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Review vocabulary & questions

What causes "day and night" on earth?

What causes our seasons (winter, spring, summer, fall)?

What is the difference between "the Earth rotates on its axis" versus "the Earth revolves around the Sun?" The Earth rotates about its axis every 24 hours. Also, the Earth revolves around the Sun every 365 days.

Explain how the tilt of the Earth's axis (by 23.5 degrees) results in the seasons due to the amount of solar energy impacting the surface of the Earth.

Be very familiar with latitude, longitude, North Pole, South Pole, Equator, Northern Hemisphere, Southern Hemisphere.

The Universe is made of galaxies which are made of an enormous number of stars. Our galaxy, the Milky Way, has billions of stars. Some stars have planetary systems similar to our solar system. The Earth is a satellite planet of one particular star, our Sun.

Explain the relative motion of the Earth in the solar system, the solar system in the galaxy, and the galaxy in the universe, including the expanding nature of the universe.

Describe daily changes due to the Earth's rotation, seasonal changes due to the Earth's tilt, the revolution of the Earth around the sun, and tidal impact due to the gravitational interaction between the Earth and moon.

Develop a "cause and effect model" for the shape of the Earth, explaining why the circumference around the Earth's equator is larger than it is around the poles (North Pole - South Pole).


Our Sun and its Radiant Energy

Is our Sun stationary in our solar system? No, it actually moves as the planets tug on it, causing it to orbit the solar system's barycenter. The Sun never strays far from the solar system barycenter.

Fusion is the process that produces the radiant energy of stars, including our Sun. (Discuss fusion on the sun versus nuclear fission at a nuclear power plant.)

Identify the forms of radiant energy, also called electromagnetic radiation, produced by the Sun. Discuss how, fortunately, the Earth's atmosphere filters out much of the Ultraviolet radiation.

Explain how energy flows from the sun to the Earth through space.


Kepler's Laws & Planetary Orbits

The orbit of a planet around the Sun is an ellipse.

A line from the planet to the Sun sweeps out equal areas in equal amounts of time.

The square of the sidereal period (of revolution) of the planet is directly proportional to the cube of the mean distance from the Sun.


Barycenter

Do you recall the "seesaw" at the children's park? The barycenter is the point between two objects where they balance each other.

In general, the barycenter is the center of mass where two or more celestial bodies orbit each other. When a moon orbits a planet, or a planet orbits a star, both bodies are actually orbiting around a point that lies outside the center of the more massive object.

For example, the moon does not orbit the exact center of the Earth. Instead, it orbits a point on a line between the Earth and the Moon. However, that point is approximately 1,710 km below the surface of the Earth, where mass of the Earth and the Moon are balanced. (This is the point about which the Earth and Moon orbit as they travel around the Sun.)


Earth and Sun

Explain the rotation of the Earth around its axis, causing day & night). Explain the orbital motion of the Earth revolving around the Sun. A complete orbit occurs once per year.

Our seasons are a result of the 23.5 degree tilt of the Earth. (The seasons are NOT due to how close the Earth is to the Sun at any given time during the year.)

Explain the Earth's precession. That is, the change in direction of the Earth's axis, but without any change in tilt. Precession results in changes to the star(s) that we observe at the Pole. However, it does not affect the seasons (as long as the tilt angle of 23.5 degrees stays the same).

Explain nutation around the Earth's precessional axis, which is a very small change in the angle of the axis. It occurs over an 18-year period and is due to the Moon. Nutation is able to slightly increase (or decrease) the amount of seasonal effects on Earth.

Why does the Earth's equator bulge?

Explain how solar energy is transformed into chemical energy through photosynthesis.


Differential Heating of the Earth's Surface - Water versus Land

Water is a slow conductor of heat. It needs to gain more energy than the sand or dry land in order for its temperature to increase. As a result, the land is warmer than the nearby ocean in the summer. On the other hand, soil loses its heat much faster. The Earth's oceans are far more important than the land as a source of the heat energy which drives the weather. Not only do the oceans cover more than two-thirds of the Earth's surface, they also absorb more sunlight and store more heat. Additionally, the oceans retain heat longer.


Earth's Magnetic Field Protects our Planet

The rotation of the Earth's molten iron core produces magnetic field lines much like a bar magnet. This magnetic field extends more than a thousand miles out from the surface of the Earth. The Sun produces a constant stream of particles called the solar wind. The charged particles of the solar wind cannot easily penetrate the Earth's magnetic field. The solar wind compresses and confines the magnetic field on the side of the Earth toward the Sun and stretches it out into a long tail on the night side of the Earth. The cavity formed by this process is called the "magnetosphere." It shelters the surface of the Earth from constant bombardment by charged particles.