1. Why Earth Always Stays in the Same Spot in the Moon's Sky
The Moon rotates exactly once while it orbits Earth. This means the Moon always shows Earth the same face. This state is called tidal locking [2]. From the Moon's side, the view is different. If you stand on the near side, Earth stays in almost the same position in the sky. It does not rise or set. Because the Moon wobbles slightly, Earth just shifts a little in that area [1]. If you stand on the far side, you cannot see Earth at all [1][2].
The phases of Earth are the opposite of what we see from here. When we see a full Moon, the Sun is on the other side of Earth. So, from the Moon, Earth looks like a "new moon" (dark side facing the Moon). Conversely, on a night with a thin crescent Moon, Earth looks almost full from the Moon [3].
When the Sun, Earth, and Moon line up, we see a lunar eclipse. From the Moon, this looks like a solar eclipse. On March 14, 2025, a total lunar eclipse was visible in parts of the Americas. The Blue Ghost lander, which had been on the Moon since March 2, photographed Earth blocking the Sun. It captured the "diamond ring" effect as the Sun emerged from Earth's edge [4][5]. It is a quiet, strange sky. But this sky lacks things found in Earth's atmosphere.
2. Why the Moon's Thin Air Causes Extreme Temperature Swings
The Moon has an atmosphere, but NASA describes it as very thin and weak, and not something people can breathe [6]. Earth's air acts like a blanket for our bodies and carries heat as wind. Since the Moon has almost none, the temperature difference between sunlight and shade is extreme. The analogy of a blanket is a simplification, but it captures how heat is stored and moved.
Temperatures vary by location and measurement. NASA states the sunlit side is about 127°C, and dark areas are about -173°C [6]. The LRO satellite measured daytime temperatures near the equator at about 107°C and nighttime at about -183°C [7]. Reports on Japan's SLIM mission mention days over 100°C and nights down to -180°C or about -170°C [8][10]. Roughly, remember days are over 100°C and nights are around -170 to -180°C.
Some places are colder. In crater bottoms near the South Pole, where sunlight never reaches, temperatures below -238°C have been measured [7]. How long do these days and nights last?
3. How Two-Week-Long Nights Cause Problems for Solar Power and Heat
Day and night on the Moon each last about 14 days [8]. With two weeks of night, solar-powered probes cannot generate electricity, and temperatures drop to around -170°C [10].
On January 20, 2024, Japan's SLIM landed on the Moon. It landed about 55 meters east of its target. The goal was within 100 meters, so it was a pinpoint landing [9][12]. However, one engine failed at about 50 meters altitude, and the craft landed nearly upside down. Its solar panels faced west and could not generate power [9][12].
On January 28, the Sun tilted west, light hit the panels, and power returned. After observations, night arrived around January 30–31 [10]. SLIM was not designed to survive the night, but it responded to commands from Earth on February 25–26 [8][10]. It survived three nights and ended operations on August 23, 2024 [11].
Some places have almost no night. A study of LRO images found that parts of the rim of Shackleton Crater near the South Pole are lit for about 94% of the lunar year. Shadows last at most about 43 hours [13]. This site is a candidate for solar-powered bases. Surviving the night is one problem. The next is invisible particles falling from the sky.
4. Why Cosmic Radiation Is a Danger and How Caves Might Help
Earth has an atmosphere and magnetic field that soften cosmic radiation. The Moon has neither [14].
On January 3, 2019, China's Chang'e 4 landed on the far side. It carried a detector developed by Kiel University in Germany to measure radiation. The paper was titled "First measurements of the radiation dose on the lunar surface" [34][15]. The result was about 60 microsieverts per hour. This is about 200 times the ground level and 5–10 times the radiation on a passenger flight from Frankfurt to New York [14][15].
Researchers suggest covering habitats with thick lunar soil for long stays [14]. Another idea is underground. Japan's Kaguya satellite found a pit in the Marius Hills in 2009, about 65 meters wide and 80–88 meters deep. The team thought the roof of a lava tube had collapsed [16]. In 2017, radar data suggested lava tubes about 50 kilometers long might remain. Researchers say these tubes could protect against radiation, micrometeorites, and temperature changes, making them suitable for bases [17]. This is estimated from images and radio waves. Even if radiation is blocked, your body faces another lunar condition.
5. How the Moon's Low Gravity Limits How Long People Can Stay
The Moon's gravity is about 1/6 of Earth's [6]. You would weigh 1/6 as much. A 30 kg person would feel like they are holding a 5 kg object. The ESA says Apollo astronauts bounced more than they walked [19].
