Lecture 28 Earth in Space Ozgur Unal NIS – PHYSICAL SCIENCE Lecture 28 Earth in Space Ozgur Unal

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?

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.

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.

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.

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

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

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.