Coriolis Effect 2 Evidence for Rotation n Coriolis

Coriolis Effect

2. Evidence for Rotation n Coriolis Effect – the tendency of objects moving over the earth (air, water, planes, projectiles) to be deflected (curve away) from a straight line path. The French scientist, Gaspard Coriolis, first explained the deflection of objects moving over the surface due to Earth’s rotation n The deflection is to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. n This deflection occurs because Earth’s surface is rotating with respect to the objects.

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Actual motion

North Pole Projectile A hockey puck is launched from the north pole. As it heads south, the earth turns to the east, causing the puck to appear to deflect to the west as viewed by an earthbound observer. n Legend: n Red: Path on rotating earth n Gray: Path on stationary earth n

Coriolis Effect n The tendency for any moving body on or above the earth's surface, e. g. , an ocean current, wind or an artillery round, to drift sideways from its course because of the earth's rotation.

The true shape of the Earth called an Oblate Spheroid. n The diameter from the North Pole to the South Pole (the shortest diameter) is approximately 12, 714 km. The equatorial diameter (the longest diameter) is approximately 12, 756 km. This is not a big difference, but it does make the Earth not quite a sphere.

Don’t Copy • Something hanging from a fixed point which, when pulled back and released, is free to swing down by force of gravity and then out and up because of its inertia. • Inertia: means that bodies in motion, will stay in motion; bodies at rest, will stay at rest, unless acted on by an outside force.

1. Evidence of Earth’s Rotation n 1851, Foucault’s pendulum will appear to change in a predictable way. n Why is this evidence? There is no force acting on the pendulum to make its plane of oscillation rotate or go around its own axis n It would continue to swing in the original path if Earth did not rotate.

No force that makes pendulum rotate – must be earth that is rotating!!!

Foucault pendulum n As you watch the pendulum for just a short time, it will appear to be moving clockwise across the mosaic map on the floor. n But, since there is no outside force making the pendulum rotate as it swings, and no other outside force interrupting the swing, it must be the floor itself that is rotating, while the path of the pendulum’s swing remains constant.

What are the APPARENT MOTIONS of Celestial Objects n An apparent motion can be real or an illusion n For example, the stars appear to move across the sky from east to west n However, the apparent motion is caused by Earth’s rotation

Pointer Stars point to Polaris

• Looking upward we see the stars fixed on the celestial sphere • Earth’s eastward rotation makes the stars between the equator and north celestial pole appear to move westward • Rise in the east and set in the west. • Timed photography showing stars rising in the east

Earth’s counter clockwise rotation makes the stars appear to rotate counter clockwise around the north celestial pole (Polaris).

Evidence of Earth’s Revolution around the Sun n Seasonal Constellations: Because of the Sun’s annual motion, some constellations are visible at night only during certain seasons. n Constellations are visible when the dark side of Earth (away from sun) faces toward the constellation.

The 13 constellations the sun appears to travel through during the year