What brings order on Earth is gravity. For all matter on Earth, gravity is always at work.
Not only does gravity sculpt planets and the universe, it’s why rocks fall downhill. Gravity is always at work on Earth.
Gravity is the constructor of our planet 4.6 billion years ago. Depending where you are on Earth, gravity varies.
For example, gravity is 9.764 m/s2 in Peru and 9.834 m/s2 in the Arctic. This is because mass (like mountains) and the bulge at the equator amplifies it.
Gravity and atmosphere on other planets
A planet or moon’s gravity dictates the thickness of an atmosphere. How gravity works is that there’s a direct relationship with the mass and gravitational pull that an object will yield.
For example, the gravity of the moon is 1/6 of Earth. This makes sense because the moon is much smaller in size compared to the Earth.
This means that the moon is too weak to hold onto an atmosphere. The lack of an atmosphere means its surface gets very hot (117°C) when facing the sun. But it also gets cold (-153°C) when facing away from the sun.
Mars has a thin atmosphere because its gravity is about 1/3 of Earth (3.711 m/s2). But the atmospheric composition of Mars is carbon dioxide (95.0%), Nitrogen (3.0%) and Argon (1.6%). On the other hand, enormous Jupiter has held onto its original composition. This is because Jupiter’s gravity is large enough to retain light gases like hydrogen and helium.
Gravity is responsible Earth’s tides and bulge
It’s not only rotation that causes Earth to flatten at the poles. But it’s also from the moon’s gravitational pull. Because the moon is close to the Earth, it stretches the planet where it’s facing.
When the Earth rotates, the bulge shifts on both sides of the planet according to the position of the moon. In full swing, this causes sea levels to rise and fall which are ocean tides.
The side closest to the moon experiences a high tide because the moon pulls the body of water close to it. But because oceans retain a set amount of water, water levels rise in one area and drop in another area.
Despite the sun’s enormous size, it has less of an effect than the moon for influencing ocean tides. Even though the moon is smaller, the moon is closer. So this means that its pull is stronger than the sun.
Earth is nearly a closed system due to gravity
The escape velocity of Earth is the speed at which an object must travel to break free of a planet’s gravitational pull into space.
Like a mason jar, Earth is nearly a closed system. We lose some hydrogen from the atmosphere due to its escape velocity.
And we get the occasional meteor strike. But in general, Earth is a closed system because it doesn’t exchange matter from or to the outside.
However, Earth exchanges energy due to incoming solar radiation. But in terms of matter, little of it leaves or enters Earth’s nearly closed system.