The Earth's Rotation
Simultaneously the Earth moves in two different ways. The Earth revolves around the sun at a slightly elliptical orbit and takes approximately 365.26 days to complete one revolution. The rotation axis of the Earth is tilted by 23.5 degrees from the direction perpendicular to the Earth's orbit around the sun.
Scientific Activity 3: Round and Round
Internet Connection: The Earth's Rotation and Revolution Around the Sun
At this site students can see a presentation of the Earth rotating and revolving around the sun.
The change in seasons is caused by the tilt of the Earth's axis. The Earth's tilt allows for northern and southern hemisphere to receive different amounts of sunlight from different angles. For example, during the summer in the northern hemisphere the sun is positioned high above the continent allowing for direct sunlight, while in the southern hemisphere the sun is striking the continent at a lower angle. Also, the northern hemisphere will receive 12 hours of sunlight, causing longer days and shorter nights. It is often a misconception that the seasons are caused by change in the distance from the Earth to the sun. The distance from the Earth to the sun only changes about 3% during a rotation. This is not enough to affect the Earth's seasons. In fact, the Earth is the closest to the sun during the winter in the northern hemisphere.
Many people believe that it is the moon that controls the tides on our Earth, while this is correct, the sun also plays a role. The gravitational forces exerted by the moon forces the Earth into the shape of a football. Because of the solid land on Earth the moon's pull cannot effect the land much, however the pull does effect the oceans and produce tides. As a result of the gravitational pull the water on earth is pulled in specific directions causing high and low tide. As the gravitational force bulges the water toward the moon a bulge is then equal on the opposite side of the Earth. However when the sun, Earth, and moon all align the tidal forces are particularly strong causing extremely high and low tides known as spring tides. When the sun and the moon are at a ninety degree angle the forces are less strong causing smaller high and low tides called neap tides.
Internet Connection: Tides
Students can view the tidal cycle in elapsed time.
Students can watch a short cartoon about how the moon effects tides.
Students can view an animated diagram of the sun's effect on the tides.
Mathematical Connection: Graphing the Tides
Students can use their local newspaper to record and create a line graph of high and low tides.
Life on Earth
Water, food, and oxygen are essential to human survival, each of which is obtainable because of the sun.
For a plant to grow it needs water, air, nutrients, and the sun. Through a process called photosynthesis, a plant can convert the sun's energy to chemical energy. While water enters the plant through the roots, sunlight reaches the leaves, forming glucose and oxygen. The glucose is stored by converting it to carbohydrates which are used to feed the plant. Aiding in the energy storage process is chlorophyll. Chlorophyll is found in leaves and is what gives them their green color.
Without the sun, plants could not produce the food they need to grow. Without plants, animal and human life could not survive. Plants are a necessary part of the food chain. Humans consume both plants and animals. The animals that we eat consume plants. Thus, without the sun there would not be food for animals to survive10.
Scientific Activity 4: Geometric Plants
Internet Connection: Photosynthesis
Students can view a fun cartoon on how photosynthesis works.
Students can watch an interactive presentation of how photosynthesis works.
Oxygen is a waste product of plants through the process of photosynthesis. As plants produce their food using carbon dioxide, water, and sunlight, they release oxygen into the air. Without oxygen humans could not breathe, an obvious essential to life on Earth.
The water we use and drink is part of a natural process known as the hydrologic or water cycle. The hydrologic cycle takes place in five steps that run simultaneously and continuously. Together, evaporation, condensation, precipitation, infiltration, and runoff constitute the hydrologic cycle. The sun's role in the water cycle takes place in evaporation. Water from the Earth's surface, is heated by the sun causing the water molecules to rise up from the Earths surface. As water vapor rises it condenses turning back to liquid in the form of clouds. When the clouds become saturated the water falls back to the Earth in precipitation. As the precipitation reaches the Earths surface it infiltrates the land or returns to a water source through runoff. This constant cycle is necessary to provide humans, plants, and animals with the water they need to survive. Without the sun, water would not be able to evaporate and we would run out of useable water. 11
Internet Connection: The Hydrologic Cycle
A power point presentation of the hydrologic cycle that students can do on their own or as a class.
