Total lunar eclipse Activity 2 1 Carry out this activity in pairs. 2 On a piece of durable, black poster board, make a hole in the centre. Make sure the size of the hole can let your head poke through. 3 Colour eight ping pong balls using a blue marker pen so that they are half blue and half white. 4 On the board, mark the direction that the sun is coming from. 5 Apply hot glue to attach all the ping pong balls to the board all around the circle as shown. Let the white side of the balls face the sun. 6 To view the moon phases, two of you will alternately poke your heads through the hole and turn the board counterclockwise. Making a Moon model to observe the phases of the moon Lunar Eclipse When the Sun, Earth and Moon align in a straight line, the Earth blocks the Sun’s light and creates a shadow. This phenomenon is known as a lunar eclipse, or an eclipse of the Moon, which occurs when the Moon moves into the Earth’s shadow. A lunar eclipse can be observed from any region of the Earth where it is night-time. The shadow cast by the Earth during a lunar eclipse is comprised of two parts, the umbra and the penumbra. A total lunar eclipse occurs when the Moon passes completely through the umbra. The sequence below depicts the changing appearance of the Moon during a lunar eclipse. Partial eclipse (penumbra) Partial eclipse (penumbra) Moon Moon’s orbit Sun Earth Total eclipse (umbra) After passing through the umbra, the Moon gradually exits the shadow, and we begin to see a section of the illuminated Moon. Over time, it progresses back into the Full Moon phase again. 194 ©Praxis Publishing_Focus On Science
Tides Have you ever wondered what causes tides to occur? Why do tides change in height and intensity throughout the month? Tides are the rhythmic rise and fall of the ocean water level that occurs twice in a day. They are primarily caused by the gravitational force of the Moon. This force attracts the ocean water to bulge out towards the Moon. Another bulge occurs at the opposite side. This creates high tides at the bulges. Moon A B D C High tides High tides Earth Occurence of tides Look at the diagram above. A and C experience high tides. B and D experience low tides. As the Earth rotates faster than the Moon revolution, every place on the Earth experiences two high tides and two low tides each day. The ocean is constantly moving from high tide to low tide, and then back to high tide. When it is New Moon or Full Moon, the gravitational forces of the Moon and Sun are combined. The high tides are very high and the low tides are very low. These are known as spring tides. They occur when the Earth, Moon and Sun are in a line. Sun Earth Moon Spring tide during New Moon Sun Earth Moon Spring tide during Full Moon Chapter 7 Earth and the Solar System 195 ©Praxis Publishing_Focus On Science
When it is First Quarter Moon or Third Quarter Moon, the effects of the gravitational forces of the Sun and Moon cancel each other. This results in a smaller difference in the high tide and low tide. This is known as neap tides. Sun Earth Moon Neap tides Tides are important as they create tidal streams that circulate the ocean, bringing fresh food and water to other areas. Tides also create a great ecology at the beaches as different living things adapt to the high tides and low tides daily. Knowledge of tides is important for navigation of ships through coastal waterways, fishing and also a variety of water-related sport activities. The Use of Space Technology Much of the technology we use today depends heavily on space technology, with one of the most widely used technologies being the Global Navigation Satellite System (GNSS). It comprises a network of satellites that transmit positioning and timing data to GNSS receivers. These receivers use the data to determine precise locations. GNSS receivers are now integrated into smartphones to support mapping and route planning applications. This system is also used in transportation to accurately determine locations, reduce delays, accidents and operating cost, as well as enhance efficiency and safety. Global Navigation Satellite System (GNSS) 196 ©Praxis Publishing_Focus On Science
Earth-observation satellites (EOS) are used to observe the Earth from space, allowing for various applications such as predicting weather patterns, improving agricultural practices, detecting forest fires and oil spills, measuring ocean waves, assessing gas emissions, monitoring climate change and reducing disaster risks. Communication satellites are also used to relay voice, video and data signals to and from multiple locations worldwide. The International Space Station (ISS) is a large spacecraft orbiting the Earth where astronauts can temporarily live and work to gain knowledge about living and working in space. The ISS’s laboratories provide the crew members with the ability to conduct research that is impossible to carry out on Earth. International Space Station Based on the 2016–2020 space chart, Indonesia’s space development has made significant progress in recent years. During the 2016–2020 period, the country achieved several noteworthy milestones in space science. For instance, it established a regional space weather information and prediction system, as well as an early warning information system for extreme atmospheres. In addition, Indonesia made significant strides in remote sensing, with the National Remote Sensing Data Bank becoming operational. Science Facts 7.3 The Sun The Sun is composed of a massive ball of gases, primarily hydrogen (76%) and helium (22%), with the remaining 2% made up of other elements. As the only star in our Solar System, the Sun is also the closest one to Earth. Its characteristics are shown in the table below. Characteristic Measurement Rotation on its axis at the equator 25.38 Earth days Mass 1.99 3 1030 kg Density 1.41 g cm–3 Surface gravity of the Sun 27.9 3 surface gravity of Earth Diameter 109 3 diameter of Earth Distance from Earth 149.6 million km Temperature of the surface 5500°C Temperature of the core 15 million°C Time taken for its light to reach the Earth 8 minutes What would happen if the Sun is further away from Earth? Think About It Characteristics of the Sun Chapter 7 Earth and the Solar System 197 ©Praxis Publishing_Focus On Science
