Earth in Space(a work in progress)

Dr. Alan F. Weekes

AstronomyPossibly the oldest science

Contrast with astrology: belief systemThe belief that the positions of the planets and the sun at the time of your birth affects your personality and your future.

CalendarsSeasons, festivals, time, flood of the NileYear

The time it takes for the sun to rise in the same place~365 ¼ days

MonthRoughly the time for the moon to go through its set of phasesSome cultures exactly a month, from new moon to new moon

Asian, Jewish, Moslem29.5 days from new moon to new moon

• Day– from sunrise to sunrise– 24 hr.

• Week– Named for visible moving objects in the sky

– Sun, Moon, Mercury, Venus, Mars, Jupiter, Saturn– Sunday, Monday, Saturday– Tiwe’s Day (Mars), Woden’s Day (Mercury),

Thor’s Day (Jupiter), Frige’s Day (Venus)– lunes, martes, miercoles, jueves, viernes,

sabado, domingo

A Little History

Geocentric TheoryEarth is the center of the universe• Everything revolves around the earth• What is apparent, what is observed• agrees with some religious views

Heliocentric Theory

Sun: the center of the solar systemCopernicus (February 19, 1473 – May 24, 1543)

– Polish priest, astronomer

• Considered heretical, not published until his death bed in 1543

– People were arrested, tortured and killed for teaching this idea

– Galileo under house arrest for years for this idea

Nicholas Copernicus

Giordano BrunoGalileo Galilei

Motions of the EarthRevolution

Time it takes to revolve around another body, the sun.Year

• 365.24 days for the Earth• Leap years are determined according to the following rule:

– Every year that is exactly divisible by 4 is a leap year– except for years that are exactly divisible by 100;

these centurial years are leap years only if they are exactly divisible by 400.

Note: The Earth is held in its orbit by the Sun’s gravity.

RotationThe time it takes for a body to rotate about an axis• Day

– 23 hr. 56 min. for the Earth– Relative to distant objects

– 24 hr for sunrise to sunrise– The earth has moved a bit in its orbit relative

to the sun, so it takes a little longer for the sun to be visible

– ~1000 mph at the equator, 800 mph here

Other important characteristics

Size- diameter: 12,756.3 km (7,926 mi)Orbit:

149,600,000 km (93,500,000 mi) from Sun1.00 astronomical unit (au) from SunElliptical, not circular• More of a squashed circle

– Closest to the sun on Jan. 4, 147.5 million km– Farthest from the sun July 4, 152.6 million km

Mass: 5.9972x1024 kg

Science 8 Goby LastVideo: Basic Astronomy Per. ___ 9/13/13

5 Things new or interesting to you in the video.1.

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The Seasons

The earth is tilted in its orbit around the sun at 23.5o

The earth is always tilted in the same direction, North Star over the North Pole• 23. 5o North Latitude- Tropic of Cancer• 23. 5o South Latitude- Tropic of Capricorn• 66.5o North Latitude- Arctic Circle• 66.5o South Latitude- Antarctic Circle

Seasons are determined by where the most direct rays of the sun are hitting the Earth.

Animation

Old Farmer’s Almanac SiteSeasons of 2013:

SPRING EQUINOX March 20, 7:02 A.M. EDT

SUMMER SOLSTICE June 21, 1:04 A.M. EDT

FALL EQUINOXSeptember 22, 4:44 P.M. EDT

WINTER SOLSTICEDecember 21, 12:11 P.M. EST

The Earth’s Moon

Earth’s companion in spaceLarge in relation to the Earth• About ¼ diameter of Earth, approx. the

size of the U.S. from coast to coast • Diameter: 3,476 km (2,172 mi)

Distance from Earth• Orbit: 384,400 km (240,000 mi)

Mass: 7.35e22 kg• Gravity, about 1/6 of Earth’s

Features of the Moon

CratersMade by impacts with meteorites

Mare“seas” made by the outpouring of lava early in the moon’s history

RaysBright lines extending out from some newer craters

The Moon’s Motions• Rotation- about 27 1/3 days• Revolution- about 27 1/3 days

– The moon keeps the same side toward the Earth as it goes around the Earth

– The moon is held in its orbit by the gravitational attraction between the Earth and the moon.

The Moon’s Phases

The geometry of the Earth- Moon- Sun determines the phases of the moon

With the phases of the moon, we are seeing different amounts of the lit portion of the moon.½ of the moon is always illuminated by the sun.

The Moon’s Phases

The Moon’s Phases 2

Eclipses

Named after what goes dark.

Solar eclipseMoon comes between the Earth and the sun.Occurs during a new moon.Only a small area sees it (totality).Next one here, August 21, 2017

Lunar Eclipse

The earth is between the moon and sun.Full moonEveryone on the night side of earth sees it.Next here: October 18, 2013

Partial

The TidesThe tides in the oceanare a result of the gravitational attraction of the moon and sun on the earth.There is always a bulge of water facing toward the moon and one away from it.

When you are under a bulge, you have high tide.When you are between bulges, you have low tide.

The sun also influences tidesThe greatest range is at full and new moon, straight line, spring tide.The least range is at the quarter moons, right angle, neap tide.