Chapter 1: The Concept of Tidally Locked Planets

Have you ever imagined living on a planet where the sun remains fixed in the sky? No dawns, no dusks—just an unchanging sky. My fascination with tidally locked planets began several years ago, as the idea of a world that exists in a perpetual state of light and darkness captivated my thoughts. I came to understand that these types of planets could represent some of the most viable options for future human settlements beyond Earth.

Astronomers propose that many planets in our galaxy with Earth-like climates are likely to be tidally locked. This phenomenon occurs when a planet's rotation period matches its orbital period around its star, resulting in one side always facing the sun—similar to how we consistently see the same side of the Moon.

The prevalence of tidally locked planets can be attributed to the fact that a significant portion of stars in our galaxy are red dwarfs, also known as M-dwarfs. These smaller, cooler stars require planets to orbit much closer to maintain conditions suitable for life. Such proximity would inevitably lead to a tidally locked state.

For instance, the TRAPPIST-1 system has yielded seven Earth-sized planets situated within the habitable zone, all of which are likely to be tidally locked. This sparked my creative journey in writing "The City in the Middle of the Night," as I sought to envision the unique geological characteristics and the potential lifestyles of inhabitants on these distant worlds.

The first video, The Bizarre Planets That Could Be Humanity's New Homes, delves into the concept of human life on tidally locked planets, exploring their potential for habitability and the challenges that lie ahead.

Section 1.1: Challenges of Life on Tidally Locked Worlds

As we speculate about the existence of life on these planets, we must consider where humans might establish settlements. My research pointed to the "terminator" zone—the narrow twilight region that separates the sunlit side from the dark side—as an optimal location. According to astrophysicist Daniel Angerhausen, this area could represent a "Goldilocks zone," where conditions are neither too hot nor too cold.

In this twilight region, we might harness geothermal energy by utilizing cold water from the nightside and hot water from the dayside to create a thermal reactor.

Subsection 1.1.1: The Role of Heat Transport

To sustain liquid water on a tidally locked planet, effective heat transport between the sides is essential. Ludmila Carone from the Max Planck Institute for Astronomy emphasizes that without a proper system to manage temperature, water could either freeze on the dark side or become vaporized on the sunny side.

Carone's computer models suggest that these planets might experience strong wind patterns, akin to Earth's jet streams, that could facilitate heat distribution. However, if a planet orbits too close to its sun, it may only have a single wind jet, which could lead to excessive heat accumulation on the dayside.

Even modest temperature differences could pose serious challenges to habitability. Laura Kreidberg, a junior fellow at Harvard University, points out that the climate on the sunny side might remain comfortable, while the opposite side could plunge into frigid conditions.

Chapter 2: The "Eyeball Earth" Model

One intriguing possibility for a tidally locked world is the "eyeball Earth" concept, where ice covers the planet entirely until it melts on the sun-facing side, creating a structure resembling an eye from space. This could lead to unique oceanic configurations, potentially resulting in a warm ocean surrounded by ice.

In extreme cases, intense heat on the sunlit side could eliminate all water, but with sufficient temperature variance, water could reappear on the nightside after drifting from the bright side.

The second video, TRAPPIST-1 - The New h, investigates the TRAPPIST-1 system and its potential for supporting life, examining the challenges and opportunities these planets present.

As we consider the implications of living on a tidally locked planet, we must also account for the potential threats posed by red dwarfs. These stars are known for their unpredictable behavior, including violent flare-ups that can strip away planetary atmospheres, similar to what Earth experienced in its early history.

Even with a stable atmosphere, the constant daylight could expose inhabitants to harmful radiation. Unlike Earth, which benefits from a protective ozone layer, a tidally locked planet around a red dwarf may lack this vital shield.

In my narrative, I imagined a world where the harsh sunlight not only poses risks but also necessitates that inhabitants remain in shaded areas to avoid severe burns.

While these planets present a fascinating array of challenges, the potential for life is not entirely bleak. Research by physicists Joseph Gale and Amri Wandel indicates that plant life might initially develop in oceanic environments, benefiting from the water's protective qualities. If conditions stabilize, land-based flora could eventually thrive.

With the right atmospheric conditions, we could see air currents strong enough to regulate temperatures and create a cloud cover that acts as a permanent sunshade, leading to a climate reminiscent of Earth's tropical regions.

As scientists refine their understanding of tidally locked planets, the possibility of human life beyond the terminator zone appears increasingly plausible. Adiv Paradise, an astronomy Ph.D. student, speculates that humans might live on the sunny side while establishing systems to transport ice from the nightside.

The primary hurdle for inhabitants may stem from the altered perception of time and the sky. Those living in perpetual daylight could lose sight of the stars, fundamentally changing their understanding of the universe.

In "The City in the Middle of the Night," I explored diverse societal adaptations to these unique challenges, showcasing how humans could leverage temperature differences for energy. While my portrayal may lean more towards fiction than strict scientific accuracy, it serves to highlight the wonder and complexity of life on a planet orbiting an alien star.

As we continue to uncover new information about tidally locked worlds, I believe this topic will gain traction in science fiction, providing fertile ground for narratives that challenge our understanding of existence and our place in the cosmos.