Why Do New Moons Matter? The Science of Eid Moon Sighting

Understanding the significance of new moons goes beyond religious observances—it is rooted in astronomy and physics. The sighting of the Eid moon, which marks the end of Ramadan and the beginning of Shawwal, is an event that blends science with tradition. In Singapore, where the Muslim community follows lunar calendars, the process of moon sighting holds particular importance. But what exactly makes the new moon so critical, and what role does physics play in determining its visibility?

The lunar cycle and why the new moon is unique

A lunar month lasts approximately 29.5 days, during which the moon goes through different phases. The cycle begins with the new moon, a phase where the moon is positioned between the Earth and the Sun. During this time, the side of the moon facing Earth receives no direct sunlight, making it invisible to the naked eye.

Unlike a full moon, which is easily seen, a new moon can only be detected under specific conditions. The transition from the new moon to the visible crescent requires precise calculations based on angles, light reflection, and the moon’s position relative to the Sun and Earth.

How the new moon becomes visible

The crescent moon appears when sunlight reflects off the moon’s surface at an angle visible from Earth. However, this does not happen immediately after the astronomical new moon. The moon must move far enough away from the Sun's glare for a small portion of it to be illuminated and observed.

Several factors determine whether the crescent moon can be seen:

• Angular separation: The moon must be at least 10 to 12 degrees away from the Sun for the crescent to become visible.
• Altitude above the horizon: The higher the moon is above the horizon at sunset, the greater the chance of sighting it.
• Atmospheric conditions: Pollution and clouds can obscure the moon, making it difficult to observe even when it is technically visible.

Scientific methods for moon sighting

Traditional moon sighting relies on the human eye, but modern techniques enhance accuracy. Astronomers use telescopes, cameras, and mathematical models to predict when and where the crescent moon will first appear.

In Singapore, moon sighting is typically conducted at designated observatories, where experts use calculations based on:

• Lunar elongation: The angle between the Sun and the moon.
• Illumination fraction: The portion of the moon’s surface reflecting sunlight.
• Geographical location: Closer proximity to the equator affects sighting possibilities due to atmospheric refraction.

These observations align with the physics of light reflection and refraction, core principles taught in physics education.

Why moon sighting varies across countries

Despite the use of precise calculations, different countries may declare Eid on different days. This discrepancy arises due to the Earth’s curvature, variations in time zones, and atmospheric conditions affecting visibility.

For instance, while the crescent moon may be visible in the Middle East, it might not be observable in Singapore due to weather conditions or its position relative to the horizon. This is why some communities rely on astronomical calculations rather than physical sightings to determine the start of Shawwal.

The role of physics in moon sighting technology

With advancements in technology, moon sighting has become more accurate. Satellites that stay in orbit, computer models, and even artificial intelligence assist in predicting the precise moment the crescent moon will be visible.

One of the key advancements is CCD imaging, where high-sensitivity cameras capture faint celestial objects. This technology, combined with data analytics, allows astronomers to detect the moon even before it becomes visible to the naked eye. These techniques utilise principles from optics, digital imaging, and atmospheric physics—topics covered extensively in advanced physics education.

Applying physics education to real-world phenomena

For students studying physics, moon sighting is a perfect example of how scientific principles apply to everyday life. Understanding how light behaves, how celestial bodies move, and how atmospheric conditions impact observations can make complex topics more relatable.

Physics education provides the tools to analyse natural events scientifically, whether it’s through O-Level physics tuition or JC Physics tuition. By learning these principles, students not only gain a deeper appreciation for astronomy but also develop critical thinking skills useful in various fields.

For those interested in exploring these concepts further, our physics programmes offer an in-depth understanding of celestial mechanics, optics, and scientific observation. Through structured lessons, students can connect theoretical physics with real-world applications like moon sighting and beyond.