I have done an extensive research and I am aware that Sun and Earth can be ordinary and proper nouns depending on the context. I am writing the engineering text, which is also concerned with transfer of energy and light between Earth/earth and Sun/sun.

I initially used capitalised forms, Sun and Earth. I gave my text for editing, and curiously, the editor changed Sun to sun and left Earth intact. So what I got in the end is something like that

A typical example of heat transfer by radiation occurs between the sun and the Earth.

This looks a bit inconsistent to me. What would you suggest?

Would it be OK if I put both Earth and Sun to uncapitalised form?

Thanks for the advices.

EDIT: this might be interesting:

  1. Serway's textbook consistently use Sun and Earth,
  2. Incropera's textbook consistently use sun, while earth in used in about 90% of cases.

They both seem to be pretty consistent to me.


I understand that your instinct, if you see sun with a lower case S, is to use the lower case for Earth as well. However, earth has a different meaning than Earth. The planet we live on is Earth or the Earth; the soil we plant our crops in is earth.

Here's a definition with the lower case:

the loose substance of which a large part of the surface of the ground is made, and in which plants can grow; the land surface of the earth rather than the sky or sea: The plowed earth looked dark and fertile.

If you read some other folks' articles with these two words written with sun and Earth, I think you'll get more used to it.

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