A Moon with a View: the extraterrestrial sky
Image: "New England sky at dusk", Adrian Pelletier for Unsplash, 2017. This magical photo captures the momentary coexistence of day and night; the transient instance before day cedes to night, sun yields to moon, and eventide prevails until dawn.
When I gaze up at the night sky and scan the firmament, feelings of both insignificance and comfort wash over me. All my troubles are put in their place when measured against the magnitude of the endlessness of space, which, existentially, we are all a part of. We are, in fact, stardust (as Joni Mitchel so aptly pointed out when she penned the song "Woodstock"), considering that everything in and of the human body was forged by the stars. I don't know a lot about the universe—comprehending black holes and the space-time continuum eludes me beyond basic definition; nonetheless, the intangible mysteriousness induces a contemplative state of mind, as I look skyward to Earth's viewing platform—the Moon.
Image: "Earthrise", William Anders/Apollo 8. Earth from lunar orbit, as it appeared Christmas Eve, 1968. (NASA)
By spaceship, traveling 25,000 mph, we can reach the Moon in just three days (to reach Mars or Venus, Earth's next closest celestial bodies, takes six months). On Christmas Eve, 1968, the first humans witnessed earthrise. Hovering just 60 miles above the Moon's surface in their spacecraft, three Apollo astronauts unexpectedly caught sight of this fleeting moment, and astonished, they sought to capture for the rest of humankind, this sublime vision of Earth. For the first time in its history the planet Earth had a human audience. Astronaut Bill Anders, who snapped the iconic photo above commented: "Here we came all this way to the Moon, and yet the most significant thing we're seeing is our own home planet".
Image: the first photo of Earth captured by rocket engine.
Applied Physics Laboratory, Oct. 24, 1946.
This was not the first extraterrestrial image of Earth. A blurry black and white photo was taken by a Nazi-engineered rocket launched from White Sands, New Mexico, in 1946. From 65 miles above, it shows just a portion of Earth's surface including its curvature. (Prior to that, a high altitude photo was obtained by balloon as it drifted 22 miles above Earth, and which, likewise, captured the curvature)
The marvelous marble.
Image: Apollo 17 crew, "The Blue Marble", 1972. (NASA)
Interstellar Earth appears round beginning at a distance of 20,000 miles. It also has phases that occur contrariwise to the Moon's. For example, when the Moon appears full to the terrestrial observer, simultaneously, Earth is in crescent phase from a lunar perspective. Just 24 humans have personally seen our globe, with only three of them having observed it as the whole-planet. The image above, taken at 28,000 miles, is the only photo of Earth in full phase captured by a human. Apollo 17 crossed the path between it and the Sun in December, 1972.
Images: during Moon's full phase, our planet, conversely, appears as a "sliver Earth (crescent)" in the extraterrestrial sky. (click on the gallery to expand photos)
From crescent to full, the Moon, in its phases, provides us an ever-changing display throughout its 8-stage revolution around the Earth. It is Earth's only natural satellite: caught in Earth's gravitational pull, the Moon revolves around the Earth, and by virtue, stabilizes Earth's axis, which regulates everything from the length of day, the tides, and climate.
Image: views of the Moon waxing and waning over the course of a
month. Lunar libration with phase, Tom Ruen, 2007. https://commons.wikimedia.org/w/index.php?curid=10200976
These conditions persist because the Moon is not currently subject to orbital decay. However, as the universe continues to expand, gravitational pull will lessen, and the Moon will eventually be released from its repetitive trajectory, drifting away to an uncertain fate (its expanding orbit grows by 1.6 inches annually). But, that's the distant endgame. The origin story, on the other hand, evolves out of an equally compelling narrative that combines cause and effect with dumb luck (and, of course, a heaping measure of mystery).
The Moon is 4.51 billion years old, slightly younger than Earth, which is 4.54 billion years old. The giant impact-hypothesis explains that the Moon was formed when a Mars-size meteor slammed into young Earth at a velocity 100 times greater than the event which extinguished the dinosaurs! Debris from this impact flew up into space, and the particles began to orbit the Earth. Eventually, they coalesced, and several hundred thousand years later (a blip in space time), the Moon was thusly formed. Initially, its entire surface consisted of a magma ocean that glowed red, and it appeared 15 times larger in Earth's sky than today.
