What is Gravity?What is Gravity?

Gravity is an Gravity is an attraction attraction that acts that acts between any two objects that have a between any two objects that have a mass.mass.

However, this is However, this is onlyonly significant if significant if one or both of the objects are very one or both of the objects are very massive (like a planet, star, or massive (like a planet, star, or moon).moon).

Force of gravity depends on…Force of gravity depends on…

MassMass- The more massive an - The more massive an

object, the greater the object, the greater the gravitygravity

DistanceDistance- The closer an object - The closer an object

is, the greater the is, the greater the gravity.gravity.

*This is why we are *This is why we are stuck on Earth and stuck on Earth and not pulled away to the not pulled away to the sun even though the sun even though the sun is much more sun is much more massive than the massive than the earthearth

Newton's Law of Universal Newton's Law of Universal GravitationGravitation

The force of attraction between The force of attraction between two objects is directly related to two objects is directly related to the masses of the objects and the masses of the objects and inversely related to the square of inversely related to the square of the distance between them.the distance between them.

Orbital SpeedOrbital Speed

The speed at which an object orbits The speed at which an object orbits around another object.around another object.

Example:Example: The Earth’s orbital speed is The Earth’s orbital speed is 67,000 mph. It travels 67,000 mph around 67,000 mph. It travels 67,000 mph around the sun. the sun.

Inertia and GravityInertia and Gravity

Inertia is too greatInertia is too great • Gravity too great

* To stay in orbit, inertia and gravity must be balanced

Moon TermsMoon Terms Waxing – The moon appears more lit each night.Waxing – The moon appears more lit each night. Waning – The moon appears less lit each night.Waning – The moon appears less lit each night. Crescent – Less than half of the moon appears lit.Crescent – Less than half of the moon appears lit. Gibbous – More than half of the moon appears lit.Gibbous – More than half of the moon appears lit. First Quarter – The right half of the moon appears lit.First Quarter – The right half of the moon appears lit. Third Quarter – The left half of the moon appears lit.Third Quarter – The left half of the moon appears lit. Full Moon – The entire moon appears lit.Full Moon – The entire moon appears lit. New Moon – No part of the moon appears lit.New Moon – No part of the moon appears lit.

REMEMBER! One half of the moon is REMEMBER! One half of the moon is lit lit at all timesat all times by the sun, by the sun, exceptexcept during a lunar eclipse. We name the during a lunar eclipse. We name the phase according to what phase according to what WEWE see! see!

Lunar EclipseLunar Eclipse

Full Moon phase, Sun, Earth, MoonFull Moon phase, Sun, Earth, Moon

Solar EclipseSolar Eclipse

Moon Phase: New Moon, Sun, Moon, Moon Phase: New Moon, Sun, Moon, EarthEarth

Why no eclipse every month?Why no eclipse every month?

The moon’s orbit is at a 5 degree angle, so The moon’s orbit is at a 5 degree angle, so Earth only occasionally gets in the way.Earth only occasionally gets in the way.

The next total lunar eclipse in this area will The next total lunar eclipse in this area will be April 14, 2014. Watch for it!be April 14, 2014. Watch for it!

Earth

Moon

TidesTides are the vertical movement of water, specifically the alternate rise (flood or flow) and fall (ebb) of water in the ocean. This is mostly noticeable along continental shorelines.

The influence of the Moon’s gravitational force acting on the Earth’s oceans and the Earth (the rocky part).

What causes tides?

Earth

Moon

Sun

High TideHigh Tide

Low Tide

Low Tide

Tides are more influenced by the gravitational effect of the Moon than they are by that of the Sun (the Moon's closeness to us outweighs by far the Sun's greater size).

Earth

Moon Moon

Spring Tides •The gravitational affects of the moon and sun combine to influence the flow of the oceans on Earth.

•Spring tides are formed when the Sun, Earth, and Moon are in a line.

New MoonPhase of the moon?

Full Moon

Phase of the moon?

Moon

New Moon

Phase of the moon?

•Higher high tides and lower low tides

Earth

Moon

MoonFirst Quarter

Phase of the moon?

Third Quarter

Phase of the moon?

Neap Tides

The gravitational affects of the moon and sun fight each other with their influence on the flow of the oceans on Earth.

Moon

Third Quarter

Phase of the moon?

Lowest high tides and highest low tides

Neap Tides form an L with the sun, moon and earth.

TTides & ides & CConsequencesonsequences• This little tidal behavior goes both ways! The Earth rises tides on the Moon.

• The Earth "brakes" the Moon's rotation AND the braking is complete! Synchronous Rotation of the Moon and its orbital period! (27.3 days!)

• Moon also brakes the Earth's Rotation

• Moon's orbit is growing because of all of this interaction.

• We see a permanent "near" and "far side" of the Moon.

• The length of the "day" is increasing! From fossil reef corals of about 4108 years old - daily growth/annual growth 400 days/year ~ 22 hours a day! Day is increasing about 0.001 seconds/century.

Therefore, the day is getting longer, Moon looks smaller, and tides are weakening.

Season’sSeason’s

The tilt of the earth causes the Season’sThe tilt of the earth causes the Season’s

How Do Days Change in Length?

Summer, days are longer and nights are shorter.

Winter, days are shorter and nights are longer.

The reason days change in length is the same reason we have seasons: Earth’s axial tilt.

Earth’s Axis Is on a Tilt.

Earth is tilted at a 23 ½ degree angle from the vertical.

The axis is always tilted in the same direction; the north pole is always pointed towards the North Star (Polaris).

Around June 21, the North Pole of the axis is tilted toward the sun. This is the longest day of the year for the Northern Hemisphere and the shortest for the Southern Hemisphere.

