Introduction
In the previous article, I described how I decided that the year in this fictional world would last about 384 days. Now I need to make sure that, apart from the different length of the year, the planet still retains the other Earth-like conditions. I’ll start with the two most important celestial bodies after the planet itself: the sun and the moon. In this article, I’ll explain what I changed and what remains Earth-like in this fictional world.
The Sun
Let’s start with the sun.
At a certain distance from our Sun, there is a habitable zone. Earth lies within that zone, which makes life as we know it possible. Enough sunlight reaches the planet, and it maintains an average temperature that allows flora and fauna to survive. I moved my planet a little farther away, so it travels along a larger orbit. That increases the time it takes to orbit the star, but in the case of an Earth-like sun, it would also reduce the intensity with which the star affects the planet. If this happened to our Earth — if we were placed on a larger orbit — the planet’s average temperature would drop. The polar regions would become larger, climate zones would shift, and some climate types would shrink significantly or even disappear entirely.
I want a longer year, but I also want to keep Earth-like conditions. So I decided to change the star’s parameters. That seemed like the better solution than changing the planet itself. Hypothetically speaking, with a few changes to the planet, we could create an Earth with a 384-day year and still preserve Earth-like conditions. I felt that the biggest challenge would be maintaining Earth’s typical average temperature. For example, I could increase atmospheric density and the amount of greenhouse gases. I could also modify the planet’s albedo and make it darker so that it absorbs more heat. Unfortunately, solving one problem that way might create several more in the future. Besides, it felt like that would change the planet too much. The changes did not seem that large, and I think they could work, but I have a feeling it will be better to modify the star instead.
So what can I say about the sun in this world? It will be a slightly larger and slightly brighter star — roughly 7% brighter than Earth’s Sun. That should compensate for the greater distance, and the planet should receive a similar amount of sunlight to Earth. The distance between the sun and the planet itself will increase by a few percent, around 3–4% compared to the distance between Earth and the Sun.
The differences a human would actually notice would be fairly subtle. If it were not for the longer year, a person living on this planet would probably not notice much of a difference. The star might appear a little less yellow and a little more white, since it is slightly hotter, but that does not necessarily mean the difference would be clearly visible to the naked eye. In the sky, the star would appear about the same size as the Sun does from Earth. It is farther away, but also slightly larger, so from the perspective of someone on the planet it should look about the same size as the Sun in our sky.
Fun fact: while sunlight takes about 8 minutes and 20 seconds to reach Earth, light from this world’s star will take about 8 minutes and 35 seconds to reach the planet.
The Moon
As for the moon, very little will change. I thought about its properties and how it affects the planet. Then I decided that it will be tidally locked, just like Earth’s moon. I considered whether I would want the moon in this fictional world to orbit faster, so that the planet’s inhabitants could eventually see different sides of it. That could add a new and interesting cycle that people might observe and interpret in their own way. Nevertheless, in the end I decided that while the idea is interesting, it does not really convince me, so I went with a tidally locked moon orbiting its planet.
A moon that is not tidally locked can suggest that it is relatively young, and that the gravitational forces of the planet it orbits have not yet managed to lock it in such a way that it always faces the planet with the same side. Thinking about this, I concluded that the Creator, while shaping the world, could have worked long enough for such synchronous rotation to develop. So from the planet’s surface, we will always see the same side of the moon.
Later, I also thought about the moon’s distance from the planet. I wondered whether I wanted to modify that as well, just as I had modified the length of the year. But then I immediately remembered how strongly Earth’s distance from the Sun affects conditions on our planet. True, the moon does not provide heat like the sun, but it has a major effect on Earth’s waters. And since I want to preserve Earth-like conditions, moving the moon closer to or farther from the planet could significantly alter how strongly it affects the planet’s waters. I also considered combining a change in distance with a change in the moon’s size. At last, I decided that Earth’s moon suits me best, and I do not need to make absolutely everything different. In short, I am sticking with an Earth-like moon.
Summary
I wanted a longer year on my fictional planet while still preserving Earth-like conditions for life. So I adjusted the star’s characteristics in this system so that life similar to what we know on Earth would still be possible on a planet with a longer year. I also addressed the moon right away, but in its case, almost nothing changed. As a result, my fictional world — apart from the length of the year — should be almost indistinguishable from Earth from the perspective of a human living on that planet.