Key Concepts What are solar and lunar eclipses? What causes the tides? Seasons, eclipses, and tides Key Concepts What are solar and lunar eclipses? What causes the tides?

WHY DO WE HAVE SEASONS? Seasons are the result of the tilt of the Earth's axis. Earth’s axis is tilted 23.5°. This tilting is why we have SEASONS like fall, winter, spring, summer. The number of daylight hours is greater for the hemisphere, or half of Earth, that is tilted toward the Sun.

SOLSTICES Solstices occur twice a year, when the tilt of the Earth's axis is oriented directly towards or away from the Sun, causing the Sun to appear to reach its northernmost and southernmost extremes. Winter solstice is the shortest day of the year. In the Northern Hemisphere. It occurs on December 21 and marks the beginning of winter. The Summer Solstice is the longest day of the year. It occurs on June 21 and marks the beginning of summer.

SOLSTICE During the winter the Northern Hemisphere day lasts fewer than 12 hours and the Southern Hemisphere day lasts more than 12 hours. During the winter solstice, the North Pole has a 24-hour night and the South Pole has a 24-hour day. Sunlight strikes the earth most directly at the Tropic of Capricorn. http://k12.ocs.ou.edu/teachers/reference/solstice.gif

EQUINOXES A day lasts 12 hours and a night lasts 12 hours at all latitudes. Equinox literally means "equal night". Sunlight strikes the earth most directly at the equator. This occurs twice a year. http://k12.ocs.ou.edu/teachers/reference/equinox.gif

EQUINOX The vernal (spring) equinox occurs March 21. The autumnal (fall) equinox occurs September 21.

Eclipses Occurs when: moon’s shadow hits Earth or Earth’s shadow hits moon When an object in space comes between the sun and a third object it casts shadow on that object = eclipse

When do solar eclipses occur? New moon – moon is between sun and Earth Most months the moon is a little above or below sun in the sky. Solar eclipse occurs when the moon passes directly between the Earth and sun, blocking light from the sun

Partial Solar Eclipse Not safe to look at the sun during a partial eclipse because an extremely bright part of the sun remains visible

When do Lunar Eclipses Occur? During the full moon when the Earth is directly between the sun and moon Moon is in Earth’s shadow

Total Lunar Eclipses Earth’s shadow has an umbra and penumbra When moon is in Earth’s umbra – you see a total lunar eclipse Can see total lunar eclipse from anywhere on Earth

Partial Lunar Eclipse Most lunar eclipses, Earth, the moon and the sun are not quite in line = partial lunar eclipse Brainpop: Eclipses Youtube: Eclipse

Tides Rise and fall of ocean water that occurs every 12.5 hours Water rises for 6 hours and then falls for 6 hours Caused by differences in how much the moon’s gravity pulls on different parts of Earth Bay of Fundy Tides Video

The Tide Cycle High tides occur on the side of the Earth closest to the moon due to the moon’s gravity pulling on the water High tides also occur on the side of the Earth farthest from the moon. The moon’s gravity pulls on the Earth more strongly than it pulls on the water leaving it behind In between the two high tides, low tides occur Study Jams video

STOP Pick up from here after moon phases

The Tide Cycle

Spring Tides Sun’s gravity pulls on Earth’s waters During a new moon – sun, moon and Earth are nearly in a line. Gravity of sun and moon pull in same direction Combination of forces produce tide with greatest difference between low and high tide Called a spring tide – occur twice a month during full and new moons

Neap Tides During moon’s 1st and 3rd quarter, line between Earth and the sun is at right angles to line between Earth and moon. Sun’s pull is at right angles to moon’s pull. Produces a neap tide = least difference between high and low tide Occur twice a month

Spring Tides and Neap Tides