Today’s Objective:
What are Earth’s Motions?
Do Now:
Rotation :
the turning or spinning
of an object on its axis. (spin)
* Gives us DAY & NIGHT *
A Foucault’s Pendulum –
is a weight hung from a fixed point that can move freely, it’s proof that the Earth is rotating
A view of Foucault's pendulum in the Pantheon, Paris; its 4:30.
Click for Video
- Although the pendulum swing back and forth it APPEARS to change its direction of swing as the day goes by.
Mean Solar Day –
- time interval from one noon to the next, about 24 hours.
Sidereal Day –
- the time it takes for Earth to make one complete rotation (360º)
Exactly 23:56:04
Revolution: motion of an object around a point in space (orbit).
* Gives us our YEAR*
Perihelion
to the sun (winter).
Aphelion
from the sun (summer).
Earths Axis:
The tilt of the earth is measured at 23.5 degrees as it revolves around the sun.
* Gives Earth SEASONS*
* The Earth is tilted toward the sun in the summer.
* The Earth is tilted away from the sun in the winter.
Precession – “Wobble” of earths axis
- Third very slow movement of Earth.
(approximately 26,000 years )
- Earth’s axis maintains about
the same angle of tilt, but the
direction in which the axis it
points continually changes.