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

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.