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Explore Earth's fascinating facts, from its size and shape to orbiting the Sun, magnetic field, auroras, and the impact of the Sun's ultraviolet radiation on skin. Discover why seasons change and how time zones are determined.
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Earth, Moon, Sun Chapter 7
Earth in Space Chapter 7, Section 1
Earth’s size and shape • Earth is a sphere • How do we know? • No matter where you are on Earth, gravity causes all objects to fall toward the center of the Earth • If you are on a ship approaching land, you see the tops of the tallest buildings first and the ground level last.
Other fun Earth facts: • Diameter: Equator=12,756 km, Pole=12,714 km • Circumference: Eq=40,075 km, Pole=40,008 km • Mass: 598,000,000,000,000,000,000,000 kg • Avg. Distance to Sun: 149,600,000 Km • Avg. Distance to Moon: 384,400 Km • Period of rotation: 23hr, 56 min, 4 sec (sidereal day relative to the distant stars) • Rotation: 24 hr 4 sec (solar day relative to sun) • Period of revolution: 365 ¼ days
Earth’s magnetic field • The outer core of the Earth spins at a different speed than the outer layers; this causes a magnetic field with North and South magnetic poles • The magnetic poles are not static and move periodically • The magnetic poles deflect the solar wind, a stream of harmful electromagnetic particles ejected by the Sun.
Earth’s magnetic field • Some of these E.M. particles are pulled into the Earth’s magnetic poles • When this occurs, their energy can cause the particles in the atmosphere to glow • This phenomenon is called the Aurora Borealis (or Aurora Australis in the Southern Hemisphere)
Space Weather site • http://spaceweather.com/
Earth orbits the Sun • Just like the orbits of all of the planets, moons, and comets, the Earth’s orbit is an ellipse. • What is another word for ellipse? • Ellipse = oval • Of the three other terrestrial (rocky surface) planets, Venus’satmosphere is the most like Earth, but conditions on Mars are most like Earth • Venus is considered to be Earth’s twin due to its size!
7.1 Earth Analysis: Date____ Name______________ Hr__ Copy and answer in complete sentences: • Evidence indicates that Mars once had liquid water on its surface. What evidence could it be? • List at least 2 reasons Mars has none today? • Earth’s circumference at the equator is about 40,075 km (24,901 miles). If it spins once each day, what is the spinning speed in miles/hour? Round your answer to 2 decimal places.
Time and Seasons Chapter 7, Section 2
Measuring time on Earth • The Earth makes one rotation in apx. 24 hours. • This spinning causes the Sun to appear to move across the sky from east to west. • If the Earth spins 360° every 24 hours then it spins 15° every hour (hence time zones). • Time zones are modified to fit cities, regions, or even countries.
International Date Line • The International Date Line is located at 180° longitude (in the middle of the Pacific) • The Earth makes one revolution around the Sun every 365.25 days • The Earth’s orbit around the Sun is in an ellipse (an elongated circular path)
Why do seasons change? • The seasons are not caused by how close we are to the Sun!!!! • The seasons are caused by the axis, or tilt, of the Earth on its axis • The tilt of the axis is 23.5° (Tropics) • During our summer, the Northern Hemisphere gets more direct sunlight and more hours of it than the Southern Hemisphere does. • During our winter, the Northern Hemisphere gets less direct sunlight and less hours of it than the Southern Hemisphere does.
Ultraviolet Radiation=UV • Exposure to ultraviolet (UV) radiation is a major risk factor for most skin cancers. Sunlight is the main source of UV rays. Tanning lamps and beds are also sources of UV rays. People who get a lot of UV exposure from these sources are at greater risk for skin cancer. • Even though UV rays make up only a very small portion of the sun’s rays, they are the main cause of the sun’s damaging effects on the skin.
How does UV hurt us? • UV rays damage the DNA of skin cells. Skin cancers start when this damage affects the DNA of genes that control skin cell growth. • There are 3 main types of UV rays: • UVA • UVB • UVC
UV rays are NOT safe! • UVA rays age skin cells and can damage DNA. They cause wrinkles, but they are also cause some skin cancers. Tanning beds give off alot of UVA, which increases skin cancer risk. • UVB rays have more energy than UVA rays. They damage DNA directly and are the main cause of sunburns. They also cause most skin cancers. • UVC rays have the most energy but are not in sunlight and do not usually cause skin cancer.
UV ray strength Strength of UV rays depends on factors such as: • Time of day: UV strongest from 10 am to 4 pm. • Season: UV stronger during spring and summer. • Distance from equator: UV exposure goes down as you get further from the equator. • Altitude: More UV rays at higher elevations. • Clouds: Some clouds block UVwhile some clouds reflect UV and can increase UV exposure. But UV can get through, even on a cloudy day.
UV Exposure • Reflection off surfaces: UV rays can bounce off surfaces like water, sand, snow, pavement, or grass, leading to an increase in UV exposure. • Wear SUNSCREEN!!! • Skin cancer may take years to show up. • The FDA says that Melanoma, the deadliest form of skin cancer, is linked to getting severe sunburns, especially at a young age.
Mole vs Cancer • All skin growths should be monitored. • Especially look for changing colors or non-round shapes. • If unsure see a doctor. • See picture…
At only two times during the year, all places on Earth have 12 hours of daylight and 12 hours of darkness. • They are called the equinox and occur on apx. March 21st and September 22nd. • On apx. June 21st, the summer solstice occurs. It is the day with the most hours of sunlight in the Northern Hemisphere and the day with the least hours of sunlight in the Southern Hemisphere. • On this day, the sun can be seen directly overhead at the Tropic of Cancer.
The opposite of the summer solstice is the winter solstice. It is the day with the most hours of sunlight in the Southern Hemisphere and the day with the least hours of sunlight in the Northern Hemisphere. • On this day, the sun can be seen directly overhead at the Tropic of Capricorn.
7.2 Time-Season Analysis Name______ Hr_ Date__ Copy and answer in complete sentences. • Why is each timezone 15 degrees wide on Earth? • 4:15 in Detroit is what time in Los Angeles? • What is the difference in rotation and revolution? • Why does Earth’s surface get warmer in summer? • Earth travels 360 degrees in its orbit taking about 365.25 days. How many degrees is that each day? Round your answer to 2 decimal places.
Earth’s Moon Chapter 7, Section 3
Movement of the Moon • The Moon revolves around the Earth every 27.3 days. • The Moon rotates (27.3 days) at the same speed that it revolves! So, the same side of the Moon always faces the Earth. • How Does the Moon affect gravity? • All objects that have mass have gravity. The Moon’s gravity also pulls on the Earth and all objects on Earth, causing ocean tides. The sun’s gravity also pulls on the tides too!
Moonlight • The Moon shines because it reflects sunlight off of its surface • Just like half of the Earth experiences day while the other half is night, so does the Moon. • Moon phases are the changing appearances of the Moon as seen from Earth. The phase you see depends on the relative positions of the Sun, Earth, and Moon.
Random Moon Phase Facts • It takes the moon 29.5 days to complete the phases. • Two full moons in one calendar month is called a blue moon. • Technically, each moon phase only lasts an instant…..but to our eyes, it looks the same for 3 ½ days! • Waxing phase: right side is reflecting light and continues to reflect more each night. • Waning phase: left side is reflecting light and reflects less light each night.
