Effects of the sun on the earth Eclipses, Tides, Seasons

Earth’s rotation The Earth rotates on its axis (it makes one complete turn) every 24 hours

Earth’s rotation is the cause of our day and night

Earth’s revolution The Earth revolves around the sun (makes one complete circuit) once every 365.26 days This is the cause of our year

Other variations in Earth’s movement Every 100,000 years the Earth’s elliptical orbit varies from more elongated to more circular Every 41,000 years the tilt of the Earth on its axis varies between 21.50 and 24.50

Precession: every 26,000 years the circular motion of the Earth on its axis...causes the Earth to spin like a top on a table Right now the axis points towards Polaris (North Star) In the future will point to the star Vega

These are called Milankovitch cycles and they are believed to be one of the causes that the Earth’s climate cycles between ice ages and warm periods

What do we mean by latitude and longitude? Latitude = Horizontal (N or S) Longitude = Vertical (E or W)

Important Lines of Latitude/longitude

Aphelion/Perihelion Because of the Earth’s elliptical orbit, the distance between the earth and the sun varies through the year We are closest at perihelion; we are furthest apart at aphelion (apart/aphelion)

Aphelion (furthest from sun) occurs around July 4th (152 million km) and Perihelion (closest to sun) occurs around January 3rd (147 million km) Closest in January??? Then why is it coldest???

What causes the seasons?? The tilt of the earth on its axis!!

During our summer: Northern hemisphere fully faces the sun During our winter: Southern hemisphere fully faces the sun

A: Summer Solstice – June 20 or 21 solstice: means “sun” “stop” – the sun stops getting higher in the sky each day The sun’s rays are directed at the Tropic of Cancer B: Autumnal Equinox – September 22 or 23 Equinox: means “equal nights”; length of day and night are equal all over the world The sun’s rays are directed at the equator

D: Spring Equinox – March 20 or 21 C: Winter Solstice – Dec. 21 or 22; sun is lowest in the sky The sun’s rays are directed at the Tropic of Capricorn D: Spring Equinox – March 20 or 21 The sun’s rays are directed at the equator

1 KW/m2 1 KW/m2 1 m2 2 m2

Autumnal Equinox (beg. of fall) Summer solstice (beg. of summer) July Winter solstice (beg. of winter) Fall Summer Winter Spring January Vernal equinox (beg. of spring)

NCP Summer Solstice Ecliptic CEq Winter Solstice SCP

Autumnal Summer Equinox Solstice Winter Vernal Solstice Equinox NCP Ecliptic CEq Winter Solstice Vernal Equinox SCP

Z Summer Solstice NCP Vernal & Autumnal Equinoxes W Winter Solstice S CEq W Winter Solstice S N E

CEq Z Summer Solstice NCP Vernal & Autumnal Equinoxes W Winter Solstice S N E CEq

Equinoxes: March 20 & Sept. 22 Northern Spring/Fall Southern Fall/Spring

December 21: Winter Solstice Northern Winter Southern Summer

June 21: Summer Solstice Northern Summer Southern Winter

Daylight Change by Latitude Can you detect the times of equinox? Can you detect the summer and winter solstices?

What is an eclipse? An eclipse occurs when one planetary body passes through the shadow of another. Eclipses are named depending on which body is eclipsed, or blocked

Shadow of the moon on the Earth as observed from the MIR space station. Moon's shadow on Earth taken by French cosmonaut Jean-Pierre Haigneré aboard the Mir

Many solar system bodies partake in eclipses, transits, and occultations. Here, Jupiter’s moon, Io, casts a shadow on Jovian cloud tops.

Solar Eclipse: (the sun is eclipsed or blocked) The moon is between the sun and earth - the shadow of the moon falls on the earth Within the umbra, you see a total eclipse (smaller area in shadow) Within the penumbra, you see a partial eclipse (larger area in the shadow) Solar eclipses never last > 7 minutes at any location. Why??

Total Solar Eclipse – can only occur if you are at the exact spot within the moon’s umbra (which isn’t very big).

Umbra Sunlight Penumbra Moon Earth

This graphic shows the path of totality for different solar eclipses through 2025. Notice there are two solar eclipses that cross the United States (2017 and 2024).

Lunar Eclipse: (the moon is eclipsed, or blocked) The earth is between the moon and the sun - the earth’s shadow falls on the lighted half of the moon Total lunar eclipse: moon must pass entirely through the earth’s umbra Partial lunar eclipse: only part of the moon passes through umbra Lunar eclipses may last hours!!

Sunlight Uneclipsed Moon Penumbral Eclipse Total Lunar Eclipse Partial Lunar Eclipse

The moon looks reddish during a lunar eclipse because the sunlight reflected off the moon is bent in the earth’s atmosphere

(Note the ruddy scattered sunlight) Total Lunar Eclipse (Note the ruddy scattered sunlight) Partial Lunar Eclipse

Why Don’t We See Lunar Eclipses More Often? Well, lunar eclipses don’t happen everyday because the Moon’s orbit is tilted. So, during most months, the Moon is above or below the Earth.

Syzygy- The times where the Moon, the Earth, and the Sun line up perfectly for an eclipse.

Tides: daily changes in the level of the ocean surface Caused by the gravitational pull of the moon (and the sun) on the Earth’s waters

Both Sun and Moon cause the tides… Because of gravity pulling on the oceans of the earth

Spring tides: S-E-M Neap Tides: S-E M Spring tides: highest high tides of the month; at times of new and full moons Neap tides: lowest high tides of the month; at 1st and last quarters

Neap and Spring Tides

Tides – 3 tidal patterns diurnal tides: one high, one low every 24 hours semidiurnal tides: two equal high, two equal low every 24 hours semidiurnal mixed tides: 2 highs of different heights, 2 lows of different heights every 24 hours

Tidal range: difference in height between the highest high and the lowest low tide Tidal period: time between one high tide and next high tide Tidal day: time between 1st high tide and last high tide in 24 hours

What kind of tides in Crescent City, CA?

What kind of tides in Eastport, ME? Look at the daily tidal range!

What kind of tides in Grand Isle, LA? Look at the daily tidal range

What kind of tides in Newport, RI ? Look at the daily tidal range

Moon 1 pager must include: Title and symbolic border Labeled illustrations of the phases of the moon A labeled diagram showing the position of the sun, earth, and moon at a new moon, 1st quarter moon, full moon, and 3rd quarter moon Illustrated definitions for 3 of the following terms: lunar eclipse, solar eclipse, apogee, spring tide, neap tide, umbra, penumbra 2 sentences explaining how length of day, latitude, and seasons are related to the tilt and orbit of the earth around the sun