Is Planet Earth Capitalized?

I believe it is capitalized when it is the planet. If you just write "earth" that means dirt. It is a proper name, but maybe you do not want to correct your dad, or maybe you do, before someone else does and embarrasses him. It is just like you capitalize the name of Pluto, or Jupiter, or Mercury. The same rule does not seem to apply to sun and moon, I guess because there are many suns and many moons around many planets. If you say Planet Earth, though, you capitalize them both.

If it's the big round shaped ball, then it's "Earth", if it's the small brown stuff on the ground, then it's "earth" ;)

I think it is. it is a proper noun, therefore it is capitalized. Now, if you are talking about digging in the earth, the earth is round, etc. it doesn't need a capital letter, but if it is Earth, on it's own, or Planet Earth, then it is a proper noun and should be capitalized.

Yes, it has to be capitalized as it is a proper noun and you should always capitalize them when you write. It is important to know that you are doing things right and grammar is extremely important in writing.

Using the word earth to describe the substance most commonly used to plant a seed, you would not capitalize it. Using the word to describe the planet upon which most of us are from, you would. It is a name in the latter case, so it is capitalized. So, the following sentence correctly utilizes the word in both forms: "Johnny Appleseed roamed the Earth planting apple trees in the earth." Because it can be used with or without a capital letter 'E' spell checkers will not flag it as a mistake in either form. Why the word 'english' tends to be caught by spell checkers, I don't know, as it can also be used correctly with a lower case 'e.' English, the language or the people from England, should be capitalized, but english, the spin put on a ball (e.g. bowling, tennis, billiards), would not be.

Earth should be capitalized whenever it is used properly. If a person is referring to the planet by name it is a proper noun and should be capitalized. (All of the other planets are capitalized.) If one is speaking of soil, then unless it is necessary to specify otherwise, it should be assumed that the soil comes from the planet Earth making it unnecessary to make the distinction. Because of this specification even Earth/soil should be capitalized in the following sentence "I was digging in the Earth." If you were an astronaut bringing home a bucket of soil from the moon then I suppose the bucket would be filled with "Moon" not "Earth". (I understand that this example is somewhat tongue-in-cheek but I think you get my point.)

If at the beginging of a sentence its Capitolized but in the sentence it is not.

it's a name of something like Venus, Mercury etc so it should be capitalized or at least that's what I was taught in English class in my native language though, the translation of Earth is not capitalized but other planet names are strange I know but I don't remember why

In usage for some people it may be different,but in my experience of Language,a Name was always capitalised...so,Big "E" for the Planet :)

I think so because it is the name of the planet. Planet is a noun while Earth is a name of a planet and so it is Proper Noun so it must be capitalized.