Earth and the Sun Science Ms. Arce

Vocabulary Rotation – a complete spin on an axis International Date Line – the 180° line of longitude. If you pass the IDL going west you add a day. Standard time zone – a belt 15° wide in longitude in which all places have the same time. Earth has 24 time zones. Revolution – one complete trip around the sun

Earth’s Rotation Does the sun move in the sky? –NO!!! It APPEARS to move, but it is actually the Earth that rotates from east to west in a 24 hour period. Earth rotates (spins) on its axis.

Earth’s Rotation One rotation is a complete spin. It takes 24 hours for the earth to make 1 rotation. (that's a rate of 1000 miles per hour!) It's Earth's rotation that gives us night and day.

How do we know? Data from satellites Foucault's PendulumFoucault's Pendulum

Foucault's Pendulum What does Foucault’s pendulum prove? Why don’t people and other objects fly off Earth if it is rotating so fast? How does the Foucault pendulum demonstrate the Earth’s rotation?

The Sun’s Path The Sun rises in the east. It seems to travel west, rising higher in the sky as the day passes. At noon the Sun reaches its highest point in the sky. After noon it appears to get lower in the sky until it sets in the west.

How can you tell the time of day by the position of the sun in the sky?

Revolution How is summer different from winter? What causes this difference? Earth takes 365 ¼ days to revolve, or travel in its orbit, once around the sun. One complete trip around the Sun is a revolution. Explore a model of Earth's yearly revolution around the sunExplore a model of Earth's yearly revolution around the sun

Earth’s Tilt While Earth is revolving, it is also rotating on its axis. The axis is not vertical. It is tilted 23½°. The effect of this tilt is the cycle of seasons. Observe the Earth’s Tilt with Earth-Sun Relations.Earth-Sun Relations

Why do we have seasons?

Seasons… Reasons for Seasons PPT Seasons and Earth - Sun Relations

Seasons Consider what a difference it would make if the earth’s orbit was very elliptical. How might this affect seasons? How would summer and winter in the northern hemisphere change if instead of being at about the same distances from the sun, summer for the northern hemisphere occurred at perihelion (the point on the orbit closest to sun) and winter for the northern hemisphere occurred at aphelion (the point on the orbit farthest from the sun)? How would seasons occurring in the southern hemisphere be affected this change in the Earth’s orbit?

What would happen during different seasons if the earth’s axis were not tilted at 23.5º, but rather at 0º? How about 60º? Or 90º? How would these different tilts affect different climate regions such as the Tropics or Polar Regions? Seasons

The Sun’s Path The Sun’s path in the sky is different in winter and in summer.

Length of Daylight The length of daylight depends on the season - longer days in summer, shorter days in winter. Have you noticed that it is getting dark earlier?

Length of Daylight The length of daylight also depends on the latitude of the location on Earth. Near the North Pole, the Sun does not set from the first day of spring to the first day of autumn. This is called midnight sun.

Time Zones Earth spins towards the east. It rotates 360° (one complete turn) in 24 hours. In one hour Earth turns 360 ÷ 24 hours = 15°. We call this a time zone. There is a one hour difference for time zones that are next to each other.

What time is it? When you cross time zones, you have to change your clock time. If you travel west, you must turn your clock back (subtract) one hour for each time zone that is crossed. If you travel east, you must set your clock ahead (add) an hour for each time zone you cross.

Jet Lag Traveling between time zones can often result in a condition called jet lag, which occurs when the body’s clock is set to the time zone that the person has just left rather than the one the person is in. Disorientation and sleep difficulties are the results of jet lag.

Time Zones

Sun = Energy Source The sun is the energy source for life on Earth. Plants require the Sun’s energy for photosynthesis. Fossil Fuels – chain of energy from past to today. Energy source for water cycle.

Let’s Review Earth Rotation & Revolution Around a Moving SunEarth Rotation & Revolution Around a Moving Sun Observing the Sky Informational Website Earth, Sun & Moon Jeopardy How does this video show Earth's rotation AND revolution?How does this video show Earth's rotation AND revolution?