Image: "Big Bertha", as this Earth rock is affectionately called, was collected
during the Apollo 14 moonwalk. It weighs 20 pounds, and is the third largest
rocklet retrieved from the Moon. It is considered Earth's oldest rock. (NASA)
Strangely enough, the "Big Splash", as this impact event is genially known, led to the discovery of an Earth rock on the Moon! As impossible as this sounds it's true. During the Apollo 14 lunar mission in 1971, astronauts gathered surface samples. Since then, the rocklets collected have been analyzed at various times over the proceeding decades as more sophisticated technologies have been developed. Recently, it was revealed that trace elements in one of the rock's minerals were unique to Earth. Scientists were initially baffled, but a narrative emerged that explained how such an oddity could be. With prior speculation that young Earth was under constant, violent asteroidal bombardment during the Hadean period (post-Moon formation), it is conceivable that Earth fragments could have been projected all the way to the Moon's surface, especially when considering these two astronomical bodies were three times closer than today. Further, that meteoroids are found on Earth supports the exchange-of-rocks premise.
An additional hypothesis with even greater implications was introduced in a 2019 German scientific study that asserts the collision also brought water to Earth by providing significant carbonaceous material. In fact, they surmise this single cosmic event accounts for the entire amount of water on Earth; inasmuch, their theory suggests if not for this collision, life on Earth would not have been possible. Without eyewitnesses, though, we are left to rely on speculation to decipher these magnificent mysteries.
Image: A million miles away. The far side of the Moon as it crosses in front of the DSCOVR spacecraft's EPIC camera and telescope—one million miles away. (NASA)
The Moon is a quarter the size of the Earth. Its distance from Earth varies as it orbits our planet, but it ranges between 28 to 32 Earths away. The Moon's appearance from the hemisphere that faces Earth typically ranges from white during daytime, to bright yellow in the evening, as it reflects the Sun's light. In actuality, the Moon's surface is nearly devoid of strong pigmentation and its true color is gray.
Image: "Day for December 25, 2015", this photo is a composite made from a series of images taken by the Lunar Reconnaissance Orbiter Camera (LROC) on October 12, 2015. The large tan area includes the Sahara Desert and Saudi Arabia. (NASA)
As the Moon spins on its axis, it revolves at the same rate around the Earth. Moving at 2,288 MPH, it takes the Moon 24 hours to fully rotate once each time it circles the Earth. This synchronicity causes only one side of the Moon, the near side, to face the Earth so
that we never see the other side, the far side of the Moon. By comparison, the Earth,
which is significantly larger, rotates at 1,000 MPH, and revolves around the Sun at 70,000 MPH. As such, its surface features are ever-changing before the near side of the Moon;
from this perspective, the Earth sometimes displays oceans while at other times, continents. Earth's dynamic atmosphere, too, presents changing patterns, unlike the Moon's atmosphere, which is negligible and visually imperceptible to Earth.
Image: June Moon, source unknown
If the Moon were to suddenly disappear tomorrow it would not signal the end of all life on Earth, but it would be an extremely different place to inhabit. Most unfortunately, Earth's axial tilt would increase dramatically, nearly doubling, resulting in a significantly cooler equator and catastrophically warmer North and South Poles. The Polar ice caps would completely melt, leading to a calamitous rise in sea levels that would flood the Earth globally. These changes would precipitate staggering consequences requiring colossal acclimation as the only option for survival. The moon, therefore, is not a static lantern but serves an integral purpose to terrestrial endurance.
Image: human footprint on the Moon made during the Apollo 11 landing on July 20, 1969, by astronauts, Neil Armstrong and Edwin Aldrin. (NASA)
Before humans landed on the Moon, it was an enigma physicists, philosophers, and poets had studied, pondered and dreamed about for eons. Since landing on the Moon, the Earth has been unexpectedly realized in a way that will long cause those who imagine, the possibilities of a new perspective. From our lunar perch, we've been allowed to grasp the profundity of the World like never before. The implications are such that they will be contemplated for generations to come—all thanks to the Moon with a view.
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