2 What causes day and night? An imaginary line that passes through Earth’s poles is called its axis. Earth’s axis is tilted about 23.5 degrees.Earth spins, or rotates, around its axis once every 24 hours, causing day and night.2
3 What causes Earth’s seasons? Earth revolves around the sun once every year.Earth is tilted at an angle of 23.5 degrees on its axis.Seasons are caused by the combination of these two factors.3
4 How does sunlight strike Earth? Near the equator, sunlight hits Earth’s surface from almost overhead.Near the poles, sunlight hits Earth at a steep angle.This makes areas near the equator warmer than areas near the poles.4
5 How does each season occur? When the Northern Hemisphere faces toward the sun, it is summer there and winter in the Southern Hemisphere.When the Northern Hemisphere faces away from the sun, it is winter there and summer in the Southern Hemisphere.5
7 Half of the Moon is always lit up by the sun Half of the Moon is always lit up by the sun. As the Moon orbits the Earth, we see different parts of the lighted area. From Earth, the lit portion we see of the moon waxes (grows) and wanes (shrinks).
8 The revolution of the Moon around the Earth makes the Moon look as if it is changing shape in the sky.
10 The Moon passes through four major shapes during a cycle that repeats itself every 29.5 days. The phases always follow one another in the same order:New moonWaxing CrescentFirst quarterWaxing GibbousFull moonWaning GibbousThird (last) QuarterWaning Crescent
11 TEST TRICK! IF LIT FROM THE RIGHT, IT IS WAXING OR GROWING IF DARKENING FROM THE RIGHT, IT IS WANING (SHRINKING)
15 TidesBesides its visual benefits, the Moon's gravitational pull on the Earth cause the seas and oceans to rise and fall in an endless cycle of low and high tides.Much of the Earth's shoreline life depends on the tides.Crabs, starfish, mussels, barnacles, etc.
16 Tides caused by the Moon The Earth's tides are caused by the gravitational pull of the Moon. The Earth bulges slightly both toward and away from the Moon. As the Earth rotates daily, the bulges move across the Earth.The moon pulls strongly on the water on the side of Earth closest to the moon, causing the water to bulge. It also pulls less strongly on Earth and on the water on the far side of Earth, which results in tides.
17 What causes tides?Tides are the rise and fall of ocean water. Water levels rise to their highest point of the day and fall to their lowest point every 12.5 hours.The tides result from the rotation of Earth on its axis as gravity from the moon and the sun pull on Earth and its water.Think of a model of Earth, without the pull of gravity from the sun or the moon, as looking something like the illustration below.17
19 High vs. Low TidesA view of the tides at Halls Harbor on Nova Scotia's Bay of Fundy. This is a time lapse of the tidal rise and fall over a period of six and a half hours. During the next six hours of ebb the fishermen unload their boats on the dock.
20 Spring Tides-Though the sun is much farther from Earth than the moon, its huge mass exerts a pull of gravity that also affects Earth’s ocean tides.Together, the effects of the sun and the moon depend on the moon’s phase—the position of the moon relative to the sun and Earth.During new moon or full moon, the sun, the moon, and Earth are in a line. The result is a spring tide.
21 Spring TideSun, Moon, and the Earth are in a straight line = strongest, largest tide but Spring Tides occur when SME are in a right angle.SunMoonEarth = Very Strong Spring TidesAt a right angle = Still high tides but not as strong21
22 Neap TidesNeap Tides:During first quarter of the lunar month, the line from the moon to Earth is at a right angle to the line between Earth and the sun. The result is a neap tide. The same effect happens during third quarter.
23 Neap TidesThese occur during first and last quarter moons. The gravitational pull is not as strong.Sun EarthMoon
24 Earth-Moon-Sun positions and the monthly tidal cycle Spring TideHighest high tide and lowest low tideNeap TideModerate tidal range
25 Description of tides High water: a water level maximum ("high tide") Low water: a water level minimum ("low tide")Tidal range: the difference between high and low tideSpring Tide: full moon and new moon (14.77 days)Neap Tide: 1st quarter and 3rd quarter (14.77 days)Intertidal zoneHigh tideLow tide
26 How many times does Earth spin on it’s axis daily? How many high tides occur daily?TwoHow many weekly?FourteenHow many in 30 days?Sixty
27 STUDY THESE NOTES AND YOUR ASTRONOMY NOTES FOR A QUIZ ON FRIDAY!