The Sun is made up of two main layers, which are the inner layers (core, radiation zone, convection zone) and the Sun’s atmospheric layers (photosphere, chromosphere, corona). Besides being the source of light and heat, there are other phenomena that occur on the surface of the Sun that affect the lives on Earth. The phenomena are solar prominence, solar flares, sunspots and solar wind. Solar prominences are large, bright features that extend out from the Sun’s surface in a ring shape, and can contain plasma, hydrogen and helium gases. They typically last for several days or months. Solar flares are explosions of hot gas that occur in the chromosphere layer. During a flare, charged particles such as electrons, protons and gamma rays are released. Flares usually occur near sunspots and last for a few minutes or hours. Sunspots are dark regions on the photosphere. They appear darker than their surroundings because they are cooler and emit less light. They typically last for a few weeks and are associated with strong magnetic fields. While sunspots do not cause droughts on Earth directly, they are sometimes associated with changes in the Sun’s activity that can affect our planet’s climate. Solar wind is a stream of charged particles, including electrons, protons and alpha particles, that flows outward from the Sun and fills the Solar System. The solar wind can reach speeds of hundreds of kilometres per second and interacts with the Earth’s magnetic field to create a protective bubble called the magnetosphere. When the solar wind is particularly strong, it can cause the aurora borealis and aurora australis. While sunspots and solar flares can affect the strength of the solar wind, they do not directly cause the aurora. Instead, they can produce energetic particles that can interact with the Earth’s magnetic field and trigger auroras. Prominence Sunspot Solar flare Chromosphere Photosphere Convection zone Radiation zone Core Corona The structure of the Sun 198 ©Praxis Publishing_Focus On Science
Solar Eclipse A solar eclipse occurs when the Moon passes between the Sun and the Earth in a straight line, causing the Moon to block some of the Sun’s light and casting a shadow on the Earth. Solar eclipses can only be seen by those in the part of the Earth experiencing daytime at the time of the eclipse. Penumbra Umbra Total eclipse Partial eclipse Moon’s orbit Sun Moon Earth Resource When the Moon blocks the Sun, it produces a shadow with two regions, the umbra and the penumbra. The part of the Earth that is in the umbra region experiences a total eclipse. The sky in that area will gradually turn dark and the people will experience total darkness for a few minutes even though it is daytime. The people in the penumbra region will not be able to see a part of the Sun and will experience a partial eclipse. The shape of the Sun during a solar eclipse is shown in the sequence below. Total solar eclipse Chapter 7 Earth and the Solar System 199 ©Praxis Publishing_Focus On Science
1 The eight planets in the Solar System are Mercury, , Earth, Mars, , Saturn, Uranus and Neptune. 2 Each planet rotates on its axis and orbits around the Sun. While orbiting, the planets do not have a fixed from the Sun. 3 The terrestrial planets are made up of while the four planets farther away from the Sun are made up of swirling layers of . 4 Saturn is the only planet that has a system made up of ice, rocky material and dust. 5 Celestial bodies that orbit other celestial bodies with higher mass are known as . 6 The difference between dwarf planets and planets is the orbital path of a dwarf planet is scattered with other objects such as and asteroids. 7 Comets are objects most of which originate from the Kuiper Belt and Oort Cloud. 8 Asteroids are rocky and metal objects that are found in asteroid belts between and . 9 Meteoroids are fragments of rock from asteroids, but they are known as when they enter the Earth’s atmosphere. 10 The Earth on its axis and around the Sun, causing day and night, and the seasons to occur. 11 We observe the Moon changing because it reflects light from the Sun when it orbits around the Earth. 12 A eclipse occurs when the Sun, Earth and Moon are in a straight line and the Moon moves into the Earth’s shadow. 13 Tides are the alternate rising and falling of the ocean water level in a day caused by the force of the Moon. 14 GNSS receivers are integrated into smartphones to support applications that show maps and which are useful in transportation to determine their precise locations. 15 The Sun is in the centre of the Solar System that is made up of core, radiation zone, convection zone, photosphere, and corona. 16 The examples of phenomena that occur on the surface of the Sun are solar prominence, solar flare, and solar wind. 17 When the Moon is in a straight line between the Sun and the Earth, it blocks some light from the Sun from reaching the Earth, forming a eclipse. RECALL Fill in the missing words. 200 ©Praxis Publishing_Focus On Science
THINKING CAP Put on your 1 Why aren’t meteors visible during the day? 2 Do you think that the Moon would still have phases if it emitted its own light? Explain your opinion. 3 How does the classification of the Sun as a star relate to its physical properties and behaviour? Chapter 7 Earth and the Solar System 201 ©Praxis Publishing_Focus On Science
Project Activity objective: Brainstorm the characteristics that make Earth a planet for living things and how an individual can contribute to save the Earth. Problem statement: Scientists believe the Earth can support life due to its characteristics such as mineral richness, surface temperature and atmospheric content. However, human activities for decades had resulted in the destruction of the natural environment, depletion of natural resources and changing of climate. It is the responsibility of every individual to save the Earth as it is the only planet that can support living things. Procedure: 1 Split the class into groups. Each group is to identify the following facts: (a) The reason why the Earth is the most suitable planet for living things. (b) Can other planets support life if Earth’s resources run out? 2 Students in each group discuss, then search information on the Internet and books. List down all the references. Concept applied: The Earth as a planet for living things Action plan: 1 Carry out a forum which consists of five students in each group. 2 Appoint a leader in each of the groups. 3 Do a brainstorming on the topic given. 4 Other group members record the outcomes of the brainstorming session. Solution: The brainstorming must include at least the following aspects. You are encouraged to add more: (a) Characteristics of the Earth that makes it a planet suitable for life, such as water content, oxygen content and sunlight (b) The role of every individual in saving the Earth, such as the use of energysaving devices and practicing 5R (refuse, reduce, reuse, repurpose, recycle). Presentation: Present the findings using Microsoft Powerpoint. Then, submit a complete report. The Earth as a Planet for Living Things 202 ©Praxis Publishing_Focus On Science
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