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NIS – PHYSICAL SCIENCE

# NIS – PHYSICAL SCIENCE

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## NIS – PHYSICAL SCIENCE

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1. NIS – PHYSICAL SCIENCE Lecture 28 Earth in Space OzgurUnal

2. Shape of Earth • If you were living in old times without technology, how would you prove that Earth is similar to a sphere in shape?

3. Earth’s Size and Shape • No matter where you are on Earth, objects fall straight down to the surface, as if they are falling • toward the enter of a sphere. Figure 1 • Earth’s shadow on the Moon during • a lunar eclipse is • always curved. • People in different parts of the world see • different stars above their horizon. More • specifically, the pole star Polaris is lower in • the sky at some locations on Earth than at • others.

4. Earth’s Size and Shape • How is gravity related to the shape of Earth and other planets? • Fg = G*M*m/r2 • The fact that the gravitational • force depends on the distance and • masses only results in the spherical • shapes of stars, planets and moons. • Check out Table 1 for the physical • properties fo Earth.

5. Earth’s Magnetic Field • Examine the magnets given to you. • Try to feel the force and the field between the magnets. • Earth’s rotation and movement of matter in the core set up a strong magnetic field in and around • the Earth. • Earth’s magnetic field is • concentrated at two ends of an • imaginary magnetic axis running • from Earth’s north magnetic pole to • its south magnetic pole. • This axis is tilted about 11.5 degrees • from Earth’s axis of rotation.

6. Earth’s Magnetic Field • The locations of Earth’s magnetic poles change slowly over time. • The magnetic north pole is carefully remapped periodically to pinpoint this location. • Van Allen Belts

7. Earth’s Magnetic Field • Earth’s magnetic field protects life from harmful radiation. • Harmful radiation coming from the Sun (solar wind) is deflected by this magnetic field. • Deflected radiation interacts with the atmosphere, producing light. • Aurora borealis and • Aurora australis

8. Earth Orbits the Sun • Earth’s orbit is an ellipse with two foci. • The Sun is located in one of the focal points. • Earth is closest to the Sun with 147 million km on January 3. • Earth is farthest from the Sun with 152 million km on July 4.