Keeping us Warm
The Earth needs the sun for heat. Without the sun's warmth, the temperature would become nearly freezing - 460 degrees Fahrenheit, known as absolute zero. In three days, we would use up all the Earth's recourses just to stay warm. Fortunately for us, the temperature stays "…between the freezing point of water (32 degrees F) and the normal body temperature of humans (98.6 degrees F). If the average temperature ever varied very far above or below these two extremes for very long, we could not survive".12, 13, 14
While the direct influence of the sun on the climate has puzzled scientists, it is clear that the sun definitely effects the weather here on Earth. Climate describes the weather over an extended period of time in one place. Weather can change on a daily basis and it is what is occurring in a place at a given time. For example, the climate in Florida is generally warm and sunny, but Florida's weather can be sunny, cold, dry, or rainy. In Connecticut the climate is generally hot in the summer and cold in the winter. According to the CIA World Fact Book, The average annual temperature ranges from 39.5 degrees Fahrenheit to 60 degrees Fahrenheit. The shoreline is generally cooler than inland. However, variations can be seen in Connecticut climate. For example, it can reach as high as 95 degrees Fahrenheit or reach lower than freezing. The sun drives the weather on the Earth. "The weather is caused by the circulation of the atmosphere which is caused by the unequal heating of the earth's surface by the sun".15 Various amounts of sunlight are reaching the Earth in different locations because of the Earth's rotation and revolution. These differences cause parts of the Earth's atmosphere to heat up at different rates. These changes in atmosphere determine our weather.16
Mathematical Connection: Graphing Temperature Change
Students can use the internet to record and create a bar graph of the changing temperature in their local area. Student could also compare it to another part of the world.
The sun's energy not only reaches the atmosphere, but also the ground. As states earlier, the sun plays a major role in our water cycle. As the sun heats the ground, the Earth's surface is heated causing evaporation. The water is evaporated into water vapor and rises to the Earth's atmosphere. As the water vapor rises it collects dust allowing the formation of clouds. As clouds form they combine with other clouds. When the clouds are large enough and heavy with water vapor precipitation occurs. The temperature determines the type of precipitation, rain, snow, hail, and sleet.17, 18
Scientific Activity 5: Cloudy Classroom
Water vapor, which is evaporated into the Earth's atmosphere by the sun, is the cause for much of the powerful weather we witness in Connecticut. Throughout the day, the sun heats the surface causing the Earth's atmosphere to become unstable. If there is enough water vapor in the air, a thunderstorm will occur. A thunderstorm will cause both thunder and lighting. Lighting occurs during a thunderstorm "…when liquid and ice particles above the freezing level collide, and build up large electrical fields in the clouds".19 This electrical filed causes a "spark". While many of us have often heard the phrase "heat lightning" and would assume that hot weather from the sun would cause such an event, it is untrue. Heat lightning is only the view of a thunderstorm in the distance.20
If a thunderstorm develops over the ocean and the temperature of the water is warmer than 81 degrees Fahrenheit and there is high relative humidity a hurricane can form. "A hurricane is a severe tropical storm, that forms in the southern Atlantic Ocean, Caribbean Sea, Gulf of Mexico or in the eastern Pacific Ocean"21 To be classified a hurricane the winds of the tropical cyclone must exceed 74 miles per hour. While the last hurricane in Connecticut was Hurricane Gloria in 1985, there are still threats especially between the months of June and November.22
Scientific Activity 6: The Eye of the Storm
Internet Connection: Hurricanes
Students can watch a video on thunderstorms and hurricanes
Students can read and view pictures about hurricanes. This site is intended for students and also provides safety tips.
The sun releases multiple types of energy, including ultraviolet light. Ultraviolet light or UV radiation can cause serious health problems. Fortunately the stratospheric ozone protects us from most of the UV light. There are three types of UV radiation, UVA, UVB, and UVC. UVC is completely absorbed by the ozone, UVB is only partially absorbed, and UVA cannot be absorbed at all. Scientists have also discovered that by using harmful chemicals here on Earth we are effecting the strength of the ozone causing more of the bad UV light to get through.
UV radiation is known to cause numerous health problems including skin cancer, cataracts, premature aging of the skin, and immune suppression. At certain times of the day, such as between 11:00 am and 2:00 pm, the sun is the strongest and can cause the most damage. Even on cloudy or cold days the sun is still strong enough to cause damage to the skin As a result of these health risks we need to protect ourselves from the harmful rays of the sun. This can be done by protecting both your skin and your eyes by wearing a hat, sunglasses, and sunscreen with UV protection.23
Scientific Activity 7: UV Beads
Internet Connections: Sun Protection
Students can read about the importance of the ozone layer, UV index, and steps to protect themselves from the sun. Fun games are provided to enhance learning at three different levels. This is a great interactive way for students to better understand the sun and its effects.
The sun can be very dangerous to humans, but it is also very important to human health. When UV radiation reaches the skin it triggers the production of Vitamin D. Vitamin D is essential to a healthy human body and the best way to obtain it is through the sun. Vitamin D can also be obtained through other sources, such as salmon, cod liver oil, and mackerel, items most people don't normally eat in their diet. This essential vitamin is also found in milk, but in such limited quantities that you would have to drink 10 glasses of milk a day to get the required amount of Vitamin D needed. Vitamin D is necessary for the human body to absorb calcium and facilitate proper bone growth. Adequate sunlight exposure is also known to prevent heart related illnesses and cancers. Recently, doctors and scientists have discovered that Vitamin D also triggers hormones in our body that affect mood. Sufficient exposure to the sun can be a mood lifter, which is why when a person spends time in the sun they tend to feel good.24