Article

[Rustamsher]

Hello Alan,

1a. We live on Earth, which is the 3rd planet in the solar system.
1b. We live on the Earth, which is the 3rd planet in the solar system.
2a. Yuri Gagarin (a Soviet Russia cosmonaut), the first man in outer space,
completed an orbit of Earth on 12 April 1961.
2b. Yuri Gagarin (a Soviet Russia cosmonaut), the first man in outer space,
completed an orbit of the Earth on 12 April 1961.

Recently the sentences above were discussed in our class and we got the following answer from our teacher:
The article is not needed, but equally it is not incorrect.
Both forms can be used with the specific examples given.

Before asking the question, I searched for a similar topic asked on the Forum and it turned out that you answered a long time ago. As language evolves rapidly, I'd like to know your opinion in this respect.
Also, I would like to know wether he is right about that.


Many thanks.

[Alan]

Yes, your teacher is quite correct!