Few celestial bodies capture our imagination quite like the moon. From its phases to its influence on Earth’s tides, the moon’s sway is undeniable and has inspired folklore, fueled scientific inquiry, and provided a canvas for countless poets and dreamers throughout history.
Situated an average of 238,855 miles away, the Moon has a radius of 1,079 miles and a circumference of 6,786 miles, which are both approximately a quarter that of the Earth’s, and a gravity that’s just 16.6% that of our planet. Read on, and find out more interesting facts about Earth’s only satellite.
1: The Sun and Moon have the same apparent size
We see solar eclipses the way we do only by a remarkable coincidence — although the Sun is 400 times bigger than the Moon, it is also 400 times further away. This fortuitous alignment allows the Moon to perfectly cover the Sun during a total solar eclipse, creating the spectacular phenomenon known as totality. The rarity of such events underscores the delicate balance of celestial mechanics and offers astronomers invaluable opportunities to study the Sun’s corona and phenomena associated with it.
2: The Moon is actually egg-shaped
Instead of being round like a beach ball, the Moon is decidedly egg-shaped, and the only reason it appears to be round is because one pointed end is aimed right at Earth. This deviation from a perfect sphere is known as lunar oblateness. Furthermore, the Moon’s center of mass is not located at its geometric center, and is instead located at a point roughly 2 miles (3.2 km) off-center. These factors combined result in the Moon’s subtle but discernible egg-shaped morphology.
3. There are 8 main Moon phases
The moon’s phases occur as sunlight illuminates different portions of its surface throughout its orbit around Earth. When the moon is between the Earth and the Sun, its dark side faces us, marking the new moon phase. As it orbits, we gradually see more of its illuminated side, leading to the waxing crescent, first quarter, waxing gibbous, and full moon phases. Subsequently, the moon wanes through the waning gibbous, last quarter, and waning crescent phases as it completes its orbit, returning to the new moon phase, with the eight stage cycle repeating every 29.5 days.
These phases not only fascinate skygazers but also play crucial roles in various cultural, religious, and scientific practices worldwide. These include Easter in Christianity, Ramadan in Islam, and China’s Mid-Autumn Festival.
4: The Moon has an atmosphere after all
Contrary to popular belief, the Moon does have an atmosphere of sorts. Findings obtained during NASA’s LADEE (Lunar Atmosphere and Dust Environment Explorer) mission point to a tenuous atmosphere consisting of helium, neon and argon around the Moon. The helium and neon components derive from the solar wind, which is a continuous emission of energetic particles by the Sun, while the argon is generated by the radioactive decay of potassium in the Moon’s crust.
5: There are regular moonquakes
Regular quakes have been found to originate several miles below the Moon’s surface, which are believed to be caused by tidal effects due to Earth’s gravitational pull. Some moon quakes are even powerful enough to cause small cracks to appear on the surface, through which various gases are known to escape.
However, the exact causes of the quakes are yet to be determined, but it seems unlikely to be the result of a molten core and plastic mantle in the Moon’s interior. By comparison, the Moon’s core accounts for only 2 to 4% of the Moon’s mass, whereas the iron core of the Earth accounts for roughly 30% of the Earth’s mass. Investigations are ongoing, but a definitive explanation of the Moon’s geological activity seems to be a long way off.
6: There’s dancing dust on the lunar surface
Some Apollo astronauts noticed that during sunrises and sunsets on the Moon, moon dust seems to rise, and hover just above the surface. Exactly why and how this happens is still a mystery, but it is believed to be caused by dust particles being electrically charged at these times. One of the functions of the LADEE mission is to study the phenomenon, and results are expected soon.
7: The Moon is moving away from the Earth
All actions have opposite and equal reactions as Newton demonstrated, but in the case of the Earth-Moon system, this reaction is causing the Moon to recede from Earth at a rate of roughly 3.8 cm (1.4 inches) every year. This is happening because the Moon is slowing Earth’s rotation, and as a result, the Moon “uses” the lost energy to propel itself away from Earth.
The rate of recession is known precisely because astronomers regularly fire powerful lasers at the Moon, and some of the light is returned by mirrors placed on the Moon by Apollo astronauts. The time the light takes to return to sensors on Earth is converted into distance measurements.
8: The flags on the Moon are now white
Many images of the Moon’s surface show that of the six flags planted on the Moon by Apollo astronauts, five are still upright. However, the harsh solar radiation on the Moon has caused the color on the flags to fade away leaving them a sparkling white, exactly like a flag fades on Earth if it is exposed to direct sunlight for extended periods.
In case you did not know, the flags were made of nylon by Annin Flagmakers, based in Roseland, New Jersey, and they cost the princely sum of $5.50 each at the time of delivery to NASA.
9: Moon landing conspiracy theories now debunked
High-resolution images released by NASA in 2011 have finally and conclusively proven that the Moon landings did indeed take place- just like NASA had been saying all along. The image below says it all.
This image is courtesy of the Lunar Reconnaissance Orbiter which has been surveying the Moon’s surface since 2009. This particular image of the Apollo 12, 14, and 17 missions has a resolution of 25 cm by 25 cm p/pixel, and was taken from an altitude of 15.5 miles (25 km).
10: There is no dark side of the Moon
Contrary to what you may have heard or read somewhere, both sides of the Moon receive the same amount of sunlight. We only see one side of the Moon, and sometimes when it is illuminated by sunlight reflecting off Earth, the side furthest away from us is illuminated by the Sun, which is also where the light comes from that is reflected on the side of the Moon that is turned towards us.