for revolution is indicated by the changing view of the stars throughout the year. The Earth’s seasons also give evidence of revolution. Star Parallax, an apparent shift in star position, is another piece of evidence. The Earth’s seasons also give evidence of revolution. Earth’s Axis is tilted at 23.5° from the vertical. This gives way to the seasons. Solstice means “sun still.” Equinox means “equal night.” Autumnal Equinox Winter Solstice September 22nd December 21st Summer Solstice June 21st Vernal Equinox March 21st Table of Seasons Season Summer Solstice (First Day of Summer: around 6/21) Autumnal Equinox (First Day of Fall: around 9/22 Winter Solstice (First Day of Winter: around 12/21) Vernal Equinox (First Day of Spring: around 3/21) Day Around 14 12 hours Length at hours LCHS Around 10 12 hours hours Sun 23.5° N at 0° at Directly Tropic of Equator overhead: Cancer 23.5° S at 0° at Tropic of Equator Capricorn Here are two animations for the reasons for our seasons. Animation 1 and Animation 2 What kinds of radiation does the sun emit? According to Wien’s Law, 2,900,000/Temp in Kelvin, the peak emission of the sun is 2,900,000/6000K. This is equal to 483 nm, the color of blue-green light. This is why our eyes have evolved to detect the visible spectrum. The electromagnetic spectrum. According to Wien’s Law, 2,900,000/Temp in Kelvin, the peak emission of the sun is 2,900,000/6000K. This is equal to 483 nm, the color of blue-green light. This is why our eyes have evolved to detect the visible spectrum. What kinds of radiation does the sun emit? According to Wien’s Law, 2,900,000/Temp in Kelvin, the peak emission of the sun is 2,900,000/6000K. This is equal to 483 nm, the color of blue-green light. This is why our eyes have evolved to detect the visible spectrum. What kinds of radiation does the sun emit? UVA and UVB light can get through to the Earth’s surface. Lucky for us, UVC light is blocked. Consequences of Not using sunscreen Sunburn Skin Cancer Melanoma Cataracts Sunscreen Lab: Chemistry of Sunscreen Active Ingredients: Contains: Octinoxate 2% (Sunscreen), Padimate O 1.4% (Sunscreen) Inactive Ingredients: Mineral Oil, Aloe Barbadensis Leaf Extract, Cocos Nucifera Oil (Coconut), Theobroma Cacao Seed Butter (Cocoa), Musa Sapientum Fruit Extract (Banana), Tocopherol Acetate (Vitamin E Acetate), Retinyl Palmitate (Vitamin A), Daucus Carota Sativa Root Extract (Carrot), Phenoxyethanol, Methylparaben, Isopropylparaben, Isobutylparaben, Butylparaben, Fragrance Sunscreen Lab Active Ingredients: Padimate O 5.4%, Oxybenzone 1.2% Inactive Ingredients: Acrylates/C10-30 Alkyl Acrylate Crosspolymer, Aloe Barbadensis (Leaf Juice), Cetyl Alcohol, Cocos Nucifera (Coconut Oil), Fragrance, Glycerl Stearate, Hydrolyzed Collagen, Imidazolidinyl Urea, Isocetyl Alcohol, Methylparaben, Mineral Oil, Mink Oil, Polyethylene, Polyglyceryl 3 Dioleate, Propylparaben, Quaternium 15, Sorbitol, Stearic Acid, Theobroma Cacao Cocoa Seed Butter, Tocopheryl Acetate, Triethanolamine, Water Sunscreen Lab Did you notice the inactive mink oil ingredient? This comes from the thick fatty tissue just under the skin of the mink. It is used in cosmetics and is used to coat shoe and baseball glove leather. Sunscreen Lab Active Ingredients: Padimate O 5.0% (Sunscreen), Oxybenzone 3% (Sunscreen), Octinoxate 2% (Sunscreen) Inactive Ingredients: Acrylates/C10-30 Alkyl Acrylate Crosspolymer, Aloe Barbadensis (Leaf Juice), Cetyl Alcohol, Cocos Nucifera Oil (Coconut), Fragrance, Glyceryl Stearate SE, Hydrolyzed Collagen, Imidazolidinyl Urea, Methylparaben, Mineral Oil, Mink Oil, Polyethylene, Polyglyceryl 3 Oleate, Propylparaben, Quaternium 15, Sorbitol, Stearic Acid, Theobroma Cacao Seed Butter (Cocoa), Tocopherol (Vitamin E), Triethanolamine, Water Sunscreen Lab Active Ingredients: Octinoxate (7.5% Sunscreen), Oxybenzone (5.25% Sunscreen), Octisalate (4.75% Sunscreen), Titanium Dioxide (1.2% Sunscreen) Inactive Ingredients: Aloe Barbadensis (Leaf Juice), Alumina, Aluminum Stearate, C12-15 Alkyl Benzoate, Ceteareth 20, DMDM Hydantoin, Glyceryl Stearate, Hydrolized Collagen, Hydroxyethylcellulose, Imidazolidinyl Urea, Iodopropynyl Butylcarbamate, Isopropyl Myristate, Magnesium Aluminum Silicate, Methyl Acetyl Ricinoleate, Octadecene/MA Copolymer, PEG 40 Castor Oil, PEG 7 Glyceryl Cocoate, Polyethylene, Polyhydroxystearic Acid, Quaternium 15, Silica, Stearic Acid, Stearyl Alcohol, Tocopheral (Vitamin E), Triethanolamine, Trisodium EDTA, Water Sunscreen Lab Active Ingredients: Avobenzone (1.5%) (Sunscreen), Homosalate (15%) (Sunscreen), Octisalate (5%) (Sunscreen), Octocrylene (1.25%) (Sunscreen), Oxybenzone (6%) (Sunscreen) Inactive Ingredients: Water, Hydrogenated Dimer Dilinoley/Dimethylcarbonate Copolymer, Stearyl Alcohol, Glycerin, Caprylyl Glycol, Aloe Barbadensis (Aloe Vera) Leaf Juice, Tocopherol Acetate (Vitamin E), Retinyl Palmitate (Vitamin A), Tocopherol, Sodium Lauroyl Sarcosinate, Behenyl Alcohol, Glyceryl Stearate, Glyceryl Stearate Citrate, Disodium Ethylene Dicocamide Peg 15 Disulfate, Cetyl Alcohol, Dimethyl Capramide, Cetearyl Alcohol, Sodium Lauroyl Lactylate, Lecithin, Carbomer, Xantham Gum, Methyldibromo Glutaronitrile, Methylchlorisothiazolinone, Methylisothiazolinone, Phenoxyethanol, Disodium EDTA, BHT Sunscreen Lab Active Ingredients: Octinoxate (7.5% Sunscreen), Oxybenzone (6.0% Sunscreen), Octisalate (6.0% - Sunscreen) Target Ultra Sunblock SPF 30 Inactive Ingredients: Water, Aloe Vera Gel, Mineral Oil, Stearic Acid, Propylene Glycol, VP/Eicosene Copolymer, Triethanolamine, Acrylates/C10-30 Alkyl Acrylate Crosspolymer, Cetyl Alcohol, Glycol Stearate, Phenoxyethanol & Methylparaben & Ethylparaben & Butylparaben & Propylparaben, Disodium EDTA. When the sun’s rays are more direct, we get more intense rays. We get more solar insolation in the summer months also because the sun has less atmosphere to travel through if it is overhead. If there is more atmosphere to travel through, less radiation reaches the surface. So, is it easier to get a sunburn when the sun is overhead, or when it is on the horizon?