Moon, Lunar Phases, and Eclipse - Class 5 Notes & Olympiad Questions

Moon

a) Earth's Moon is a fascinating celestial body and the only place beyond Earth where humans have actually set foot.
b) Rather than generating its own light, the Moon reflects sunlight, illuminating its surface and allowing us to see it from Earth.
c) The Moon is the brightest and largest object we can see in the night sky. It is the fifth largest moon out of over 200 moons orbiting planets in our solar system.
d) Interestingly, it is simply known as "the Moon" because people were unaware of other moons until Galileo Galilei discovered four moons orbiting Jupiter in 1610.
e) The Moon's surface is solid and rocky, with numerous craters and pits caused by impacts from asteroids, meteorites, and comets. However, it lacks an atmosphere that is breathable for humans. It only has a very thin exosphere.
f) Over 105 robotic spacecraft have been sent to explore the Moon, making it the only celestial body besides Earth that has been visited by humans.
g) The Moon's gravitational pull has a noticeable impact on Earth's ocean tides. It attracts the water, causing the rise and fall of waves, creating the high and low tides we observe along coastlines.

Phases of the Moon

Lunar Phases

The Moon's shape appears to change because it moves around the Earth, and different parts of it receive sunlight at different times. We can only see the part of the Moon that is illuminated by the Sun, which creates the different phases of the Moon.

These phases are also known as Lunar Phases. The cycle of these phases repeats about once a month, which is around 29.5 days.

a) New Moon (0 days): The Moon is not visible during this phase. It happens when the Sun, Moon, and Earth align, and the side facing us is not illuminated.

b) Waxing Crescent Moon: Following the new moon, a small sliver of the Moon becomes visible. This is called the waxing crescent phase.

c) First Quarter Moon: The Moon continues to move, and when exactly half of its illuminated side is visible, it is called the first quarter moon. It appears as a half-circle shape.

d) Waxing Gibbous Moon: After the first quarter, the lit-up part of the Moon becomes larger. This phase is called the waxing gibbous moon. It's more than a half-circle but not yet a full circle.

e) Full Moon (14 days): About two weeks after the new moon, we have a full moon. This occurs when the Moon, Earth, and Sun align, with the Earth in the middle. The full moon appears as a big, round circle in the night sky.

f) Waning Gibbous Moon: Following the full moon, the illuminated part of the Moon gradually decreases in size. This phase is known as the waning gibbous moon. It is still significant but not as round as a full moon.

g) Third Quarter Moon: The third quarter moon happens when we can see exactly half of the illuminated side again, but this time, it's the opposite side compared to the first quarter. It appears as a half-circle shape.

h) Waning Crescent Moon (28-30 days): As the Moon continues to move, less and less of its illuminated side is visible. This phase is called the waning crescent moon. Sometimes, a faint glow of the dark part of the Moon, known as Earthshine, can be observed.

Lunar Eclipse

a) Normally, the Moon shines brightly because it reflects the light from the Sun. But sometimes Earth gets in the way between the Sun and the Moon, and this creates a lunar eclipse.
b) During a lunar eclipse, Earth blocks the sunlight that usually falls on the Moon. It's like Earth is standing in the middle, casting a shadow on the Moon. There are two main types of lunar eclipses:

1. Total Lunar Eclipse: During a total lunar eclipse, Earth's shadow completely covers the Moon. The Moon can turn a dark, reddish colour during this time. It's like the Moon is hiding in Earth's shadow.
2. Partial Lunar Eclipse: In a partial lunar eclipse, only part of Earth's shadow covers the Moon. It's like a shadowy bite has been taken out of the Moon.

c) When the Moon is in Earth's shadow, the only light that reaches it is sunlight that has passed through Earth's atmosphere. This light is scattered by the Earth's atmosphere and this creates a reddish colour on the Moon during the eclipse.

Solar Eclipse

a) During a solar eclipse, the Moon comes between the Sun and Earth, casting a shadow on our planet.
b) There are a few different types of solar eclipses:

1. Total Solar Eclipse: In a total solar eclipse, the Moon completely blocks out the Sun, and the sky becomes dark for a short period of time.
2. Partial Solar Eclipse: In a partial solar eclipse, the Moon covers only part of the Sun, leaving a crescent shape visible in the sky.
3. Annular Solar Eclipse: An annular solar eclipse occurs when the Moon is farther away from Earth, so it doesn't completely cover the Sun. This creates a ring of sunlight around the Moon, giving it a unique appearance.

c) During a solar eclipse, it's important to remember never to look directly at the Sun without proper eye protection, as it can cause serious damage to your eyes. Special eclipse glasses or other safe viewing methods should be used to protect your eyes if you want to observe a solar eclipse.

Formation of Tides

a) One fascinating thing about the Moon is that it has a gravitational pull. Gravity is the force that pulls things toward each other. Because the Moon is relatively close to Earth, its gravity affects our planet and has a special impact on our oceans.
b) The gravitational forces of the Moon and, to a lesser extent, the Sun acting on the Earth creates something called tides in the oceans. Tides are the rising and falling of the sea level along the coastline.
c) The Moon's gravity pulls on Earth, but it pulls more strongly on the water on the side of Earth that is facing the Moon. This creates a bulge of water, which we call the high tide, on the side of Earth that is closest to the Moon.
d) On the opposite side of Earth, away from the Moon, there is also a high tide. This happens because the Moon's gravity is pulling Earth itself toward it, creating a bulge on the other side. So, there are two high tides on opposite sides of the planet.
e) In between these two high tides, there are areas where the water level is lower than usual. We call these areas low tides. As Earth rotates, different parts of the coastline experience the changing tides.
f) We have two high tides and two low tides each day. That's because Earth not only rotates but also revolves around the Sun. As Earth rotates, it takes about 24 hours to complete a full day. But during that time, it also moves a little bit in its orbit around the Sun. So, it takes a little longer for a specific location on Earth to line up with the Moon again, resulting in two high tides and two low tides.
g) During Full Moon and New Moon, when the Sun, Earth, and Moon are aligned, the gravitational forces are strongest, leading to the highest tides. These are called spring tides.