How Gravity Works
What brings order on Earth is gravity. Gravity is always at work.
Not only does gravity sculpt planets and the universe, it’s why rocks fall downhill.
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. For example, the gravity of the moon is 1/6 of Earth.
This means that it is too weak to hold onto an atmosphere. The lack of an atmosphere means moon’s 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).
On the other hand, enormous Jupiter had held onto its original composition. This is because Jupiter’s gravity is large enough to hold onto light gases like hydrogen and helium. This way, we can get a sneak peak of our early solar system
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 sun has lesser effect than the moon. Even though the moon is smaller, the moon is closer. So this means that it’s 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.
Earth exchanges energy due to incoming solar radiation but little matter leaves or enters.