Physics (P71)

Physics (P71)

1. The earth rotates west-east on its axis once in under 24 hours while the sun travels every 24 hours. The rotation makes stars appear to move east-west across the sky in under 24 hours. Sun, Planets and Moon travel east-west but their motion and time is affected by orbits.

2. Sidereal day: the time it takes for the Earth to rotate 360 degrees on its axis. It is shorter than a solar day because the earth rotates once on its axis whilst it orbits the sun; it is 4 minutes shorter.

3. Solar day: the time from noon on one day to noon on the next e.g. 24 hours.

4. Different stars move at different times of the year. The stars that are seen depend on the Earth's position in relation to the Suns.

5. Declination: measured south and north of the celestial equator; its the number of degrees away from the celestial pole. Positive declination- visible from northern hemisphere; negative declination- visinle from southern hemisphere.

6. Right Ascension are lines going away from the the celestial pole.

7. Retrograde motion is when planets or stars appear to move backwards against the background of fixed stars.

8. The Earth rotates on its axis and the moon orbits in the same direction. The moon appears to travel east-west across the sky in over 24 hours.

9. Lunar cycle: the moon's appearance during its 28 day orbit. The moons shape during this orbit is due to the part of the Moon that is visible from Earth. We can see the moon because the Sun's light reflects from it. The side of the moon facing away from sun is dark and the side facing towards is light.

10. A dark face (new moon); light face (full moon) and the points between the new moon and full moon

11. Solar eclipse: the moon passes between earth and the sun. It can happen during a new moon- the moon casts a shadow on Earth. A total solar eclipse: the moon is in front of the sun and obscures the view of the sun. A lunar eclipse: the earh is between the sun and moon- it casts a shadow on the moon.