Astronomical Terms Rotation –Motion around an axis –Produces day/night From: physicalgeography.net.
Day, Night & seasons?harwordacademy.com/wp-content/uploads/2019/07/11.-Day-Night-Seasons.pdf ·...
Transcript of Day, Night & seasons?harwordacademy.com/wp-content/uploads/2019/07/11.-Day-Night-Seasons.pdf ·...
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Day, Night &
seasons?
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Earth’s rotation
• The Earth rotates on its axis (imaginary vertical line around which Earth spins) every 23hours & 56 minutes.
• One day on Earth is one rotation of the Earth.
• One Day on Earth is when our side of the Earth faces the sun.
• Night on Earth is when the side of Earth we are on faces away from the sun.
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CYCLE OF NIGHT AND DAY
• The cycle of night and day occurs because the Earth rotates.
• To ROTATE means to turn on an axis.
• An AXIS is an imaginary line through the center of an object. The Earth’s axis passes through the North and South poles.
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• Remember that the Earth is a sphere. Only one half of the Earth receives light and heat from the Sun at any given time.
• The other half of the Earth is dark, and it is nighttime there.
• Since the Earth rotates, the half that receives light and the half that is dark changes positions throughout the rotation of the Earth.
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• As the day goes on, the Sun appears to move across the sky.
• THE SUN IS NOT MOVING. Instead, Earth is rotating, causing the Sun to look like it is moving.
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Earth’s revolution
• It takes the Earth 365.25days (or rotations) to travel or revolve around the Sun once.
• This is called a year.
Orbit
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Motion Terminology
• Rotation – to spin on an axis
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Motion Terminology
• Revolution – the motion of a body around another body
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Motion Terminology
• Orbit – the path that is followed around another body in space
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Why do we have seasons?
• The Earth’s orbit around the sun is NOT a perfect circle. It is an ellipse.
• Seasons are not caused by how close the Earth is to the sun.
• In fact, the Earth is closest to the sun around January 3 and farthest away from the sun around July 4.
Ellipse
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Why do we have seasons?
• Seasons are the result of the tiltof 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.
• Seasons Interactive
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Why do we have seasons?• Summer is warmer than winter (in each hemisphere)
because the Sun's rays hit the Earth at a more directangle during summer than during winter
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Why do we have seasons?
• Also the days are much longer than the nights during the summer.
• During the winter, the Sun's rays hit the Earth at an extreme angle, and the days are very short. These effects are due to the tilt of the Earth's axis.
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Seasons…in a nut shell
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Solstices
• Occur twice a year, when the tilt of the Earth's axis is oriented at its extremes. Tilted the farthest or closest
• Winter solstice is the shortest day of the year. In the Northern Hemisphere. It occurs on December 21 or 22 and marks the beginning of winter.
• The Summer Solstice is the longest day of the year. It occurs on June 20 or 21 and marks the beginning of summer.
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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.
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Equinox
• The vernal (spring) equinox occurs March 20.
• The autumnal (fall) equinox occurs September 22 or 23.
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The Earth's seasons are not caused by the differences in the distance from the Sun throughout the year.
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ReviewLook closely at where the Sun is hitting the Earth during each season:
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Thanks