本文解释了月相变化的科学原理，这是一个大约29.5天的周期，由月球围绕地球的轨道以及太阳对其不同部分的照明所决定。文章指出，在7月23日，我们正处于“残月”阶段，月球只有2%被照亮，几乎完全不可见。文中还回顾了上一个满月（7月10日）和即将到来的满月（8月9日），并详细列出了包括新月、娥眉月、上弦月、盈凸月、满月、亏凸月、下弦月和残月在内的八个主要月相，帮助读者理解月球可见度的周期性变化。

🌕 月相的形成源于月球围绕地球的29.5天轨道周期，这改变了太阳、月球和地球之间的角度。月相是我们从地球上看到的月球外观变化，其可见部分被太阳照亮程度随轨道位置而异。

✨ 在7月23日，月相为“残月”，月球仅有2%的可见度，几乎完全被黑暗笼罩，这是月球周期接近尾声的表现。这意味着在这一天，月球大部分区域未被太阳照亮。

🌑 月球的八个主要阶段按顺序循环：新月（不可见）、娥眉月（一小 sliver 亮）、上弦月（半边亮）、盈凸月（超过一半亮）、满月（完全可见）、亏凸月（右侧开始变暗）、下弦月（左侧半边亮）和残月（左侧 sliver 亮）。

🗓️ 月球的周期性变化意味着特定的月相会周期性出现。例如，文章提到上一个满月发生在7月10日，而下一个满月将在8月9日出现，这体现了月相的规律性。

Looking up at the sky and wondering where the moon is? Today's lack of beautiful moonlight isn't a mystery; it's to do with where we are in the lunar cycle. What's that, you ask? Keep reading to find out.

The lunar cycle is a series of eight unique phases of the moon's visibility. The whole cycle takes about 29.5 days, according to NASA, and these different phases happen as the Sun lights up different parts of the moon whilst it orbits Earth. 

So, what's happening tonight, July 23, and where are we in the lunar cycle? Keep reading to find out.

What is today’s moon phase?

As of Wednesday, July 23, the moon phase is Waning Crescent, and it is almost completely hidden to us on Earth. The moon will only be 2% visible to us tonight, according to NASA's Daily Moon Observation.

On day 28 of the lunar cycle, there's unfortunately nothing visible on the moon due to how little of it is illuminated.

When is the next full moon?

The next full moon will be on August 9. The last full moon was on July 10.

What are moon phases?

According to NASA, moon phases are caused by the 29.5-day cycle of the moon’s orbit, which changes the angles between the Sun, Moon, and Earth. Moon phases are how the moon looks from Earth as it goes around us. We always see the same side of the moon, but how much of it is lit up by the Sun changes depending on where it is in its orbit. This is how we get full moons, half moons, and moons that appear completely invisible. There are eight main moon phases, and they follow a repeating cycle:

New Moon - The moon is between Earth and the sun, so the side we see is dark (in other words, it's invisible to the eye).

Waxing Crescent - A small sliver of light appears on the right side (Northern Hemisphere).

First Quarter - Half of the moon is lit on the right side. It looks like a half-moon.

Waxing Gibbous - More than half is lit up, but it’s not quite full yet.

Full Moon - The whole face of the moon is illuminated and fully visible.

Waning Gibbous - The moon starts losing light on the right side.

Last Quarter (or Third Quarter) - Another half-moon, but now the left side is lit.

Waning Crescent - A thin sliver of light remains on the left side before going dark again.