Notes on Solar System, Earth, Moon, and Eclipses

Kondisi Bumi (Earth's Condition)

  • Bentuk Bumi (Shape of the Earth):
    • 1522, Ferdinand Magellan: Proved the Earth is round by circumnavigating it. He sailed in a straight direction and returned to his starting point.
    • Sailors observe that the top of a ship is the first thing visible at sea, further proving Earth's curvature.
    • 1543, Nicolaus Copernicus: Published that the Moon orbits the Earth, while the Earth and other planets orbit the Sun.

Rotasi Bumi (Earth's Rotation)

  • Terjadinya siang dan malam (Day and Night):

    • The Earth has a day side (facing the Sun) and a night side (facing away from the Sun).
    • This rotation causes the apparent daily motion of the Sun.

  • Gerak semu harian matahari (Apparent Daily Motion of the Sun): The sun appears to move around the Earth.

  • Perbedaan waktu (Time Zones):

    • The Earth rotates 360 degrees, resulting in 24 local time zones.
    • The 0-degree longitude line is Greenwich, London.
    • Each 15-degree increment corresponds to a 1-hour difference.

  • Pembelokan arah angin (Wind Deflection):

    • The Coriolis effect deflects wind direction.
    • Winds from the north deflect to the right towards the equator, and winds from the south deflect to the left towards the equator.
    • Gaya Coriolis (Coriolis Force): The force responsible for the deflection of wind and ocean currents.

  • Pembelokan arah arus laut (Ocean Current Deflection):

    • Ocean currents follow wind direction due to the Coriolis effect.

Revolusi Bumi (Earth's Revolution)

  • Perbedaan lama siang dan malam (Variation in Day and Night Length): Changes in day and night duration.

  • Pergantian Musim (Seasons): Occurs because of the tilt of the Earth’s axis.

  • Terjadinya gerak semu tahunan matahari (Apparent Annual Motion of the Sun):

    • The Earth's revolution with a 23.5∘23.5^{\circ} tilted axis causes the Sun to appear to shift.
    • The 23.5∘23.5^{\circ} tilt causes the Northern Hemisphere to receive more direct sunlight for half the year, and vice versa.

  • Perbedaan lama siang dan lama menyebabkan perbedaan musim pada belahan bumi utara dan selatan (The difference in the length of day and night causes differences in seasons in the northern and southern hemispheres )

Kondisi Bulan (Moon's Condition)

  • The Moon has three simultaneous movements: rotation, revolution, and movement with the Earth around the Sun.

  • The Moon's rotation period equals its revolution period (approximately 27.3 days), so the same side of the Moon always faces the Earth.

  • Pembagian Bulan (Lunar Periods):

    • Bulan Sideris (Sidereal Month): The time it takes for the Moon to orbit the Earth, about 27.3 days.
    • Bulan Sinodis (Synodic Month): The time it takes for the Moon to complete a cycle of phases, about 29.5 days (used in the Islamic calendar).

  • Pasang Purnama (Spring Tide):

    • Influenced by the Moon's gravity and occurs during a Full Moon.
    • Maximum tides occur during a Solar Eclipse because the gravitational forces of the Moon and Sun align.

  • Pasang Perbani (Neap Tide):

    • Lowest low tides.
    • Occur during the first and third quarter Moon phases when the gravitational forces of the Moon and Sun are perpendicular.

Fase-Fase Bulan (Lunar Phases)

  1. Bulan baru (New Moon): Occurs when the Moon is between the Earth and Sun. The side of the Moon facing the Sun appears bright, while the side facing the Earth appears dark.
  2. Bulan sabit (Crescent Moon): About one-quarter of the Moon is illuminated by the Sun.
  3. Bulan separuh (Half Moon): About half of the Moon is illuminated (first quarter).
  4. Bulan cembung (Gibbous Moon): About three-quarters of the Moon is illuminated.
  5. Bulan purnama (Full Moon): The entire Moon is illuminated (second quarter).

Gerhana (Eclipses)

  • Due to the Moon being smaller than the Earth and Sun, three types of solar eclipses can occur:
  1. Gerhana Matahari total (Total Solar Eclipse): Occurs in areas within the umbra (the darkest part of the shadow), where the Sun is completely blocked. Total solar eclipses last only about 6 minutes.
  2. Gerhana Matahari cincin (Annular Solar Eclipse): Occurs in areas that are an extension of the umbra, where the Sun appears as a ring.
  3. Gerhana Matahari sebagian (Partial Solar Eclipse): Occurs in areas between the umbra and penumbra (the lighter part of the shadow), where only part of the Sun is blocked.
  • Gerhana Bulan (Lunar Eclipse):
    • Occurs when the Moon enters the Earth's shadow.
    • Can only occur during a Full Moon.
    • Happens when the Earth is between the Sun and Moon.
    • Gerhana Bulan total (Total Lunar Eclipse): Occurs when the entire Moon is within the Earth's umbra. The Moon can be in the penumbra for up to 6 hours and in the umbra for about 40 minutes.

Perbedaan Gerhana Matahari dan Gerhana Bulan (Differences Between Solar and Lunar Eclipses)

  • Full shadow (Umbra): The darkest part of the shadow, appearing very dark during the eclipse.
  • Partial shadow (Penumbra): The lighter part of the shadow, appearing dim during the eclipse.