Moon Phases, Seasons, and Tides Study Guide

Respiration Word Equation:
- $\text{glucose} + \text{oxygen} \rightarrow \text{carbon dioxide} + \text{water} + (\text{energy})$
Photosynthesis Word Equation:
- $\text{carbon dioxide} + \text{water} \rightarrow \text{glucose} + \text{oxygen}$

Definition of the Moon: The Earth possesses one natural moon that revolves around it.
Classification: The moon is classified as a satellite of Earth because it orbits (revolves around) the planet.
Observational Overview: When viewing the night sky from Earth, the appearance of the moon changes throughout the month. These changes are referred to as the phases of the moon, which constitute a cycle in nature.
Mechanism of Appearance:
- As the moon moves (revolves) around the Earth, its shape appears to change to an observer on the surface.
- The physical shape of the moon does not actually change; it remains a sphere.
- The perceived change in shape is strictly due to the moon's changing location in space relative to the Earth and the Sun.

Cycle Duration: It takes the moon approximately one month ( $29\,1/2$ days) to complete a full cycle of phases.
New Moon: During this phase, the moon looks dark from Earth because the side facing Earth is not receiving direct sunlight.
Waxing Phases (Increasing Illumination):
- Waxing Crescent: This occurs as the visible surface of the moon begins to get larger. It appears as a small sliver of light.
- First Quarter Moon: This occurs when the moon is exactly $1/4$ of the way around the Earth in its orbit. To an observer, the moon appears half-lit.
- Waxing Gibbous: This phase occurs after the first quarter as the moon moves toward becoming a full moon. During this time, the bright part of the moon continues to get larger. "Waxing" specifically denotes this increase in the illuminated area visible from Earth.
Full Moon:
- At this point in the cycle, the entire face of the moon that is visible from Earth is fully illuminated by the Sun.
Waning Phases (Decreasing Illumination):
- Waning Gibbous: Following the full moon, the visible surface appears to start getting smaller. This transition phase is called a waning moon.
- Third (Last) Quarter Moon: This occurs when the moon is $3/4$ of the way around the Earth. Like the first quarter, it appears half-lit to an observer.
- Waning Crescent: This is the final sliver of light seen in the sky before the cycle returns to the new moon phase.

Orbital Path: The Earth’s orbit around the sun is not a perfect circle; rather, it is an ellipse.
Common Misconception: Seasons are NOT caused by the distance between the Earth and the sun.
- Numerical Data on Proximity:
  - Earth is closest to the sun around January 3rd.
  - Earth is farthest away from the sun around July 4th.
The Primary Cause of Seasons: Seasons are the direct result of the tilt of the Earth's axis.
- Axial Tilt: The Earth’s axis is tilted at an angle of $23.5^\circ$ .
- Consequences of the Tilt: This tilting creates the four distinct seasons: autumn, winter, spring, and summer.
Hemispheric Effects:
- The number of daylight hours is significantly greater for the hemisphere (half of the Earth) that is tilted toward the Sun.
- Regional Example (Australia):
  - When it is winter in Australia, the Southern Hemisphere is tilted away from the hot, bright rays of the sun.
  - When it is summer in Australia, the Southern Hemisphere is tilted toward the sun’s rays.

Definition of Tides: Tides are the rise and fall of sea levels caused by the effects of gravity pulling on the bodies of water on the Earth and upon the Earth itself.
Gravitational Bodies: There are two primary gravitational bodies that affect Earth's tides:
1. The Sun
2. The Moon
Influence Hierarchy: Although the Sun is much larger, the Moon is much closer to the Earth. Therefore, the Moon has a much greater influence on the tides than the Sun.
Spring Tides:
- Configuration: These occur when the Earth, Moon, and Sun are all aligned in a straight line.
- Lunar Timing: This alignment happens during the Full Moon and New Moon phases.
- Effect: The high tides are much higher than they are at any other time during the lunar cycle.
Neap Tides:
- Configuration: These occur when the Moon and Sun are at right angles ( $90^\circ$ ) to each other relative to the Earth.
- Effect: The high tides are lower than they are at other times during the cycle.