Lightness is not always easy on the body. On the International Space Station, without exercise, bones lose about 1% of mass per month. Crews exercise about 2 hours a day [20]. What happens in 1/6 gravity? The ESA states the effects on the body working in lunar gravity are "not yet known" [19]. Researchers think bouncing on the Moon might stress bones similarly to walking or running on Earth [19].
People have spent little time on the Moon. The ESA says 12 people have stood on the surface [21]. The last mission, Apollo 17, lasted about 75 hours on the surface, with 22 hours and 4 minutes of spacewalks [18]. NASA calls these 3 days one of the most extensive lunar explorations in the Apollo program [33]. No one has lived there for months. During those 75 hours, astronauts struggled with the sand at their feet.
6. Why Moon Dust (Regolith) Is Sharp and Sticky
Lunar sand is called regolith. It is particles formed by rocks being smashed by meteorites. Earth sand is rounded by wind and water. On the Moon, there is no wind or water, so grains are sharp like glass shards [21][22]. Static electricity makes them stick to everything [22].
Apollo 17 geologist Harrison Schmitt sneezed and had a stuffy nose in the spacecraft. He called it "lunar hay fever." The ESA says all 12 astronauts had some symptoms [21]. The dust wore down boot layers and broke vacuum seals on sample containers [21]. The ESA notes that particles 1/50th the width of a hair could stay in lungs for months, and says "we do not know how harmful this dust is" [21].
Some see the dust as a material. By mass, lunar sand is about 40–45% oxygen. However, it is bound to metals like iron and titanium, so you cannot breathe it directly [23][24]. The ESA and UK company Metalysis experimented with simulated sand. They heated simulated sand in molten salt to about 950°C and passed electricity through it. They extracted about 96% of the oxygen in about 50 hours [23]. This was with simulated sand, not real Moon dust [24]. Oxygen is underfoot. What about water?
7. Why Scientists Search for Water Ice in Dark Craters Near the South Pole
Near the Moon's South Pole, there are crater bottoms that never see sunlight. It has long been thought that water ice might remain there without melting [7].
On October 9, 2009, NASA's LCROSS probe crashed a spent rocket stage into Cabeus Crater. LCROSS then observed the plume of material thrown up by the impact. About 155 kg of water vapor and ice were detected in the plume. The team estimated that about 5.6% (plus or minus 2.9%) of the soil mass was water ice [25][26]. This is for one location.
Where and how much water exists is still being investigated. India's Chandrayaan-3 landed at about 69° South latitude on August 23, 2023. It measured surface temperatures of about 57°C, higher than predicted by lunar orbiters. The team says temperature differences vary greatly by location at high latitudes [27]. Temperature determines how fast ice is lost, so these details help find ice.
More missions are coming. Japan and India plan to launch LUPEX in fiscal 2028. A rover will collect soil from as deep as about 1.5 meters to test how much water there is and what it is like [28]. China's Chang'e 7 plans to land near Shackleton Crater to look for ice. Its launch was delayed to 2027, possibly due to typhoons [29]. If ice is found, it has uses beyond drinking.
8. How Using Resources Found on the Moon Could Reduce What Must Be Carried from Earth
Carrying everything from Earth is heavy and expensive. So, "In-Situ Resource Utilization" (ISRU) is considered. It is like using water found at the destination instead of carrying it all from home. But there are no rivers on the Moon; you must find ice and melt it first.
JAXA envisions a "Lunar Propellant Production Plant." It would extract water from lunar sand, split it into hydrogen and oxygen, and use it as fuel for landers. JAXA calls this a core system for sustainable lunar exploration from the 2040s onward [30]. An article citing JAXA studies says that if there are 7 or more crewed missions, making fuel on the Moon uses fewer supplies from Earth [32].
On July 22, 2026, JGC Holdings was selected for a JAXA project to design and test a ground-based plant. They will experiment with extracting water from sand by March 31, 2027 [31]. Combined with ESA's oxygen extraction experiments, lunar factories are currently at the design and lab stage.
9. Why the Dark Part of a Thin Crescent Moon Glows with Earth's Light
Two weeks after the full moon, a thin crescent moon appears in the western evening sky. After sunset, the dark part of the crescent may glow faintly. This is earthshine.
If you stood on the Moon at that time, Earth would be almost full and bright. Sunlight hitting Earth illuminates the Moon's night side [3]. If you see the dark part of a thin moon, you are seeing Earth's light reflected on the Moon. NASA explains that spring is often easier to see depending on sky conditions, so some autumn nights may not show it [3]. To protect your eyes from the Sun, wait until the Sun has completely set before looking.
You can read what scientists want to verify in lunar exploration on the JAXA LUPEX page [28].