Definition:Earth
Definition
Earth is the planet on which we live.
It is the third planet of the solar system from the sun.
Its orbit lies between those of Venus and Mars.
Shape
First Approximation
To a first approximation, the shape of Earth can be considered to be spherical.
Second Approximation
To a second approximation, Earth is an oblate spheroid.
Also known as
Earth can sometimes be seen referred to as the globe (sometimes with a capital: the Globe), which is of course just a synonym for sphere.
This nickname is of no more significance than referring to one's own home as (for example) the house, but it gives rise to the adjective global, which is new-age speak for worldwide.
In the field of science fiction the name Terra is more frequently seen than anywhere else, often used to refer affectionately as the original homeworld of the human race.
Linguistic Note
Earth is a proper name: that of the planet on which (at time of writing) all humans live.
As such, its correct styling is for it to start with a capital letter.
This is the convention to be used on $\mathsf{Pr} \infty \mathsf{fWiki}$.
However, in much literature it can be seen referred to as the earth, which is a bit like, for example, referring to Albert Einstein as the albert.
In recent literature, particularly popular, new-age and poetic, there is a trend to referring to the place as Planet Earth.
Sources
- 1976: W.M. Smart: Textbook on Spherical Astronomy (6th ed.) ... (previous) ... (next): Chapter $\text I$. Spherical Trigonometry: $4$. Terrestrial latitude and longitude.
- 2014: Christopher Clapham and James Nicholson: The Concise Oxford Dictionary of Mathematics (5th ed.) ... (previous) ... (next): Earth