The sun, the moon and the earth

2. The Effect of the Sun and the Moon on the Earth

2.1 Solar Radiation

• Nuclear reactions of the Sun transform hydrogen into helium which in turn produces energy.

• Solar energy is radiated across the solar system and reaches Earth in 8 minutes.

• Earth’s magnetic field shields and deflects some some of the radiation.

Solar radiation

• Solar radiation contains a wide range of the waves in the electromagnetic spectrum;

• But with different intensities:

Only some of the solar radiation reaches Earth:

• Deflection by magnetic field

• Reflection by atmosphere

• Absorption by atmosphere

• Only visible light, infrared rays and some ultraviolet rays reach Earth’s surface.– These rays heat the oceans, the land and the

atmosphere.– Equatorial regions are hotter because they receive more

solar energy due to Earth’s shape and orientation.

Solar energy• Solar energy = energy that comes from the sun in

the form of radiation through the atmosphere.• Technologies that take advantage of solar energy:

– Passive heating systems: position houses in such a way as to capture as much light and heat as possible.

– Photovoltaic cells: electrons of silicon in these “cells” are activated by light and are set in motion creating an electric current. (solar panels = large assembly of photovoltaic cells)

– Solar collectors = large glass panels that capture heat from sunlight and transfer that heat to water in copper pipes just below the panels.

• notes

• The moon revolves around the Earth and rotates on its own axis.– Rotation and revolution of the moon: 27.3 days.

2.2 The Earth-Moon System

We always face the same side of the moon

• Far side of the moon has a lot more craters from meteor impacts

near far

earth’s bad day: Formation of the moon

• A giant mars sized object hits the early earth

• Debris are splattered into space and form a ring around the earth.

• The moon forms from the ring of debris

Why do we believe this?

Moon composition resembles that of outer earth

Effect of Moon on Earth:

• Tide: the daily rise and fall of water in the seas and oceans.

• It is caused by the gravitational force (pull) of the Moon and, to a lesser extent, the Sun.

• The water bulges in the direction of the Moon.

TIDES

The opposite side of Earth

• Why does the opposite side of the Earth also experience simultaneous tides?

• Centrifugal force pushes water out on opposite side of the earth; here moon’s gravitational pull weakest.

• Two tides per day: once when facing moon and once when on opposite side.

Spring and Neap Tides

• Twice each month, at the time of the new moon and the full moon, the gravitational influences of the moon and sun reinforce one another and cause the tides to rise to greater heights and fall lower than average tides. These are called spring tides

• At the time of the quarter moon, when the sun, earth, and moon form a right angle, the difference between high and low tide is less than average. These are neap tides.

The Bay of Fun…..dy!

• The difference in water levels at low and high tide is called the tidal range.

• The Bay of Fundy (near Nova Scotia) has tides with a range of up to 17 meters.

Tidal Energy

• Tidal energy: the energy obtained from the ebb and flow of tides.

• When the tide comes in it fills a water basin. When the tide goes out it creates a difference in water level between the basin and the sea.

• When a gate is opened, the water in the basin is released to flow through a turbine which generates an electric current.

Tidal energy• Advantages

– Renewable energy source– No GHG– Reliable because tides are predictable according to

the positions of the Sun and the Moon.• Disadvantages

– Costly installation– Few places with high tidal range (minimum of five

meters required)

• Notes• Homework: – p. 104 #3, 4– P. 110 all– P 126 # 4– P. 128 all– P 130 all