It has life
It has running water
It is a planet with only one moon (Pluto used to be one, too, but it's no longer considered a planet)
You can compare it to many other planets including: Earth, Uranus, and Mars.
Earth is the biggest of the terrestrial or rocky planets, but smaller than any of the gas giants.
Studying the earth helps scientists to understand other planets since the earth is part of the solar system. Scientists use the features of the earth to compare them with what other planets hold.
The Earth's diameter of 8000 miles compares with 33,000-88,000 miles for the four outer planets.
The other planets do have gravity.
Earth has an average eccentricity in its orbit of 0.0167. This compares with 0.0068 for Venus and 0.205 for Mercury, which are the minimum and maximum eccentricities in the eight planets. So, the Earth's orbit is not too far from circular. In order of increasing eccentricity, the list of planets is: Venus Neptune Earth Uranus Jupiter Saturn Mars Mercury.
Since no one from Earth has visited another planet, and we have no indication that there is anyone on the other planets, Earth does not help other planets in any way. Why do you think there is something Earth does to help them- whoever them is.
Earth and the other planets are mostly made of rock.
larger
Astronomers have found Earth-sized planets in other solar systems.
No, other planets are rotating at other speeds.
rotate