UNIT 4 ASTRONOMY: Space Cycles, Seasons, Moon Phases & Tides-8th grade

Lunar Cycle

A sequence of phases of the moon as it revolves around the Earth once every 27.3 days. It takes the moon approximately ONE MONTH to complete one lunar cycle.

Axis

An imaginary line that passes through Earth's center and its North and South Poles

When do Neap Tides occur?

During 1st & 3rd/Last Quarter of the Lunar Cycle

When do Spring Tides occur?

During New and Full Moon of the Lunar Cycle

Why does Earth have seasons?

Earth's axis is TILTED, causing part to "lean" into the sun during certain times of the year and part to "lean" away from the sun. If we were not titled, we'd have NO seasons!

Revolution

Earth's movement around the sun, which takes about 365 1/4 days to complete. This gives us our year and seasons.

Why is the Moon's influence on Earth's tides greater than the Sun?

Even though the Sun is MUCH bigger than our Moon, because the Moon is closer to Earth, it has more *gravitational* influence on our tides.

Autumnal Equinox

First day of Fall Occurs on September 22nd in the Northern Hemisphere

Vernal Equinox

First day of Spring Occurs on March 19th in the Northern Hemisphere

Summer Solstice

First day of Summer Occurs on June 20th in the Northern Hemisphere *Days are LONGER* (have more daylight hours)

Winter Solstice

First day of Winter Occurs around December 21st in the Northern Hemisphere *Days are SHORTER* (have fewer daylight hours)

Summer Solstice

Longest amount of daylight hours (days are longest). Sunlight hitting Earth is *DIRECT* so we receive more energy. It's hotter.

First Quarter

Looks like a "D"

Third or Last Quarter

Looks like a backward "D"

Full Moon

Moon phase that occurs when the Earth is between the Moon and the Sun. The moon's surface facing Earth is fully visible during this phase. HINT: The moon is FARTHEST from the sun during Full Moon. F=Furthest F=Full

New Moon

Moon phase that occurs when the Moon is between Earth and the Sun, at which point the Moon cannot be seen on Earth. HINT: The moon is NEAREST to the sun at New Moon. N = Near N = New

Neap Tides - How are Earth, Moon & Sun aligned?

Occur when the Sun, Earth, and Moon are in a NINETY degree angle.

Spring Tides - How are Earth, Moon & Sun aligned?

Occur when the Sun, Earth, and Moon are in a STRAIGHT LINE.

Lunar

Relating to the moon.

Solar

Relating to the sun.

Winter Solstice

Shortest amount of daylight hours (days are shortest). Sunlight hitting Earth is *INDIRECT* so we receive less energy. It's colder.

Rotation

Spinning of Earth on its imaginary axis, which takes about 24 hours to complete. This gives us day and night.

North Pole Pointed Toward Sun

Summer in Northern Hemisphere

South Pole Pointed Toward Sun

Summer in Southern Hemisphere

What causes tides on Earth?

The *gravitational* pull of the Moon / Sun and Earth rotating on it's axis.

High Tides

The Moon's gravitational pull is greatest on the part of Earth directly facing it -AND- the opposite side of Earth. This is when the water goes up onto the shore (less beach showing).

Waxing

The lit portion of the moon gets larger. In the Northern Hemisphere, the moon waxes (appears to grow) from the right side.

Waning

The lit portion of the moon gets smaller. In the Northern Hemisphere, the moon wanes (appears to get smaller) to the left side.

Time Between Each Phase (Step) of the Lunar Cycle

There are approximately 3.5 days in between each phase (step) of the lunar cycle. For example, it takes approximately 3.5 days to go from new moon to waxing crescent. Another example: it takes about 1 week to go from full moon to new moon.

Time Between Each Season

There are ~ 3 months in between in each season.

Spring Tides - What are they?

This is when the low tides are the lowest, and the high tides are the highest. *BIG* difference between high and low tides.

Neap Tides - What are they?

This is when there is very little difference between low and high tides.

Low Tides

This occurs on the areas of Earth not being directly pulled by the Moon's gravity at that moment. This is when the water goes back into the ocean (more beach showing).

How often does a water-lined area (example: a beach) have high and low tides?

Water-lined areas (for example, beaches) experience TWO high tides and TWO low tides EVERY SINGLE day. But during certain times of the month, there is a BIG difference between the high and low tides (called *Spring Tides*). During other times of the month, there is LITTLE difference between the high and low tides (called *Neap Tides*).

Equinoxes

When day and night hours are of equal length in both hemispheres. Equinox = "Equi" means equal

North Pole Pointed Away From Sun

Winter in Northern Hemisphere

South Pole Pointed Away From Sun

Winter in Southern Hemisphere