GoKawiilLet’s take a look at the Moon as seen from space in all its sunlit glory. You can drag it around to change your point of view, and you can also use the slider to control the date and time:
In this convenient view, we can freely pan the camera around to see the Moon and its marvelous craters and mountains from various angles. Unfortunately, we don’t have that freedom of motion in our daily experience – the Moon wanders on its own path across the daily and nightly skies.
We can simulate these travels below, where you can see the current position of the Moon in the sky. You can drag that panorama around to adjust your viewing direction – this lets you see the breadth of the sky both above and below the horizon. By dragging the sliders you can witness how the position of the Moon changes in the sky across and hours of your local time. As the Moon’s placement in the sky shifts, the little arrow will guide you to its position.
You can also drag the little figurine on the globe in the bottom-right corner to see how the sky looks at that location on Earth. If your browser allows it, clickingtapping the button will automatically put the figurine at your current location. This may all feel quite overwhelming at the moment, but we’ll eventually see how all these pieces fit together:
Over the course of one day, the Moon travels on an arc in the sky almost completing a loop around the Earth. As the pass, the Moon’s illumination also visibly changes.
You’ll probably admit that it’s a little hard to focus on the tiny Moon as it shifts its position in the sky. To make things easier to see, I’ll zoom in the camera and lock its position on the Moon:
Notice that across a single day the Moon seems to rotate, and over it quite visibly wobbles. These wobbly variations let us occasionally see some hidden parts on the “edges” of the Moon, but our neighbor ultimately shows us only one of its sides. In our space-floating demo we could easily see the Moon from all sides, but on Earth we can never see most of the far side of the Moon.
Over the course of , the lighting on the Moon also changes dramatically. The line between the lit and unlit parts of the Moon, known as the terminator, sweeps across the Moon, revealing the details of its surface. Although the Moon has a spherical shape, the fully lit Moon looks more like a flat disk.
In this article I’ll explain all the effects we’ve just seen, and we’ll also learn about gravity, ocean tides, and eclipses. Let’s begin by exploring how celestial bodies move through space and how their mere presence influences the motion of their neighbors.
Motion in Space
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