The Earth in Space (2012).pot

The Earth in Space

• The earth revolves around the sun and rotates on it’s axis.

Day and Night

• The earth rotates once on it’s axis

every 24 hours. A day is equal to 24 hours.

• _{As the earth rotates 1/2 of it is facing}

the sun, the other 1/2 is in darkness.

• Since the earth’s axis is tilted at an

angle of 23 1/2º the actual length of day and night varies.

• _{If the Northern Hemisphere is pointing}

toward the sun it has longer days and shorter nights. The Southern

Hemisphere has long nights and short days.

Seasons on Earth

• The tilt of the earth’s axis causes the seasons on earth.

• When the Northern Hemisphere is tilted toward the sun, it has summer. Southern Hemisphere has winter (tilted away).

• _{When Southern Hemisphere is tilted toward}

the sun, it has summer. Northern Hemisphere has winter (tilted away).

• June 20 or 21: summer begins N. Hem., longest day of the year, Summer

Solstice.

• Dec 20 or 21: winter begins N. Hem., shortest day of the year, Winter

Solstice.

• March 20 or 21: Vernal Equinox, day and night are equal length, first day of spring.

Magnetosphere

• The earth has a magnetic field around it in space (acts like a bar magnet in the center). The magnetic field is called the magnetosphere.

• It begins at 1000 km above the surface and extends to 64,000 km on the side facing the sun. On the side away from the sun it is blown out into space by

• Two areas in the magnetosphere trap the deadly solar wind and protect the earth. They are called the Van Allen Radiation Belts.

• Made up of positively charged protons and negatively charged electrons.

• Charged particles are concentrated into Van Allen Radiation Belts.

• Particles trapped by VARB gather at the poles where they collide with each other, friction causes them to glow

• Aurora borealis (northern lights)

The Earth’s Moon

• Less dense than earth- 1/6 gravity

• _{Average distance to moon is 384,403 km} • _{Experiences up to 3,000 moonquakes per}

year

• Crust is 60 km thick, second layer of denser rock about 800 km thick

• 4.6 billion years old

• No liquid water, no atmosphere, no weather

Features of the Moon

highlands) many thousands of meters tall. These are the light areas we see on the

moon.

• _{Has large, smooth, lowland plains called}

Maria. These are the dark areas seen on the moon.

• Has craters which may be the remains of volcanoes.

• _{Has rilles (large, long valleys) which may}

Movements of the Moon

• The moon revolves around the earth in an elliptical orbit.

• Perigee- the point when the moon is closest to the earth (ab. 350,000 km).

• _{Apogee- the point when the moon is}

farthest from the earth (ab. 400,000 km).

• _{The moon’s period of revolution is the}

Origin of the Moon

• 3 theories:

• 1. The moon formed millions or billions of km away and was captured by the

earth’s gravity.

• 2. The moon was formed from the same matter in the nebula as the earth and

sun were.

The Earth, The Sun and The Moon

• Although we have talked about the

motions of the earth, the moon and the sun separately, it’s important to note that they don’t occur separately.

• _{The relative motions of the Earth, the}

moon and the sun result in the phases of the moon, and occasionally an

Phases of the moon

• The moon does not shine with it’s own light but instead reflects sunlight. Depending on the position of the moon, earth and sun we will see different phases.

• _{New Moon: moon is between earth and sun,}

side facing earth is dark, we don’t see a moon

• Waxing Crescent: we can see a lighted slice of the moon

• Full Moon: 1/2 of moon visible

• Waning Gibbous: 3/4 of moon (opposite side)

• Last Quarter: 1/4 of moon (other side)

• Waning Crescent: small slice

• New Moon again.

• Full cycle of phases occurs every 29.5 days.

• A waxing moon is growing larger to the viewer, a waning moon is getting

Eclipses

• 2 types named according to which body, the sun or moon, is blocked

• Solar Eclipse: moon comes between earth and sun, blocks out sunlight

• 2 parts: umbra and penumbra

• umbra- light is totally blocked (total solar eclipse)

• penumbra- light is not totally blocked (partial solar eclipse)

Tides

• Because of the proximity of the moon and

the earth, the moon exerts a gravitational pull on the earth. This pull creates tides.

• _{The side of the earth facing the moon is}

pulled into a bulge (high tide).

• _{The opposite side is also having high tide.} • _{In between the two bulges, the other areas}

• Higher than usual high tides occur

when the earth, moon and sun are in a direct line (during full or new moon).

• These are called spring tides.

• _{Lower than usual high tides occur}

when the earth, moon and sun are at a right angle (first and last quarter).

The Space Age

• Began on Oct. 4, 1957. Russian rocket Sputnik 1 was first artificial satellite to orbit the earth

• _{Artificial Satellites: travel just fast}

enough so that they don’t escape

• There are several different types:

• Communication: telephone, television, radio => are in a geosynchronous orbit (same

speed as earth, so they stay in the same position relative to earth).

• Weather: track and predict weather patterns.

• Navigation: ships and airplanes can determine their locations and avoid collisions.

• Scientific: Laboratories in Space

• Skylab- launched in 1973 by the US