Around December 22, the North Pole of the axis is tilted away from the sun. This is the shortest day of the year for the Northern Hemisphere and the longest day of the year for the Southern Hemisphere.

Around March 20 and September 23, the sun is directly over the equator. Days and nights are equal length everywhere on Earth.

Earth’s Uneven Heating

Earth’s temperature varies with latitude.

At higher latitudes, solar radiation is less intense.

The same thing happens to the sun’s energy when it reaches the south pole at an angle.

Why is it not the distance?Why is it not the distance?

The distance of the Sun and Earth is not The distance of the Sun and Earth is not that different at different positions, so light that different at different positions, so light intensity is affected very little.intensity is affected very little.

1. Gravity is a repelling force:

Tru

e

Fal

se

0%0%

A. True

B. False

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2. All planets orbit around the ___.

Moon

Jupite

r S

un

gal

axy

0% 0%0%0%

A. Moon

B. Jupiter

C. Sun

D. galaxy

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3. Gravity is highly effective if one or more objects is extremely massive.

Tru

e fa

lse

0%0%

A. True

B. false

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4. During a solar eclipse the moon is in this phase:

Firs

t quar

ter

Gib

bous F

ull

New

0% 0%0%0%

A. First quarter

B. Gibbous

C. Full

D. New

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5. Even though the Sun has more mass than the moon, the moon has more effect on tides because:

The

moo

n is m

o...

The

moo

n is c

o...

The

moo

n is c

l...

The

moo

n is fu

...

0% 0%0%0%

A. The moon is more dense

B. The moon is cooler

C. The moon is closer

D. The moon is further away

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6. The distance the earth is from the Sun causes seasons.

Tru

e

Fal

se

0%0%

A. True

B. False

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7. Why are the days getting longer?

Bec

ause

the

mo...

Bec

ause

the

un...

Bec

ause

stu

den...

Bec

ause

we

are.

..

0% 0%0%0%

A. Because the moon is braking the earth’s rotation

B. Because the universe is expanding

C. Because students are dying of boredom

D. Because we are shifting to the red end of the spectrum

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8. What type of tides cause lower high tides and higher low tides?

Tid

al

sprin

g

Tsu

nami

Nea

p

0% 0%0%0%

A. Tidal

B. spring

C. Tsunami

D. Neap

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9. Gravity is dependent on:

Mas

s an

d iner

t...

Mas

s an

d dis

ta...

Dis

tanc

e an

d i...

Den

sity

and in

...

0% 0%0%0%

A. Mass and inertia

B. Mass and distance

C. Distance and inertia

D. Density and inertia

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10. During a solar eclipse ___ is between the ___ and the Sun.

Ear

th, m

oon

Plu

to, m

oon

Moon

, ear

th

Sola

r rad

iatio

...

0% 0%0%0%

A. Earth, moon

B. Pluto, moon

C. Moon, earth

D. Solar radiation, earth

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11. What scientist discovered the Law of Universal gravitation?

Hubbl

e

Her

schel

Gal

ileo

New

ton

0% 0%0%0%

A. Hubble

B. Herschel

C. Galileo

D. Newton

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12. The earth is tilted ____.

5 d

egre

es

23

degre

es

25

degre

es

23.

5 deg

rees

0% 0%0%0%

A. 5 degrees

B. 23 degrees

C. 25 degrees

D. 23.5 degrees

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13. The tilt of the earth is important because it:

Allo

ws th

e ea

r...

Cau

ses

the

sea.

..

Hel

ps th

e ea

rt...

Shows

that

eve

...

0% 0%0%0%

A. Allows the earth to rotate which gives us night and day.

B. Causes the seasons

C. Helps the earth revolve around the Sun

D. Shows that even planets can be off balance…not just students.

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14. Why is there not a lunar eclipse every month?

Bec

ause

the

ea...

Bec

ause

of t

he...

Bec

ause

of t

he...

Bec

ause

the

mo...

0% 0%0%0%

A. Because the earth’s tilt

B. Because of the changes of revolution between the earth and moon

C. Because of the distance between the earth and the Sun changes

D. Because the moon’s tilt

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15. The earth’s orbital speed is around:

67,

000

mph

12,

756

mph

150

,000

,000

mp...

The

spee

d of l

...

0% 0%0%0%

A. 67,000 mph

B. 12,756 mph

C. 150,000,000 mph

D. The speed of light

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16. We see both sides of the moon because the moon rotates.

Tru

e

Fal

se

0%0%

A. True

B. False

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17. What is the main reason we have tides?

The

Sun’s

grav.

..

The

push p

ull .

..

The

moo

n’s g

ra...

Due

to Z

ues’s

...

0% 0%0%0%

A. The Sun’s gravitational force acting on earth.

B. The push pull relationship between the moon and the Sun.

C. The moon’s gravitational force acting on the earth.

D. Due to Zues’s footsteps

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18. During a lunar eclipse:

The

moo

n is c

o...

The

moo

n is c

o...

The

moo

n appea

...

The

moo

n is in

...

0% 0%0%0%

A. The moon is completely blocked by the Sun.

B. The moon is completely blocked by earth and we can’t see the moon.

C. The moon appears red

D. The moon is in a new moon phase

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19. Spring tides cause Higher High tides and Lower Low tides because of the position of the moon.

Tru

e

Fal

se

0%0%

A. True

B. False

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20. During a lunar eclipse the moon is in this phase:

Las

t Quar

ter

Gib

bous F

ull

New

0% 0%0%0%

A. Last Quarter

B. Gibbous

C. Full

D. New

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