Phases, Eclipses, and Tides 2015

Motions of the Moon The moon rotates on its axis. Its period of rotation equals its time to revolve around the Earth. So we always see the same side of the moon. The far side (dark side) of the moon remained a mystery until 1959 when the Russian space probe Luna 3 took the first pictures of it.

Phases of the Moon The Moon goes through its entire set of phases once 29.5 days. The phase depends on how much of the sunlit side is visible from the Earth. Waxing moons are showing us more of the sunlit side (getting bigger), while waning moons are showing us less of the sunlit side (getting smaller).

Visual Phases

Eclipses Eclipses occur when the Earth’s shadow hits the moon, or the moon’s shadow hits the Earth. Since the moon’s orbit is slanted at 5°, we do not get an eclipse every month. They are named for what gets eclipsed: The sun is eclipsed in a solar eclipse. The moon is eclipsed in a lunar eclipse. Solar and lunar eclipses occur in almost equal number.

Moon’s Shadow The umbra is the darkest part of the moon’s shadow. This narrow cone just reaches the surface of the Earth. The penumbra is the wider, less dark portion of the shadow.

Solar Eclipses Solar eclipses occur when the moon passes between the Earth and the sun. This blocks sunlight from a small portion of the Earth. The moons shadow hits the Earth. So a solar eclipse is really just a new moon that blocks your view of the sun.

Eclipse Drawings

Total Solar Eclipse Light from the sun is completely blocked by the moon. The sky will be dark. You can see stars and the solar corona, which is the faint outer atmosphere of the sun.

7 min/ 2.4 x year Partial Solar Eclipse Part of the sun will be visible as the Earth passes through the moon’s penumbra. 7 min/ 2.4 x year

Lunar Eclipses Occurs at a full moon as the Earth passes between the moon and the sun. The Earth blocks sunlight from the moon. The moon is in the Earth’s shadow.

Total Lunar Eclipses Total eclipses occur when the moon passes into the Earth’s umbra. You see the Earth’s shadow on the moon before and after the eclipse. Unlike a solar eclipse, they can be seen anywhere the moon is visible.

Partial Lunar Eclipses Most of the time the earth, moon, and sun are not in a perfect straight line. Only part of the moon is in the Earth’s umbra. 2-4 x per year/ 3 hours

Tides Tides occur because of the differences in how much the moon (and sun) pull on different parts of the Earth. Most places will see two high and two low tides per day.

Spring Tides Occur when the Earth, Moon, and Sun are lined up. Highest tides occur, called maximum daily tide range. Occur at new and full moons

Neap Tides Occur when Sun, Earth, and Moon are at 90° to each other. Will have minimum daily tide range. Occur at 1st and 3rd quarter moons

Earth’s Moon 19-4

The Moon There is no atmosphere on the moon. Temperatures on the surface range from over 100°C to -170°C. To survive on the moon the astronauts had to wear bulky spacesuits to keep them warm and carry their oxygen. These suits weighed as much as the astronauts themselves. But because the moon’s gravity is only 1/6th of the Earth’s, they could move around very easily. The moon is about 384,400-km (240,000-mi) from the Earth. A day on the Moon is two Earth weeks! Also, so is a night on the moon.

Structure of the Moon Diameter is about 3,476-km, a little less than the distance across the USA. This is 1/4th the Earth’s diameter, but the moon has only 1/80th the mass of the Earth. Since the Moon’s average density is about the same as the Earth’s outer layers, it is believed the moon lacks a dense core.

Origin of the Moon While there have been many ideas, the theory that best fits the evidence is the collision theory. About 4.5bya, when the Earth was very young, an object the size of Mars collided with the Earth. Lots of material from the outer layer was flung into orbit, where it eventually combined to form the moon.

Features of the Moon The early Greeks thought the moon was perfectly smooth. Galileo was first to use a telescope to study the moon. He saw that the moon had craters, highlands and maria.

Craters Caused by impacts from meteoroids. Some are hundreds of kilometers across. Many are named after famous scientists from long ago. Tycho is the bright crater at the bottom of the picture to the right.

Highlands Mountainous areas covered with craters. Apollo 15 landed near the Apennine Mountains in 1971.

Maria Large, dark, flat areas. Maria is Latin for “seas.” Galileo thought that they might be oceans. They are low, dry areas that were flooded with molten material billions of years ago.

Rilles Are meandering, valley like structures. Thought to be the remains of collapsed lava tubes or extinct lava flows. They usually begin at an extinct volcano, then meander and sometimes split as they are followed across the surface. Pictures from Apollo 15 at the edge of the Hadley Rill.

Apollo to the Moon First, I believe that this nation should commit itself to achieving the goal, before this decade is out, of landing a man on the moon and returning him safely to the earth. No single space project in this period will be more impressive to mankind, or more important for the long-range exploration of space; and none will be so difficult or expensive to accomplish. John F. Kennedy 1961 We choose to go to the moon. We choose to go to the moon in this decade and do the other things, not because they are easy, but because they are hard, because that goal will serve to organize and measure the best of our energies and skills, because that challenge is one that we are willing to accept, one we are unwilling to postpone, and one which we intend to win, and the others, too. John F. Kennedy 1961

Moon Exploration The Apollo missions explored the moon from 1968 to 1972. Six missions successfully landed on the moon. Apollo 11 was the first in July 1969. Apollo 17 was the last, in December 1972. We have not gone back since.

Apollo 11 First lunar landing: July 20, 1969. Neil Armstrong and Buzz Aldrin took the Lunar Module Eagle down to the surface of the moon. Michael Collins remained in orbit in the Command Module. “That’s one small step for man, one giant leap for mankind.”

Apollo Contributions Returned 382-kg of rocks. Genesis rock showed that the moon was almost as old as the Earth (4by). Spinoffs include cordless tools, computers, CAT/MRI technologies, kidney dialysis machines, freeze dried food, and countless others have benefited mankind.

Phases of the Moon Rap

The Moon Phases Poem The Moon is a sphere, big and white It loves to reflect the sun’s bright light. It goes on a journey every 28th day Around the Earth, hide and seek it will play. In the beginning, it is new Out of sight from me and you! Then it waxes in white light As it grows on its right. Waxing, Crescent, Quarter, then gibbous, too. When it’s full, the phases are halfway through! Now it shines more to the left and starts to wane As it fades away in its orbit lane. Waning, gibbous, quarter, then crescent, too. It’s completed its orbit and back to new! The Moon Phases Poem